/* * create-diff-object.c * * Copyright (C) 2014 Seth Jennings * Copyright (C) 2013-2014 Josh Poimboeuf * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA, * 02110-1301, USA. */ /* * This file contains the heart of the ELF object differencing engine. * * The tool takes two ELF objects from two versions of the same source * file; a "base" object and a "patched" object. These object need to have * been compiled with the -ffunction-sections and -fdata-sections GCC options. * * The tool compares the objects at a section level to determine what * sections have changed. Once a list of changed sections has been generated, * various rules are applied to determine any object local sections that * are dependencies of the changed section and also need to be included in * the output object. */ #include #include #include #include #include #include #include #include #include #include #include #include "list.h" #include "lookup.h" #include "asm/insn.h" #include "kpatch-patch.h" #include "kpatch-elf.h" #include "kpatch-intermediate.h" #include "kpatch.h" #define DIFF_FATAL(format, ...) \ ({ \ fprintf(stderr, "ERROR: %s: " format "\n", childobj, ##__VA_ARGS__); \ error(EXIT_STATUS_DIFF_FATAL, 0, "unreconcilable difference"); \ }) #ifdef __powerpc64__ #define ABSOLUTE_RELA_TYPE R_PPC64_ADDR64 #else #define ABSOLUTE_RELA_TYPE R_X86_64_64 #endif char *childobj; enum loglevel loglevel = NORMAL; /******************* * Data structures * ****************/ struct special_section { char *name; int (*group_size)(struct kpatch_elf *kelf, int offset); }; /************* * Functions * **********/ static int is_bundleable(struct symbol *sym) { if (sym->type == STT_FUNC && !strncmp(sym->sec->name, ".text.",6) && !strcmp(sym->sec->name + 6, sym->name)) return 1; if (sym->type == STT_FUNC && !strncmp(sym->sec->name, ".text.unlikely.",15) && (!strcmp(sym->sec->name + 15, sym->name) || (strstr(sym->name, ".cold.") && !strncmp(sym->sec->name + 15, sym->name, strlen(sym->sec->name) - 15)))) return 1; if (sym->type == STT_OBJECT && !strncmp(sym->sec->name, ".data.",6) && !strcmp(sym->sec->name + 6, sym->name)) return 1; if (sym->type == STT_OBJECT && !strncmp(sym->sec->name, ".rodata.",8) && !strcmp(sym->sec->name + 8, sym->name)) return 1; if (sym->type == STT_OBJECT && !strncmp(sym->sec->name, ".bss.",5) && !strcmp(sym->sec->name + 5, sym->name)) return 1; return 0; } #ifdef __powerpc64__ /* Symbol st_others value for powerpc */ #define STO_PPC64_LOCAL_BIT 5 #define STO_PPC64_LOCAL_MASK (7 << STO_PPC64_LOCAL_BIT) #define PPC64_LOCAL_ENTRY_OFFSET(other) \ (((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2) /* * On ppc64le, the function prologue generated by GCC 6+ has the sequence: * * .globl my_func * .type my_func, @function * .quad .TOC.-my_func * my_func: * .reloc ., R_PPC64_ENTRY ; optional * ld r2,-8(r12) * add r2,r2,r12 * .localentry my_func, .-my_func * * my_func is the global entry point, which, when called, sets up the TOC. * .localentry is the local entry point, for calls to the function from within * the object file. The local entry point is 8 bytes after the global entry * point. */ static int is_gcc6_localentry_bundled_sym(struct symbol *sym) { return ((PPC64_LOCAL_ENTRY_OFFSET(sym->sym.st_other) != 0) && sym->sym.st_value == 8); } #else static int is_gcc6_localentry_bundled_sym(struct symbol *sym) { return 0; } #endif static struct rela *toc_rela(const struct rela *rela) { if (rela->type != R_PPC64_TOC16_HA && rela->type != R_PPC64_TOC16_LO_DS) return (struct rela *)rela; /* Will return NULL for .toc constant entries */ return find_rela_by_offset(rela->sym->sec->rela, rela->addend); } /* * When compiling with -ffunction-sections and -fdata-sections, almost every * symbol gets its own dedicated section. We call such symbols "bundled" * symbols. They're indicated by "sym->sec->sym == sym". */ static void kpatch_bundle_symbols(struct kpatch_elf *kelf) { struct symbol *sym; list_for_each_entry(sym, &kelf->symbols, list) { if (is_bundleable(sym)) { if (sym->sym.st_value != 0 && !is_gcc6_localentry_bundled_sym(sym)) { ERROR("symbol %s at offset %lu within section %s, expected 0", sym->name, sym->sym.st_value, sym->sec->name); } sym->sec->sym = sym; } } } /* * This function detects whether the given symbol is a "special" static local * variable (for lack of a better term). * * Special static local variables should never be correlated and should always * be included if they are referenced by an included function. */ static int is_special_static(struct symbol *sym) { static char *prefixes[] = { "__key.", "__warned.", "descriptor.", "__func__.", "_rs.", "CSWTCH.", NULL, }; char **prefix; if (!sym) return 0; if (sym->type == STT_SECTION) { /* __verbose section contains the descriptor variables */ if (!strcmp(sym->name, "__verbose")) return 1; /* otherwise make sure section is bundled */ if (!sym->sec->sym) return 0; /* use bundled object/function symbol for matching */ sym = sym->sec->sym; } if (sym->type != STT_OBJECT || sym->bind != STB_LOCAL) return 0; for (prefix = prefixes; *prefix; prefix++) if (!strncmp(sym->name, *prefix, strlen(*prefix))) return 1; return 0; } /* * This is like strcmp, but for gcc-mangled symbols. It skips the comparison * of any substring which consists of '.' followed by any number of digits. */ static int kpatch_mangled_strcmp(char *s1, char *s2) { while (*s1 == *s2) { if (!*s1) return 0; if (*s1 == '.' && isdigit(s1[1])) { if (!isdigit(s2[1])) return 1; while (isdigit(*++s1)) ; while (isdigit(*++s2)) ; } else { s1++; s2++; } } return 1; } static int rela_equal(struct rela *rela1, struct rela *rela2) { struct rela *rela_toc1, *rela_toc2; unsigned long toc_data1 = 0, toc_data2 = 0; /* = 0 to prevent gcc warning */ if (rela1->type != rela2->type || rela1->offset != rela2->offset) return 0; /* * With -mcmodel=large on ppc64le, GCC might generate entries in the .toc * section for relocation symbol references. The .toc offsets may change * between the original and patched .o, so comparing ".toc + offset" isn't * right. Compare the .toc-based symbols by reading the corresponding relas * from the .toc section. */ rela_toc1 = toc_rela(rela1); if (!rela_toc1) { /* * .toc section entries are mostly place holder for relocation entries, specified * in .rela.toc section. Sometimes, .toc section may have constants as entries. * These constants are not reference to any symbols, but plain instructions mostly * due to some arithmetics in the functions referring them. * * They are referred by the functions like normal .toc entries, these entries can * not be resolved to any symbols. * * Disassembly of section .toc: * * 0000000000000000 <.toc>: * ... * 148: R_PPC64_ADDR64 .data.capacity_margin * 150: 0b d7 a3 70 andi. r3,r5,55051 * 154: 3d 0a d7 a3 lhz r30,2621(r23) * 158: R_PPC64_ADDR64 sched_max_numa_distance * * Relocation section '.rela.toc' at offset 0xadac0 contains 160 entries: * Offset Info Type Symbol's Value Symbol's Name + Addend * ... * 0000000000000148 0000009100000026 R_PPC64_ADDR64 0000000000000000 .data.capacity_margin + 0 * 0000000000000158 000001a500000026 R_PPC64_ADDR64 0000000000000000 sched_max_numa_distance + 0 * * Relocation section '.rela.text.select_task_rq_fair' at offset 0x90e98 contains 37 entries: * Offset Info Type Symbol's Value Symbol's Name + Addend * ... * 00000000000004a0 0000008800000032 R_PPC64_TOC16_HA 0000000000000000 .toc + 148 * 00000000000004ac 0000008800000040 R_PPC64_TOC16_LO_DS 0000000000000000 .toc + 148 * 0000000000000514 0000008800000032 R_PPC64_TOC16_HA 0000000000000000 .toc + 150 * 000000000000051c 0000008800000040 R_PPC64_TOC16_LO_DS 0000000000000000 .toc + 150 */ memcpy(&toc_data1, rela1->sym->sec->data->d_buf + rela1->addend, sizeof(toc_data1)); if (!toc_data1) ERROR(".toc entry not found %s + %x", rela1->sym->name, rela1->addend); } rela_toc2 = toc_rela(rela2); if (!rela_toc2) { memcpy(&toc_data2, rela2->sym->sec->data->d_buf + rela2->addend, sizeof(toc_data2)); if (!toc_data2) ERROR(".toc entry not found %s + %x", rela2->sym->name, rela2->addend); } if (!rela_toc1 && !rela_toc2) return toc_data1 == toc_data2; if (rela_toc1->string) return rela_toc2->string && !strcmp(rela_toc1->string, rela_toc2->string); if (rela_toc1->addend != rela_toc2->addend) return 0; if (is_special_static(rela_toc1->sym)) return !kpatch_mangled_strcmp(rela_toc1->sym->name, rela_toc2->sym->name); return !strcmp(rela_toc1->sym->name, rela_toc2->sym->name); } static void kpatch_compare_correlated_rela_section(struct section *sec) { struct rela *rela1, *rela2 = NULL; /* * On ppc64le, don't compare the .rela.toc section. The .toc and * .rela.toc sections are included as standard elements. */ if (!strcmp(sec->name, ".rela.toc")) { sec->status = SAME; return; } rela2 = list_entry(sec->twin->relas.next, struct rela, list); list_for_each_entry(rela1, &sec->relas, list) { if (rela_equal(rela1, rela2)) { rela2 = list_entry(rela2->list.next, struct rela, list); continue; } sec->status = CHANGED; return; } sec->status = SAME; } static void kpatch_compare_correlated_nonrela_section(struct section *sec) { struct section *sec1 = sec, *sec2 = sec->twin; if (sec1->sh.sh_type != SHT_NOBITS && memcmp(sec1->data->d_buf, sec2->data->d_buf, sec1->data->d_size)) sec->status = CHANGED; else sec->status = SAME; } static void kpatch_compare_correlated_section(struct section *sec) { struct section *sec1 = sec, *sec2 = sec->twin; /* Compare section headers (must match or fatal) */ if (sec1->sh.sh_type != sec2->sh.sh_type || sec1->sh.sh_flags != sec2->sh.sh_flags || sec1->sh.sh_addralign != sec2->sh.sh_addralign || sec1->sh.sh_entsize != sec2->sh.sh_entsize) DIFF_FATAL("%s section header details differ", sec1->name); /* Short circuit for mcount sections, we rebuild regardless */ if (!strcmp(sec->name, ".rela__mcount_loc") || !strcmp(sec->name, "__mcount_loc")) { sec->status = SAME; goto out; } if (sec1->sh.sh_size != sec2->sh.sh_size || sec1->data->d_size != sec2->data->d_size) { sec->status = CHANGED; goto out; } if (is_rela_section(sec)) kpatch_compare_correlated_rela_section(sec); else kpatch_compare_correlated_nonrela_section(sec); out: if (sec->status == CHANGED) log_debug("section %s has changed\n", sec->name); } #ifdef __x86_64__ /* * Determine if a section has changed only due to a WARN* or might_sleep * macro call's embedding of the line number into an instruction operand. * * Warning: Hackery lies herein. It's hopefully justified by the fact that * this issue is very common. * * Example WARN*: * * 938: be 70 00 00 00 mov $0x70,%esi * 93d: 48 c7 c7 