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(__sparc__) || defined(__mips__)
  20   return pc + 8;
  21 #elif defined(__powerpc__) || defined(__arm__) || defined(__aarch64__)
  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 // Sparc implemention is in its own file.
  42 #if !defined(__sparc__)
  43
  44 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
  45 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
  46 // pointer to saved frame pointer in any case.
  47 static inline uhwptr *GetCanonicFrame(uptr bp,
  48                                       uptr stack_top,
  49                                       uptr stack_bottom) {
  50 #ifdef __arm__
  51   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
  52   uhwptr *bp_prev = (uhwptr *)bp;
  53   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
  54   // The next frame pointer does not look right. This could be a GCC frame, step
  55   // back by 1 word and try again.
  56   if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
  57     return bp_prev - 1;
  58   // Nope, this does not look right either. This means the frame after next does
  59   // not have a valid frame pointer, but we can still extract the caller PC.
  60   // Unfortunately, there is no way to decide between GCC and LLVM frame
  61   // layouts. Assume GCC.
  62   return bp_prev - 1;
  63 #else
  64   return (uhwptr*)bp;
  65 #endif
  66 }
  67
  68 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
  69                                          uptr stack_bottom, u32 max_depth) {
  70   const uptr kPageSize = GetPageSizeCached();
  71   CHECK_GE(max_depth, 2);
  72   trace_buffer[0] = pc;
  73   size = 1;
  74   if (stack_top < 4096) return;  // Sanity check for stack top.
  75   uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
  76   // Lowest possible address that makes sense as the next frame pointer.
  77   // Goes up as we walk the stack.
  78   uptr bottom = stack_bottom;
  79   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
  80   while (IsValidFrame((uptr)frame, stack_top, bottom) &&
  81          IsAligned((uptr)frame, sizeof(*frame)) &&
  82          size < max_depth) {
  83 #ifdef __powerpc__
  84     // PowerPC ABIs specify that the return address is saved on the
  85     // *caller's* stack frame.  Thus we must dereference the back chain
  86     // to find the caller frame before extracting it.
  87     uhwptr *caller_frame = (uhwptr*)frame[0];
  88     if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
  89         !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
  90       break;
  91     // For most ABIs the offset where the return address is saved is two
  92     // register sizes.  The exception is the SVR4 ABI, which uses an
  93     // offset of only one register size.
  94 #ifdef _CALL_SYSV
  95     uhwptr pc1 = caller_frame[1];
  96 #else
  97     uhwptr pc1 = caller_frame[2];
  98 #endif
  99 #elif defined(__s390__)
 100     uhwptr pc1 = frame[14];
 101 #else
 102     uhwptr pc1 = frame[1];
 103 #endif
 104     // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
 105     // x86_64) is invalid and stop unwinding here.  If we're adding support for
 106     // a platform where this isn't true, we need to reconsider this check.
 107     if (pc1 < kPageSize)
 108       break;
 109     if (pc1 != pc) {
 110       trace_buffer[size++] = (uptr) pc1;
 111     }
 112     bottom = (uptr)frame;
 113     frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom);
 114   }
 115 }
 116
 117 #endif  // !defined(__sparc__)
 118
 119 void BufferedStackTrace::PopStackFrames(uptr count) {
 120   CHECK_LT(count, size);
 121   size -= count;
 122   for (uptr i = 0; i < size; ++i) {
 123     trace_buffer[i] = trace_buffer[i + count];
 124   }
 125 }
 126
 127 static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
 128
 129 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
 130   uptr best = 0;
 131   for (uptr i = 1; i < size; ++i) {
 132     if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
 133   }
 134   return best;
 135 }
 136
 137 }  // namespace __sanitizer