--- /dev/null
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Produce stack trace. I'm guessing (hoping!) the code is much like
+// for x86. For apple machines, at least, it seems to be; see
+// https://developer.apple.com/documentation/mac/runtimehtml/RTArch-59.html
+// https://www.linux-foundation.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html#STACK
+// Linux has similar code: http://patchwork.ozlabs.org/linuxppc/patch?id=8882
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
+
+#if defined(__linux__)
+#include <asm/ptrace.h> // for PT_NIP.
+#include <ucontext.h> // for ucontext_t
+#endif
+
+#include <unistd.h>
+#include <cassert>
+#include <cstdint>
+#include <cstdio>
+
+#include "absl/base/attributes.h"
+#include "absl/base/optimization.h"
+#include "absl/base/port.h"
+#include "absl/debugging/stacktrace.h"
+#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
+
+// Given a stack pointer, return the saved link register value.
+// Note that this is the link register for a callee.
+static inline void *StacktracePowerPCGetLR(void **sp) {
+ // PowerPC has 3 main ABIs, which say where in the stack the
+ // Link Register is. For DARWIN and AIX (used by apple and
+ // linux ppc64), it's in sp[2]. For SYSV (used by linux ppc),
+ // it's in sp[1].
+#if defined(_CALL_AIX) || defined(_CALL_DARWIN)
+ return *(sp+2);
+#elif defined(_CALL_SYSV)
+ return *(sp+1);
+#elif defined(__APPLE__) || defined(__FreeBSD__) || \
+ (defined(__linux__) && defined(__PPC64__))
+ // This check is in case the compiler doesn't define _CALL_AIX/etc.
+ return *(sp+2);
+#elif defined(__linux)
+ // This check is in case the compiler doesn't define _CALL_SYSV.
+ return *(sp+1);
+#else
+#error Need to specify the PPC ABI for your archiecture.
+#endif
+}
+
+// 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 IS_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_sp, const void *uc) {
+ void **new_sp = (void **) *old_sp;
+ enum { kStackAlignment = 16 };
+
+ // Check that the transition from frame pointer old_sp to frame
+ // pointer new_sp isn't clearly bogus
+ if (STRICT_UNWINDING) {
+ // With the stack growing downwards, older stack frame must be
+ // at a greater address that the current one.
+ if (new_sp <= old_sp) return nullptr;
+ // Assume stack frames larger than 100,000 bytes are bogus.
+ if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return nullptr;
+ } else {
+ // In the non-strict mode, allow discontiguous stack frames.
+ // (alternate-signal-stacks for example).
+ if (new_sp == old_sp) return nullptr;
+ // And allow frames upto about 1MB.
+ if ((new_sp > old_sp)
+ && ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return nullptr;
+ }
+ if ((uintptr_t)new_sp % kStackAlignment != 0) return nullptr;
+
+#if defined(__linux__)
+ enum StackTraceKernelSymbolStatus {
+ kNotInitialized = 0, kAddressValid, kAddressInvalid };
+
+ if (IS_WITH_CONTEXT && uc != nullptr) {
+ static StackTraceKernelSymbolStatus kernel_symbol_status =
+ kNotInitialized; // Sentinel: not computed yet.
+ // Initialize with sentinel value: __kernel_rt_sigtramp_rt64 can not
+ // possibly be there.
+ static const unsigned char *kernel_sigtramp_rt64_address = nullptr;
+ if (kernel_symbol_status == kNotInitialized) {
+ absl::debugging_internal::VDSOSupport vdso;
+ if (vdso.IsPresent()) {
+ absl::debugging_internal::VDSOSupport::SymbolInfo
+ sigtramp_rt64_symbol_info;
+ if (!vdso.LookupSymbol(
+ "__kernel_sigtramp_rt64", "LINUX_2.6.15",
+ absl::debugging_internal::VDSOSupport::kVDSOSymbolType,
+ &sigtramp_rt64_symbol_info) ||
+ sigtramp_rt64_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");
+ kernel_symbol_status = kAddressInvalid;
+ } else {
+ kernel_sigtramp_rt64_address =
+ reinterpret_cast<const unsigned char *>(
+ sigtramp_rt64_symbol_info.address);
+ kernel_symbol_status = kAddressValid;
+ }
+ } else {
+ kernel_symbol_status = kAddressInvalid;
+ }
+ }
+
+ if (new_sp != nullptr &&
+ kernel_symbol_status == kAddressValid &&
+ StacktracePowerPCGetLR(new_sp) == kernel_sigtramp_rt64_address) {
+ const ucontext_t* signal_context =
+ reinterpret_cast<const ucontext_t*>(uc);
+ void **const sp_before_signal =
+ reinterpret_cast<void**>(signal_context->uc_mcontext.gp_regs[PT_R1]);
+ // Check that alleged sp before signal is nonnull and is reasonably
+ // aligned.