00 00 00 00 mov $0x0,%rdi * 940: R_X86_64_32S .rodata.tcp_conn_request.str1.8+0x88 * 944: c6 05 00 00 00 00 01 movb $0x1,0x0(%rip) # 94b * 946: R_X86_64_PC32 .data.unlikely-0x1 * 94b: e8 00 00 00 00 callq 950 * 94c: R_X86_64_PC32 warn_slowpath_null-0x4 * * Example might_sleep: * * 50f: be f7 01 00 00 mov $0x1f7,%esi * 514: 48 c7 c7 00 00 00 00 mov $0x0,%rdi * 517: R_X86_64_32S .rodata.do_select.str1.8+0x98 * 51b: e8 00 00 00 00 callq 520 * 51c: R_X86_64_PC32 ___might_sleep-0x4 * * The pattern which applies to all cases: * 1) immediate move of the line number to %esi * 2) (optional) string section rela * 3) (optional) __warned.xxxxx static local rela * 4) warn_slowpath_* or __might_sleep or some other similar rela */ static int kpatch_line_macro_change_only(struct section *sec) { struct insn insn1, insn2; unsigned long start1, start2, size, offset, length; struct rela *rela; int lineonly = 0, found; if (sec->status != CHANGED || is_rela_section(sec) || !is_text_section(sec) || sec->sh.sh_size != sec->twin->sh.sh_size || !sec->rela || sec->rela->status != SAME) return 0; start1 = (unsigned long)sec->twin->data->d_buf; start2 = (unsigned long)sec->data->d_buf; size = sec->sh.sh_size; for (offset = 0; offset < size; offset += length) { insn_init(&insn1, (void *)(start1 + offset), 1); insn_init(&insn2, (void *)(start2 + offset), 1); insn_get_length(&insn1); insn_get_length(&insn2); length = insn1.length; if (!insn1.length || !insn2.length) ERROR("can't decode instruction in section %s at offset 0x%lx", sec->name, offset); if (insn1.length != insn2.length) return 0; if (!memcmp((void *)start1 + offset, (void *)start2 + offset, length)) continue; /* verify it's a mov immediate to %edx or %esi */ insn_get_opcode(&insn1); insn_get_opcode(&insn2); if (!(insn1.opcode.value == 0xba && insn2.opcode.value == 0xba) && !(insn1.opcode.value == 0xbe && insn2.opcode.value == 0xbe)) return 0; /* * Verify zero or more string relas followed by a * warn_slowpath_* or another similar rela. */ found = 0; list_for_each_entry(rela, &sec->rela->relas, list) { if (rela->offset < offset + length) continue; if (rela->string) continue; if (!strncmp(rela->sym->name, "__warned.", 9)) continue; if (!strncmp(rela->sym->name, "warn_slowpath_", 14) || (!strcmp(rela->sym->name, "__warn_printk")) || (!strcmp(rela->sym->name, "__might_sleep")) || (!strcmp(rela->sym->name, "___might_sleep")) || (!strcmp(rela->sym->name, "__might_fault")) || (!strcmp(rela->sym->name, "printk")) || (!strcmp(rela->sym->name, "lockdep_rcu_suspicious"))) { found = 1; break; } return 0; } if (!found) return 0; lineonly = 1; } if (!lineonly) ERROR("no instruction changes detected for changed section %s", sec->name); return 1; } #elif __powerpc64__ #define PPC_INSTR_LEN 4 #define PPC_RA_OFFSET 16 static int kpatch_line_macro_change_only(struct section *sec) { unsigned long start1, start2, size, offset; unsigned int instr1, instr2; struct rela *rela; int lineonly = 0, found; if (sec->status != CHANGED || is_rela_section(sec) || !is_text_section(sec) || sec->sh.sh_size != sec->twin->sh.sh_size || !sec->rela || sec->rela->status != SAME) return 0; start1 = (unsigned long)sec->twin->data->d_buf; start2 = (unsigned long)sec->data->d_buf; size = sec->sh.sh_size; for (offset = 0; offset < size; offset += PPC_INSTR_LEN) { if (!memcmp((void *)start1 + offset, (void *)start2 + offset, PPC_INSTR_LEN)) continue; instr1 = *(unsigned int *)(start1 + offset) >> PPC_RA_OFFSET; instr2 = *(unsigned int *)(start2 + offset) >> PPC_RA_OFFSET; /* verify it's a load immediate to r5 */ if (!(instr1 == 0x38a0 && instr2 == 0x38a0)) return 0; found = 0; list_for_each_entry(rela, &sec->rela->relas, list) { if (rela->offset < offset + PPC_INSTR_LEN) continue; if (toc_rela(rela) && toc_rela(rela)->string) continue; if (!strncmp(rela->sym->name, "__warned.", 9)) continue; if (!strncmp(rela->sym->name, "warn_slowpath_", 14) || (!strcmp(rela->sym->name, "__warn_printk")) || (!strcmp(rela->sym->name, "__might_sleep")) || (!strcmp(rela->sym->name, "___might_sleep")) || (!strcmp(rela->sym->name, "__might_fault")) || (!strcmp(rela->sym->name, "printk")) || (!strcmp(rela->sym->name, "lockdep_rcu_suspicious"))) { found = 1; break; } return 0; } if (!found) return 0; lineonly = 1; } if (!lineonly) ERROR("no instruction changes detected for changed section %s", sec->name); return 1; } #else static int kpatch_line_macro_change_only(struct section *sec) { return 0; } #endif static void kpatch_compare_sections(struct list_head *seclist) { struct section *sec; /* compare all sections */ list_for_each_entry(sec, seclist, list) { if (sec->twin) kpatch_compare_correlated_section(sec); else sec->status = NEW; } /* exclude WARN-only, might_sleep changes */ list_for_each_entry(sec, seclist, list) { if (kpatch_line_macro_change_only(sec)) { log_debug("reverting macro / line number section %s status to SAME\n", sec->name); sec->status = SAME; } } /* sync symbol status */ list_for_each_entry(sec, seclist, list) { if (is_rela_section(sec)) { if (sec->base->sym && sec->base->sym->status != CHANGED) sec->base->sym->status = sec->status; } else { if (sec->sym && sec->sym->status != CHANGED) sec->sym->status = sec->status; } } } static void kpatch_compare_correlated_symbol(struct symbol *sym) { struct symbol *sym1 = sym, *sym2 = sym->twin; if (sym1->sym.st_info != sym2->sym.st_info || (sym1->sec && !sym2->sec) || (sym2->sec && !sym1->sec)) DIFF_FATAL("symbol info mismatch: %s", sym1->name); /* * If two symbols are correlated but their sections are not, then the * symbol has changed sections. This is only allowed if the symbol is * moving out of an ignored section. */ if (sym1->sec && sym2->sec && sym1->sec->twin != sym2->sec) { if (sym2->sec->twin && sym2->sec->twin->ignore) sym->status = CHANGED; else DIFF_FATAL("symbol changed sections: %s", sym1->name); } if (sym1->type == STT_OBJECT && sym1->sym.st_size != sym2->sym.st_size) DIFF_FATAL("object size mismatch: %s", sym1->name); if (sym1->sym.st_shndx == SHN_UNDEF || sym1->sym.st_shndx == SHN_ABS) sym1->status = SAME; /* * The status of LOCAL symbols is dependent on the status of their * matching section and is set during section comparison. */ } static void kpatch_compare_symbols(struct list_head *symlist) { struct symbol *sym; list_for_each_entry(sym, symlist, list) { if (sym->twin) kpatch_compare_correlated_symbol(sym); else sym->status = NEW; log_debug("symbol %s is %s\n", sym->name, status_str(sym->status)); } } static void kpatch_correlate_sections(struct list_head *seclist1, struct list_head *seclist2) { struct section *sec1, *sec2; list_for_each_entry(sec1, seclist1, list) { list_for_each_entry(sec2, seclist2, list) { if (strcmp(sec1->name, sec2->name)) continue; if (is_special_static(is_rela_section(sec1) ? sec1->base->secsym : sec1->secsym)) continue; /* * Group sections must match exactly to be correlated. * Changed group sections are currently not supported. */ if (sec1->sh.sh_type == SHT_GROUP) { if (sec1->data->d_size != sec2->data->d_size) continue; if (memcmp(sec1->data->d_buf, sec2->data->d_buf, sec1->data->d_size)) continue; } sec1->twin = sec2; sec2->twin = sec1; /* set initial status, might change */ sec1->status = sec2->status = SAME; break; } } } static void kpatch_correlate_symbols(struct list_head *symlist1, struct list_head *symlist2) { struct symbol *sym1, *sym2; list_for_each_entry(sym1, symlist1, list) { list_for_each_entry(sym2, symlist2, list) { if (strcmp(sym1->name, sym2->name) || sym1->type != sym2->type) continue; if (is_special_static(sym1)) continue; /* * The .LCx symbols point to strings, usually used for * the bug table. Don't correlate and compare the * symbols themselves, because the suffix number might * change. * * If the symbol is used by the bug table (usual case), * it may get pulled in by * kpatch_regenerate_special_section(). * * If the symbol is used outside of the bug table (not * sure if this actually happens anywhere), any string * changes will be detected elsewhere in rela_equal(). */ if (sym1->type == STT_NOTYPE && !strncmp(sym1->name, ".LC", 3)) continue; /* group section symbols must have correlated sections */ if (sym1->sec && sym1->sec->sh.sh_type == SHT_GROUP && sym1->sec->twin != sym2->sec) continue; sym1->twin = sym2; sym2->twin = sym1; /* set initial status, might change */ sym1->status = sym2->status = SAME; break; } } } static void kpatch_compare_elf_headers(Elf *elf1, Elf *elf2) { GElf_Ehdr eh1, eh2; if (!gelf_getehdr(elf1, &eh1)) ERROR("gelf_getehdr"); if (!gelf_getehdr(elf2, &eh2)) ERROR("gelf_getehdr"); if (memcmp(eh1.e_ident, eh2.e_ident, EI_NIDENT) || eh1.e_type != eh2.e_type || eh1.e_machine != eh2.e_machine || eh1.e_version != eh2.e_version || eh1.e_entry != eh2.e_entry || eh1.e_phoff != eh2.e_phoff || eh1.e_flags != eh2.e_flags || eh1.e_ehsize != eh2.e_ehsize || eh1.e_phentsize != eh2.e_phentsize || eh1.e_shentsize != eh2.e_shentsize) DIFF_FATAL("ELF headers differ"); } static void kpatch_check_program_headers(Elf *elf) { size_t ph_nr; if (elf_getphdrnum(elf, &ph_nr)) ERROR("elf_getphdrnum"); if (ph_nr != 0) DIFF_FATAL("ELF contains program header"); } static void kpatch_mark_grouped_sections(struct kpatch_elf *kelf) { struct section *groupsec, *sec; unsigned int *data, *end; list_for_each_entry(groupsec, &kelf->sections, list) { if (groupsec->sh.sh_type != SHT_GROUP) continue; data = groupsec->data->d_buf; end = groupsec->data->d_buf + groupsec->data->d_size; data++; /* skip first flag word (e.g. GRP_COMDAT) */ while (data < end) { sec = find_section_by_index(&kelf->sections, *data); if (!sec) ERROR("group section not found"); sec->grouped = 1; log_debug("marking section %s (%d) as grouped\n", sec->name, sec->index); data++; } } } /* * When gcc makes compiler optimizations which affect a function's calling * interface, it mangles the function's name. For example, sysctl_print_dir is * renamed to sysctl_print_dir.isra.2. The problem is that the trailing number * is chosen arbitrarily, and the patched version of the function may end up * with a different trailing number. Rename any mangled patched functions to * match their base counterparts. */ static void kpatch_rename_mangled_functions(struct kpatch_elf *base, struct kpatch_elf *patched) { struct symbol *sym, *basesym; char name[256], *origname; struct section *sec, *basesec; int found; list_for_each_entry(sym, &patched->symbols, list) { if (sym->type != STT_FUNC) continue; if (!strstr(sym->name, ".isra.") && !strstr(sym->name, ".constprop.") && !strstr(sym->name, ".cold.") && !strstr(sym->name, ".part.")) continue; found = 0; list_for_each_entry(basesym, &base->symbols, list) { if (!kpatch_mangled_strcmp(basesym->name, sym->name)) { found = 1; break; } } if (!found) continue; if (!strcmp(sym->name, basesym->name)) continue; log_debug("renaming %s to %s\n", sym->name, basesym->name); origname = sym->name; sym->name = strdup(basesym->name); if (sym != sym->sec->sym) continue; sym->sec->name = strdup(basesym->sec->name); if (sym->sec->rela) sym->sec->rela->name = strdup(basesym->sec->rela->name); /* * When function foo.isra.1 has a switch statement, it might * have a corresponding bundled .rodata.foo.isra.1 section (in * addition to .text.foo.isra.1 which we renamed above). */ sprintf(name, ".rodata.