The Tor Browser: comparison toolkit/crashreporter/google-breakpad/src/processor/stackwalker

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+:315a83757a72
+// Copyright (c) 2010 Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+// stackwalker_x86.cc: x86-specific stackwalker.
+//
+// See stackwalker_x86.h for documentation.
+//
+// Author: Mark Mentovai
+#include <assert.h>
+#include <string>
+#include "common/scoped_ptr.h"
+#include "google_breakpad/processor/call_stack.h"
+#include "google_breakpad/processor/code_modules.h"
+#include "google_breakpad/processor/memory_region.h"
+#include "google_breakpad/processor/source_line_resolver_interface.h"
+#include "google_breakpad/processor/stack_frame_cpu.h"
+#include "common/logging.h"
+#include "processor/postfix_evaluator-inl.h"
+#include "processor/stackwalker_x86.h"
+#include "processor/windows_frame_info.h"
+#include "processor/cfi_frame_info.h"
+namespace google_breakpad {
+const StackwalkerX86::CFIWalker::RegisterSet
+StackwalkerX86::cfi_register_map_[] = {
+// It may seem like $eip and $esp are callee-saves, because (with Unix or
+// cdecl calling conventions) the callee is responsible for having them
+// restored upon return. But the callee_saves flags here really means
+// that the walker should assume they're unchanged if the CFI doesn't
+// mention them, which is clearly wrong for $eip and $esp.
+{ ToUniqueString("$eip"), ToUniqueString(".ra"),  false,
+StackFrameX86::CONTEXT_VALID_EIP, &MDRawContextX86::eip },
+{ ToUniqueString("$esp"), ToUniqueString(".cfa"), false,
+StackFrameX86::CONTEXT_VALID_ESP, &MDRawContextX86::esp },
+{ ToUniqueString("$ebp"), NULL,   true,
+StackFrameX86::CONTEXT_VALID_EBP, &MDRawContextX86::ebp },
+{ ToUniqueString("$eax"), NULL,   false,
+StackFrameX86::CONTEXT_VALID_EAX, &MDRawContextX86::eax },
+{ ToUniqueString("$ebx"), NULL,   true,
+StackFrameX86::CONTEXT_VALID_EBX, &MDRawContextX86::ebx },
+{ ToUniqueString("$ecx"), NULL,   false,
+StackFrameX86::CONTEXT_VALID_ECX, &MDRawContextX86::ecx },
+{ ToUniqueString("$edx"), NULL,   false,
+StackFrameX86::CONTEXT_VALID_EDX, &MDRawContextX86::edx },
+{ ToUniqueString("$esi"), NULL,   true,
+StackFrameX86::CONTEXT_VALID_ESI, &MDRawContextX86::esi },
+{ ToUniqueString("$edi"), NULL,   true,
+StackFrameX86::CONTEXT_VALID_EDI, &MDRawContextX86::edi },
+};
+StackwalkerX86::StackwalkerX86(const SystemInfo* system_info,
+const MDRawContextX86* context,
+MemoryRegion* memory,
+const CodeModules* modules,
+StackFrameSymbolizer* resolver_helper)
+: Stackwalker(system_info, memory, modules, resolver_helper),
+context_(context),
+cfi_walker_(cfi_register_map_,
+(sizeof(cfi_register_map_) / sizeof(cfi_register_map_[0]))) {
+if (memory_ && memory_->GetBase() + memory_->GetSize() - 1 > 0xffffffff) {
+// The x86 is a 32-bit CPU, the limits of the supplied stack are invalid.
+// Mark memory_ = NULL, which will cause stackwalking to fail.
+BPLOG(ERROR) << "Memory out of range for stackwalking: " <<
+HexString(memory_->GetBase()) << "+" <<
+HexString(memory_->GetSize());
+memory_ = NULL;
+}
+}
+StackFrameX86::~StackFrameX86() {
+if (windows_frame_info)
+delete windows_frame_info;
+windows_frame_info = NULL;
+if (cfi_frame_info)
+delete cfi_frame_info;
+cfi_frame_info = NULL;
+}
+uint64_t StackFrameX86::ReturnAddress() const
+{
+assert(context_validity & StackFrameX86::CONTEXT_VALID_EIP);
+return context.eip;
+}
+StackFrame* StackwalkerX86::GetContextFrame() {
+if (!context_) {
+BPLOG(ERROR) << "Can't get context frame without context";
+return NULL;
+}
+StackFrameX86* frame = new StackFrameX86();
+// The instruction pointer is stored directly in a register, so pull it
+// straight out of the CPU context structure.
+frame->context = *context_;
+frame->context_validity = StackFrameX86::CONTEXT_VALID_ALL;
+frame->trust = StackFrame::FRAME_TRUST_CONTEXT;
+frame->instruction = frame->context.eip;
+return frame;
+}
+StackFrameX86* StackwalkerX86::GetCallerByWindowsFrameInfo(
+const vector<StackFrame*> &frames,
+WindowsFrameInfo* last_frame_info,
+bool stack_scan_allowed) {
+StackFrame::FrameTrust trust = StackFrame::FRAME_TRUST_NONE;
+StackFrameX86* last_frame = static_cast<StackFrameX86*>(frames.back());
+// Save the stack walking info we found, in case we need it later to
+// find the callee of the frame we're constructing now.
+last_frame->windows_frame_info = last_frame_info;
+// This function only covers the full STACK WIN case. If
+// last_frame_info is VALID_PARAMETER_SIZE-only, then we should
+// assume the traditional frame format or use some other strategy.
