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dwarf: Improve support for binaries missing the GNU_EH_FRAME segment

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Improves support for binaries missing the GNU_EH_FRAME segment
(.eh_frame_hdr section) by adding a function
'dwarf_find_eh_frame_section' that can create a synthetic one.
This commit is contained in:
Jonathan Byrd 2016-02-23 15:28:14 -08:00 committed by Dave Watson
parent 32e3e93b01
commit 25413c729a
1 changed files with 101 additions and 2 deletions
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103
src/dwarf/Gfind_proc_info-lsb.c
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@ -525,6 +525,79 @@ dwarf_find_debug_frame (int found, unw_dyn_info_t *di_debug, unw_word_t ip,
#ifndef UNW_REMOTE_ONLY
#define EH_FRAME_LEN /* strlen(".eh_frame") + 1 */ 10
static ElfW(Addr)
dwarf_find_eh_frame_section(struct dl_phdr_info *info)
{
int fd;
Elf_W (Ehdr) ehdr;
Elf_W (Half) shstrndx;
Elf_W (Addr) eh_frame;
unsigned int i;
const char *file = info->dlpi_name;
char secname[EH_FRAME_LEN];
static Elf_W (Shdr) sec_hdrs[100];
if (strlen(file) == 0)
file = "/proc/self/exe";
Debug (1, "looking for .eh_frame section in %s\n",
file);
fd = open(file, O_RDONLY);
if (fd == -1)
return 0;
if (read (fd, &ehdr, sizeof (Elf_W (Ehdr))) != sizeof (Elf_W (Ehdr)))
goto file_error;
if (ehdr.e_shnum > sizeof(sec_hdrs) / sizeof(Elf_W (Shdr)))
{
Debug (4, "too many sections (%d > %d)\n", (int) ehdr.e_shnum, (int) (sizeof(sec_hdrs) / sizeof(Elf_W (Shdr))));
goto file_error;
}
shstrndx = ehdr.e_shstrndx;
Debug (4, "opened file '%s'. Section header at offset %d\n",
file, (int) ehdr.e_shoff);
if (lseek (fd, ehdr.e_shoff, SEEK_SET) == (off_t) -1)
goto file_error;
if (read (fd, sec_hdrs, sizeof (Elf_W (Shdr)) * ehdr.e_shnum) != (ssize_t) sizeof (Elf_W (Shdr)) * ehdr.e_shnum)
goto file_error;
for (i = 1; i < ehdr.e_shnum; i++)
{
if (sec_hdrs[shstrndx].sh_size - sec_hdrs[i].sh_name < EH_FRAME_LEN)
goto file_error;
if (lseek (fd, sec_hdrs[shstrndx].sh_offset + sec_hdrs[i].sh_name, SEEK_SET) == (off_t) -1)
goto file_error;
if (read (fd, secname, EH_FRAME_LEN) < (ssize_t) sizeof(EH_FRAME_LEN))
goto file_error;
if (strncmp (secname, ".eh_frame", EH_FRAME_LEN) == 0)
{
eh_frame = sec_hdrs[i].sh_addr + info->dlpi_addr;
Debug (4, "found .eh_frame at address %lx\n",
eh_frame);
break;
}
}
close (fd);
return eh_frame;
/* An error reading image file. Release resources and return error code */
file_error:
close(fd);
return 0;
}
/* ptr is a pointer to a dwarf_callback_data structure and, on entry,
member ip contains the instruction-pointer we're looking
for. */
@ -538,10 +611,11 @@ dwarf_callback (struct dl_phdr_info *info, size_t size, void *ptr)
Elf_W(Addr) load_base, max_load_addr = 0;
int ret, need_unwind_info = cb_data->need_unwind_info;
unw_proc_info_t *pi = cb_data->pi;
struct dwarf_eh_frame_hdr *hdr;
struct dwarf_eh_frame_hdr *hdr = NULL;
unw_accessors_t *a;
long n;
int found = 0;
struct dwarf_eh_frame_hdr synth_eh_frame_hdr;
#ifdef CONFIG_DEBUG_FRAME
unw_word_t start, end;
#endif /* CONFIG_DEBUG_FRAME*/
@ -586,6 +660,29 @@ dwarf_callback (struct dl_phdr_info *info, size_t size, void *ptr)
return 0;
if (p_eh_hdr)
{
hdr = (struct dwarf_eh_frame_hdr *) (p_eh_hdr->p_vaddr + load_base);
}
else
{
ElfW(Addr) eh_frame;
Debug (1, "no .eh_frame_hdr section found\n");
eh_frame = dwarf_find_eh_frame_section (info);
if (eh_frame)
{
unsigned char *p = (unsigned char *) &synth_eh_frame_hdr;
Debug (1, "using synthetic .eh_frame_hdr section for %s\n",
info->dlpi_name);
/* synth_eh_frame_hdr.version */ p[0] = DW_EH_VERSION;
/* synth_eh_frame_hdr.eh_frame_ptr_enc */ p[1] = DW_EH_PE_absptr | ((sizeof(ElfW(Addr)) == 4) ? DW_EH_PE_udata4 : DW_EH_PE_udata8);
/* synth_eh_frame_hdr.fde_count_enc */ p[2] = DW_EH_PE_omit;
/* synth_eh_frame_hdr.table_enc */ p[3] = DW_EH_PE_omit;
*(ElfW(Addr) *)(&p[4]) = eh_frame;
hdr = &synth_eh_frame_hdr;
}
}
if (hdr)
{
if (p_dynamic)
{
@ -609,7 +706,6 @@ dwarf_callback (struct dl_phdr_info *info, size_t size, void *ptr)
di->gp = 0;
pi->gp = di->gp;
hdr = (struct dwarf_eh_frame_hdr *) (p_eh_hdr->p_vaddr + load_base);
if (hdr->version != DW_EH_VERSION)
{
Debug (1, "table `%s' has unexpected version %d\n",
@ -650,6 +746,9 @@ dwarf_callback (struct dl_phdr_info *info, size_t size, void *ptr)
if (hdr->eh_frame_ptr_enc == DW_EH_PE_omit)
abort ();
Debug (1, "eh_frame_start = %lx eh_frame_end = %lx\n",
eh_frame_start, eh_frame_end);
/* XXX we know how to build a local binary search table for
.debug_frame, so we could do that here too. */
cb_data->single_fde = 1;