%s", origname); sec = find_section_by_name(&patched->sections, name); if (!sec) continue; sprintf(name, ".rodata.%s", basesym->name); basesec = find_section_by_name(&base->sections, name); if (!basesec) continue; sec->name = strdup(basesec->name); sec->secsym->name = sec->name; if (sec->rela) sec->rela->name = strdup(basesec->rela->name); } } static char *kpatch_section_function_name(struct section *sec) { if (is_rela_section(sec)) sec = sec->base; return sec->sym ? sec->sym->name : sec->name; } /* * Given a static local variable symbol and a rela section which references it * in the base object, find a corresponding usage of a similarly named symbol * in the patched object. */ static struct symbol *kpatch_find_static_twin(struct section *sec, struct symbol *sym) { struct rela *rela, *rela_toc; if (!sec->twin) return NULL; /* find the patched object's corresponding variable */ list_for_each_entry(rela, &sec->twin->relas, list) { rela_toc = toc_rela(rela); if (!rela_toc) continue; /* skip toc constants */ if (rela_toc->sym->twin) continue; if (kpatch_mangled_strcmp(rela_toc->sym->name, sym->name)) continue; return rela_toc->sym; } return NULL; } static int kpatch_is_normal_static_local(struct symbol *sym) { if (sym->type != STT_OBJECT || sym->bind != STB_LOCAL) return 0; if (!strchr(sym->name, '.')) return 0; if (is_special_static(sym)) return 0; return 1; } /* * gcc renames static local variables by appending a period and a number. For * example, __foo could be renamed to __foo.31452. Unfortunately this number * can arbitrarily change. Correlate them by comparing which functions * reference them, and rename the patched symbols to match the base symbol * names. * * Some surprising facts about static local variable symbols: * * - It's possible for multiple functions to use the same * static local variable if the variable is defined in an * inlined function. * * - It's also possible for multiple static local variables * with the same name to be used in the same function if they * have different scopes. (We have to assume that in such * cases, the order in which they're referenced remains the * same between the base and patched objects, as there's no * other way to distinguish them.) * * - Static locals are usually referenced by functions, but * they can occasionally be referenced by data sections as * well. */ static void kpatch_correlate_static_local_variables(struct kpatch_elf *base, struct kpatch_elf *patched) { struct symbol *sym, *patched_sym; struct section *sec; struct rela *rela, *rela2; int bundled, patched_bundled, found; /* * First undo the correlations for all static locals. Two static * locals can have the same numbered suffix in the base and patched * objects by coincidence. */ list_for_each_entry(sym, &base->symbols, list) { if (!kpatch_is_normal_static_local(sym)) continue; if (sym->twin) { sym->twin->twin = NULL; sym->twin = NULL; } bundled = sym == sym->sec->sym; if (bundled && sym->sec->twin) { sym->sec->twin->twin = NULL; sym->sec->twin = NULL; sym->sec->secsym->twin->twin = NULL; sym->sec->secsym->twin = NULL; if (sym->sec->rela) { sym->sec->rela->twin->twin = NULL; sym->sec->rela->twin = NULL; } } } /* * Do the correlations: for each section reference to a static local, * look for a corresponding reference in the section's twin. */ list_for_each_entry(sec, &base->sections, list) { if (!is_rela_section(sec) || is_debug_section(sec) || !strcmp(sec->name, ".rela.toc")) continue; list_for_each_entry(rela, &sec->relas, list) { if (!toc_rela(rela)) continue; /* skip toc constants */ sym = toc_rela(rela)->sym; if (!kpatch_is_normal_static_local(sym)) continue; if (sym->twin) continue; bundled = sym == sym->sec->sym; if (bundled && sym->sec == sec->base) { /* * A rare case where a static local data * structure references itself. There's no * reliable way to correlate this. Hopefully * there's another reference to the symbol * somewhere that can be used. */ log_debug("can't correlate static local %s's reference to itself\n", sym->name); continue; } patched_sym = kpatch_find_static_twin(sec, sym); if (!patched_sym) DIFF_FATAL("reference to static local variable %s in %s was removed", sym->name, kpatch_section_function_name(sec)); patched_bundled = patched_sym == patched_sym->sec->sym; if (bundled != patched_bundled) ERROR("bundle mismatch for symbol %s", sym->name); if (!bundled && sym->sec->twin != patched_sym->sec) ERROR("sections %s and %s aren't correlated", sym->sec->name, patched_sym->sec->name); log_debug("renaming and correlating static local %s to %s\n", patched_sym->name, sym->name); patched_sym->name = strdup(sym->name); sym->twin = patched_sym; patched_sym->twin = sym; /* set initial status, might change */ sym->status = patched_sym->status = SAME; if (bundled) { sym->sec->twin = patched_sym->sec; patched_sym->sec->twin = sym->sec; sym->sec->secsym->twin = patched_sym->sec->secsym; patched_sym->sec->secsym->twin = sym->sec->secsym; if (sym->sec->rela && patched_sym->sec->rela) { sym->sec->rela->twin = patched_sym->sec->rela; patched_sym->sec->rela->twin = sym->sec->rela; } } } } /* * Make sure that: * * 1. all the base object's referenced static locals have been * correlated; and * * 2. each reference to a static local in the base object has a * corresponding reference in the patched object (because a static * local can be referenced by more than one section). */ list_for_each_entry(sec, &base->sections, list) { if (!is_rela_section(sec) || is_debug_section(sec)) continue; list_for_each_entry(rela, &sec->relas, list) { sym = rela->sym; if (!kpatch_is_normal_static_local(sym)) continue; if (!sym->twin || !sec->twin) DIFF_FATAL("reference to static local variable %s in %s was removed", sym->name, kpatch_section_function_name(sec)); found = 0; list_for_each_entry(rela2, &sec->twin->relas, list) { if (rela2->sym == sym->twin) { found = 1; break; } } if (!found) DIFF_FATAL("static local %s has been correlated with %s, but patched %s is missing a reference to it", sym->name, sym->twin->name, kpatch_section_function_name(sec->twin)); } } /* * Now go through the patched object and look for any uncorrelated * static locals to see if we need to print any warnings about new * variables. */ list_for_each_entry(sec, &patched->sections, list) { if (!is_rela_section(sec) || is_debug_section(sec)) continue; list_for_each_entry(rela, &sec->relas, list) { sym = rela->sym; if (!kpatch_is_normal_static_local(sym)) continue; if (sym->twin) continue; log_normal("WARNING: unable to correlate static local variable %s used by %s, assuming variable is new\n", sym->name, kpatch_section_function_name(sec)); return; } } } static void kpatch_correlate_elfs(struct kpatch_elf *kelf1, struct kpatch_elf *kelf2) { kpatch_correlate_sections(&kelf1->sections, &kelf2->sections); kpatch_correlate_symbols(&kelf1->symbols, &kelf2->symbols); } static void kpatch_compare_correlated_elements(struct kpatch_elf *kelf) { /* lists are already correlated at this point */ kpatch_compare_sections(&kelf->sections); kpatch_compare_symbols(&kelf->symbols); } #ifdef __x86_64__ static void rela_insn(struct section *sec, struct rela *rela, struct insn *insn) { unsigned long insn_addr, start, end, rela_addr; start = (unsigned long)sec->base->data->d_buf; end = start + sec->base->sh.sh_size; rela_addr = start + rela->offset; for (insn_addr = start; insn_addr < end; insn_addr += insn->length) { insn_init(insn, (void *)insn_addr, 1); insn_get_length(insn); if (!insn->length) ERROR("can't decode instruction in section %s at offset 0x%lx", sec->base->name, insn_addr); if (rela_addr >= insn_addr && rela_addr < insn_addr + insn->length) return; } } #endif /* * Mangle the relas a little. The compiler will sometimes use section symbols * to reference local objects and functions rather than the object or function * symbols themselves. We substitute the object/function symbols for the * section symbol in this case so that the relas can be properly correlated and * so that the existing object/function in vmlinux can be linked to. */ static void kpatch_replace_sections_syms(struct kpatch_elf *kelf) { struct section *sec; struct rela *rela; struct symbol *sym; int add_off; log_debug("\n"); list_for_each_entry(sec, &kelf->sections, list) { if (!is_rela_section(sec) || is_debug_section(sec)) continue; list_for_each_entry(rela, &sec->relas, list) { if (rela->sym->type != STT_SECTION) continue; /* * Replace references to bundled sections with their * symbols. */ if (rela->sym->sec && rela->sym->sec->sym) { rela->sym = rela->sym->sec->sym; continue; } #ifdef __powerpc64__ add_off = 0; #else if (rela->type == R_X86_64_PC32) { struct insn insn; rela_insn(sec, rela, &insn); add_off = (long)insn.next_byte - (long)sec->base->data->d_buf - rela->offset; } else if (rela->type == R_X86_64_64 || rela->type == R_X86_64_32S) add_off = 0; else continue; #endif /* * Attempt to replace references to unbundled sections * with their symbols. */ list_for_each_entry(sym, &kelf->symbols, list) { int start, end; if (sym->type == STT_SECTION || sym->sec != rela->sym->sec) continue; start = sym->sym.st_value; end = sym->sym.st_value + sym->sym.st_size; if (!is_text_section(sym->sec) && rela->type == R_X86_64_32S && rela->addend == (int)sym->sec->sh.sh_size && end == (int)sym->sec->sh.sh_size) { /* * A special case where gcc needs a * pointer to the address at the end of * a data section. * * This is usually used with a compare * instruction to determine when to end * a loop. The code doesn't actually * dereference the pointer so this is * "normal" and we just replace the * section reference with a reference * to the last symbol in the section. * * Note that this only catches the * issue when it happens at the end of * a section. It can also happen in * the middle of a section. In that * case, the wrong symbol will