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
16namespace __sanitizer {
17
18uptr 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
28uptr StackTrace::GetCurrentPc() {
29  return GET_CALLER_PC();
30}
31
32void 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.
47static 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
68void 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
119void 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
127static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
128
129uptr 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
138