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Diffstat (limited to 'src')
| -rw-r--r-- | src/processor/stackwalker_selftest.cc | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/src/processor/stackwalker_selftest.cc b/src/processor/stackwalker_selftest.cc new file mode 100644 index 00000000..08dea134 --- /dev/null +++ b/src/processor/stackwalker_selftest.cc @@ -0,0 +1,252 @@ +// Copyright (C) 2006 Google Inc. +// +// 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 +// +// http://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. + +// stackwalker_selftest.cc: Tests StackwalkerX86 or StackwalkerPPC using the +// running process' stack as test data, if running on an x86 or ppc and +// compiled with gcc. This test is not enabled in the "make check" suite +// by default, because certain optimizations interfere with its proper +// operation. To turn it on, configure with --enable-selftest. +// +// Optimizations that cause problems: +// - stack frame reuse. The Recursor function here calls itself with +// |return Recursor|. When the caller's frame is reused, it will cause +// CountCallerFrames to correctly return the same number of frames +// in both the caller and callee. This is considered an unexpected +// condition in the test, which expects a callee to have one more +// caller frame in the stack than its caller. +// - frame pointer omission. Even with a stackwalker that understands +// this optimization, the code to harness debug information currently +// only exists to retrieve it from minidumps, not the current process. +// +// This test can also serve as a developmental and debugging aid if +// PRINT_STACKS is defined. +// +// Author: Mark Mentovai + +#if defined(__GNUC__) && (defined(__i386__) || defined(__ppc__)) + + +#include <cstdio> + +#include "google/airbag_types.h" +#include "google/stack_frame.h" +#include "processor/memory_region.h" +#include "processor/minidump_format.h" + +using google_airbag::MemoryRegion; +using google_airbag::StackFrame; +using google_airbag::StackFrames; + +#if defined(__i386__) +#include "processor/stackwalker_x86.h" +using google_airbag::StackwalkerX86; +#elif defined(__ppc__) +#include "processor/stackwalker_ppc.h" +using google_airbag::StackwalkerPPC; +#endif // __i386__ || __ppc__ + +#define RECURSION_DEPTH 100 + + +// A simple MemoryRegion subclass that provides direct access to this +// process' memory space by pointer. +class SelfMemoryRegion : public MemoryRegion { + public: + virtual u_int64_t GetBase() { return 0; } + virtual u_int32_t GetSize() { return 0xffffffff; } + + bool GetMemoryAtAddress(u_int64_t address, u_int8_t* value) { + return GetMemoryAtAddressInternal(address, value); } + bool GetMemoryAtAddress(u_int64_t address, u_int16_t* value) { + return GetMemoryAtAddressInternal(address, value); } + bool GetMemoryAtAddress(u_int64_t address, u_int32_t* value) { + return GetMemoryAtAddressInternal(address, value); } + bool GetMemoryAtAddress(u_int64_t address, u_int64_t* value) { + return GetMemoryAtAddressInternal(address, value); } + + private: + template<typename T> bool GetMemoryAtAddressInternal(u_int64_t address, + T* value) { + u_int8_t* memory = 0; + *value = *reinterpret_cast<const T*>(&memory[address]); + return true; + } +}; + + +#if defined(__i386__) + +// GetEBP returns the current value of the %ebp register. Because it's +// implemented as a function, %ebp itself contains GetEBP's frame pointer +// and not the caller's frame pointer. Dereference %ebp to obtain the +// caller's frame pointer, which the compiler-generated preamble stored +// on the stack (provided frame pointers are not being omitted.) Because +// this function depends on the compiler-generated preamble, inlining is +// disabled. +static u_int32_t GetEBP() __attribute__((noinline)); +static u_int32_t GetEBP() { + u_int32_t ebp; + __asm__ __volatile__( + "movl (%%ebp), %0" + : "=a" (ebp) + ); + return ebp; +} + + +// GetEIP returns the instruction pointer identifying the next instruction +// to execute after GetEIP returns. It obtains this information from the +// stack, where it was placed by the call instruction that called GetEIP. +// This function depends on frame pointers not being omitted. It is possible +// to write a pure asm version of this routine that has no compiler-generated +// preamble and uses %esp instead of %ebp; that would function in the +// absence of frame pointers. However, the simpler approach is used here +// because