/* Locate source files or functions which caused text relocations.
Copyright (C) 2005-2010, 2012, 2014, 2018 Red Hat, Inc.
This file is part of elfutils.
Written by Ulrich Drepper <drepper@redhat.com>, 2005.
This file 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 3 of the License, or
(at your option) any later version.
elfutils 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, see <http://www.gnu.org/licenses/>. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <argp.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <gelf.h>
#include <libdw.h>
#include <libintl.h>
#include <locale.h>
#include <search.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <printversion.h>
#include "system.h"
struct segments
{
GElf_Addr from;
GElf_Addr to;
};
/* Name and version of program. */
ARGP_PROGRAM_VERSION_HOOK_DEF = print_version;
/* Bug report address. */
ARGP_PROGRAM_BUG_ADDRESS_DEF = PACKAGE_BUGREPORT;
/* Values for the parameters which have no short form. */
#define OPT_DEBUGINFO 0x100
/* Definitions of arguments for argp functions. */
static const struct argp_option options[] =
{
{ NULL, 0, NULL, 0, N_("Input Selection:"), 0 },
{ "root", 'r', "PATH", 0, N_("Prepend PATH to all file names"), 0 },
{ "debuginfo", OPT_DEBUGINFO, "PATH", 0,
N_("Use PATH as root of debuginfo hierarchy"), 0 },
{ NULL, 0, NULL, 0, N_("Miscellaneous:"), 0 },
{ NULL, 0, NULL, 0, NULL, 0 }
};
/* Short description of program. */
static const char doc[] = N_("\
Locate source of text relocations in FILEs (a.out by default).");
/* Strings for arguments in help texts. */
static const char args_doc[] = N_("[FILE...]");
/* Prototype for option handler. */
static error_t parse_opt (int key, char *arg, struct argp_state *state);
/* Data structure to communicate with argp functions. */
static struct argp argp =
{
options, parse_opt, args_doc, doc, NULL, NULL, NULL
};
/* Print symbols in file named FNAME. */
static int process_file (const char *fname, bool more_than_one);
/* Check for text relocations in the given file. The segment
information is known. */
static void check_rel (size_t nsegments, struct segments segments[nsegments],
GElf_Addr addr, Elf *elf, Elf_Scn *symscn, Dwarf *dw,
const char *fname, bool more_than_one,
void **knownsrcs);
/* User-provided root directory. */
static const char *rootdir = "/";
/* Root of debuginfo directory hierarchy. */
static const char *debuginfo_root;
int
main (int argc, char *argv[])
{
int remaining;
int result = 0;
/* Set locale. */
(void) setlocale (LC_ALL, "");
/* Make sure the message catalog can be found. */
(void) bindtextdomain (PACKAGE_TARNAME, LOCALEDIR);
/* Initialize the message catalog. */
(void) textdomain (PACKAGE_TARNAME);
/* Parse and process arguments. */
(void) argp_parse (&argp, argc, argv, 0, &remaining, NULL);
/* Tell the library which version we are expecting. */
elf_version (EV_CURRENT);
/* If the user has not specified the root directory for the
debuginfo hierarchy, we have to determine it ourselves. */
if (debuginfo_root == NULL)
{
// XXX The runtime should provide this information.
