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::GetPreviousInstructionPc(uptr pc) {
  19 #if defined(__arm__)
  20   // Cancel Thumb bit.
  21   pc = pc & (~1);
  22 #endif
  23 #if defined(__powerpc__) || defined(__powerpc64__)
  24   // PCs are always 4 byte aligned.
  25   return pc - 4;
  26 #elif defined(__sparc__) || defined(__mips__)
  27   return pc - 8;
  28 #else
  29   return pc - 1;
  30 #endif
  31 }
  32
  33 uptr StackTrace::GetCurrentPc() {
  34   return GET_CALLER_PC();
  35 }
  36
  37 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
  38   size = cnt + !!extra_top_pc;
  39   CHECK_LE(size, kStackTraceMax);
  40   internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
  41   if (extra_top_pc)
  42     trace_buffer[cnt] = extra_top_pc;
  43   top_frame_bp = 0;
  44 }
  45
  46 // Check if given pointer points into allocated stack area.
  47 static inline bool IsValidFrame(uptr frame, uptr stack_top, uptr stack_bottom) {
  48   return frame > stack_bottom && frame < stack_top - 2 * sizeof (uhwptr);
  49 }
  50
  51 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
  52 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
  53 // pointer to saved frame pointer in any case.
  54 static inline uhwptr *GetCanonicFrame(uptr bp,
  55                                       uptr stack_top,
  56                                       uptr stack_bottom) {
  57 #ifdef __arm__
  58   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
  59   uhwptr *bp_prev = (uhwptr *)bp;
  60   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
  61   // The next frame pointer does not look right. This could be a GCC frame, step
  62   // back by 1 word and try again.
  63   if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
  64     return bp_prev - 1;
  65   // Nope, this does not look right either. This means the frame after next does
  66   // not have a valid frame pointer, but we can still extract the caller PC.
  67   // Unfortunately, there is no way to decide between GCC and LLVM frame
  68   // layouts. Assume LLVM.
  69   return bp_prev;
  70 #else
  71   return (uhwptr*)bp;
  72 #endif
  73 }
  74
  75 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
  76                                          uptr stack_bottom, uptr max_depth) {
  77   CHECK_GE(max_depth, 2);
  78   trace_buffer[0] = pc;
  79   size = 1;
  80   if (stack_top < 4096) return;  // Sanity check for stack top.
  81   uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
  82   // Lowest possible address that makes sense as the next frame pointer.
  83   // Goes up as we walk the stack.
  84   uptr bottom = stack_bottom;
  85   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
  86   while (IsValidFrame((uptr)frame, stack_top, bottom) &&
  87          IsAligned((uptr)frame, sizeof(*frame)) &&
  88          size < max_depth) {
  89 #ifdef __powerpc__
  90     // PowerPC ABIs specify that the return address is saved at offset
  91     // 16 of the *caller's* stack frame.  Thus we must dereference the
  92     // back chain to find the caller frame before extracting it.
  93     uhwptr *caller_frame = (uhwptr*)frame[0];
  94     if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
  95         !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
  96       break;
  97     uhwptr pc1 = caller_frame[2];
  98 #else
  99     uhwptr pc1 = frame[1];
 100 #endif
 101     if (pc1 != pc) {
 102       trace_buffer[size++] = (uptr) pc1;
 103     }
 104     bottom = (uptr)frame;
 105     frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom);
 106   }
 107 }
 108
 109 static bool MatchPc(uptr cur_pc, uptr trace_pc, uptr threshold) {
 110   return cur_pc - trace_pc <= threshold || trace_pc - cur_pc <= threshold;
 111 }
 112
 113 void BufferedStackTrace::PopStackFrames(uptr count) {
 114   CHECK_LT(count, size);
 115   size -= count;
 116   for (uptr i = 0; i < size; ++i) {
 117     trace_buffer[i] = trace_buffer[i + count];
 118   }
 119 }
 120
 121 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
 122   // Use threshold to find PC in stack trace, as PC we want to unwind from may
 123   // slightly differ from return address in the actual unwinded stack trace.
 124   const int kPcThreshold = 288;
 125   for (uptr i = 0; i < size; ++i) {
 126     if (MatchPc(pc, trace[i], kPcThreshold))
 127       return i;
 128   }
 129   return 0;
 130 }
 131
 132 }  // namespace __sanitizer