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__) || defined(__sparc__) || defined(__arm__) || \
  22     defined(__aarch64__)
  23   return pc + 4;
  24 #else
  25   return pc + 1;
  26 #endif
  27 }
  28
  29 uptr StackTrace::GetCurrentPc() {
  30   return GET_CALLER_PC();
  31 }
  32
  33 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
  34   size = cnt + !!extra_top_pc;
  35   CHECK_LE(size, kStackTraceMax);
  36   internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
  37   if (extra_top_pc)
  38     trace_buffer[cnt] = extra_top_pc;
  39   top_frame_bp = 0;
  40 }
  41
  42 // Sparc implemention is in its own file.
  43 #if !defined(__sparc__)
  44
  45 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
  46 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
  47 // pointer to saved frame pointer in any case.
  48 static inline uhwptr *GetCanonicFrame(uptr bp,
  49                                       uptr stack_top,
  50                                       uptr stack_bottom) {
  51 #ifdef __arm__
  52   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
  53   uhwptr *bp_prev = (uhwptr *)bp;
  54   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
  55   // The next frame pointer does not look right. This could be a GCC frame, step
  56   // back by 1 word and try again.
  57   if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
  58     return bp_prev - 1;
  59   // Nope, this does not look right either. This means the frame after next does
  60   // not have a valid frame pointer, but we can still extract the caller PC.
  61   // Unfortunately, there is no way to decide between GCC and LLVM frame
  62   // layouts. Assume GCC.
  63   return bp_prev - 1;
  64 #else
  65   return (uhwptr*)bp;
  66 #endif
  67 }
  68
  69 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
  70                                          uptr stack_bottom, u32 max_depth) {
  71   const uptr kPageSize = GetPageSizeCached();
  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 #elif defined(__s390__)
  94     uhwptr pc1 = frame[14];
  95 #else
  96     uhwptr pc1 = frame[1];
  97 #endif
  98     // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
  99     // x86_64) is invalid and stop unwinding here.  If we're adding support for
 100     // a platform where this isn't true, we need to reconsider this check.
 101     if (pc1 < kPageSize)
 102       break;
 103     if (pc1 != pc) {
 104       trace_buffer[size++] = (uptr) pc1;
 105     }
 106     bottom = (uptr)frame;
 107     frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom);
 108   }
 109 }
 110
 111 #endif  // !defined(__sparc__)
 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 static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
 122
 123 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
 124   uptr best = 0;
 125   for (uptr i = 1; i < size; ++i) {
 126     if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
 127   }
 128   return best;
 129 }
 130
 131 }  // namespace __sanitizer