#if defined __ia64__ || defined __alpha__
debuginfo_root = "/usr/lib/debug";
#else
debuginfo_root = (sizeof (long int) == 4
? "/usr/lib/debug" : "/usr/lib64/debug");
#endif
}
if (remaining == argc)
result = process_file ("a.out", false);
else
{
/* Process all the remaining files. */
const bool more_than_one = remaining + 1 < argc;
do
result |= process_file (argv[remaining], more_than_one);
while (++remaining < argc);
}
return result;
}
/* Handle program arguments. */
static error_t
parse_opt (int key, char *arg,
struct argp_state *state __attribute__ ((unused)))
{
switch (key)
{
case 'r':
rootdir = arg;
break;
case OPT_DEBUGINFO:
debuginfo_root = arg;
break;
default:
return ARGP_ERR_UNKNOWN;
}
return 0;
}
static void
noop (void *arg __attribute__ ((unused)))
{
}
static int
process_file (const char *fname, bool more_than_one)
{
int result = 0;
void *knownsrcs = NULL;
size_t fname_len = strlen (fname);
size_t rootdir_len = strlen (rootdir);
const char *real_fname = fname;
if (fname[0] == '/' && (rootdir[0] != '/' || rootdir[1] != '\0'))
{
/* Prepend the user-provided root directory. */
char *new_fname = alloca (rootdir_len + fname_len + 2);
*((char *) mempcpy (stpcpy (mempcpy (new_fname, rootdir, rootdir_len),
"/"),
fname, fname_len)) = '\0';
real_fname = new_fname;
}
int fd = open (real_fname, O_RDONLY);
if (fd == -1)
{
error (0, errno, gettext ("cannot open '%s'"), fname);
return 1;
}
Elf *elf = elf_begin (fd, ELF_C_READ_MMAP, NULL);
if (elf == NULL)
{
error (0, 0, gettext ("cannot create ELF descriptor for '%s': %s"),
fname, elf_errmsg (-1));
goto err_close;
}
/* Make sure the file is a DSO. */
GElf_Ehdr ehdr_mem;
GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
if (ehdr == NULL)
{
error (0, 0, gettext ("cannot get ELF header '%s': %s"),
fname, elf_errmsg (-1));
err_elf_close:
elf_end (elf);
err_close:
close (fd);
return 1;
}
if (ehdr->e_type != ET_DYN)
{
error (0, 0, gettext ("'%s' is not a DSO or PIE"), fname);
goto err_elf_close;
}
/* Determine whether the DSO has text relocations at all and locate
the symbol table. */
Elf_Scn *symscn = NULL;
Elf_Scn *scn = NULL;
bool seen_dynamic = false;
bool have_textrel = false;
while ((scn = elf_nextscn (elf, scn)) != NULL
&& (!seen_dynamic || symscn == NULL))
{
/* Handle the section if it is a symbol table. */
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr == NULL)
{
error (0, 0,
gettext ("getting get section header of section %zu: %s"),
elf_ndxscn (scn), elf_errmsg (-1));
goto err_elf_close;
}
switch (shdr->sh_type)
{
case SHT_DYNAMIC:
if (!seen_dynamic)
{
seen_dynamic = true;
Elf_Data *data = elf_getdata (scn, NULL);
size_t entries = (shdr->sh_entsize == 0
? 0 : shdr->sh_size / shdr->sh_entsize);
for (size_t cnt = 0; cnt < entries; ++cnt)
{
GElf_Dyn dynmem;
GElf_Dyn *dyn;
dyn = gelf_getdyn (data, cnt, &dynmem);
if (dyn == NULL)
{
error (0, 0, gettext ("cannot read dynamic section: %s"),
elf_errmsg (-1));
goto err_elf_close;
}
if (dyn->d_tag == DT_TEXTREL
|| (dyn->d_tag == DT_FLAGS
&& (dyn->d_un.d_val & DF_TEXTREL) != 0))
have_textrel = true;
}
}
break;
case SHT_SYMTAB:
symscn = scn;
break;
}
}
if (!have_textrel)
{
error (0, 0, gettext ("no text relocations reported in '%s'"), fname);
goto err_elf_close;
}
int fd2 = -1;
Elf *elf2 = NULL;
/* Get the address ranges for the loaded segments. */
size_t nsegments_max = 10;
size_t nsegments = 0;
struct segments *segments
