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Merge "Modify ip to get the instr being executed."

This commit is contained in:
Christopher Ferris 2015-08-19 18:25:38 +00:00 committed by Gerrit Code Review
parent df0891adcf 224bef8ec4
commit 079fc83313
1 changed files with 15 additions and 8 deletions
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23
libc/bionic/debug_stacktrace.cpp
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@ -85,14 +85,14 @@ static _Unwind_Reason_Code trace_function(__unwind_context* context, void* arg)
return _URC_NO_REASON;
}
#if defined(__arm__)
/*
* The instruction pointer is pointing at the instruction after the bl(x), and
* the _Unwind_Backtrace routine already masks the Thumb mode indicator (LSB
* in PC). So we need to do a quick check here to find out if the previous
* instruction is a Thumb-mode BLX(2). If so subtract 2 otherwise 4 from PC.
*/
// The instruction pointer is pointing at the instruction after the return
// call on all architectures.
// Modify the pc to point at the real function.
if (ip != 0) {
#if defined(__arm__)
// We need to do a quick check here to find out if the previous
// instruction is a Thumb-mode BLX(2). If so subtract 2 otherwise
// 4 from PC.
short* ptr = reinterpret_cast<short*>(ip);
// Thumb BLX(2)
if ((*(ptr-1) & 0xff80) == 0x4780) {
@ -100,8 +100,15 @@ static _Unwind_Reason_Code trace_function(__unwind_context* context, void* arg)
} else {
ip -= 4;
}
}
#elif defined(__aarch64__)
// All instructions are 4 bytes long, skip back one instruction.
ip -= 4;
#elif defined(__i386__) || defined(__x86_64__)
// It's difficult to decode exactly where the previous instruction is,
// so subtract 1 to estimate where the instruction lives.
ip--;
#endif
}
state->frames[state->frame_count++] = ip;
return (state->frame_count >= state->max_depth) ? _URC_END_OF_STACK : _URC_NO_REASON;