Improve stack unwinder robustness.
Keep track of whether memory maps are readable. Use the information
in try_get_word to try to avoid accidentally dereferencing an invalid
pointer within the current process. (Note that I haven't ever
seen that happen during normal unwinding, but it pays to be
a little more careful.)
Refactored try_get_word a little to make it easier to pass it the
needed state for validation checks by way of a little memory_t struct.
Improved how the memory map for the current process is cached. This is
important because we need up to date information about readable maps.
Use a 5 second cache expiration.
Improved the PC -> LR fallback logic in the unwinder so we can
eke out an extra frame sometimes.
Fixed a bug reading ELF program headers. The phnum & phentsize
fields are half-words. We were incorrectly interpreting
phnum as a whole word.
Used android_atomic_* operations carefully in the unwinder
to prevent possible memory races between the dumper and the dumpee.
This was highly unlikely (or even impossible due to the presence
of other barriers along the way) but the code is clearer now about
its invariants.
Fixed a bug in debuggerd where the pid was being passed to have
its stack dump taken instead of the tid, resulting in short
stacks because ptrace couldn't read the data if pid != tid.
Did a full sweep to ensure that we use pid / tid correctly everywhere.
Ported old code from debuggerd to rewind the program counter back
one instruction so that it points to the branch instruction itself
instead of the return address.
Change-Id: Icc4eb08320052975a4ae7f0f5f0ac9308a2d33d7
diff --git a/libcorkscrew/arch-arm/ptrace-arm.c b/libcorkscrew/arch-arm/ptrace-arm.c
index fd15505..868230c 100644
--- a/libcorkscrew/arch-arm/ptrace-arm.c
+++ b/libcorkscrew/arch-arm/ptrace-arm.c
@@ -29,26 +29,31 @@
static void load_exidx_header(pid_t pid, map_info_t* mi,
uintptr_t* out_exidx_start, size_t* out_exidx_size) {
uint32_t elf_phoff;
- uint32_t elf_phnum;
- if (try_get_word(pid, mi->start + offsetof(Elf32_Ehdr, e_phoff), &elf_phoff)
- && try_get_word(pid, mi->start + offsetof(Elf32_Ehdr, e_phnum), &elf_phnum)) {
+ uint32_t elf_phentsize_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_phnum),
+ &elf_phentsize_phnum)) {
+ uint32_t elf_phentsize = elf_phentsize_phnum >> 16;
+ uint32_t elf_phnum = elf_phentsize_phnum & 0xffff;
for (uint32_t i = 0; i < elf_phnum; i++) {
- uintptr_t elf_phdr = mi->start + elf_phoff + i * sizeof(Elf32_Phdr);
+ uintptr_t elf_phdr = mi->start + elf_phoff + i * elf_phentsize;
uint32_t elf_phdr_type;
- if (!try_get_word(pid, elf_phdr + offsetof(Elf32_Phdr, p_type), &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_ARM_EXIDX) {
uint32_t elf_phdr_offset;
uint32_t elf_phdr_filesz;
- if (!try_get_word(pid, elf_phdr + offsetof(Elf32_Phdr, p_offset),
+ if (!try_get_word_ptrace(pid, elf_phdr + offsetof(Elf32_Phdr, p_offset),
&elf_phdr_offset)
- || !try_get_word(pid, elf_phdr + offsetof(Elf32_Phdr, p_filesz),
+ || !try_get_word_ptrace(pid, elf_phdr + offsetof(Elf32_Phdr, p_filesz),
&elf_phdr_filesz)) {
break;
}
*out_exidx_start = mi->start + elf_phdr_offset;
- *out_exidx_size = elf_phdr_filesz;
+ *out_exidx_size = elf_phdr_filesz / 8;
+ ALOGV("Parsed EXIDX header info for %s: start=0x%08x, size=%d", mi->name,
+ *out_exidx_start, *out_exidx_size);
return;
}
}