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stacktrace_aarch64-inl.inc (11115B)

---

#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 <signal.h>
#include <sys/mman.h>
#include <ucontext.h>
#include <unistd.h>
#endif

#include <atomic>
#include <cassert>
#include <cstdint>
#include <iostream>
#include <limits>

#include "absl/base/attributes.h"
#include "absl/debugging/internal/address_is_readable.h"
#include "absl/debugging/internal/addresses.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 size_t kUnknownFrameSize = 0;
// Stack end to use when we don't know the actual stack end
// (effectively just the end of address space).
constexpr uintptr_t kUnknownStackEnd =
   std::numeric_limits<size_t>::max() - sizeof(void *);

#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;
 ABSL_CONST_INIT 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::debugging_internal::VDSOSupport vdso;
 if (vdso.IsPresent()) {
   absl::debugging_internal::VDSOSupport::SymbolInfo symbol_info;
   auto lookup = [&](int type) {
     return vdso.LookupSymbol("__kernel_rt_sigreturn", "LINUX_2.6.39", type,
                              &symbol_info);
   };
   if ((!lookup(STT_FUNC) && !lookup(STT_NOTYPE)) ||
       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 size_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 ? static_cast<size_t>(high_char_ptr - low_char_ptr)
                   : kUnknownFrameSize;
}

// Saves stack info that is expensive to calculate to avoid recalculating per frame.
struct StackInfo {
 uintptr_t stack_low;
 uintptr_t stack_high;
 uintptr_t sig_stack_low;
 uintptr_t sig_stack_high;
};

static bool InsideSignalStack(void** ptr, const StackInfo* stack_info) {
 uintptr_t comparable_ptr = reinterpret_cast<uintptr_t>(ptr);
 if (stack_info->sig_stack_high == kUnknownStackEnd)
   return false;
 return (comparable_ptr >= stack_info->sig_stack_low &&
         comparable_ptr < stack_info->sig_stack_high);
}

// 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>
ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY  // May read random elements from stack.
static void **NextStackFrame(void **old_frame_pointer, const void *uc,
                            const StackInfo *stack_info) {
 void **new_frame_pointer = reinterpret_cast<void**>(*old_frame_pointer);

#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]);

     // The most recent signal always needs special handling to find the frame
     // pointer, but a nested signal does not.  If pre_signal_frame_pointer is
     // earlier in the stack than the old_frame_pointer, then use it. If it is
     // later, then we have already unwound through it and it needs no special
     // handling.
     if (pre_signal_frame_pointer >= old_frame_pointer) {
       new_frame_pointer = pre_signal_frame_pointer;
     }
 }
#endif

 // The frame pointer should be 8-byte aligned.
 if ((reinterpret_cast<uintptr_t>(new_frame_pointer) & 7) != 0)
   return nullptr;

 // 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::debugging_internal::AddressIsReadable(
         new_frame_pointer))
   return nullptr;
 }

 // Only check the size if both frames are in the same stack.
 if (InsideSignalStack(new_frame_pointer, stack_info) ==
     InsideSignalStack(old_frame_pointer, stack_info)) {
   // 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.
   const size_t max_size = STRICT_UNWINDING ? 100000 : 1000000;
   const size_t frame_size =
       ComputeStackFrameSize(old_frame_pointer, new_frame_pointer);
   if (frame_size == kUnknownFrameSize)
      return nullptr;
   // A very large frame may mean corrupt memory or an erroneous frame
   // pointer. But also maybe just a plain-old large frame.  Assume that if the
   // frame is within a known stack, then it is valid.
   if (frame_size > max_size) {
     size_t stack_low = stack_info->stack_low;
     size_t stack_high = stack_info->stack_high;
     if (InsideSignalStack(new_frame_pointer, stack_info)) {
       stack_low = stack_info->sig_stack_low;
       stack_high = stack_info->sig_stack_high;
     }
     if (stack_high < kUnknownStackEnd &&
         static_cast<size_t>(getpagesize()) < stack_low) {
       const uintptr_t new_fp_u =
           reinterpret_cast<uintptr_t>(new_frame_pointer);
       // Stack bounds are known.
       if (!(stack_low < new_fp_u && new_fp_u <= stack_high)) {
         // new_frame_pointer is not within a known stack.
         return nullptr;
       }
     } else {
       // Stack bounds are unknown, prefer truncated stack to possible crash.
       return nullptr;
     }
   }
 }

 return new_frame_pointer;
}

template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
// We count on the bottom frame being this one. See the comment
// at prev_return_address
ABSL_ATTRIBUTE_NOINLINE
ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY   // May read random elements from stack.
static int UnwindImpl(void **result, uintptr_t *frames, 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;

 // Assume that the first page is not stack.
 StackInfo stack_info;
 stack_info.stack_low = static_cast<uintptr_t>(getpagesize());
 stack_info.stack_high = kUnknownStackEnd;
 stack_info.sig_stack_low = stack_info.stack_low;
 stack_info.sig_stack_high = kUnknownStackEnd;

 // 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 address 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;
 // The nth frame size is the difference between the nth frame pointer and the
 // the frame pointer below it in the call chain. There is no frame below the
 // leaf frame, but this function is the leaf anyway, and we skip it.
 void** prev_frame_pointer = nullptr;

  while (frame_pointer && n < max_depth) {
   if (skip_count > 0) {
     skip_count--;
   } else {
     result[n] = reinterpret_cast<void *>(
         absl::debugging_internal::StripPointerMetadata(prev_return_address));
     if (IS_STACK_FRAMES) {
       if (frames != nullptr) {
         frames[n] = absl::debugging_internal::StripPointerMetadata(
                         prev_frame_pointer) +
                     2 * sizeof(void *) /* go past the return address */;
       }
       if (sizes != nullptr) {
         sizes[n] = static_cast<int>(
             ComputeStackFrameSize(prev_frame_pointer, frame_pointer));
       }
     }
     n++;
   }
   prev_return_address = frame_pointer[1];
   prev_frame_pointer = frame_pointer;
   // 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).
   frame_pointer = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
       frame_pointer, ucp, &stack_info);
 }

 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 num_dropped_frames = 0;
   for (int j = 0; frame_pointer != nullptr && j < kMaxUnwind; j++) {
     if (skip_count > 0) {
       skip_count--;
     } else {
       num_dropped_frames++;
     }
     frame_pointer = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
         frame_pointer, ucp, &stack_info);
   }
   *min_dropped_frames = num_dropped_frames;
 }
 return n;
}

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace debugging_internal {
bool StackTraceWorksForTest() {
 return true;
}
}  // namespace debugging_internal
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_