+ if (sp_before_signal != nullptr &&
+ ((uintptr_t)sp_before_signal % kStackAlignment) == 0) {
+ // Check that alleged stack pointer is actually readable. This is to
+ // prevent a "double fault" in case we hit the first fault due to e.g.
+ // a stack corruption.
+ if (absl::debugging_internal::AddressIsReadable(sp_before_signal)) {
+ // Alleged stack pointer is readable, use it for further unwinding.
+ new_sp = sp_before_signal;
+ }
+ }
+ }
+ }
+#endif
+
+ return new_sp;
+}
+
+// This ensures that absl::GetStackTrace sets up the Link Register properly.
+ABSL_ATTRIBUTE_NOINLINE static void AbslStacktracePowerPCDummyFunction() {
+ ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+
+template <bool IS_STACK_FRAMES, bool IS_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 int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
+ const void *ucp, int *min_dropped_frames) {
+ void **sp;
+ // Apple OS X uses an old version of gnu as -- both Darwin 7.9.0 (Panther)
+ // and Darwin 8.8.1 (Tiger) use as 1.38. This means we have to use a
+ // different asm syntax. I don't know quite the best way to discriminate
+ // systems using the old as from the new one; I've gone with __APPLE__.
+#ifdef __APPLE__
+ __asm__ volatile ("mr %0,r1" : "=r" (sp));
+#else
+ __asm__ volatile ("mr %0,1" : "=r" (sp));
+#endif
+
+ // On PowerPC, the "Link Register" or "Link Record" (LR), is a stack
+ // entry that holds the return address of the subroutine call (what
+ // instruction we run after our function finishes). This is the
+ // same as the stack-pointer of our parent routine, which is what we
+ // want here. While the compiler will always(?) set up LR for
+ // subroutine calls, it may not for leaf functions (such as this one).
+ // This routine forces the compiler (at least gcc) to push it anyway.
+ AbslStacktracePowerPCDummyFunction();
+
+ // The LR save area is used by the callee, so the top entry is bogus.
+ skip_count++;
+
+ int n = 0;
+
+ // Unlike ABIs of X86 and ARM, PowerPC ABIs say that return address (in
+ // the link register) of a function call is stored in the caller's stack
+ // frame instead of the callee's. When we look for the return address
+ // associated with a stack frame, we need to make sure that there is a
+ // caller frame before it. So we call NextStackFrame before entering the
+ // loop below and check next_sp instead of sp for loop termination.
+ // The outermost frame is set up by runtimes and it does not have a
+ // caller frame, so it is skipped.
+
+ // 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_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(sp, ucp);
+
+ while (next_sp && n < max_depth) {
+ if (skip_count > 0) {
+ skip_count--;
+ } else {
+ result[n] = StacktracePowerPCGetLR(sp);
+ if (IS_STACK_FRAMES) {
+ if (next_sp > sp) {
+ sizes[n] = (uintptr_t)next_sp - (uintptr_t)sp;
+ } else {
+ // A frame-size of 0 is used to indicate unknown frame size.
+ sizes[n] = 0;
+ }
+ }
+ n++;
+ }
+
+ sp = next_sp;
+ next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(sp, ucp);
+ }
+
+ 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 = 1000;
+ int j = 0;
+ for (; next_sp != nullptr && j < kMaxUnwind; j++) {
+ next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(next_sp, ucp);
+ }
+ *min_dropped_frames = j;
+ }
+ return n;
+}
+
+namespace absl {
+namespace debugging_internal {
+bool StackTraceWorksForTest() {
+ return true;
+}
+} // namespace debugging_internal
+} // namespace absl
+
+#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
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