xref: /freebsd/contrib/llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.cpp (revision cfd6422a5217410fbd66f7a7a8a64d9d85e61229)
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_common.h"
14 #include "sanitizer_flags.h"
15 #include "sanitizer_stacktrace.h"
16 
17 namespace __sanitizer {
18 
19 uptr StackTrace::GetNextInstructionPc(uptr pc) {
20 #if defined(__sparc__) || defined(__mips__)
21   return pc + 8;
22 #elif defined(__powerpc__) || defined(__arm__) || defined(__aarch64__)
23   return pc + 4;
24 #else
25   return pc + 1;
26 #endif
27 }
28 
29 uptr StackTrace::GetCurrentPc() {
30   return GET_CALLER_PC();
31 }
32 
33 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
34   size = cnt + !!extra_top_pc;
35   CHECK_LE(size, kStackTraceMax);
36   internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
37   if (extra_top_pc)
38     trace_buffer[cnt] = extra_top_pc;
39   top_frame_bp = 0;
40 }
41 
42 // Sparc implemention is in its own file.
43 #if !defined(__sparc__)
44 
45 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
46 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
47 // pointer to saved frame pointer in any case.
48 static inline uhwptr *GetCanonicFrame(uptr bp,
49                                       uptr stack_top,
50                                       uptr stack_bottom) {
51   CHECK_GT(stack_top, stack_bottom);
52 #ifdef __arm__
53   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
54   uhwptr *bp_prev = (uhwptr *)bp;
55   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
56   // The next frame pointer does not look right. This could be a GCC frame, step
57   // back by 1 word and try again.
58   if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
59     return bp_prev - 1;
60   // Nope, this does not look right either. This means the frame after next does
61   // not have a valid frame pointer, but we can still extract the caller PC.
62   // Unfortunately, there is no way to decide between GCC and LLVM frame
63   // layouts. Assume LLVM.
64   return bp_prev;
65 #else
66   return (uhwptr*)bp;
67 #endif
68 }
69 
70 void BufferedStackTrace::UnwindFast(uptr pc, uptr bp, uptr stack_top,
71                                     uptr stack_bottom, u32 max_depth) {
72   // TODO(yln): add arg sanity check for stack_top/stack_bottom
73   CHECK_GE(max_depth, 2);
74   const uptr kPageSize = GetPageSizeCached();
75   trace_buffer[0] = pc;
76   size = 1;
77   if (stack_top < 4096) return;  // Sanity check for stack top.
78   uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
79   // Lowest possible address that makes sense as the next frame pointer.
80   // Goes up as we walk the stack.
81   uptr bottom = stack_bottom;
82   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
83   while (IsValidFrame((uptr)frame, stack_top, bottom) &&
84          IsAligned((uptr)frame, sizeof(*frame)) &&
85          size < max_depth) {
86 #ifdef __powerpc__
87     // PowerPC ABIs specify that the return address is saved at offset
88     // 16 of the *caller's* stack frame.  Thus we must dereference the
89     // back chain to find the caller frame before extracting it.
90     uhwptr *caller_frame = (uhwptr*)frame[0];
91     if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
92         !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
93       break;
94     uhwptr pc1 = caller_frame[2];
95 #elif defined(__s390__)
96     uhwptr pc1 = frame[14];
97 #else
98     uhwptr pc1 = frame[1];
99 #endif
100     // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
101     // x86_64) is invalid and stop unwinding here.  If we're adding support for
102     // a platform where this isn't true, we need to reconsider this check.
103     if (pc1 < kPageSize)
104       break;
105     if (pc1 != pc) {
106       trace_buffer[size++] = (uptr) pc1;
107     }
108     bottom = (uptr)frame;
109     frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom);
110   }
111 }
112 
113 #endif  // !defined(__sparc__)
114 
115 void BufferedStackTrace::PopStackFrames(uptr count) {
116   CHECK_LT(count, size);
117   size -= count;
118   for (uptr i = 0; i < size; ++i) {
119     trace_buffer[i] = trace_buffer[i + count];
120   }
121 }
122 
123 static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
124 
125 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
126   uptr best = 0;
127   for (uptr i = 1; i < size; ++i) {
128     if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
129   }
130   return best;
131 }
132 
133 }  // namespace __sanitizer
134