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