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
18namespace __sanitizer {
19
20uptr 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
30uptr StackTrace::GetCurrentPc() {
31  return GET_CALLER_PC();
32}
33
34void 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.
46static 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
67void 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
109static bool MatchPc(uptr cur_pc, uptr trace_pc, uptr threshold) {
110  return cur_pc - trace_pc <= threshold || trace_pc - cur_pc <= threshold;
111}
112
113void 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
121uptr 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
133