1//===-- sanitizer_stacktrace.cpp ------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file is shared between AddressSanitizer and ThreadSanitizer
10// run-time libraries.
11//===----------------------------------------------------------------------===//
12
13#include "sanitizer_stacktrace.h"
14
15#include "sanitizer_common.h"
16#include "sanitizer_flags.h"
17#include "sanitizer_platform.h"
18#include "sanitizer_ptrauth.h"
19
20namespace __sanitizer {
21
22uptr StackTrace::GetNextInstructionPc(uptr pc) {
23#if defined(__sparc__) || defined(__mips__)
24  return pc + 8;
25#elif defined(__powerpc__) || defined(__arm__) || defined(__aarch64__) || \
26    defined(__hexagon__)
27  return STRIP_PAC_PC((void *)pc) + 4;
28#elif SANITIZER_RISCV64
29  // Current check order is 4 -> 2 -> 6 -> 8
30  u8 InsnByte = *(u8 *)(pc);
31  if (((InsnByte & 0x3) == 0x3) && ((InsnByte & 0x1c) != 0x1c)) {
32    // xxxxxxxxxxxbbb11 | 32 bit | bbb != 111
33    return pc + 4;
34  }
35  if ((InsnByte & 0x3) != 0x3) {
36    // xxxxxxxxxxxxxxaa | 16 bit | aa != 11
37    return pc + 2;
38  }
39  // RISC-V encoding allows instructions to be up to 8 bytes long
40  if ((InsnByte & 0x3f) == 0x1f) {
41    // xxxxxxxxxx011111 | 48 bit |
42    return pc + 6;
43  }
44  if ((InsnByte & 0x7f) == 0x3f) {
45    // xxxxxxxxx0111111 | 64 bit |
46    return pc + 8;
47  }
48  // bail-out if could not figure out the instruction size
49  return 0;
50#else
51  return pc + 1;
52#endif
53}
54
55uptr StackTrace::GetCurrentPc() {
56  return GET_CALLER_PC();
57}
58
59void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
60  size = cnt + !!extra_top_pc;
61  CHECK_LE(size, kStackTraceMax);
62  internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
63  if (extra_top_pc)
64    trace_buffer[cnt] = extra_top_pc;
65  top_frame_bp = 0;
66}
67
68// Sparc implementation is in its own file.
69#if !defined(__sparc__)
70
71// In GCC on ARM bp points to saved lr, not fp, so we should check the next
72// cell in stack to be a saved frame pointer. GetCanonicFrame returns the
73// pointer to saved frame pointer in any case.
74static inline uhwptr *GetCanonicFrame(uptr bp,
75                                      uptr stack_top,
76                                      uptr stack_bottom) {
77  CHECK_GT(stack_top, stack_bottom);
78#ifdef __arm__
79  if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
80  uhwptr *bp_prev = (uhwptr *)bp;
81  if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
82  // The next frame pointer does not look right. This could be a GCC frame, step
83  // back by 1 word and try again.
84  if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
85    return bp_prev - 1;
86  // Nope, this does not look right either. This means the frame after next does
87  // not have a valid frame pointer, but we can still extract the caller PC.
88  // Unfortunately, there is no way to decide between GCC and LLVM frame
89  // layouts. Assume GCC.
90  return bp_prev - 1;
91#else
92  return (uhwptr*)bp;
93#endif
94}
95
96void BufferedStackTrace::UnwindFast(uptr pc, uptr bp, uptr stack_top,
97                                    uptr stack_bottom, u32 max_depth) {
98  // TODO(yln): add arg sanity check for stack_top/stack_bottom
99  CHECK_GE(max_depth, 2);
100  const uptr kPageSize = GetPageSizeCached();
101  trace_buffer[0] = pc;
102  size = 1;
103  if (stack_top < 4096) return;  // Sanity check for stack top.
104  uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
105  // Lowest possible address that makes sense as the next frame pointer.
106  // Goes up as we walk the stack.
107  uptr bottom = stack_bottom;
108  // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
109  while (IsValidFrame((uptr)frame, stack_top, bottom) &&
110         IsAligned((uptr)frame, sizeof(*frame)) &&
111         size < max_depth) {
112#ifdef __powerpc__
113    // PowerPC ABIs specify that the return address is saved on the
114    // *caller's* stack frame.  Thus we must dereference the back chain
115    // to find the caller frame before extracting it.
116    uhwptr *caller_frame = (uhwptr*)frame[0];
117    if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
118        !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
119      break;
120    // For most ABIs the offset where the return address is saved is two
121    // register sizes.  The exception is the SVR4 ABI, which uses an
122    // offset of only one register size.
123#ifdef _CALL_SYSV
124    uhwptr pc1 = caller_frame[1];
125#else
126    uhwptr pc1 = caller_frame[2];
127#endif
128#elif defined(__s390__)
129    uhwptr pc1 = frame[14];
130#elif defined(__riscv)
131    // frame[-1] contains the return address
132    uhwptr pc1 = frame[-1];
133#else
134    uhwptr pc1 = STRIP_PAC_PC((void *)frame[1]);
135#endif
136    // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
137    // x86_64) is invalid and stop unwinding here.  If we're adding support for
138    // a platform where this isn't true, we need to reconsider this check.
139    if (pc1 < kPageSize)
140      break;
141    if (pc1 != pc) {
142      trace_buffer[size++] = (uptr) pc1;
143    }
144    bottom = (uptr)frame;
145#if defined(__riscv)
146    // frame[-2] contain fp of the previous frame
147    uptr new_bp = (uptr)frame[-2];
148#else
149    uptr new_bp = (uptr)frame[0];
150#endif
151    frame = GetCanonicFrame(new_bp, stack_top, bottom);
152  }
153}
154
155#endif  // !defined(__sparc__)
156
157void BufferedStackTrace::PopStackFrames(uptr count) {
158  CHECK_LT(count, size);
159  size -= count;
160  for (uptr i = 0; i < size; ++i) {
161    trace_buffer[i] = trace_buffer[i + count];
162  }
163}
164
165static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
166
167uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
168  uptr best = 0;
169  for (uptr i = 1; i < size; ++i) {
170    if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
171  }
172  return best;
173}
174
175}  // namespace __sanitizer
176