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