= (struct segments *) malloc (nsegments_max * sizeof (segments[0]));
if (segments == NULL)
error (1, errno, gettext ("while reading ELF file"));
size_t phnum;
if (elf_getphdrnum (elf, &phnum) != 0)
error (1, 0, gettext ("cannot get program header count: %s"),
elf_errmsg (-1));
for (size_t i = 0; i < phnum; ++i)
{
GElf_Phdr phdr_mem;
GElf_Phdr *phdr = gelf_getphdr (elf, i, &phdr_mem);
if (phdr == NULL)
{
error (0, 0,
gettext ("cannot get program header index at offset %zd: %s"),
i, elf_errmsg (-1));
result = 1;
goto next;
}
if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_W) == 0)
{
if (nsegments == nsegments_max)
{
nsegments_max *= 2;
segments
= (struct segments *) realloc (segments,
nsegments_max
* sizeof (segments[0]));
if (segments == NULL)
{
error (0, 0, gettext ("\
cannot get program header index at offset %zd: %s"),
i, elf_errmsg (-1));
result = 1;
goto next;
}
}
segments[nsegments].from = phdr->p_vaddr;
segments[nsegments].to = phdr->p_vaddr + phdr->p_memsz;
++nsegments;
}
}
if (nsegments > 0)
{
Dwarf *dw = dwarf_begin_elf (elf, DWARF_C_READ, NULL);
/* Look for debuginfo files if the information is not the in
opened file itself. This makes only sense if the input file
is specified with an absolute path. */
if (dw == NULL && fname[0] == '/')
{
size_t debuginfo_rootlen = strlen (debuginfo_root);
char *difname = (char *) alloca (rootdir_len + debuginfo_rootlen
+ fname_len + 8);
strcpy (mempcpy (stpcpy (mempcpy (mempcpy (difname, rootdir,
rootdir_len),
debuginfo_root,
debuginfo_rootlen),
"/"),
fname, fname_len),
".debug");
fd2 = open (difname, O_RDONLY);
if (fd2 != -1
&& (elf2 = elf_begin (fd2, ELF_C_READ_MMAP, NULL)) != NULL)
dw = dwarf_begin_elf (elf2, DWARF_C_READ, NULL);
}
/* Look at all relocations and determine which modify
write-protected segments. */
scn = NULL;
while ((scn = elf_nextscn (elf, scn)) != NULL)
{
/* Handle the section if it is a symbol table. */
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr == NULL)
{
error (0, 0,
gettext ("cannot get section header of section %zu: %s"),
elf_ndxscn (scn), elf_errmsg (-1));
result = 1;
goto next;
}
if ((shdr->sh_type == SHT_REL || shdr->sh_type == SHT_RELA)
&& symscn == NULL)
{
symscn = elf_getscn (elf, shdr->sh_link);
if (symscn == NULL)
{
error (0, 0, gettext ("\
cannot get symbol table section %zu in '%s': %s"),
(size_t) shdr->sh_link, fname, elf_errmsg (-1));
result = 1;
goto next;
}
}
if (shdr->sh_type == SHT_REL)
{
Elf_Data *data = elf_getdata (scn, NULL);
size_t entries = (shdr->sh_entsize == 0
? 0 : shdr->sh_size / shdr->sh_entsize);
for (int cnt = 0;
(size_t) cnt < entries; ++cnt)
{
GElf_Rel rel_mem;
GElf_Rel *rel = gelf_getrel (data, cnt, &rel_mem);
if (rel == NULL)
{
error (0, 0, gettext ("\
cannot get relocation at index %d in section %zu in '%s': %s"),
cnt, elf_ndxscn (scn), fname, elf_errmsg (-1));
result = 1;
goto next;
}
check_rel (nsegments, segments, rel->r_offset, elf,
symscn, dw, fname, more_than_one, &knownsrcs);
}
}
else if (shdr->sh_type == SHT_RELA)
{
Elf_Data *data = elf_getdata (scn, NULL);
size_t entries = (shdr->sh_entsize == 0
? 0 : shdr->sh_size / shdr->sh_entsize);
for (int cnt = 0; (size_t) cnt < entries; ++cnt)
{
GElf_Rela rela_mem;
GElf_Rela *rela = gelf_getrela (data, cnt, &rela_mem);
if (rela == NULL)
{
error (0, 0, gettext ("\
cannot get relocation at index %d in section %zu in '%s': %s"),
