| // 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_ |