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 16 namespace __sanitizer { 17 18 uptr StackTrace::GetNextInstructionPc(uptr pc) { 19 #if defined(__mips__) 20 return pc + 8; 21 #elif defined(__powerpc__) 22 return pc + 4; 23 #else 24 return pc + 1; 25 #endif 26 } 27 28 uptr StackTrace::GetCurrentPc() { 29 return GET_CALLER_PC(); 30 } 31 32 void 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 // In GCC on ARM bp points to saved lr, not fp, so we should check the next 42 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the 43 // pointer to saved frame pointer in any case. 44 static inline uhwptr *GetCanonicFrame(uptr bp, 45 uptr stack_top, 46 uptr stack_bottom) { 47 #ifdef __arm__ 48 if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0; 49 uhwptr *bp_prev = (uhwptr *)bp; 50 if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev; 51 // The next frame pointer does not look right. This could be a GCC frame, step 52 // back by 1 word and try again. 53 if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom)) 54 return bp_prev - 1; 55 // Nope, this does not look right either. This means the frame after next does 56 // not have a valid frame pointer, but we can still extract the caller PC. 57 // Unfortunately, there is no way to decide between GCC and LLVM frame 58 // layouts. Assume GCC. 59 return bp_prev - 1; 60 #else 61 return (uhwptr*)bp; 62 #endif 63 } 64 65 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top, 66 uptr stack_bottom, u32 max_depth) { 67 const uptr kPageSize = GetPageSizeCached(); 68 CHECK_GE(max_depth, 2); 69 trace_buffer[0] = pc; 70 size = 1; 71 if (stack_top < 4096) return; // Sanity check for stack top. 72 uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom); 73 // Lowest possible address that makes sense as the next frame pointer. 74 // Goes up as we walk the stack. 75 uptr bottom = stack_bottom; 76 // Avoid infinite loop when frame == frame[0] by using frame > prev_frame. 77 while (IsValidFrame((uptr)frame, stack_top, bottom) && 78 IsAligned((uptr)frame, sizeof(*frame)) && 79 size < max_depth) { 80 #ifdef __powerpc__ 81 // PowerPC ABIs specify that the return address is saved at offset 82 // 16 of the *caller's* stack frame. Thus we must dereference the 83 // back chain to find the caller frame before extracting it. 84 uhwptr *caller_frame = (uhwptr*)frame[0]; 85 if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) || 86 !IsAligned((uptr)caller_frame, sizeof(uhwptr))) 87 break; 88 uhwptr pc1 = caller_frame[2]; 89 #elif defined(__s390__) 90 uhwptr pc1 = frame[14]; 91 #else 92 uhwptr pc1 = frame[1]; 93 #endif 94 // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and 95 // x86_64) is invalid and stop unwinding here. If we're adding support for 96 // a platform where this isn't true, we need to reconsider this check. 97 if (pc1 < kPageSize) 98 break; 99 if (pc1 != pc) { 100 trace_buffer[size++] = (uptr) pc1; 101 } 102 bottom = (uptr)frame; 103 frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom); 104 } 105 } 106 107 static bool MatchPc(uptr cur_pc, uptr trace_pc, uptr threshold) { 108 return cur_pc - trace_pc <= threshold || trace_pc - cur_pc <= threshold; 109 } 110 111 void BufferedStackTrace::PopStackFrames(uptr count) { 112 CHECK_LT(count, size); 113 size -= count; 114 for (uptr i = 0; i < size; ++i) { 115 trace_buffer[i] = trace_buffer[i + count]; 116 } 117 } 118 119 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) { 120 // Use threshold to find PC in stack trace, as PC we want to unwind from may 121 // slightly differ from return address in the actual unwinded stack trace. 122 const int kPcThreshold = 350; 123 for (uptr i = 0; i < size; ++i) { 124 if (MatchPc(pc, trace[i], kPcThreshold)) 125 return i; 126 } 127 return 0; 128 } 129 130 } // namespace __sanitizer 131