/*
SPDX-License-Identifier: GPL-2.0-only
Copyright (C) 2019 Facebook
Derived from ctf_encoder.c, which is:
Copyright (C) Arnaldo Carvalho de Melo <acme@redhat.com>
Copyright (C) Red Hat Inc
*/
#include "dwarves.h"
#include "libbtf.h"
#include "lib/bpf/include/uapi/linux/btf.h"
#include "lib/bpf/src/libbpf.h"
#include "hash.h"
#include "elf_symtab.h"
#include "btf_encoder.h"
#include <ctype.h> /* for isalpha() and isalnum() */
#include <stdlib.h> /* for qsort() and bsearch() */
#include <inttypes.h>
/*
* This corresponds to the same macro defined in
* include/linux/kallsyms.h
*/
#define KSYM_NAME_LEN 128
struct funcs_layout {
unsigned long mcount_start;
unsigned long mcount_stop;
unsigned long mcount_sec_idx;
};
struct elf_function {
const char *name;
unsigned long addr;
bool generated;
};
static struct elf_function *functions;
static int functions_alloc;
static int functions_cnt;
static int functions_cmp(const void *_a, const void *_b)
{
const struct elf_function *a = _a;
const struct elf_function *b = _b;
return strcmp(a->name, b->name);
}
static void delete_functions(void)
{
free(functions);
functions_alloc = functions_cnt = 0;
functions = NULL;
}
#ifndef max
#define max(x, y) ((x) < (y) ? (y) : (x))
#endif
static int collect_function(struct btf_elf *btfe, GElf_Sym *sym)
{
struct elf_function *new;
if (elf_sym__type(sym) != STT_FUNC)
return 0;
if (!elf_sym__value(sym))
return 0;
if (functions_cnt == functions_alloc) {
functions_alloc = max(1000, functions_alloc * 3 / 2);
new = realloc(functions, functions_alloc * sizeof(*functions));
if (!new) {
/*
* The cleanup - delete_functions is called
* in cu__encode_btf error path.
*/
return -1;
}
functions = new;
}
functions[functions_cnt].name = elf_sym__name(sym, btfe->symtab);
functions[functions_cnt].addr = elf_sym__value(sym);
functions[functions_cnt].generated = false;
functions_cnt++;
return 0;
}
static int addrs_cmp(const void *_a, const void *_b)
{
const unsigned long *a = _a;
const unsigned long *b = _b;
if (*a == *b)
return 0;
return *a < *b ? -1 : 1;
}
static int filter_functions(struct btf_elf *btfe, struct funcs_layout *fl)
{
unsigned long *addrs, count, offset, i;
int functions_valid = 0;
Elf_Data *data;
GElf_Shdr shdr;
Elf_Scn *sec;
/*
* Find mcount addressed marked by __start_mcount_loc
* and __stop_mcount_loc symbols and load them into
* sorted array.
*/
sec = elf_getscn(btfe->elf, fl->mcount_sec_idx);
if (!sec || !gelf_getshdr(sec, &shdr)) {
fprintf(stderr, "Failed to get section(%lu) header.\n",
fl->mcount_sec_idx);
return -1;
}
offset = fl->mcount_start - shdr.sh_addr;
count = (fl->mcount_stop - fl->mcount_start) / 8;
data = elf_getdata(sec, 0);
if (!data) {
fprintf(stderr, "Failed to get section(%lu) data.\n",
fl->mcount_sec_idx);
return -1;
}
addrs = malloc(count * sizeof(addrs[0]));
if (!addrs) {
fprintf(stderr, "Failed to allocate memory for ftrace addresses.\n");
return -1;
}
memcpy(addrs, data->d_buf + offset, count * sizeof(addrs[0]));
qsort(addrs, count, sizeof(addrs[0]), addrs_cmp);
/*
* Let's got through all collected functions and filter
* out those that are not in ftrace.
*/
for (i = 0; i < functions_cnt; i++) {
struct elf_function *func = &functions[i];
/* Make sure function is within ftrace addresses. */
if (bsearch(&func->addr, addrs, count, sizeof(addrs[0]), addrs_cmp)) {
/*
* We iterate over sorted array, so we can easily skip
* not valid item and move following valid field into
* its place, and still keep the 'new' array sorted.
