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//===-- sanitizer_stacktrace.cc -------------------------------------------===//
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is shared between AddressSanitizer and ThreadSanitizer
// run-time libraries.
//===----------------------------------------------------------------------===//
#include "sanitizer_common.h"
#include "sanitizer_flags.h"
#include "sanitizer_stacktrace.h"
namespace __sanitizer {
uptr StackTrace::GetPreviousInstructionPc(uptr pc) {
#if defined(__arm__)
// Cancel Thumb bit.
pc = pc & (~1);
#endif
#if defined(__powerpc__) || defined(__powerpc64__)
// PCs are always 4 byte aligned.
return pc - 4;
#elif defined(__sparc__) || defined(__mips__)
return pc - 8;
#else
return pc - 1;
#endif
}
uptr StackTrace::GetCurrentPc() {
return GET_CALLER_PC();
}
void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
size = cnt + !!extra_top_pc;
CHECK_LE(size, kStackTraceMax);
internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
if (extra_top_pc)
trace_buffer[cnt] = extra_top_pc;
top_frame_bp = 0;
}
// Check if given pointer points into allocated stack area.
static inline bool IsValidFrame(uptr frame, uptr stack_top, uptr stack_bottom) {
return frame > stack_bottom && frame < stack_top - 2 * sizeof (uhwptr);
}
// In GCC on ARM bp points to saved lr, not fp, so we should check the next
// cell in stack to be a saved frame pointer. GetCanonicFrame returns the
// pointer to saved frame pointer in any case.
static inline uhwptr *GetCanonicFrame(uptr bp,
uptr stack_top,
uptr stack_bottom) {
#ifdef __arm__
if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
uhwptr *bp_prev = (uhwptr *)bp;
if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
// The next frame pointer does not look right. This could be a GCC frame, step
// back by 1 word and try again.
if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
return bp_prev - 1;
// Nope, this does not look right either. This means the frame after next does
// not have a valid frame pointer, but we can still extract the caller PC.
// Unfortunately, there is no way to decide between GCC and LLVM frame
// layouts. Assume LLVM.
return bp_prev;
#else
return (uhwptr*)bp;
#endif
}
void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
uptr stack_bottom, uptr max_depth) {
CHECK_GE(max_depth, 2);
trace_buffer[0] = pc;
size = 1;
if (stack_top < 4096) return; // Sanity check for stack top.
uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
// Lowest possible address that makes sense as the next frame pointer.
// Goes up as we walk the stack.
uptr bottom = stack_bottom;
// Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
while (IsValidFrame((uptr)frame, stack_top, bottom) &&
IsAligned((uptr)frame, sizeof(*frame)) &&
size < max_depth) {
#ifdef __powerpc__
// PowerPC ABIs specify that the return address is saved at offset
// 16 of the *caller's* stack frame. Thus we must dereference the
// back chain to find the caller frame before extracting it.
uhwptr *caller_frame = (uhwptr*)frame[0];
if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
!IsAligned((uptr)caller_frame, sizeof(uhwptr)))
break;
uhwptr pc1 = caller_frame[2];
#else
uhwptr pc1 = frame[1];
#endif
if (pc1 != pc) {
trace_buffer[size++] = (uptr) pc1;
}
bottom = (uptr)frame;
frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom);
}
}
static bool MatchPc(uptr cur_pc, uptr trace_pc, uptr threshold) {
return cur_pc - trace_pc <= threshold || trace_pc - cur_pc <= threshold;
}
void BufferedStackTrace::PopStackFrames(uptr count) {
CHECK_LT(count, size);
size -= count;
for (uptr i = 0; i < size; ++i) {
trace_buffer[i] = trace_buffer[i + count];
}
}
uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
// Use threshold to find PC in stack trace, as PC we want to unwind from may
// slightly differ from return address in the actual unwinded stack trace.
const int kPcThreshold = 288;
for (uptr i = 0; i < size; ++i) {
if (MatchPc(pc, trace[i], kPcThreshold))
return i;
}
return 0;
}
} // namespace __sanitizer
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