be * associated with the reference. But * that's ok because: * * 1) This situation only occurs when * gcc is trying to get the address * of the symbol, not the contents * of its data; and * * 2) Because kpatch doesn't allow data * sections to change, * &(var1+sizeof(var1)) will always * be the same as &var2. */ } else if (rela->addend + add_off < start || rela->addend + add_off >= end) continue; log_debug("%s: replacing %s+%d reference with %s+%d\n", sec->name, rela->sym->name, rela->addend, sym->name, rela->addend - start); rela->sym = sym; rela->addend -= start; break; } } } log_debug("\n"); } static void kpatch_check_func_profiling_calls(struct kpatch_elf *kelf) { struct symbol *sym; int errs = 0; list_for_each_entry(sym, &kelf->symbols, list) { if (sym->type != STT_FUNC || sym->status != CHANGED) continue; if (!sym->twin->has_func_profiling) { log_normal("function %s has no fentry/mcount call, unable to patch\n", sym->name); errs++; } } if (errs) DIFF_FATAL("%d function(s) can not be patched", errs); } static void kpatch_verify_patchability(struct kpatch_elf *kelf) { struct section *sec; int errs = 0; list_for_each_entry(sec, &kelf->sections, list) { if (sec->status == CHANGED && !sec->include) { log_normal("changed section %s not selected for inclusion\n", sec->name); errs++; } if (sec->status != SAME && sec->grouped) { log_normal("changed section %s is part of a section group\n", sec->name); errs++; } if (sec->sh.sh_type == SHT_GROUP && sec->status == NEW) { log_normal("new/changed group sections are not supported\n"); errs++; } /* * ensure we aren't including .data.* or .bss.* * (.data.unlikely and .data.once is ok b/c it only has __warned vars) */ if (sec->include && sec->status != NEW && (!strncmp(sec->name, ".data", 5) || !strncmp(sec->name, ".bss", 4)) && (strcmp(sec->name, ".data.unlikely") && strcmp(sec->name, ".data.once"))) { log_normal("data section %s selected for inclusion\n", sec->name); errs++; } } if (errs) DIFF_FATAL("%d unsupported section change(s)", errs); } static void kpatch_include_symbol(struct symbol *sym); static void kpatch_include_section(struct section *sec) { struct rela *rela; /* Include the section and its section symbol */ if (sec->include) return; sec->include = 1; if (sec->secsym) sec->secsym->include = 1; /* * Include the section's rela section and then recursively include the * symbols needed by its relas. */ if (!sec->rela) return; sec->rela->include = 1; list_for_each_entry(rela, &sec->rela->relas, list) kpatch_include_symbol(rela->sym); } static void kpatch_include_symbol(struct symbol *sym) { /* * This function is called recursively from kpatch_include_section(). * Make sure we don't get into an endless loop. */ if (sym->include) return; /* * The symbol gets included even if its section isn't needed, as it * might be needed: either permanently for a rela, or temporarily for * the later creation of a dynrela. */ sym->include = 1; /* * For a function/object symbol, if it has a section, we only need to * include the section if it has changed. Otherwise the symbol will be * used by relas/dynrelas to link to the real symbol externally. * * For section symbols, we always include the section because * references to them can't otherwise be resolved externally. */ if (sym->sec && (sym->type == STT_SECTION || sym->status != SAME)) kpatch_include_section(sym->sec); } static void kpatch_include_standard_elements(struct kpatch_elf *kelf) { struct section *sec; list_for_each_entry(sec, &kelf->sections, list) { /* * Include the following sections even if they haven't changed. * * Notes about some of the more interesting sections: * * - With -fdata-sections, .rodata is only used for: * * switch jump tables; * KASAN data (with KASAN enabled, which is rare); and * an ugly hack in vmx_vcpu_run(). * * Those data are all local to the functions which use them. * So it's safe to include .rodata. * * - On ppc64le, the .toc section is used for all data * accesses. * * Note that if any of these sections have rela sections, they * will also be included in their entirety. That may result in * some extra (unused) dynrelas getting created, which should * be harmless. */ if (!strcmp(sec->name, ".shstrtab") || !strcmp(sec->name, ".strtab") || !strcmp(sec->name, ".symtab") || !strcmp(sec->name, ".toc") || !strcmp(sec->name, ".rodata") || (!strncmp(sec->name, ".rodata.", 8) && strstr(sec->name, ".str1."))) { kpatch_include_section(sec); } } /* include the NULL symbol */ list_entry(kelf->symbols.next, struct symbol, list)->include = 1; } static int kpatch_include_callback_elements(struct kpatch_elf *kelf) { struct section *sec; struct symbol *sym; struct rela *rela; int found = 0; static char *callback_sections[] = { ".kpatch.callbacks.pre_patch", ".kpatch.callbacks.post_patch", ".kpatch.callbacks.pre_unpatch", ".kpatch.callbacks.post_unpatch", ".rela.kpatch.callbacks.pre_patch", ".rela.kpatch.callbacks.post_patch", ".rela.kpatch.callbacks.pre_unpatch", ".rela.kpatch.callbacks.post_unpatch", NULL, }; char **callback_section; /* include load/unload sections */ list_for_each_entry(sec, &kelf->sections, list) { for (callback_section = callback_sections; *callback_section; callback_section++) { if (strcmp(*callback_section, sec->name)) continue; sec->include = 1; found = 1; if (is_rela_section(sec)) { /* include callback dependencies */ rela = list_entry(sec->relas.next, struct rela, list); sym = rela->sym; log_normal("found callback: %s\n",sym->name); kpatch_include_symbol(sym); /* strip the callback symbol */ sym->include = 0; sym->sec->sym = NULL; /* use section symbol instead */ rela->sym = sym->sec->secsym; } else { sec->secsym->include = 1; } } } /* Strip temporary global structures used by the callback macros. */ list_for_each_entry(sym, &kelf->symbols, list) { if (!sym->sec) continue; for (callback_section = callback_sections; *callback_section; callback_section++) { if (!strcmp(*callback_section, sym->sec->name)) { sym->include = 0; break; } } } return found; } static void kpatch_include_force_elements(struct kpatch_elf *kelf) { struct section *sec; struct symbol *sym; struct rela *rela; /* include force sections */ list_for_each_entry(sec, &kelf->sections, list) { if (!strcmp(sec->name, ".kpatch.force") || !strcmp(sec->name, ".rela.kpatch.force")) { sec->include = 1; if (!is_rela_section(sec)) { /* .kpatch.force */ sec->secsym->include = 1; continue; } /* .rela.kpatch.force */ list_for_each_entry(rela, &sec->relas, list) log_normal("function '%s' marked with KPATCH_FORCE_UNSAFE!\n", rela->sym->name); } } /* strip temporary global kpatch_force_func_* symbols */ list_for_each_entry(sym, &kelf->symbols, list) if (!strncmp(sym->name, "__kpatch_force_func_", strlen("__kpatch_force_func_"))) sym->include = 0; } static int kpatch_include_new_globals(struct kpatch_elf *kelf) { struct symbol *sym; int nr = 0; list_for_each_entry(sym, &kelf->symbols, list) { if (sym->bind == STB_GLOBAL && sym->sec && sym->status == NEW) { kpatch_include_symbol(sym); nr++; } } return nr; } static int kpatch_include_changed_functions(struct kpatch_elf *kelf) { struct symbol *sym; int changed_nr = 0; list_for_each_entry(sym, &kelf->symbols, list) { if (sym->status == CHANGED && sym->type == STT_FUNC) { changed_nr++; kpatch_include_symbol(sym); } if (sym->type == STT_FILE) sym->include = 1; } return changed_nr; } static void kpatch_print_changes(struct kpatch_elf *kelf) { struct symbol *sym; list_for_each_entry(sym, &kelf->symbols, list) { if (!sym->include || !sym->sec || sym->type != STT_FUNC) continue; if (sym->status == NEW) log_normal("new function: %s\n", sym->name); else if (sym->status == CHANGED) log_normal("changed function: %s\n", sym->name); } } static void kpatch_migrate_symbols(struct list_head *src, struct list_head *dst, int (*select)(struct symbol *)) { struct symbol *sym, *safe; list_for_each_entry_safe(sym, safe, src, list) { if (select && !select(sym)) continue; list_del(&sym->list); list_add_tail(&sym->list, dst); } } static void kpatch_migrate_included_elements(struct kpatch_elf *kelf, struct kpatch_elf **kelfout) { struct section *sec, *safesec; struct symbol *sym, *safesym; struct kpatch_elf *out; /* allocate output kelf */ out = malloc(sizeof(*out)); if (!out) ERROR("malloc"); memset(out, 0, sizeof(*out)); INIT_LIST_HEAD(&out->sections); INIT_LIST_HEAD(&out->symbols); INIT_LIST_HEAD(&out->strings); /* migrate included sections from kelf to out */ list_for_each_entry_safe(sec, safesec, &kelf->sections, list) { if (!sec->include) continue; list_del(&sec->list); list_add_tail(&sec->list, &out->sections); sec->index = 0; if (!is_rela_section(sec) && sec->secsym && !sec->secsym->include) /* break link to non-included section symbol */ sec->secsym = NULL; } /* migrate included symbols from kelf to out */ list_for_each_entry_safe(sym, safesym, &kelf->symbols, list) { if (!sym->include) continue; list_del(&sym->list); list_add_tail(&sym->list, &out->symbols); sym->index = 0; sym->strip = 0; if (sym->sec && !sym->sec->include) /* break link to non-included section */ sym->sec = NULL; } *kelfout = out; } static void kpatch_reorder_symbols(struct kpatch_elf *kelf) { LIST_HEAD(symbols); /* migrate NULL sym */ kpatch_migrate_symbols(&kelf->symbols, &symbols, is_null_sym); /* migrate LOCAL FILE sym */ kpatch_migrate_symbols(&kelf->symbols, &symbols, is_file_sym); /* migrate LOCAL FUNC syms */ kpatch_migrate_symbols(&kelf->symbols, &symbols, is_local_func_sym); /* migrate all other LOCAL syms */ kpatch_migrate_symbols(&kelf->symbols, &symbols, is_local_sym); /* migrate all other (GLOBAL) syms */ kpatch_migrate_symbols(&kelf->symbols, &symbols, NULL); list_replace(&symbols, &kelf->symbols); } static int bug_table_group_size(struct kpatch_elf *kelf, int offset) { static int size = 0; char *str; if (!size) { str = getenv("BUG_STRUCT_SIZE"); if (!str) ERROR("BUG_STRUCT_SIZE not set"); size = atoi(str); } return size; } static int ex_table_group_size(struct kpatch_elf *kelf, int offset) { static int size = 0; char *str; if (!size) { str = getenv("EX_STRUCT_SIZE"); if (!str) ERROR("EX_STRUCT_SIZE not set"); size = atoi(str); } return size; } #ifdef __x86_64__ static int parainstructions_group_size(struct kpatch_elf *kelf, int offset) { static int size = 0; char *str; if (!size) { str = getenv("PARA_STRUCT_SIZE"); if (!str) ERROR("PARA_STRUCT_SIZE not set"); size = atoi(str); } return size; } static int altinstructions_group_size(struct kpatch_elf *kelf, int offset) { static int size = 0; char *str; if (!size) { str = getenv("ALT_STRUCT_SIZE"); if (!str) ERROR("ALT_STRUCT_SIZE not set"); size = atoi(str); } return size; } static int smp_locks_group_size(struct kpatch_elf *kelf, int offset) { return 4; } #endif #ifdef __powerpc64__ static int fixup_entry_group_size(struct kpatch_elf *kelf, int offset) { static int size = 0; char *str; if (!size) { str = getenv("FIXUP_STRUCT_SIZE"); if (!str) ERROR("FIXUP_STRUCT_SIZE not set"); size = atoi(str); } return size; } static int fixup_lwsync_group_size(struct kpatch_elf *kelf, int offset) { return 4; } #endif /* * The rela groups in the .fixup section vary in size. The beginning of each * .fixup rela group is referenced by the __ex_table section. To find the size * of a .fixup rela group, we have to traverse the __ex_table relas. */ static int fixup_group_size(struct kpatch_elf *kelf, int offset) { struct section *sec; struct rela *rela; int found; sec = find_section_by_name(&kelf->sections, ".rela__ex_table"); if (!sec) ERROR("missing .rela__ex_table section"); /* find beginning of this group */ found = 0; list_for_each_entry(rela, &sec->relas, list) { if (!strcmp(rela->sym->name, ".fixup") && rela->addend == offset) { found = 1; break; } } if (!found) ERROR("can't find .fixup rela group at offset %d\n", offset); /* find beginning of next group */ found = 0; list_for_each_entry_continue(rela, &sec->relas, list) { if (!strcmp(rela->sym->name, ".fixup") && rela->addend > offset) { found = 1; break; } } if (!found) { /* last group */ struct section *fixupsec; fixupsec = find_section_by_name(&kelf->sections, ".fixup"); return fixupsec->sh.sh_size - offset; } return rela->addend - offset; } static struct special_section special_sections[] = { { .name = "__bug_table", .group_size = bug_table_group_size, }, #ifdef __x86_64__ { .name = ".smp_locks", .group_size = smp_locks_group_size, }, { .name = ".parainstructions", .group_size = parainstructions_group_size, }, #endif { .name = ".fixup", .group_size = fixup_group_size, }, { .name = "__ex_table", /* must come after .fixup */ .group_size = ex_table_group_size, }, #ifdef __x86_64__ { .name = ".altinstructions", .group_size = altinstructions_group_size, }, #endif #ifdef __powerpc64__ { .name = "__ftr_fixup", .group_size = fixup_entry_group_size, }, { .name = "__mmu_ftr_fixup", .group_size = fixup_entry_group_size, }, { .name = "__fw_ftr_fixup", .group_size = fixup_entry_group_size, }, { .name = "__lwsync_fixup", .group_size = fixup_lwsync_group_size, }, #endif {}, }; static int should_keep_rela_group(struct section *sec, unsigned int start, unsigned int size) { struct rela *rela; int found = 0; /* check if any relas in the group reference any changed functions */ list_for_each_entry(rela, &sec->relas, list) { if (rela->offset >= start && rela->offset < start + size && rela->sym->type == STT_FUNC && rela->sym->sec->include) { found = 1; log_debug("new/changed symbol %s found in special section %s\n", rela->sym->name, sec->name); } } return found; } /* * When updating .fixup, the corresponding addends in .ex_table need to be * updated too. Stash the result in rela.r_addend so that the calculation in * fixup_group_size() is not affected. */ static void kpatch_update_ex_table_addend(struct kpatch_elf *kelf, struct special_section *special, int src_offset, int dest_offset, int group_size) { struct rela *rela; struct section *sec; sec = find_section_by_name(&kelf->sections, ".rela__ex_table"); if (!sec) ERROR("missing .rela__ex_table section"); list_for_each_entry(rela, &sec->relas, list) { if (!strcmp(rela->sym->name, ".fixup") && rela->addend >= src_offset && rela->addend < src_offset + group_size) rela->rela.r_addend = rela->addend - (src_offset - dest_offset); } } static void kpatch_regenerate_special_section(struct kpatch_elf *kelf, struct special_section *special, struct section *sec) { struct rela *rela, *safe; char *src, *dest; unsigned int group_size, src_offset, dest_offset, include; LIST_HEAD(newrelas); src = sec->base->data->d_buf; /* alloc buffer for new base section */ dest = malloc(sec->base->sh.sh_size); if (!dest) ERROR("malloc"); /* Restore the stashed r_addend from kpatch_update_ex_table_addend. */ if (!strcmp(special->name, "__ex_table")) { list_for_each_entry(rela, &sec->relas, list) { if (!strcmp(rela->sym->name, ".fixup")) rela->addend = rela->rela.r_addend; } } group_size = 0; src_offset = 0; dest_offset = 0; for ( ; src_offset < sec->base->sh.sh_size; src_offset += group_size) { group_size = special->group_size(kelf, src_offset); /* * In some cases the struct has padding at the end to ensure * that all structs after it are properly aligned. But the * last struct in the section may not be padded. In that case, * shrink the group_size such that it still (hopefully) * contains the data but doesn't go past the end of the * section. */ if (src_offset + group_size > sec->base->sh.sh_size) group_size = sec->base->sh.sh_size - src_offset; include = should_keep_rela_group(sec, src_offset, group_size); if (!include) continue; /* * Copy all relas in the group. It's possible that the relas * aren't sorted (e.g. .rela.fixup), so go through the entire * rela list each time. */ list_for_each_entry_safe(rela, safe, &sec->relas, list) { if (rela->offset >= src_offset && rela->offset < src_offset + group_size) { /* copy rela entry */ list_del(&rela->list); list_add_tail(&rela->list, &newrelas); rela->offset -= src_offset - dest_offset; rela->rela.r_offset = rela->offset; rela->sym->include = 1; if (!strcmp(special->name, ".fixup")) kpatch_update_ex_table_addend(kelf, special, src_offset, dest_offset, group_size); } } /* copy base section group */ memcpy(dest + dest_offset, src + src_offset, group_size); dest_offset += group_size; } if (!dest_offset) { /* no changed or global functions referenced */ sec->status = sec->base->status = SAME; sec->include = sec->base->include = 0; free(dest); return; } /* overwrite with new relas list */ list_replace(&newrelas, &sec->relas); /* include both rela and base sections */ sec->include = 1; sec->base->include = 1; /* include secsym so .kpatch.arch relas can point to section symbols */ sec->base->secsym->include = 1; /* * Update text section data buf and size. * * The rela section's data buf and size will be regenerated in * kpatch_rebuild_rela_section_data(). */ sec->base->data->d_buf = dest; sec->base->data->d_size = dest_offset; } #define ORC_IP_PTR_SIZE 4 /* * This function is similar to kpatch_regenerate_special_section(), but * customized for the ORC-related sections. ORC is more special than the other * special sections because each ORC entry is split into .orc_unwind (struct * orc_entry) and .orc_unwind_ip. */ static void kpatch_regenerate_orc_sections(struct kpatch_elf *kelf) { struct rela *rela, *safe; char *src, *dest, *str; unsigned int src_idx = 0, dest_idx = 0, orc_entry_size; struct section *orc_sec, *ip_sec; str = getenv("ORC_STRUCT_SIZE"); if (!str) return; orc_entry_size = atoi(str); LIST_HEAD(newrelas); orc_sec = find_section_by_name(&kelf->sections, ".orc_unwind"); ip_sec = find_section_by_name(&kelf->sections, ".orc_unwind_ip"); if (!orc_sec || !ip_sec) return; if (orc_sec->sh.sh_size % orc_entry_size != 0) ERROR("bad .orc_unwind size"); if (ip_sec->sh.sh_size != (orc_sec->sh.sh_size / orc_entry_size) * ORC_IP_PTR_SIZE) ERROR(".orc_unwind/.orc_unwind_ip size mismatch"); src = orc_sec->data->d_buf; dest = malloc(orc_sec->sh.sh_size); if (!dest) ERROR("malloc"); list_for_each_entry_safe(rela, safe, &ip_sec->rela->relas, list) { if (rela->sym->type != STT_FUNC || !rela->sym->sec->include) goto next; /* copy orc entry */ memcpy(dest + (dest_idx * orc_entry_size), src + (src_idx * orc_entry_size), orc_entry_size); /* move ip rela */ list_del(&rela->list); list_add_tail(&rela->list, &newrelas); rela->offset = dest_idx * ORC_IP_PTR_SIZE; rela->sym->include = 1; dest_idx++; next: src_idx++; } if (!dest_idx) { /* no changed or global functions referenced */ orc_sec->status = ip_sec->status = ip_sec->rela->status = SAME; orc_sec->include = ip_sec->include = ip_sec->rela->include = 0; free(dest); return; } /* overwrite with new relas list */ list_replace(&newrelas, &ip_sec->rela->relas); /* include the sections */ orc_sec->include = ip_sec->include = ip_sec->rela->include = 1; /* * Update data buf/size. * * The ip section can keep its old (zeroed data), though its size has * possibly decreased. The ip rela section's data buf and size will be * regenerated in kpatch_rebuild_rela_section_data(). */ orc_sec->data->d_buf = dest; orc_sec->data->d_size = dest_idx * orc_entry_size; ip_sec->data->d_size = dest_idx * ORC_IP_PTR_SIZE; } static void kpatch_check_relocations(struct kpatch_elf *kelf) { struct rela *rela; struct section *sec; Elf_Data *sdata; list_for_each_entry(sec, &kelf->sections, list) { if (!is_rela_section(sec)) continue; list_for_each_entry(rela, &sec->relas, list) { if (rela->sym->sec) { sdata = rela->sym->sec->data; if (rela->addend > (int)sdata->d_size) { ERROR("out-of-range relocation %s+%x in %s", rela->sym->sec->name, rela->addend, sec->name); } } } } } static void kpatch_include_debug_sections(struct kpatch_elf *kelf) { struct section *sec; struct rela *rela, *saferela; /* include all .debug_* sections */ list_for_each_entry(sec, &kelf->sections, list) { if (is_debug_section(sec)) { sec->include = 1; if (!is_rela_section(sec)) sec->secsym->include = 1; } } /* * Go through the .rela.debug_ sections and strip entries * referencing unchanged symbols */ list_for_each_entry(sec, &kelf->sections, list) { if (!is_rela_section(sec) || !is_debug_section(sec)) continue; list_for_each_entry_safe(rela, saferela, &sec->relas, list) if (!rela->sym->sec->include) list_del(&rela->list); } } static void kpatch_mark_ignored_sections(struct kpatch_elf *kelf) { struct section *sec, *strsec, *ignoresec; struct rela *rela; char *name; /* Ignore any discarded sections */ list_for_each_entry(sec, &kelf->sections, list) { if (!strncmp(sec->name, ".discard", 8) || !strncmp(sec->name, ".rela.discard", 13)) sec->ignore = 1; } sec = find_section_by_name(&kelf->sections, ".kpatch.ignore.sections"); if (!sec) return; list_for_each_entry(rela, &sec->rela->relas, list) { strsec = rela->sym->sec; strsec->status = CHANGED; /* * Include the string section here. This is because the * KPATCH_IGNORE_SECTION() macro is passed a literal string * by the patch author, resulting in a change to the string * section. If we don't include it, then we will potentially * get a "changed section not included" error in * kpatch_verify_patchability() if no other function based change * also changes