Unwinding implementation via eh_frame sections for x86
Backtracing through eh_frame section is more effective allowing to reuse
ebp register for other purposes within routine. GCC with turned on
optimizations (-O1 and above) implicitly defines -fomit-frame-pointer
anyway. eh_frame sections are generated by default with GCC on any
optimization level.
This change implements remote unwinding (separate process unwinding).
Local unwinding is already implemented through _Unwind_Backtrace call
which is implemented in libgcc.
Change-Id: I1aea1ecd19c21710f9cf5f05dc272fc51b67b7aa
Signed-off-by: Pavel Chupin <pavel.v.chupin@intel.com>
diff --git a/libcorkscrew/arch-x86/ptrace-x86.c b/libcorkscrew/arch-x86/ptrace-x86.c
old mode 100644
new mode 100755
index 07cfd3a..9c49b93
--- a/libcorkscrew/arch-x86/ptrace-x86.c
+++ b/libcorkscrew/arch-x86/ptrace-x86.c
@@ -19,11 +19,44 @@
#include "../ptrace-arch.h"
+#include <stddef.h>
+#include <elf.h>
#include <cutils/log.h>
-void load_ptrace_map_info_data_arch(pid_t pid __attribute__((unused)),
- map_info_t* mi __attribute__((unused)),
- map_info_data_t* data __attribute__((unused))) {
+static void load_eh_frame_hdr(pid_t pid, map_info_t* mi, uintptr_t *eh_frame_hdr) {
+ uint32_t elf_phoff;
+ uint32_t elf_phentsize_ehsize;
+ uint32_t elf_shentsize_phnum;
+ if (try_get_word_ptrace(pid, mi->start + offsetof(Elf32_Ehdr, e_phoff), &elf_phoff)
+ && try_get_word_ptrace(pid, mi->start + offsetof(Elf32_Ehdr, e_ehsize),
+ &elf_phentsize_ehsize)
+ && try_get_word_ptrace(pid, mi->start + offsetof(Elf32_Ehdr, e_phnum),
+ &elf_shentsize_phnum)) {
+ uint32_t elf_phentsize = elf_phentsize_ehsize >> 16;
+ uint32_t elf_phnum = elf_shentsize_phnum & 0xffff;
+ for (uint32_t i = 0; i < elf_phnum; i++) {
+ uintptr_t elf_phdr = mi->start + elf_phoff + i * elf_phentsize;
+ uint32_t elf_phdr_type;
+ if (!try_get_word_ptrace(pid, elf_phdr + offsetof(Elf32_Phdr, p_type), &elf_phdr_type)) {
+ break;
+ }
+ if (elf_phdr_type == PT_GNU_EH_FRAME) {
+ uint32_t elf_phdr_offset;
+ if (!try_get_word_ptrace(pid, elf_phdr + offsetof(Elf32_Phdr, p_offset),
+ &elf_phdr_offset)) {
+ break;
+ }
+ *eh_frame_hdr = mi->start + elf_phdr_offset;
+ ALOGV("Parsed .eh_frame_hdr info for %s: start=0x%08x", mi->name, *eh_frame_hdr);
+ return;
+ }
+ }
+ }
+ *eh_frame_hdr = 0;
+}
+
+void load_ptrace_map_info_data_arch(pid_t pid, map_info_t* mi, map_info_data_t* data) {
+ load_eh_frame_hdr(pid, mi, &data->eh_frame_hdr);
}
void free_ptrace_map_info_data_arch(map_info_t* mi __attribute__((unused)),