*/
if (i != functions_valid)
functions[functions_valid] = functions[i];
functions_valid++;
}
}
functions_cnt = functions_valid;
free(addrs);
return 0;
}
static struct elf_function *find_function(const struct btf_elf *btfe,
const char *name)
{
struct elf_function key = { .name = name };
return bsearch(&key, functions, functions_cnt, sizeof(functions[0]),
functions_cmp);
}
static bool btf_name_char_ok(char c, bool first)
{
if (c == '_' || c == '.')
return true;
return first ? isalpha(c) : isalnum(c);
}
/* Check whether the given name is valid in vmlinux btf. */
static bool btf_name_valid(const char *p)
{
const char *limit;
if (!btf_name_char_ok(*p, true))
return false;
/* set a limit on identifier length */
limit = p + KSYM_NAME_LEN;
p++;
while (*p && p < limit) {
if (!btf_name_char_ok(*p, false))
return false;
p++;
}
return !*p;
}
static void dump_invalid_symbol(const char *msg, const char *sym,
int verbose, bool force)
{
if (force) {
if (verbose)
fprintf(stderr, "PAHOLE: Warning: %s, ignored (sym: '%s').\n",
msg, sym);
return;
}
fprintf(stderr, "PAHOLE: Error: %s (sym: '%s').\n", msg, sym);
fprintf(stderr, "PAHOLE: Error: Use '--btf_encode_force' to ignore such symbols and force emit the btf.\n");
}
extern struct debug_fmt_ops *dwarves__active_loader;
static int tag__check_id_drift(const struct tag *tag,
uint32_t core_id, uint32_t btf_type_id,
uint32_t type_id_off)
{
if (btf_type_id != (core_id + type_id_off)) {
fprintf(stderr,
"%s: %s id drift, core_id: %u, btf_type_id: %u, type_id_off: %u\n",
__func__, dwarf_tag_name(tag->tag),
core_id, btf_type_id, type_id_off);
return -1;
}
return 0;
}
static int32_t structure_type__encode(struct btf_elf *btfe, struct cu *cu, struct tag *tag, uint32_t type_id_off)
{
struct type *type = tag__type(tag);
struct class_member *pos;
const char *name;
int32_t type_id;
uint8_t kind;
kind = (tag->tag == DW_TAG_union_type) ?
BTF_KIND_UNION : BTF_KIND_STRUCT;
name = dwarves__active_loader->strings__ptr(cu, type->namespace.name);
type_id = btf_elf__add_struct(btfe, kind, name, type->size);
if (type_id < 0)
return type_id;
type__for_each_data_member(type, pos) {
/*
* dwarf_loader uses DWARF's recommended bit offset addressing
* scheme, which conforms to BTF requirement, so no conversion
* is required.
*/
name = dwarves__active_loader->strings__ptr(cu, pos->name);
if (btf_elf__add_member(btfe, name, type_id_off + pos->tag.type, pos->bitfield_size, pos->bit_offset))
return -1;
}
return type_id;
}
static uint32_t array_type__nelems(struct tag *tag)
{
int i;
uint32_t nelem = 1;
struct array_type *array = tag__array_type(tag);
for (i = array->dimensions - 1; i >= 0; --i)
nelem *= array->nr_entries[i];
return nelem;
}
static int32_t enumeration_type__encode(struct btf_elf *btfe, struct cu *cu, struct tag *tag)
{
struct type *etype = tag__type(tag);
struct enumerator *pos;
const char *name;
int32_t type_id;
name = dwarves__active_loader->strings__ptr(cu, etype->namespace.name);
type_id = btf_elf__add_enum(btfe, name, etype->size);
if (type_id < 0)
return type_id;
type__for_each_enumerator(etype, pos) {
name = dwarves__active_loader->strings__ptr(cu, pos->name);
if (btf_elf__add_enum_val(btfe, name, pos->value))
return -1;
}
return type_id;
}
static bool need_index_type;
static int tag__encode_btf(struct cu *cu, struct tag *tag, uint32_t core_id, struct btf_elf *btfe,
uint32_t array_index_id, uint32_t type_id_off)
{
