src/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.cc

   1 //===-- sanitizer_stacktrace.cc -------------------------------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file is shared between AddressSanitizer and ThreadSanitizer
  11 // run-time libraries.
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "sanitizer_common.h"
  15 #include "sanitizer_flags.h"
  16 #include "sanitizer_stacktrace.h"
  17
  18 namespace __sanitizer {
  19
  20 uptr StackTrace::GetNextInstructionPc(uptr pc) {
  21 #if defined(__mips__)
  22   return pc + 8;
  23 #elif defined(__powerpc__)
  24   return pc + 4;
  25 #else
  26   return pc + 1;
  27 #endif
  28 }
  29
  30 uptr StackTrace::GetCurrentPc() {
  31   return GET_CALLER_PC();
  32 }
  33
  34 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
  35   size = cnt + !!extra_top_pc;
  36   CHECK_LE(size, kStackTraceMax);
  37   internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
  38   if (extra_top_pc)
  39     trace_buffer[cnt] = extra_top_pc;
  40   top_frame_bp = 0;
  41 }
  42
  43 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
  44 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
  45 // pointer to saved frame pointer in any case.
  46 static inline uhwptr *GetCanonicFrame(uptr bp,
  47                                       uptr stack_top,
  48                                       uptr stack_bottom) {
  49 #ifdef __arm__
  50   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
  51   uhwptr *bp_prev = (uhwptr *)bp;
  52   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
  53   // The next frame pointer does not look right. This could be a GCC frame, step
  54   // back by 1 word and try again.
  55   if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
  56     return bp_prev - 1;
  57   // Nope, this does not look right either. This means the frame after next does
  58   // not have a valid frame pointer, but we can still extract the caller PC.
  59   // Unfortunately, there is no way to decide between GCC and LLVM frame
  60   // layouts. Assume LLVM.
  61   return bp_prev;
  62 #else
  63   return (uhwptr*)bp;
  64 #endif
  65 }
  66
  67 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
  68                                          uptr stack_bottom, u32 max_depth) {
  69   const uptr kPageSize = GetPageSizeCached();
  70   CHECK_GE(max_depth, 2);
  71   trace_buffer[0] = pc;
  72   size = 1;
  73   if (stack_top < 4096) return;  // Sanity check for stack top.
  74   uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
  75   // Lowest possible address that makes sense as the next frame pointer.
  76   // Goes up as we walk the stack.
  77   uptr bottom = stack_bottom;
  78   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
  79   while (IsValidFrame((uptr)frame, stack_top, bottom) &&
  80          IsAligned((uptr)frame, sizeof(*frame)) &&
  81          size < max_depth) {
  82 #ifdef __powerpc__
  83     // PowerPC ABIs specify that the return address is saved at offset
  84     // 16 of the *caller's* stack frame.  Thus we must dereference the
  85     // back chain to find the caller frame before extracting it.
  86     uhwptr *caller_frame = (uhwptr*)frame[0];
  87     if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
  88         !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
  89       break;
  90     uhwptr pc1 = caller_frame[2];
  91 #elif defined(__s390__)
  92     uhwptr pc1 = frame[14];
  93 #else
  94     uhwptr pc1 = frame[1];
  95 #endif
  96     // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
  97     // x86_64) is invalid and stop unwinding here.  If we're adding support for
  98     // a platform where this isn't true, we need to reconsider this check.
  99     if (pc1 < kPageSize)
 100       break;
 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 = 350;
 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