cnt, elf_ndxscn (scn), fname, elf_errmsg (-1));
result = 1;
goto next;
}
check_rel (nsegments, segments, rela->r_offset, elf,
symscn, dw, fname, more_than_one, &knownsrcs);
}
}
}
dwarf_end (dw);
}
next:
elf_end (elf);
elf_end (elf2);
close (fd);
if (fd2 != -1)
close (fd2);
free (segments);
tdestroy (knownsrcs, noop);
return result;
}
static int
ptrcompare (const void *p1, const void *p2)
{
if ((uintptr_t) p1 < (uintptr_t) p2)
return -1;
if ((uintptr_t) p1 > (uintptr_t) p2)
return 1;
return 0;
}
static void
check_rel (size_t nsegments, struct segments segments[nsegments],
GElf_Addr addr, Elf *elf, Elf_Scn *symscn, Dwarf *dw,
const char *fname, bool more_than_one, void **knownsrcs)
{
for (size_t cnt = 0; cnt < nsegments; ++cnt)
if (segments[cnt].from <= addr && segments[cnt].to > addr)
{
Dwarf_Die die_mem;
Dwarf_Die *die;
Dwarf_Line *line;
const char *src;
if (more_than_one)
printf ("%s: ", fname);
if ((die = dwarf_addrdie (dw, addr, &die_mem)) != NULL
&& (line = dwarf_getsrc_die (die, addr)) != NULL
&& (src = dwarf_linesrc (line, NULL, NULL)) != NULL)
{
/* There can be more than one relocation against one file.
Try to avoid multiple messages. And yes, the code uses
pointer comparison. */
if (tfind (src, knownsrcs, ptrcompare) == NULL)
{
printf (gettext ("%s not compiled with -fpic/-fPIC\n"), src);
tsearch (src, knownsrcs, ptrcompare);
}
return;
}
else
{
/* At least look at the symbol table to see which function
the modified address is in. */
Elf_Data *symdata = elf_getdata (symscn, NULL);
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (symscn, &shdr_mem);
if (shdr != NULL)
{
GElf_Addr lowaddr = 0;
int lowidx = -1;
GElf_Addr highaddr = ~0ul;
int highidx = -1;
GElf_Sym sym_mem;
GElf_Sym *sym;
size_t entries = (shdr->sh_entsize == 0
? 0 : shdr->sh_size / shdr->sh_entsize);
for (int i = 0; (size_t) i < entries; ++i)
{
sym = gelf_getsym (symdata, i, &sym_mem);
if (sym == NULL)
continue;
if (sym->st_value < addr && sym->st_value > lowaddr)
{
lowaddr = sym->st_value;
lowidx = i;
}
if (sym->st_value > addr && sym->st_value < highaddr)
{
highaddr = sym->st_value;
highidx = i;
}
}
if (lowidx != -1)
{
sym = gelf_getsym (symdata, lowidx, &sym_mem);
assert (sym != NULL);
const char *lowstr = elf_strptr (elf, shdr->sh_link,
sym->st_name);
if (sym->st_value + sym->st_size > addr)
{
/* It is this function. */
if (tfind (lowstr, knownsrcs, ptrcompare) == NULL)
{
printf (gettext ("\
the file containing the function '%s' is not compiled with -fpic/-fPIC\n"),
lowstr);
tsearch (lowstr, knownsrcs, ptrcompare);
}
}
else if (highidx == -1)
printf (gettext ("\
the file containing the function '%s' might not be compiled with -fpic/-fPIC\n"),
lowstr);
else
{
sym = gelf_getsym (symdata, highidx, &sym_mem);
assert (sym != NULL);
printf (gettext ("\
either the file containing the function '%s' or the file containing the function '%s' is not compiled with -fpic/-fPIC\n"),
lowstr, elf_strptr (elf, shdr->sh_link,
sym->st_name));
}
return;
}
else if (highidx != -1)
{
sym = gelf_getsym (symdata, highidx, &sym_mem);
assert (sym != NULL);
printf (gettext ("\
the file containing the function '%s' might not be compiled with -fpic/-fPIC\n"),
elf_strptr (elf, shdr->sh_link, sym->st_name));
return;
}
}
}
printf (gettext ("\
a relocation modifies memory at offset %llu in a write-protected segment\n"),
(unsigned long long int) addr);
break;
}
}
#include "debugpred.h"