/* single out type 0 as it represents special type "void" */
uint32_t ref_type_id = tag->type == 0 ? 0 : type_id_off + tag->type;
const char *name;
switch (tag->tag) {
case DW_TAG_base_type:
name = dwarves__active_loader->strings__ptr(cu, tag__base_type(tag)->name);
return btf_elf__add_base_type(btfe, tag__base_type(tag), name);
case DW_TAG_const_type:
return btf_elf__add_ref_type(btfe, BTF_KIND_CONST, ref_type_id, NULL, false);
case DW_TAG_pointer_type:
return btf_elf__add_ref_type(btfe, BTF_KIND_PTR, ref_type_id, NULL, false);
case DW_TAG_restrict_type:
return btf_elf__add_ref_type(btfe, BTF_KIND_RESTRICT, ref_type_id, NULL, false);
case DW_TAG_volatile_type:
return btf_elf__add_ref_type(btfe, BTF_KIND_VOLATILE, ref_type_id, NULL, false);
case DW_TAG_typedef:
name = dwarves__active_loader->strings__ptr(cu, tag__namespace(tag)->name);
return btf_elf__add_ref_type(btfe, BTF_KIND_TYPEDEF, ref_type_id, name, false);
case DW_TAG_structure_type:
case DW_TAG_union_type:
case DW_TAG_class_type:
name = dwarves__active_loader->strings__ptr(cu, tag__namespace(tag)->name);
if (tag__type(tag)->declaration)
return btf_elf__add_ref_type(btfe, BTF_KIND_FWD, 0, name, tag->tag == DW_TAG_union_type);
else
return structure_type__encode(btfe, cu, tag, type_id_off);
case DW_TAG_array_type:
/* TODO: Encode one dimension at a time. */
need_index_type = true;
return btf_elf__add_array(btfe, ref_type_id, array_index_id, array_type__nelems(tag));
case DW_TAG_enumeration_type:
return enumeration_type__encode(btfe, cu, tag);
case DW_TAG_subroutine_type:
return btf_elf__add_func_proto(btfe, cu, tag__ftype(tag), type_id_off);
default:
fprintf(stderr, "Unsupported DW_TAG_%s(0x%x)\n",
dwarf_tag_name(tag->tag), tag->tag);
return -1;
}
}
static struct btf_elf *btfe;
static uint32_t array_index_id;
static bool has_index_type;
int btf_encoder__encode()
{
int err;
if (gobuffer__size(&btfe->percpu_secinfo) != 0)
btf_elf__add_datasec_type(btfe, PERCPU_SECTION, &btfe->percpu_secinfo);
err = btf_elf__encode(btfe, 0);
delete_functions();
btf_elf__delete(btfe);
btfe = NULL;
return err;
}
#define MAX_PERCPU_VAR_CNT 4096
struct var_info {
uint64_t addr;
uint32_t sz;
const char *name;
};
static struct var_info percpu_vars[MAX_PERCPU_VAR_CNT];
static int percpu_var_cnt;
static int percpu_var_cmp(const void *_a, const void *_b)
{
const struct var_info *a = _a;
const struct var_info *b = _b;
if (a->addr == b->addr)
return 0;
return a->addr < b->addr ? -1 : 1;
}
static bool percpu_var_exists(uint64_t addr, uint32_t *sz, const char **name)
{
const struct var_info *p;
struct var_info key = { .addr = addr };
p = bsearch(&key, percpu_vars, percpu_var_cnt,
sizeof(percpu_vars[0]), percpu_var_cmp);
if (!p)
return false;
*sz = p->sz;
*name = p->name;
return true;
}
static int collect_percpu_var(struct btf_elf *btfe, GElf_Sym *sym)
{
const char *sym_name;
uint64_t addr;
uint32_t size;
/* compare a symbol's shndx to determine if it's a percpu variable */
if (elf_sym__section(sym) != btfe->percpu_shndx)
return 0;
if (elf_sym__type(sym) != STT_OBJECT)
return 0;
addr = elf_sym__value(sym);
/*
* Store only those symbols that have allocated space in the percpu section.
* This excludes the following three types of symbols:
*
* 1. __ADDRESSABLE(sym), which are forcely emitted as symbols.
* 2. __UNIQUE_ID(prefix), which are introduced to generate unique ids.
* 3. __exitcall(fn), functions which are labeled as exit calls.
