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authorJeff Brown <jeffbrown@google.com>2011-11-03 17:58:44 -0700
committerJeff Brown <jeffbrown@google.com>2011-11-04 01:11:04 -0700
commitf0c5872637a63e28e3cd314cfc915c07f76df9c6 (patch)
treef4eebc44d0345e4bb2cf6636f55ea51defbe1307 /debuggerd/arm
parentfe6c59489cbac15ddd3b68115cd872c06365096c (diff)
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
Diffstat (limited to 'debuggerd/arm')
-rw-r--r--debuggerd/arm/machine.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/debuggerd/arm/machine.c b/debuggerd/arm/machine.c
index d941684f5..ca45c9b51 100644
--- a/debuggerd/arm/machine.c
+++ b/debuggerd/arm/machine.c
@@ -87,7 +87,7 @@ static void dump_memory_and_code(int tfd, pid_t tid, bool at_fault) {
}
}
-void dump_registers(ptrace_context_t* context __attribute((unused)),
+void dump_registers(const ptrace_context_t* context __attribute((unused)),
int tfd, pid_t tid, bool at_fault)
{
struct pt_regs r;
@@ -125,7 +125,7 @@ void dump_registers(ptrace_context_t* context __attribute((unused)),
#endif
}
-void dump_thread(ptrace_context_t* context, int tfd, pid_t tid, bool at_fault) {
+void dump_thread(const ptrace_context_t* context, int tfd, pid_t tid, bool at_fault) {
dump_registers(context, tfd, tid, at_fault);
dump_backtrace_and_stack(context, tfd, tid, at_fault);