the string section. We could try to exclude each * literal string added to the section by KPATCH_IGNORE_SECTION() * from the section data comparison, but this is a simpler way. */ strsec->include = 1; name = strsec->data->d_buf + rela->addend; ignoresec = find_section_by_name(&kelf->sections, name); if (!ignoresec) ERROR("KPATCH_IGNORE_SECTION: can't find %s", name); log_normal("ignoring section: %s\n", name); if (is_rela_section(ignoresec)) ignoresec = ignoresec->base; ignoresec->ignore = 1; if (ignoresec->twin) ignoresec->twin->ignore = 1; } } static void kpatch_mark_ignored_sections_same(struct kpatch_elf *kelf) { struct section *sec; struct symbol *sym; list_for_each_entry(sec, &kelf->sections, list) { if (!sec->ignore) continue; sec->status = SAME; if (!is_rela_section(sec)) { if (sec->secsym) sec->secsym->status = SAME; if (sec->rela) sec->rela->status = SAME; } list_for_each_entry(sym, &kelf->symbols, list) { if (sym->sec != sec) continue; sym->status = SAME; } } /* strip temporary global __UNIQUE_ID_kpatch_ignore_section_* symbols */ list_for_each_entry(sym, &kelf->symbols, list) if (!strncmp(sym->name, "__UNIQUE_ID_kpatch_ignore_section_", strlen("__UNIQUE_ID_kpatch_ignore_section_"))) sym->status = SAME; } static void kpatch_mark_ignored_functions_same(struct kpatch_elf *kelf) { struct section *sec; struct symbol *sym; struct rela *rela; sec = find_section_by_name(&kelf->sections, ".kpatch.ignore.functions"); if (!sec) return; list_for_each_entry(rela, &sec->rela->relas, list) { if (!rela->sym->sec) ERROR("expected bundled symbol"); if (rela->sym->type != STT_FUNC) ERROR("expected function symbol"); log_normal("ignoring function: %s\n", rela->sym->name); if (rela->sym->status != CHANGED) log_normal("NOTICE: no change detected in function %s, unnecessary KPATCH_IGNORE_FUNCTION()?\n", rela->sym->name); rela->sym->status = SAME; rela->sym->sec->status = SAME; if (rela->sym->sec->secsym) rela->sym->sec->secsym->status = SAME; if (rela->sym->sec->rela) rela->sym->sec->rela->status = SAME; } /* strip temporary global kpatch_ignore_func_* symbols */ list_for_each_entry(sym, &kelf->symbols, list) if (!strncmp(sym->name, "__kpatch_ignore_func_", strlen("__kpatch_ignore_func_"))) sym->status = SAME; } static void kpatch_create_kpatch_arch_section(struct kpatch_elf *kelf, char *objname) { struct special_section *special; struct kpatch_arch *entries; struct symbol *strsym; struct section *sec, *karch_sec; struct rela *rela; int nr, index = 0; nr = sizeof(special_sections) / sizeof(special_sections[0]); karch_sec = create_section_pair(kelf, ".kpatch.arch", sizeof(*entries), nr); entries = karch_sec->data->d_buf; /* lookup strings symbol */ strsym = find_symbol_by_name(&kelf->symbols, ".kpatch.strings"); if (!strsym) ERROR("can't find .kpatch.strings symbol"); for (special = special_sections; special->name; special++) { if (strcmp(special->name, ".parainstructions") && strcmp(special->name, ".altinstructions")) continue; sec = find_section_by_name(&kelf->sections, special->name); if (!sec) continue; /* entries[index].sec */ ALLOC_LINK(rela, &karch_sec->rela->relas); rela->sym = sec->secsym; rela->type = ABSOLUTE_RELA_TYPE; rela->addend = 0; rela->offset = index * sizeof(*entries) + \ offsetof(struct kpatch_arch, sec); /* entries[index].objname */ ALLOC_LINK(rela, &karch_sec->rela->relas); rela->sym = strsym; rela->type = ABSOLUTE_RELA_TYPE; rela->addend = offset_of_string(&kelf->strings, objname); rela->offset = index * sizeof(*entries) + \ offsetof(struct kpatch_arch, objname); index++; } karch_sec->data->d_size = index * sizeof(struct kpatch_arch); karch_sec->sh.sh_size = karch_sec->data->d_size; } static void kpatch_process_special_sections(struct kpatch_elf *kelf) { struct special_section *special; struct section *sec; struct symbol *sym; struct rela *rela; int altinstr = 0; for (special = special_sections; special->name; special++) { sec = find_section_by_name(&kelf->sections, special->name); if (!sec) continue; sec = sec->rela; if (!sec) continue; kpatch_regenerate_special_section(kelf, special, sec); if (!strcmp(special->name, ".altinstructions") && sec->base->include) altinstr = 1; } /* * The following special sections don't have relas which reference * non-included symbols, so their entire rela section can be included. */ list_for_each_entry(sec, &kelf->sections, list) { if (strcmp(sec->name, ".altinstr_replacement")) continue; /* * Only include .altinstr_replacement if .altinstructions * is also included. */ if (!altinstr) break; /* include base section */ sec->include = 1; /* include all symbols in the section */ list_for_each_entry(sym, &kelf->symbols, list) if (sym->sec == sec) sym->include = 1; /* include rela section */ if (sec->rela) { sec->rela->include = 1; /* include all symbols referenced by relas */ list_for_each_entry(rela, &sec->rela->relas, list) rela->sym->include = 1; } } /* * The following special sections aren't supported, so make sure we * don't ever try to include them. Otherwise the kernel will see the * jump table during module loading and get confused. Generally it * should be safe to exclude them, it just means that you can't modify * jump labels and enable tracepoints in a patched function. */ list_for_each_entry(sec, &kelf->sections, list) { if (strcmp(sec->name, "__jump_table") && strcmp(sec->name, "__tracepoints") && strcmp(sec->name, "__tracepoints_ptrs") && strcmp(sec->name, "__tracepoints_strings")) continue; sec->status = SAME; sec->include = 0; if (sec->rela) { sec->rela->status = SAME; sec->rela->include = 0; } } kpatch_regenerate_orc_sections(kelf); } static struct sym_compare_type *kpatch_elf_locals(struct kpatch_elf *kelf) { struct symbol *sym; int i = 0, sym_num = 0; struct sym_compare_type *sym_array; list_for_each_entry(sym, &kelf->symbols, list) { if (sym->bind != STB_LOCAL) continue; if (sym->type != STT_FUNC && sym->type != STT_OBJECT) continue; sym_num++; } if (!sym_num) return NULL; sym_array = malloc((sym_num + 1) * sizeof(struct sym_compare_type)); if (!sym_array) ERROR("malloc"); list_for_each_entry(sym, &kelf->symbols, list) { if (sym->bind != STB_LOCAL) continue; if (sym->type != STT_FUNC && sym->type != STT_OBJECT) continue; sym_array[i].type = sym->type; sym_array[i++].name = sym->name; } sym_array[i].type = 0; sym_array[i].name = NULL; return sym_array; } static void kpatch_create_patches_sections(struct kpatch_elf *kelf, struct lookup_table *table, char *objname) { int nr, index, objname_offset; struct section *sec, *relasec; struct symbol *sym, *strsym; struct rela *rela; struct lookup_result result; struct kpatch_patch_func *funcs; /* count patched functions */ nr = 0; list_for_each_entry(sym, &kelf->symbols, list) if (sym->type == STT_FUNC && sym->status == CHANGED) nr++; /* create text/rela section pair */ sec = create_section_pair(kelf, ".kpatch.funcs", sizeof(*funcs), nr); relasec = sec->rela; funcs = sec->data->d_buf; /* lookup strings symbol */ strsym = find_symbol_by_name(&kelf->symbols, ".kpatch.strings"); if (!strsym) ERROR("can't find .kpatch.strings symbol"); /* add objname to strings */ objname_offset = offset_of_string(&kelf->strings, objname); /* populate sections */ index = 0; list_for_each_entry(sym, &kelf->symbols, list) { if (sym->type == STT_FUNC && sym->status == CHANGED) { if (sym->bind == STB_LOCAL) { if (lookup_local_symbol(table, sym->name, &result)) ERROR("lookup_local_symbol %s", sym->name); } else { if(lookup_global_symbol(table, sym->name, &result)) ERROR("lookup_global_symbol %s", sym->name); } log_debug("lookup for %s @ 0x%016lx len %lu\n", sym->name, result.value, result.size); /* * Convert global symbols to local so other objects in * the patch module (like the patch callback object's init * code) won't link to this function and call it before * its relocations have been applied. */ sym->bind = STB_LOCAL; sym->sym.st_info = GELF_ST_INFO(sym->bind, sym->type); /* add entry in text section */ funcs[index].old_addr = result.value; funcs[index].old_size = result.size; funcs[index].new_size = sym->sym.st_size; funcs[index].sympos = result.pos; /* * Add a relocation that will populate * the funcs[index].new_addr field at * module load time. */ ALLOC_LINK(rela, &relasec->relas); rela->sym = sym; rela->type = ABSOLUTE_RELA_TYPE; rela->addend = 0; rela->offset = index * sizeof(*funcs); /* * Add a relocation that will populate * the funcs[index].name field. */ ALLOC_LINK(rela, &relasec->relas); rela->sym = strsym; rela->type = ABSOLUTE_RELA_TYPE; rela->addend = offset_of_string(&kelf->strings, sym->name); rela->offset = index * sizeof(*funcs) + offsetof(struct kpatch_patch_func, name); /* * Add a relocation that will populate * the funcs[index].objname field. */ ALLOC_LINK(rela, &relasec->relas); rela->sym = strsym; rela->type = ABSOLUTE_RELA_TYPE; rela->addend = objname_offset; rela->offset = index * sizeof(*funcs) + offsetof(struct kpatch_patch_func,objname); index++; } } /* sanity check, index should equal nr */ if (index != nr) ERROR("size mismatch in funcs sections"); } static int kpatch_is_core_module_symbol(char *name) { return (!strcmp(name, "kpatch_shadow_alloc") || !strcmp(name, "kpatch_shadow_free") || !strcmp(name, "kpatch_shadow_get")); } /* * If the patched code refers to a symbol, for example, calls a function * or stores a pointer to a function somewhere, the address of that symbol * must be resolved somehow before the patch is applied. The symbol may be * present in the original code too, so the patch may refer either to that * version of the symbol (dynrela is used for that) or to its patched * version directly (with a normal relocation). * * Dynrelas may be needed for the symbols not present in this object file * (rela->sym->sec is NULL), because it is unknown if the patched versions * of these symbols exist and where they are. * * The patched code can usually refer to a symbol from this object file * directly. If it is a function, this may also improve performance because * it will not be needed to call the original function first, find the * patched one and then use Ftrace to pass control to it. * * There is an exception though, at least on x86. It is safer to use * a dynrela if the patched code stores a pointer to a function somewhere * (relocation of type R_X86_64_32S). The function could be used as * a callback and some kinds of callbacks are called asynchronously. If * the patch module sets such callback and is unloaded shortly after, * the kernel could try to call the function via an invalid pointer and * would crash. With dynrela, the