*
* In addition, the variables defined using DEFINE_PERCPU_FIRST are
* also not included, which currently includes:
*
* 1. fixed_percpu_data
*/
if (!addr)
return 0;
size = elf_sym__size(sym);
if (!size)
return 0; /* ignore zero-sized symbols */
sym_name = elf_sym__name(sym, btfe->symtab);
if (!btf_name_valid(sym_name)) {
dump_invalid_symbol("Found symbol of invalid name when encoding btf",
sym_name, btf_elf__verbose, btf_elf__force);
if (btf_elf__force)
return 0;
return -1;
}
if (btf_elf__verbose)
printf("Found per-CPU symbol '%s' at address 0x%lx\n", sym_name, addr);
if (percpu_var_cnt == MAX_PERCPU_VAR_CNT) {
fprintf(stderr, "Reached the limit of per-CPU variables: %d\n",
MAX_PERCPU_VAR_CNT);
return -1;
}
percpu_vars[percpu_var_cnt].addr = addr;
percpu_vars[percpu_var_cnt].sz = size;
percpu_vars[percpu_var_cnt].name = sym_name;
percpu_var_cnt++;
return 0;
}
static void collect_symbol(GElf_Sym *sym, struct funcs_layout *fl)
{
if (!fl->mcount_start &&
!strcmp("__start_mcount_loc", elf_sym__name(sym, btfe->symtab))) {
fl->mcount_start = sym->st_value;
fl->mcount_sec_idx = sym->st_shndx;
}
if (!fl->mcount_stop &&
!strcmp("__stop_mcount_loc", elf_sym__name(sym, btfe->symtab)))
fl->mcount_stop = sym->st_value;
}
static int has_all_symbols(struct funcs_layout *fl)
{
return fl->mcount_start && fl->mcount_stop;
}
static int collect_symbols(struct btf_elf *btfe, bool collect_percpu_vars)
{
struct funcs_layout fl = { };
uint32_t core_id;
GElf_Sym sym;
/* cache variables' addresses, preparing for searching in symtab. */
percpu_var_cnt = 0;
/* search within symtab for percpu variables */
elf_symtab__for_each_symbol(btfe->symtab, core_id, sym) {
if (collect_percpu_vars && collect_percpu_var(btfe, &sym))
return -1;
if (collect_function(btfe, &sym))
return -1;
collect_symbol(&sym, &fl);
}
if (collect_percpu_vars) {
if (percpu_var_cnt)
qsort(percpu_vars, percpu_var_cnt, sizeof(percpu_vars[0]), percpu_var_cmp);
if (btf_elf__verbose)
printf("Found %d per-CPU variables!\n", percpu_var_cnt);
}
if (functions_cnt && has_all_symbols(&fl)) {
qsort(functions, functions_cnt, sizeof(functions[0]), functions_cmp);
if (filter_functions(btfe, &fl)) {
fprintf(stderr, "Failed to filter dwarf functions\n");
return -1;
}
if (btf_elf__verbose)
printf("Found %d functions!\n", functions_cnt);
} else {
if (btf_elf__verbose)
printf("ftrace symbols not detected, falling back to DWARF data\n");
delete_functions();
}
return 0;
}
static bool has_arg_names(struct cu *cu, struct ftype *ftype)
{
struct parameter *param;
const char *name;
ftype__for_each_parameter(ftype, param) {
name = dwarves__active_loader->strings__ptr(cu, param->name);
if (name == NULL)
return false;
}
return true;
}
int cu__encode_btf(struct cu *cu, int verbose, bool force,
bool skip_encoding_vars)
{
uint32_t type_id_off;
uint32_t core_id;
struct variable *var;
struct function *fn;
struct tag *pos;
int err = 0;
btf_elf__verbose = verbose;
btf_elf__force = force;
if (btfe && strcmp(btfe->filename, cu->filename)) {
err = btf_encoder__encode();
if (err)
goto out;
/* Finished one file, add one empty line */
if (verbose)
printf("\n");
}
if (!btfe) {
btfe = btf_elf__new(cu->filename, cu->elf, base_btf);
if (!btfe)
return -1;
err = collect_symbols(btfe, !skip_encoding_vars);
if (err)
goto out;
has_index_type = false;
need_index_type = false;
array_index_id = 0;
if (verbose)
printf("File %s:\n", btfe->filename);
}
