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__)
  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 // Check if given pointer points into allocated stack area.
  38 static inline bool IsValidFrame(uptr frame, uptr stack_top, uptr stack_bottom) {
  39   return frame > stack_bottom && frame < stack_top - 2 * sizeof (uhwptr);
  40 }
  41
  42 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
  43 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
  44 // pointer to saved frame pointer in any case.
  45 static inline uhwptr *GetCanonicFrame(uptr bp,
  46                                       uptr stack_top,
  47                                       uptr stack_bottom) {
  48 #ifdef __arm__
  49   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
  50   uhwptr *bp_prev = (uhwptr *)bp;
  51   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
  52   return bp_prev - 1;
  53 #else
  54   return (uhwptr*)bp;
  55 #endif
  56 }
  57
  58 void StackTrace::FastUnwindStack(uptr pc, uptr bp,
  59                                  uptr stack_top, uptr stack_bottom,
  60                                  uptr max_depth) {
  61   CHECK_GE(max_depth, 2);
  62   trace[0] = pc;
  63   size = 1;
  64   if (stack_top < 4096) return;  // Sanity check for stack top.
  65   uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
  66   uhwptr *prev_frame = 0;
  67   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
  68   while (frame > prev_frame &&
  69          IsValidFrame((uptr)frame, stack_top, stack_bottom) &&
  70          IsAligned((uptr)frame, sizeof(*frame)) &&
  71          size < max_depth) {
  72     uhwptr pc1 = frame[1];
  73     if (pc1 != pc) {
  74       trace[size++] = (uptr) pc1;
  75     }
  76     prev_frame = frame;
  77     frame = GetCanonicFrame((uptr)frame[0], stack_top, stack_bottom);
  78   }
  79 }
  80
  81 static bool MatchPc(uptr cur_pc, uptr trace_pc, uptr threshold) {
  82   return cur_pc - trace_pc <= threshold || trace_pc - cur_pc <= threshold;
  83 }
  84
  85 void StackTrace::PopStackFrames(uptr count) {
  86   CHECK_LT(count, size);
  87   size -= count;
  88   for (uptr i = 0; i < size; ++i) {
  89     trace[i] = trace[i + count];
  90   }
  91 }
  92
  93 uptr StackTrace::LocatePcInTrace(uptr pc) {
  94   // Use threshold to find PC in stack trace, as PC we want to unwind from may
  95   // slightly differ from return address in the actual unwinded stack trace.
  96   const int kPcThreshold = 288;
  97   for (uptr i = 0; i < size; ++i) {
  98     if (MatchPc(pc, trace[i], kPcThreshold))
  99       return i;
 100   }
 101   return 0;
 102 }
 103
 104 }  // namespace __sanitizer