libsanitizer/sanitizer_common/sanitizer_stacktrace.cc

   1 //===-- sanitizer_stacktrace.cc -------------------------------------------===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // This file is shared between AddressSanitizer and ThreadSanitizer
   9 // run-time libraries.
  10 //===----------------------------------------------------------------------===//
  11
  12 #include "sanitizer_common.h"
  13 #include "sanitizer_flags.h"
  14 #include "sanitizer_stacktrace.h"
  15
  16 namespace __sanitizer {
  17
  18 uptr StackTrace::GetNextInstructionPc(uptr pc) {
  19 #if defined(__mips__)
  20   return pc + 8;
  21 #elif defined(__powerpc__)
  22   return pc + 4;
  23 #else
  24   return pc + 1;
  25 #endif
  26 }
  27
  28 uptr StackTrace::GetCurrentPc() {
  29   return GET_CALLER_PC();
  30 }
  31
  32 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
  33   size = cnt + !!extra_top_pc;
  34   CHECK_LE(size, kStackTraceMax);
  35   internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
  36   if (extra_top_pc)
  37     trace_buffer[cnt] = extra_top_pc;
  38   top_frame_bp = 0;
  39 }
  40
  41 // Check if given pointer points into allocated stack area.
  42 static inline bool IsValidFrame(uptr frame, uptr stack_top, uptr stack_bottom) {
  43   return frame > stack_bottom && frame < stack_top - 2 * sizeof (uhwptr);
  44 }
  45
  46 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
  47 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
  48 // pointer to saved frame pointer in any case.
  49 static inline uhwptr *GetCanonicFrame(uptr bp,
  50                                       uptr stack_top,
  51                                       uptr stack_bottom) {
  52 #ifdef __arm__
  53   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
  54   uhwptr *bp_prev = (uhwptr *)bp;
  55   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
  56   // The next frame pointer does not look right. This could be a GCC frame, step
  57   // back by 1 word and try again.
  58   if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
  59     return bp_prev - 1;
  60   // Nope, this does not look right either. This means the frame after next does
  61   // not have a valid frame pointer, but we can still extract the caller PC.
  62   // Unfortunately, there is no way to decide between GCC and LLVM frame
  63   // layouts. Assume GCC.
  64   return bp_prev - 1;
  65 #else
  66   return (uhwptr*)bp;
  67 #endif
  68 }
  69
  70 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
  71                                          uptr stack_bottom, u32 max_depth) {
  72   CHECK_GE(max_depth, 2);
  73   trace_buffer[0] = pc;
  74   size = 1;
  75   if (stack_top < 4096) return;  // Sanity check for stack top.
  76   uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
  77   // Lowest possible address that makes sense as the next frame pointer.
  78   // Goes up as we walk the stack.
  79   uptr bottom = stack_bottom;
  80   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
  81   while (IsValidFrame((uptr)frame, stack_top, bottom) &&
  82          IsAligned((uptr)frame, sizeof(*frame)) &&
  83          size < max_depth) {
  84 #ifdef __powerpc__
  85     // PowerPC ABIs specify that the return address is saved at offset
  86     // 16 of the *caller's* stack frame.  Thus we must dereference the
  87     // back chain to find the caller frame before extracting it.
  88     uhwptr *caller_frame = (uhwptr*)frame[0];
  89     if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
  90         !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
  91       break;
  92     uhwptr pc1 = caller_frame[2];
  93 #else
  94     uhwptr pc1 = frame[1];
  95 #endif
  96     if (pc1 != pc) {
  97       trace_buffer[size++] = (uptr) pc1;
  98     }
  99     bottom = (uptr)frame;
 100     frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom);
 101   }
 102 }
 103
 104 static bool MatchPc(uptr cur_pc, uptr trace_pc, uptr threshold) {
 105   return cur_pc - trace_pc <= threshold || trace_pc - cur_pc <= threshold;
 106 }
 107
 108 void BufferedStackTrace::PopStackFrames(uptr count) {
 109   CHECK_LT(count, size);
 110   size -= count;
 111   for (uptr i = 0; i < size; ++i) {
 112     trace_buffer[i] = trace_buffer[i + count];
 113   }
 114 }
 115
 116 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
 117   // Use threshold to find PC in stack trace, as PC we want to unwind from may
 118   // slightly differ from return address in the actual unwinded stack trace.
 119   const int kPcThreshold = 304;
 120   for (uptr i = 0; i < size; ++i) {
 121     if (MatchPc(pc, trace[i], kPcThreshold))
 122       return i;
 123   }
 124   return 0;
 125 }
 126
 127 }  // namespace __sanitizer