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 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
  42 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
  43 // pointer to saved frame pointer in any case.
  44 static inline uhwptr *GetCanonicFrame(uptr bp,
  45                                       uptr stack_top,
  46                                       uptr stack_bottom) {
  47 #ifdef __arm__
  48   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
  49   uhwptr *bp_prev = (uhwptr *)bp;
  50   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
  51   // The next frame pointer does not look right. This could be a GCC frame, step
  52   // back by 1 word and try again.
  53   if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
  54     return bp_prev - 1;
  55   // Nope, this does not look right either. This means the frame after next does
  56   // not have a valid frame pointer, but we can still extract the caller PC.
  57   // Unfortunately, there is no way to decide between GCC and LLVM frame
  58   // layouts. Assume GCC.
  59   return bp_prev - 1;
  60 #else
  61   return (uhwptr*)bp;
  62 #endif
  63 }
  64
  65 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
  66                                          uptr stack_bottom, u32 max_depth) {
  67   const uptr kPageSize = GetPageSizeCached();
  68   CHECK_GE(max_depth, 2);
  69   trace_buffer[0] = pc;
  70   size = 1;
  71   if (stack_top < 4096) return;  // Sanity check for stack top.
  72   uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
  73   // Lowest possible address that makes sense as the next frame pointer.
  74   // Goes up as we walk the stack.
  75   uptr bottom = stack_bottom;
  76   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
  77   while (IsValidFrame((uptr)frame, stack_top, bottom) &&
  78          IsAligned((uptr)frame, sizeof(*frame)) &&
  79          size < max_depth) {
  80 #ifdef __powerpc__
  81     // PowerPC ABIs specify that the return address is saved at offset
  82     // 16 of the *caller's* stack frame.  Thus we must dereference the
  83     // back chain to find the caller frame before extracting it.
  84     uhwptr *caller_frame = (uhwptr*)frame[0];
  85     if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
  86         !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
  87       break;
  88     uhwptr pc1 = caller_frame[2];
  89 #elif defined(__s390__)
  90     uhwptr pc1 = frame[14];
  91 #else
  92     uhwptr pc1 = frame[1];
  93 #endif
  94     // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
  95     // x86_64) is invalid and stop unwinding here.  If we're adding support for
  96     // a platform where this isn't true, we need to reconsider this check.
  97     if (pc1 < kPageSize)
  98       break;
  99     if (pc1 != pc) {
 100       trace_buffer[size++] = (uptr) pc1;
 101     }
 102     bottom = (uptr)frame;
 103     frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom);
 104   }
 105 }
 106
 107 void BufferedStackTrace::PopStackFrames(uptr count) {
 108   CHECK_LT(count, size);
 109   size -= count;
 110   for (uptr i = 0; i < size; ++i) {
 111     trace_buffer[i] = trace_buffer[i + count];
 112   }
 113 }
 114
 115 static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
 116
 117 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
 118   uptr best = 0;
 119   for (uptr i = 1; i < size; ++i) {
 120     if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
 121   }
 122   return best;
 123 }
 124
 125 }  // namespace __sanitizer