Hello,
The attached patch 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.
Regards,
Jonathan Byrd
Senior Application Developer
Allinea Software Ltd.
diff --git a/src/dwarf/Gfind_proc_info-lsb.c b/src/dwarf/Gfind_proc_info-lsb.c
index 6e1f4c3..ce53086 100644
--- a/src/dwarf/Gfind_proc_info-lsb.c
+++ b/src/dwarf/Gfind_proc_info-lsb.c
@@ -523,6 +523,79 @@ 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. */
@@ -536,10 +609,11 @@ 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*/
@@ -585,6 +659,29 @@ dwarf_callback (struct dl_phdr_info *info, size_t size, void *ptr)
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)
{
/* For dynamicly linked executables and shared libraries,
@@ -607,7 +704,6 @@ 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",
@@ -648,6 +744,9 @@ 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;
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