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+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_
+
+// Generate stack tracer for aarch64
+
+#if defined(__linux__)
+#include <sys/mman.h>
+#include <ucontext.h>
+#include <unistd.h>
+#endif
+
+#include <atomic>
+#include <cassert>
+#include <cstdint>
+#include <iostream>
+
+#include "absl/debugging/internal/address_is_readable.h"
+#include "absl/debugging/internal/vdso_support.h" // a no-op on non-elf or non-glibc systems
+#include "absl/debugging/stacktrace.h"
+
+static const uintptr_t kUnknownFrameSize = 0;
+
+#if defined(__linux__)
+// Returns the address of the VDSO __kernel_rt_sigreturn function, if present.
+static const unsigned char* GetKernelRtSigreturnAddress() {
+ constexpr uintptr_t kImpossibleAddress = 1;
+ static std::atomic<uintptr_t> memoized{kImpossibleAddress};
+ uintptr_t address = memoized.load(std::memory_order_relaxed);
+ if (address != kImpossibleAddress) {
+ return reinterpret_cast<const unsigned char*>(address);
+ }
+
+ address = reinterpret_cast<uintptr_t>(nullptr);
+
+#ifdef ABSL_HAVE_VDSO_SUPPORT
+ absl::debug_internal::VDSOSupport vdso;
+ if (vdso.IsPresent()) {
+ absl::debug_internal::VDSOSupport::SymbolInfo symbol_info;
+ if (!vdso.LookupSymbol("__kernel_rt_sigreturn", "LINUX_2.6.39", STT_FUNC,
+ &symbol_info) ||
+ symbol_info.address == nullptr) {
+ // Unexpected: VDSO is present, yet the expected symbol is missing
+ // or null.
+ assert(false && "VDSO is present, but doesn't have expected symbol");
+ } else {
+ if (reinterpret_cast<uintptr_t>(symbol_info.address) !=
+ kImpossibleAddress) {
+ address = reinterpret_cast<uintptr_t>(symbol_info.address);
+ } else {
+ assert(false && "VDSO returned invalid address");
+ }
+ }
+ }
+#endif
+
+ memoized.store(address, std::memory_order_relaxed);
+ return reinterpret_cast<const unsigned char*>(address);
+}
+#endif // __linux__
+
+// Compute the size of a stack frame in [low..high). We assume that
+// low < high. Return size of kUnknownFrameSize.
+template<typename T>
+static inline uintptr_t ComputeStackFrameSize(const T* low,
+ const T* high) {
+ const char* low_char_ptr = reinterpret_cast<const char *>(low);
+ const char* high_char_ptr = reinterpret_cast<const char *>(high);
+ return low < high ? high_char_ptr - low_char_ptr : kUnknownFrameSize;
+}
+
+// Given a pointer to a stack frame, locate and return the calling
+// stackframe, or return null if no stackframe can be found. Perform sanity
+// checks (the strictness of which is controlled by the boolean parameter
+// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
+template<bool STRICT_UNWINDING, bool WITH_CONTEXT>
+static void **NextStackFrame(void **old_frame_pointer, const void *uc) {
+ void **new_frame_pointer = reinterpret_cast<void**>(*old_frame_pointer);
+ bool check_frame_size = true;
+
+#if defined(__linux__)
+ if (WITH_CONTEXT && uc != nullptr) {
+ // Check to see if next frame's return address is __kernel_rt_sigreturn.
+ if (old_frame_pointer[1] == GetKernelRtSigreturnAddress()) {
+ const ucontext_t *ucv = static_cast<const ucontext_t *>(uc);
+ // old_frame_pointer[0] is not suitable for unwinding, look at
+ // ucontext to discover frame pointer before signal.
+ void **const pre_signal_frame_pointer =
+ reinterpret_cast<void **>(ucv->uc_mcontext.regs[29]);
+
+ // Check that alleged frame pointer is actually readable. This is to
+ // prevent "double fault" in case we hit the first fault due to e.g.
+ // stack corruption.
+ if (!absl::debug_internal::AddressIsReadable(
+ pre_signal_frame_pointer))
+ return nullptr;
+
+ // Alleged frame pointer is readable, use it for further unwinding.
+ new_frame_pointer = pre_signal_frame_pointer;
+
+ // Skip frame size check if we return from a signal. We may be using a
+ // an alternate stack for signals.
+ check_frame_size = false;
+ }
+ }
+#endif
+
+ // aarch64 ABI requires stack pointer to be 16-byte-aligned.
+ if ((reinterpret_cast<uintptr_t>(new_frame_pointer) & 15) != 0)
+ return nullptr;
+
+ // Check frame size. In strict mode, we assume frames to be under
+ // 100,000 bytes. In non-strict mode, we relax the limit to 1MB.
+ if (check_frame_size) {
+ const uintptr_t max_size = STRICT_UNWINDING ? 100000 : 1000000;
+ const uintptr_t frame_size =
+ ComputeStackFrameSize(old_frame_pointer, new_frame_pointer);
+ if (frame_size == kUnknownFrameSize || frame_size > max_size)
+ return nullptr;
+ }
+
+ return new_frame_pointer;
+}
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
+ const void *ucp, int *min_dropped_frames) {
+#ifdef __GNUC__
+ void **frame_pointer = reinterpret_cast<void**>(__builtin_frame_address(0));
+#else
+# error reading stack point not yet supported on this platform.
+#endif
+
+ skip_count++; // Skip the frame for this function.
+ int n = 0;
+
+ // The frame pointer points to low address of a frame. The first 64-bit
+ // word of a frame points to the next frame up the call chain, which normally
+ // is just after the high address of the current frame. The second word of
+ // a frame contains return adress of to the caller. To find a pc value
+ // associated with the current frame, we need to go down a level in the call
+ // chain. So we remember return the address of the last frame seen. This
+ // does not work for the first stack frame, which belongs to UnwindImp() but
+ // we skip the frame for UnwindImp() anyway.
+ void* prev_return_address = nullptr;
+
+ while (frame_pointer && n < max_depth) {
+ // The absl::GetStackFrames routine is called when we are in some
+ // informational context (the failure signal handler for example).
+ // Use the non-strict unwinding rules to produce a stack trace
+ // that is as complete as possible (even if it contains a few bogus
+ // entries in some rare cases).
+ void **next_frame_pointer =
+ NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp);
+
+ if (skip_count > 0) {
+ skip_count--;
+ } else {
+ result[n] = prev_return_address;
+ if (IS_STACK_FRAMES) {
+ sizes[n] = ComputeStackFrameSize(frame_pointer, next_frame_pointer);
+ }
+ n++;
+ }
+ prev_return_address = frame_pointer[1];
+ frame_pointer = next_frame_pointer;
+ }
+ if (min_dropped_frames != nullptr) {
+ // Implementation detail: we clamp the max of frames we are willing to
+ // count, so as not to spend too much time in the loop below.
+ const int kMaxUnwind = 200;
+ int j = 0;
+ for (; frame_pointer != nullptr && j < kMaxUnwind; j++) {
+ frame_pointer =
+ NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp);
+ }
+ *min_dropped_frames = j;
+ }
+ return n;
+}
+
+#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_