kernel would call the original function * in that case. */ static int function_ptr_rela(const struct rela *rela) { const struct rela *rela_toc = toc_rela(rela); return (rela_toc && rela_toc->sym->type == STT_FUNC && /* skip switch table on PowerPC */ rela_toc->addend == (int)rela_toc->sym->sym.st_value && (rela->type == R_X86_64_32S || rela->type == R_PPC64_TOC16_HA || rela->type == R_PPC64_TOC16_LO_DS)); } static int may_need_dynrela(const struct rela *rela) { /* * References to .TOC. are treated specially by the module loader and * should never be converted to dynrelas. */ if (rela->type == R_PPC64_REL16_HA || rela->type == R_PPC64_REL16_LO || rela->type == R_PPC64_REL64) return 0; if (!rela->sym->sec) return 1; /* * Nested functions used as callbacks are a special case. * They are not supposed to be visible outside of the * function that defines them. Their names may differ in * the original and the patched kernels which makes it * difficult to use dynrelas. Fortunately, nested functions * are rare and are unlikely to be used as asynchronous * callbacks, so the patched code can refer to them directly. * It seems, one can only distinguish such functions by their * names containing a dot. Other kinds of functions with * such names (e.g. optimized copies of functions) are * unlikely to be used as callbacks. */ return (function_ptr_rela(rela) && toc_rela(rela)->sym->status != NEW && !strchr(toc_rela(rela)->sym->name, '.')); } static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf, struct lookup_table *table, char *objname, char *pmod_name) { int nr, index; struct section *sec, *ksym_sec, *krela_sec; struct rela *rela, *rela2, *safe; struct symbol *strsym, *ksym_sec_sym; struct kpatch_symbol *ksyms; struct kpatch_relocation *krelas; struct lookup_result result; char *sym_objname; int ret, vmlinux, external; vmlinux = !strcmp(objname, "vmlinux"); /* count rela entries that need to be dynamic */ nr = 0; list_for_each_entry(sec, &kelf->sections, list) { if (!is_rela_section(sec)) continue; if (!strcmp(sec->name, ".rela.kpatch.funcs")) continue; list_for_each_entry(rela, &sec->relas, list) { nr++; /* upper bound on number of kpatch relas and symbols */ /* * Relocation section '.rela.toc' at offset 0xcc6b0 contains 46 entries: * ... * 0000000000000138 0000002a00000026 R_PPC64_ADDR64 0000000000000000 .text.deferred_put_nlk_sk + 8 * * Relocation section '.rela.text.netlink_release' at offset 0xcadf0 contains 44 entries: * ... * 0000000000000398 0000007300000032 R_PPC64_TOC16_HA 0000000000000000 .toc + 138 * 00000000000003a0 0000007300000040 R_PPC64_TOC16_LO_DS 0000000000000000 .toc + 138 * * On PowerPC, may_need_dynrela() should be using rela's reference in .rela.toc for * the rela like in the example, where the sym name is .toc + offset. In such case, * the checks are performed on both rela and its reference in .rela.toc. Where the * rela is checked for rela->type and its corresponding rela in .rela.toc for function * pointer/switch label. If rela->need_dynrela needs to be set, it's referenced rela * in (.rela.toc)->need_dynrela is set, as they represent the function sym. */ if (may_need_dynrela(rela)) toc_rela(rela)->need_dynrela = 1; } } /* create .kpatch.relocations text/rela section pair */ krela_sec = create_section_pair(kelf, ".kpatch.relocations", sizeof(*krelas), nr); krelas = krela_sec->data->d_buf; /* create .kpatch.symbols text/rela section pair */ ksym_sec = create_section_pair(kelf, ".kpatch.symbols", sizeof(*ksyms), nr); ksyms = ksym_sec->data->d_buf; /* create .kpatch.symbols section symbol (to set rela->sym later) */ ALLOC_LINK(ksym_sec_sym, &kelf->symbols); ksym_sec_sym->sec = ksym_sec; ksym_sec_sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION); ksym_sec_sym->type = STT_SECTION; ksym_sec_sym->bind = STB_LOCAL; ksym_sec_sym->name = ".kpatch.symbols"; /* lookup strings symbol */ strsym = find_symbol_by_name(&kelf->symbols, ".kpatch.strings"); if (!strsym) ERROR("can't find .kpatch.strings symbol"); /* populate sections */ index = 0; list_for_each_entry(sec, &kelf->sections, list) { if (!is_rela_section(sec)) continue; if (!strcmp(sec->name, ".rela.kpatch.funcs") || !strcmp(sec->name, ".rela.kpatch.dynrelas")) continue; list_for_each_entry_safe(rela, safe, &sec->relas, list) { if (!rela->need_dynrela) continue; /* * Allow references to core module symbols to remain as * normal relas, since the core module may not be * compiled into the kernel, and they should be * exported anyway. */ if (kpatch_is_core_module_symbol(rela->sym->name)) continue; external = 0; /* * sym_objname is the name of the object to which * rela->sym belongs. We'll need this to build * ".klp.sym." symbol names later on. * * By default sym_objname is the name of the * component being patched (vmlinux or module). * If it's an external symbol, sym_objname * will get reassigned appropriately. */ sym_objname = objname; /* * On ppc64le, the function prologue generated by GCC 6 * has the sequence: * * .globl my_func * .type my_func, @function * .quad .TOC.-my_func * my_func: * .reloc ., R_PPC64_ENTRY ; optional * ld r2,-8(r12) * add r2,r2,r12 * .localentry my_func, .-my_func * * The R_PPC64_ENTRY is optional and its symbol might * have an empty name. Leave it as a normal rela. */ if (rela->type == R_PPC64_ENTRY) continue; if (rela->sym->bind == STB_LOCAL) { /* An unchanged local symbol */ ret = lookup_local_symbol(table, rela->sym->name, &result); if (ret) ERROR("lookup_local_symbol %s needed for %s", rela->sym->name, sec->base->name); } else if (vmlinux) { /* * We have a patch to vmlinux which references * a global symbol. Use a normal rela for * exported symbols and a dynrela otherwise. */ #ifdef __powerpc64__ /* * An exported symbol might be local to an * object file and any access to the function * might be through localentry (toc+offset) * instead of global offset. * * fs/proc/proc_sysctl::sysctl_head_grab: * 166: 0000000000000000 256 FUNC GLOBAL DEFAULT [: 8] 42 unregister_sysctl_table * 167: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND .TOC. * * These type of symbols have a type of * STT_FUNC. Treat them like local symbols. * They will be handled by the livepatch * relocation code. */ if (lookup_is_exported_symbol(table, rela->sym->name)) { if (rela->sym->type != STT_FUNC) continue; } #else if (lookup_is_exported_symbol(table, rela->sym->name)) continue; #endif /* * If lookup_global_symbol() fails, assume the * symbol is defined in another object in the * patch module. */ if (lookup_global_symbol(table, rela->sym->name, &result)) continue; } else { /* * We have a patch to a module which references * a global symbol. Try to find the symbol in * the module being patched. */ if (lookup_global_symbol(table, rela->sym->name, &result)) { /* * Not there, see if the symbol is * exported, and set sym_objname to the * object the exported symbol belongs * to. If it's not exported, assume sym * is provided by another .o in the * patch module. */ sym_objname = lookup_exported_symbol_objname(table, rela->sym->name); if (!sym_objname) sym_objname = pmod_name; /* * For a symbol exported by vmlinux, use * the original rela. * * For a symbol exported by a module, * convert to a dynrela because the * module might not be loaded yet. */ if (!strcmp(sym_objname, "vmlinux")) continue; external = 1; } } log_debug("lookup for %s @ 0x%016lx len %lu\n", rela->sym->name, result.value, result.size); /* Fill in ksyms[index] */ if (vmlinux) ksyms[index].src = result.value; else /* for modules, src is discovered at runtime */ ksyms[index].src = 0; ksyms[index].pos = result.pos; ksyms[index].type = rela->sym->type; ksyms[index].bind = rela->sym->bind; /* add rela to fill in ksyms[index].name field */ ALLOC_LINK(rela2, &ksym_sec->rela->relas); rela2->sym = strsym; rela2->type = ABSOLUTE_RELA_TYPE; rela2->addend = offset_of_string(&kelf->strings, rela->sym->name); rela2->offset = index * sizeof(*ksyms) + \ offsetof(struct kpatch_symbol, name); /* add rela to fill in ksyms[index].objname field */ ALLOC_LINK(rela2, &ksym_sec->rela->relas); rela2->sym = strsym; rela2->type = ABSOLUTE_RELA_TYPE; rela2->addend = offset_of_string(&kelf->strings, sym_objname); rela2->offset = index * sizeof(*ksyms) + \ offsetof(struct kpatch_symbol, objname); /* Fill in krelas[index] */ if (is_gcc6_localentry_bundled_sym(rela->sym) && rela->addend == (int)rela->sym->sym.st_value) rela->addend -= rela->sym->sym.st_value; krelas[index].addend = rela->addend; krelas[index].type = rela->type; krelas[index].external = external; /* add rela to fill in krelas[index].dest field */ ALLOC_LINK(rela2, &krela_sec->rela->relas); if (sec->base->secsym) rela2->sym = sec->base->secsym; else ERROR("can't create dynrela for section %s (symbol %s): no bundled or section symbol", sec->name, rela->sym->name); rela2->type = ABSOLUTE_RELA_TYPE; rela2->addend = rela->offset; rela2->offset = index * sizeof(*krelas) + \ offsetof(struct kpatch_relocation, dest); /* add rela to fill in krelas[index].objname field */ ALLOC_LINK(rela2, &krela_sec->rela->relas); rela2->sym = strsym; rela2->type = ABSOLUTE_RELA_TYPE; rela2->addend = offset_of_string(&kelf->strings, objname); rela2->offset = index * sizeof(*krelas) + \ offsetof(struct kpatch_relocation, objname); /* add rela to fill in krelas[index].ksym field */ ALLOC_LINK(rela2, &krela_sec->rela->relas); rela2->sym = ksym_sec_sym; rela2->type = ABSOLUTE_RELA_TYPE; rela2->addend = index * sizeof(*ksyms); rela2->offset = index * sizeof(*krelas) + \ offsetof(struct kpatch_relocation, ksym); /* * Mark the referred to symbol for removal but * only if it is not from this object file. * The symbols from this object file may be needed * later (for example, they may have relocations * of their own which should be processed). */ if (!rela->sym->sec) rela->sym->strip = 1; list_del(&rela->list); free(rela); index++; } } /* set size to actual number of ksyms/krelas */ ksym_sec->data->d_size = index * sizeof(struct kpatch_symbol); ksym_sec->sh.sh_size = ksym_sec->data->d_size; krela_sec->data->d_size = index * sizeof(struct kpatch_relocation); krela_sec->sh.sh_size = krela_sec->data->d_size; } static void kpatch_create_callbacks_objname_rela(struct kpatch_elf *kelf, char *objname) { struct section *sec; struct rela *rela; struct symbol *strsym; int objname_offset; struct callback { char *name; int offset; }; static struct callback callbacks[] = { { .name = ".rela.kpatch.callbacks.pre_patch", .offset = offsetof(struct kpatch_pre_patch_callback, objname) }, { .name = ".rela.kpatch.callbacks.post_patch", .offset = offsetof(struct kpatch_post_patch_callback, objname) }, { .name = ".rela.kpatch.callbacks.pre_unpatch", .offset = offsetof(struct kpatch_pre_unpatch_callback, objname) }, { .name = ".rela.kpatch.callbacks.post_unpatch", .offset = offsetof(struct kpatch_post_patch_callback, objname) }, { .name = NULL, .offset = 0 }, }; struct callback *callbackp; /* lookup strings symbol */ strsym = find_symbol_by_name(&kelf->symbols, ".kpatch.strings"); if (!strsym) ERROR("can't find .kpatch.strings symbol"); /* add objname to strings */ objname_offset = offset_of_string(&kelf->strings, objname); list_for_each_entry(sec, &kelf->sections, list) { for (callbackp = callbacks; callbackp->name; callbackp++) { if (!strcmp(callbackp->name, sec->name)) { ALLOC_LINK(rela, &sec->relas); rela->sym = strsym; rela->type = ABSOLUTE_RELA_TYPE; rela->addend = objname_offset; rela->offset = callbackp->offset; break; } } } } #ifdef __powerpc64__ void kpatch_create_mcount_sections(struct kpatch_elf *kelf) { } #else /* * This function basically reimplements the functionality of the Linux * recordmcount script, so that patched functions can be recognized by ftrace. * * TODO: Eventually we can modify recordmount so that it recognizes our bundled * sections as valid and does this work for us. */ static void kpatch_create_mcount_sections(struct kpatch_elf *kelf) { int nr, index; struct section *sec, *relasec; struct symbol *sym; struct rela *rela; void **funcs, *newdata; unsigned char *insn; nr = 0; list_for_each_entry(sym, &kelf->symbols, list) if (sym->type == STT_FUNC && sym->status != SAME && sym->has_func_profiling) nr++; /* create text/rela section pair */ sec = create_section_pair(kelf, "__mcount_loc", sizeof(*funcs), nr); relasec = sec->rela; funcs = sec->data->d_buf; /* populate sections */ index = 0; list_for_each_entry(sym, &kelf->symbols, list) { if (sym->type != STT_FUNC || sym->status == SAME) continue; if (!sym->has_func_profiling) { log_debug("function %s has no fentry/mcount call, no mcount record is needed\n", sym->name); continue; } /* add rela in .rela__mcount_loc to fill in function pointer */ ALLOC_LINK(rela, &relasec->relas); rela->sym = sym; rela->type = R_X86_64_64; rela->addend = 0; rela->offset = index * sizeof(*funcs); /* * Modify the first instruction of the function to "callq * __fentry__" so that ftrace will be happy. */ newdata = malloc(sym->sec->data->d_size); memcpy(newdata, sym->sec->data->d_buf, sym->sec->data->d_size); sym->sec->data->d_buf = newdata; insn = newdata; if (insn[0] != 0xf) ERROR("%s: unexpected instruction at the start of the function", sym->name); insn[0] = 0xe8; insn[1] = 0; insn[2] = 0; insn[3] = 0; insn[4] = 0; rela = list_first_entry(&sym->sec->rela->relas, struct rela, list); rela->type = R_X86_64_PC32; index++; } /* sanity check, index should equal nr */ if (index != nr) ERROR("size mismatch in funcs sections"); } #endif /* * This function strips out symbols that were referenced by changed rela * sections, but the rela entries that referenced them were converted to * dynrelas and are no longer needed. */ static void kpatch_strip_unneeded_syms(struct kpatch_elf *kelf, struct lookup_table *table) { struct symbol *sym, *safe; list_for_each_entry_safe(sym, safe, &kelf->symbols, list) { if (sym->strip) { list_del(&sym->list); free(sym); } } } static void kpatch_create_strings_elements(struct kpatch_elf *kelf) { struct section *sec; struct symbol *sym; /* create .kpatch.strings */ /* allocate section resources */ ALLOC_LINK(sec, &kelf->sections); sec->name = ".kpatch.strings"; /* set data */ sec->data = malloc(sizeof(*sec->data)); if (!sec->data) ERROR("malloc"); sec->data->d_type = ELF_T_BYTE; /* set section header */ sec->sh.sh_type = SHT_PROGBITS; sec->sh.sh_entsize = 1; sec->sh.sh_addralign = 1; sec->sh.sh_flags = SHF_ALLOC; /* create .kpatch.strings section symbol (reuse sym variable) */ ALLOC_LINK(sym, &kelf->symbols); sym->sec = sec; sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION); sym->type = STT_SECTION; sym->bind = STB_LOCAL; sym->name = ".kpatch.strings"; } static void kpatch_build_strings_section_data(struct kpatch_elf *kelf) { struct string *string; struct section *sec; int size; char *strtab; sec = find_section_by_name(&kelf->sections, ".kpatch.strings"); if (!sec) ERROR("can't find .kpatch.strings"); /* determine size */ size = 0; list_for_each_entry(string, &kelf->strings, list) size += strlen(string->name) + 1; /* allocate section resources */ strtab = malloc(size); if (!strtab) ERROR("malloc"); sec->data->d_buf = strtab; sec->data->d_size = size; /* populate strings section data */ list_for_each_entry(string, &kelf->strings, list) { strcpy(strtab, string->name); strtab += strlen(string->name) + 1; } } struct arguments { char *args[7]; int debug; }; static char args_doc[] = "original.o patched.o parent-name parent-symtab Module.symvers patch-module-name output.o"; static struct argp_option options[] = { {"debug", 'd', NULL, 0, "Show debug output" }, { NULL } }; static error_t parse_opt (int key, char *arg, struct argp_state *state) { /* Get the input argument from argp_parse, which we know is a pointer to our arguments structure. */ struct arguments *arguments = state->input; switch (key) { case 'd': arguments->debug = 1; break; case ARGP_KEY_ARG: if (state->arg_num >= 7) /* Too many arguments. */ argp_usage (state); arguments->args[state->arg_num] = arg; break; case ARGP_KEY_END: if (state->arg_num < 7) /* Not enough arguments. */ argp_usage (state); break; default: return ARGP_ERR_UNKNOWN; } return 0; } static struct argp argp = { options, parse_opt, args_doc, NULL }; int main(int argc, char *argv[]) { struct kpatch_elf *kelf_base, *kelf_patched, *kelf_out; struct arguments arguments; int num_changed, callbacks_exist, new_globals_exist; struct lookup_table *lookup; struct section *sec, *symtab; struct symbol *sym; char *hint = NULL, *orig_obj, *patched_obj, *parent_name; char *parent_symtab, *mod_symvers, *patch_name, *output_obj; struct sym_compare_type *base_locals; arguments.debug = 0; argp_parse (&argp, argc, argv, 0, NULL, &arguments); if (arguments.debug) loglevel = DEBUG; elf_version(EV_CURRENT); orig_obj = arguments.args[0]; patched_obj = arguments.args[1]; parent_name = arguments.args[2]; parent_symtab = arguments.args[3]; mod_symvers = arguments.args[4]; patch_name = arguments.args[5]; output_obj = arguments.args[6]; childobj = basename(orig_obj); kelf_base = kpatch_elf_open(orig_obj); kelf_patched = kpatch_elf_open(patched_obj); kpatch_bundle_symbols(kelf_base); kpatch_bundle_symbols(kelf_patched); kpatch_compare_elf_headers(kelf_base->elf, kelf_patched->elf); kpatch_check_program_headers(kelf_base->elf); kpatch_check_program_headers(kelf_patched->elf); list_for_each_entry(sym, &kelf_base->symbols, list) { if (sym->type == STT_FILE) { hint = sym->name; break; } } if (!hint) { log_normal("WARNING: FILE symbol not found in base. Stripped object file or assembly source?\n"); return EXIT_STATUS_NO_CHANGE; } /* create symbol lookup table */ base_locals = kpatch_elf_locals(kelf_base); lookup = lookup_open(parent_symtab, mod_symvers, hint, base_locals); free(base_locals); kpatch_mark_grouped_sections(kelf_patched); kpatch_replace_sections_syms(kelf_base); kpatch_replace_sections_syms(kelf_patched); kpatch_rename_mangled_functions(kelf_base, kelf_patched); kpatch_correlate_elfs(kelf_base, kelf_patched); kpatch_correlate_static_local_variables(kelf_base, kelf_patched); /* * After this point, we don't care about kelf_base anymore. * We access its sections via the twin pointers in the * section, symbol, and rela lists of kelf_patched. */ kpatch_mark_ignored_sections(kelf_patched); kpatch_compare_correlated_elements(kelf_patched); kpatch_check_func_profiling_calls(kelf_patched); kpatch_elf_teardown(kelf_base); kpatch_elf_free(kelf_base); kpatch_mark_ignored_functions_same(kelf_patched); kpatch_mark_ignored_sections_same(kelf_patched); kpatch_include_standard_elements(kelf_patched); num_changed = kpatch_include_changed_functions(kelf_patched); kpatch_include_debug_sections(kelf_patched); callbacks_exist = kpatch_include_callback_elements(kelf_patched); kpatch_include_force_elements(kelf_patched); new_globals_exist = kpatch_include_new_globals(kelf_patched); kpatch_print_changes(kelf_patched); kpatch_dump_kelf(kelf_patched); kpatch_process_special_sections(kelf_patched); kpatch_verify_patchability(kelf_patched); if (!num_changed && !new_globals_exist) { if (callbacks_exist) log_debug("no changed functions were found, but callbacks exist\n"); else { log_debug("no changed functions were found\n"); return EXIT_STATUS_NO_CHANGE; } } /* this is destructive to kelf_patched */ kpatch_migrate_included_elements(kelf_patched, &kelf_out); /* * Teardown kelf_patched since we shouldn't access sections or symbols * through it anymore. Don't free however, since our section and symbol * name fields still point to strings in the Elf object owned by * kpatch_patched. */ kpatch_elf_teardown(kelf_patched); /* create strings, patches, and dynrelas sections */ kpatch_create_strings_elements(kelf_out); kpatch_create_patches_sections(kelf_out, lookup, parent_name); kpatch_create_intermediate_sections(kelf_out, lookup, parent_name, patch_name); kpatch_create_kpatch_arch_section(kelf_out, parent_name); kpatch_create_callbacks_objname_rela(kelf_out, parent_name); kpatch_build_strings_section_data(kelf_out); kpatch_create_mcount_sections(kelf_out); /* * At this point, the set of output sections and symbols is * finalized. Reorder the symbols into linker-compliant * order and index all the symbols and sections. After the * indexes have been established, update index data * throughout the structure. */ kpatch_reorder_symbols(kelf_out); kpatch_strip_unneeded_syms(kelf_out, lookup); kpatch_reindex_elements(kelf_out); /* * Update rela section headers and rebuild the rela section data * buffers from the relas lists. */ symtab = find_section_by_name(&kelf_out->sections, ".symtab"); list_for_each_entry(sec, &kelf_out->sections, list) { if (!is_rela_section(sec)) continue; sec->sh.sh_link = symtab->index; sec->sh.sh_info = sec->base->index; kpatch_rebuild_rela_section_data(sec); } kpatch_check_relocations(kelf_out); kpatch_create_shstrtab(kelf_out); kpatch_create_strtab(kelf_out); kpatch_create_symtab(kelf_out); kpatch_dump_kelf(kelf_out); kpatch_write_output_elf(kelf_out, kelf_patched->elf, output_obj); kpatch_elf_free(kelf_patched); kpatch_elf_teardown(kelf_out); kpatch_elf_free(kelf_out); return EXIT_STATUS_SUCCESS; }