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//===-- sanitizer_stacktrace.h ----------------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file is shared between AddressSanitizer and ThreadSanitizer
// run-time libraries.
#include "sanitizer_common.h"
#include "sanitizer_internal_defs.h"
#include "sanitizer_platform.h"
namespace __sanitizer {
struct BufferedStackTrace;
static const u32 kStackTraceMax = 255;
#if SANITIZER_LINUX && defined(__mips__)
// Fast unwind is the only option on Mac for now; we will need to
// revisit this macro when slow unwind works on Mac, see
struct StackTrace {
const uptr *trace;
u32 size;
u32 tag;
static const int TAG_UNKNOWN = 0;
static const int TAG_ALLOC = 1;
static const int TAG_DEALLOC = 2;
static const int TAG_CUSTOM = 100; // Tool specific tags start here.
StackTrace() : trace(nullptr), size(0), tag(0) {}
StackTrace(const uptr *trace, u32 size) : trace(trace), size(size), tag(0) {}
StackTrace(const uptr *trace, u32 size, u32 tag)
: trace(trace), size(size), tag(tag) {}
// Prints a symbolized stacktrace, followed by an empty line.
void Print() const;
// Prints a symbolized stacktrace to the output string, followed by an empty
// line.
void PrintTo(InternalScopedString *output) const;
// Prints a symbolized stacktrace to the output buffer, followed by an empty
// line. Returns the number of symbols that should have been written to buffer
// (not including trailing '\0'). Thus, the string is truncated iff return
// value is not less than "out_buf_size".
uptr PrintTo(char *out_buf, uptr out_buf_size) const;
static bool WillUseFastUnwind(bool request_fast_unwind) {
return false;
return true;
return request_fast_unwind;
static uptr GetCurrentPc();
static inline uptr GetPreviousInstructionPc(uptr pc);
static uptr GetNextInstructionPc(uptr pc);
// Performance-critical, must be in the header.
uptr StackTrace::GetPreviousInstructionPc(uptr pc) {
#if defined(__arm__)
// T32 (Thumb) branch instructions might be 16 or 32 bit long,
// so we return (pc-2) in that case in order to be safe.
// For A32 mode we return (pc-4) because all instructions are 32 bit long.
return (pc - 3) & (~1);
#elif defined(__sparc__) || defined(__mips__)
return pc - 8;
// RV-64 has variable instruciton length...
// C extentions gives us 2-byte instructoins
// RV-64 has 4-byte instructions
// + RISCV architecture allows instructions up to 8 bytes
// It seems difficult to figure out the exact instruction length -
// pc - 2 seems like a safe option for the purposes of stack tracing
return pc - 2;
return pc - 1;
return pc - 4;
// StackTrace that owns the buffer used to store the addresses.
struct BufferedStackTrace : public StackTrace {
uptr trace_buffer[kStackTraceMax];
uptr top_frame_bp; // Optional bp of a top frame.
BufferedStackTrace() : StackTrace(trace_buffer, 0), top_frame_bp(0) {}
void Init(const uptr *pcs, uptr cnt, uptr extra_top_pc = 0);
// Get the stack trace with the given pc and bp.
// The pc will be in the position 0 of the resulting stack trace.
// The bp may refer to the current frame or to the caller's frame.
void Unwind(uptr pc, uptr bp, void *context, bool request_fast,
u32 max_depth = kStackTraceMax) {
top_frame_bp = (max_depth > 0) ? bp : 0;
// Small max_depth optimization
if (max_depth <= 1) {
if (max_depth == 1)
trace_buffer[0] = pc;
size = max_depth;
UnwindImpl(pc, bp, context, request_fast, max_depth);
void Unwind(u32 max_depth, uptr pc, uptr bp, void *context, uptr stack_top,
uptr stack_bottom, bool request_fast_unwind);
void Reset() {
*static_cast<StackTrace *>(this) = StackTrace(trace_buffer, 0);
top_frame_bp = 0;
// Every runtime defines its own implementation of this method
void UnwindImpl(uptr pc, uptr bp, void *context, bool request_fast,
u32 max_depth);
// UnwindFast/Slow have platform-specific implementations
void UnwindFast(uptr pc, uptr bp, uptr stack_top, uptr stack_bottom,
u32 max_depth);
void UnwindSlow(uptr pc, u32 max_depth);
void UnwindSlow(uptr pc, void *context, u32 max_depth);
void PopStackFrames(uptr count);
uptr LocatePcInTrace(uptr pc);
BufferedStackTrace(const BufferedStackTrace &) = delete;
void operator=(const BufferedStackTrace &) = delete;
friend class FastUnwindTest;
#if defined(__s390x__)
static const uptr kFrameSize = 160;
#elif defined(__s390__)
static const uptr kFrameSize = 96;
static const uptr kFrameSize = 2 * sizeof(uhwptr);
// Check if given pointer points into allocated stack area.
static inline bool IsValidFrame(uptr frame, uptr stack_top, uptr stack_bottom) {
return frame > stack_bottom && frame < stack_top - kFrameSize;
} // namespace __sanitizer
// Use this macro if you want to print stack trace with the caller
// of the current function in the top frame.
#define GET_CALLER_PC_BP \
uptr bp = GET_CURRENT_FRAME(); \
uptr pc = GET_CALLER_PC();
uptr local_stack; \
uptr sp = (uptr)&local_stack
// Use this macro if you want to print stack trace with the current
// function in the top frame.
uptr bp = GET_CURRENT_FRAME(); \
uptr pc = StackTrace::GetCurrentPc()
uptr local_stack; \
uptr sp = (uptr)&local_stack
// GET_CURRENT_PC() is equivalent to StackTrace::GetCurrentPc().
// Optimized x86 version is faster than GetCurrentPc because
// it does not involve a function call, instead it reads RIP register.
// Reads of RIP by an instruction return RIP pointing to the next
// instruction, which is exactly what we want here, thus 0 offset.
// It needs to be a macro because otherwise we will get the name
// of this function on the top of most stacks. Attribute artificial
// does not do what it claims to do, unfortunatley. And attribute
// __nodebug__ is clang-only. If we would have an attribute that
// would remove this function from debug info, we could simply make
// StackTrace::GetCurrentPc() faster.
#if defined(__x86_64__)
# define GET_CURRENT_PC() \
(__extension__({ \
uptr pc; \
asm("lea 0(%%rip), %0" : "=r"(pc)); \
pc; \
# define GET_CURRENT_PC() StackTrace::GetCurrentPc()