GetEBP and stackwalking necessarily depends on access to frame +// pointers. Because this function depends on a call instruction and the +// compiler-generated preamble, inlining is disabled. +static u_int32_t GetEIP() __attribute__((noinline)); +static u_int32_t GetEIP() { + u_int32_t eip; + __asm__ __volatile__( + "movl 4(%%ebp), %0" + : "=a" (eip) + ); + return eip; +} + + +#elif defined(__ppc__) + + +// GetSP returns the current value of the %r1 register, which by convention, +// is the stack pointer on ppc. Because it's implemented as a function, +// %r1 itself contains GetSP's own stack pointer and not the caller's stack +// pointer. Dereference %r1 to obtain the caller's stack pointer, which the +// compiler-generated prolog stored on the stack. Because this function +// depends on the compiler-generated prolog, inlining is disabled. +static u_int32_t GetSP() __attribute__((noinline)); +static u_int32_t GetSP() { + u_int32_t sp; + __asm__ __volatile__( + "lwz %0, 0(r1)" + : "=r" (sp) + ); + return sp; +} + + +// GetPC returns the program counter identifying the next instruction to +// execute after GetPC returns. It obtains this information from the +// link register, where it was placed by the branch instruction that called +// GetPC. Because this function depends on the caller's use of a branch +// instruction, inlining is disabled. +static u_int32_t GetPC() __attribute__((noinline)); +static u_int32_t GetPC() { + u_int32_t lr; + __asm__ __volatile__( + "mflr %0" + : "=r" (lr) + ); + return lr; +} + + +#endif // __i386__ || __ppc__ + + +// CountCallerFrames returns the number of stack frames beneath the function +// that called CountCallerFrames. Because this function's return value +// is dependent on the size of the stack beneath it, inlining is disabled, +// and any function that calls this should not be inlined either. +static unsigned int CountCallerFrames() __attribute__((noinline)); +static unsigned int CountCallerFrames() { + SelfMemoryRegion memory; + +#if defined(__i386__) + MDRawContextX86 context = MDRawContextX86(); + context.eip = GetEIP(); + context.ebp = GetEBP(); + + StackwalkerX86 stackwalker = StackwalkerX86(&context, &memory, NULL, NULL); +#elif defined(__ppc__) + MDRawContextPPC context = MDRawContextPPC(); + context.srr0 = GetPC(); + context.gpr[1] = GetSP(); + + StackwalkerPPC stackwalker = StackwalkerPPC(&context, &memory, NULL, NULL); +#endif // __i386__ || __ppc__ + + StackFrames stack; + stackwalker.Walk(&stack); + +#ifdef PRINT_STACKS + printf("\n"); + for(unsigned int frame_index = 0; + frame_index < stack.size(); + ++frame_index) { + StackFrame *frame = &stack[frame_index]; + printf("frame %-3d instruction = 0x%08llx frame_pointer = 0x%08llx\n", + frame_index, frame->instruction, frame->frame_pointer); + } +#endif // PRINT_STACKS + + // Subtract 1 because the caller wants the number of frames beneath + // itself. Because the caller called us, subract two for our frame and its + // frame, which are included in stack->size(). + return stack.size() - 2; +} + + +// Recursor verifies that the number stack frames beneath itself is one more +// than the number of stack frames beneath its parent. When depth frames +// have been reached, Recursor stops checking and returns success. If the +// frame count check fails at any depth, Recursor will stop and return false. +// Because this calls CountCallerFrames, inlining is disabled. +static bool Recursor(unsigned int depth, unsigned int parent_callers) + __attribute__((noinline)); +static bool Recursor(unsigned int depth, unsigned int parent_callers) { + unsigned int callers = CountCallerFrames(); + if (callers != parent_callers + 1) + return false; + + if (depth) + return Recursor(depth - 1, callers); + + // depth == 0 + return true; +} + + +// Because this calls CountCallerFrames, inlining is disabled - but because +// it's main (and nobody calls it other than the entry point), it wouldn't +// be inlined anyway. +int main(int argc, char** argv) __attribute__((noinline)); +int main(int argc, char** argv) { + return Recursor(RECURSION_DEPTH, CountCallerFrames()) ? 0 : 1; +} + + +#else // __GNUC__ && (__i386__ || __ppc__) +// Not gcc? We use gcc's __asm__. +// Not i386 or ppc? We can only test stacks we know how to walk. + + +int main(int argc, char **argv) { + // "make check" interprets an exit status of 77 to mean that the test is + // not supported. + return 77; +} + + +#endif // __GNUC__ && (__i386__ || __ppc__) |