type_id_off = btf__get_nr_types(btfe->btf);
if (!has_index_type) {
/* cu__find_base_type_by_name() takes "type_id_t *id" */
type_id_t id;
if (cu__find_base_type_by_name(cu, "int", &id)) {
has_index_type = true;
array_index_id = type_id_off + id;
} else {
has_index_type = false;
array_index_id = type_id_off + cu->types_table.nr_entries;
}
}
cu__for_each_type(cu, core_id, pos) {
int32_t btf_type_id = tag__encode_btf(cu, pos, core_id, btfe, array_index_id, type_id_off);
if (btf_type_id < 0 ||
tag__check_id_drift(pos, core_id, btf_type_id, type_id_off)) {
err = -1;
goto out;
}
}
if (need_index_type && !has_index_type) {
struct base_type bt = {};
bt.name = 0;
bt.bit_size = 32;
btf_elf__add_base_type(btfe, &bt, "__ARRAY_SIZE_TYPE__");
has_index_type = true;
}
cu__for_each_function(cu, core_id, fn) {
int btf_fnproto_id, btf_fn_id;
const char *name;
/*
* Skip functions that:
* - are marked as declarations
* - do not have full argument names
* - are not in ftrace list (if it's available)
* - are not external (in case ftrace filter is not available)
*/
if (fn->declaration)
continue;
if (!has_arg_names(cu, &fn->proto))
continue;
if (functions_cnt) {
struct elf_function *func;
func = find_function(btfe, function__name(fn, cu));
if (!func || func->generated)
continue;
func->generated = true;
} else {
if (!fn->external)
continue;
}
btf_fnproto_id = btf_elf__add_func_proto(btfe, cu, &fn->proto, type_id_off);
name = dwarves__active_loader->strings__ptr(cu, fn->name);
btf_fn_id = btf_elf__add_ref_type(btfe, BTF_KIND_FUNC, btf_fnproto_id, name, false);
if (btf_fnproto_id < 0 || btf_fn_id < 0) {
err = -1;
printf("error: failed to encode function '%s'\n", function__name(fn, cu));
goto out;
}
}
if (skip_encoding_vars)
goto out;
if (btfe->percpu_shndx == 0 || !btfe->symtab)
goto out;
if (verbose)
printf("search cu '%s' for percpu global variables.\n", cu->name);
cu__for_each_variable(cu, core_id, pos) {
uint32_t size, type, linkage, offset;
const char *name;
uint64_t addr;
int id;
var = tag__variable(pos);
if (var->declaration && !var->spec)
continue;
/* percpu variables are allocated in global space */
if (variable__scope(var) != VSCOPE_GLOBAL && !var->spec)
continue;
/* addr has to be recorded before we follow spec */
addr = var->ip.addr;
if (var->spec)
var = var->spec;
if (!percpu_var_exists(addr, &size, &name))
continue; /* not a per-CPU variable */
if (var->ip.tag.type == 0) {
fprintf(stderr, "error: found variable '%s' in CU '%s' that has void type\n",
name, cu->name);
if (force)
continue;
err = -1;
break;
}
type = var->ip.tag.type + type_id_off;
linkage = var->external ? BTF_VAR_GLOBAL_ALLOCATED : BTF_VAR_STATIC;
if (btf_elf__verbose) {
printf("Variable '%s' from CU '%s' at address 0x%lx encoded\n",
name, cu->name, addr);
}
/* add a BTF_KIND_VAR in btfe->types */
id = btf_elf__add_var_type(btfe, type, name, linkage);
if (id < 0) {
err = -1;
fprintf(stderr, "error: failed to encode variable '%s' at addr 0x%lx\n",
name, addr);
break;
}
/*
* add a BTF_VAR_SECINFO in btfe->percpu_secinfo, which will be added into
* btfe->types later when we add BTF_VAR_DATASEC.
*/
offset = addr - btfe->percpu_base_addr;
id = btf_elf__add_var_secinfo(&btfe->percpu_secinfo, id, offset, size);
if (id < 0) {
err = -1;
fprintf(stderr, "error: failed to encode section info for variable '%s' at addr 0x%lx\n",
name, addr);
break;
}
}
out:
if (err) {
delete_functions();
btf_elf__delete(btfe);
btfe = NULL;
}
return err;
}