+if (last_frame_info->valid != WindowsFrameInfo::VALID_ALL)
+return NULL;
+// This stackwalker sets each frame's %esp to its value immediately prior
+// to the CALL into the callee.  This means that %esp points to the last
+// callee argument pushed onto the stack, which may not be where %esp points
+// after the callee returns.  Specifically, the value is correct for the
+// cdecl calling convention, but not other conventions.  The cdecl
+// convention requires a caller to pop its callee's arguments from the
+// stack after the callee returns.  This is usually accomplished by adding
+// the known size of the arguments to %esp.  Other calling conventions,
+// including stdcall, thiscall, and fastcall, require the callee to pop any
+// parameters stored on the stack before returning.  This is usually
+// accomplished by using the RET n instruction, which pops n bytes off
+// the stack after popping the return address.
+//
+// Because each frame's %esp will point to a location on the stack after
+// callee arguments have been PUSHed, when locating things in a stack frame
+// relative to %esp, the size of the arguments to the callee need to be
+// taken into account.  This seems a little bit unclean, but it's better
+// than the alternative, which would need to take these same things into
+// account, but only for cdecl functions.  With this implementation, we get
+// to be agnostic about each function's calling convention.  Furthermore,
+// this is how Windows debugging tools work, so it means that the %esp
+// values produced by this stackwalker directly correspond to the %esp
+// values you'll see there.
+//
+// If the last frame has no callee (because it's the context frame), just
+// set the callee parameter size to 0: the stack pointer can't point to
+// callee arguments because there's no callee.  This is correct as long
+// as the context wasn't captured while arguments were being pushed for
+// a function call.  Note that there may be functions whose parameter sizes
+// are unknown, 0 is also used in that case.  When that happens, it should
+// be possible to walk to the next frame without reference to %esp.
+uint32_t last_frame_callee_parameter_size = 0;
+int frames_already_walked = frames.size();
+if (frames_already_walked >= 2) {
+const StackFrameX86* last_frame_callee
+= static_cast<StackFrameX86*>(frames[frames_already_walked - 2]);
+WindowsFrameInfo* last_frame_callee_info
+= last_frame_callee->windows_frame_info;
+if (last_frame_callee_info &&
+(last_frame_callee_info->valid
+& WindowsFrameInfo::VALID_PARAMETER_SIZE)) {
+last_frame_callee_parameter_size =
+last_frame_callee_info->parameter_size;
+}
+}
+// Set up the dictionary for the PostfixEvaluator.  %ebp and %esp are used
+// in each program string, and their previous values are known, so set them
+// here.
+PostfixEvaluator<uint32_t>::DictionaryType dictionary;
+// Provide the current register values.
+dictionary.set(ustr__ZSebp(), last_frame->context.ebp);
+dictionary.set(ustr__ZSesp(), last_frame->context.esp);
+// Provide constants from the debug info for last_frame and its callee.
+// .cbCalleeParams is a Breakpad extension that allows us to use the
+// PostfixEvaluator engine when certain types of debugging information
+// are present without having to write the constants into the program
+// string as literals.
+dictionary.set(ustr__ZDcbCalleeParams(), last_frame_callee_parameter_size);
+dictionary.set(ustr__ZDcbSavedRegs(), last_frame_info->saved_register_size);
+dictionary.set(ustr__ZDcbLocals(), last_frame_info->local_size);
+uint32_t raSearchStart = last_frame->context.esp +
+last_frame_callee_parameter_size +
+last_frame_info->local_size +
+last_frame_info->saved_register_size;
+uint32_t raSearchStartOld = raSearchStart;
+uint32_t found = 0;  // dummy value
+// Scan up to three words above the calculated search value, in case
+// the stack was aligned to a quadword boundary.
+if (ScanForReturnAddress(raSearchStart, &raSearchStart, &found, 3) &&
+last_frame->trust == StackFrame::FRAME_TRUST_CONTEXT &&
+last_frame->windows_frame_info != NULL &&
+last_frame_info->type_ == WindowsFrameInfo::STACK_INFO_FPO &&
+raSearchStartOld == raSearchStart &&
+found == last_frame->context.eip) {
+// The context frame represents an FPO-optimized Windows system call.
+// On the top of the stack we have a pointer to the current instruction.
+// This means that the callee has returned but the return address is still
+// on the top of the stack which is very atypical situaltion.
+// Skip one slot from the stack and do another scan in order to get the
+// actual return address.
+raSearchStart += 4;
+ScanForReturnAddress(raSearchStart, &raSearchStart, &found, 3);
+}
+// The difference between raSearch and raSearchStart is unknown,
+// but making them the same seems to work well in practice.
+dictionary.set(ustr__ZDraSearchStart(), raSearchStart);
+dictionary.set(ustr__ZDraSearch(), raSearchStart);
+dictionary.set(ustr__ZDcbParams(), last_frame_info->parameter_size);
+// Decide what type of program string to use. The program string is in
+// postfix notation and will be passed to PostfixEvaluator::Evaluate.
+// Given the dictionary and the program string, it is possible to compute
+// the return address and the values of other registers in the calling
+// function. Because of bugs described below, the stack may need to be
+// scanned for these values. The results of program string evaluation
+// will be used to determine whether to scan for better values.
+string program_string;
+bool recover_ebp = true;
+trust = StackFrame::FRAME_TRUST_CFI;
+if (!last_frame_info->program_string.empty()) {
+// The FPO data has its own program string, which will tell us how to
+// get to the caller frame, and may even fill in the values of
+// nonvolatile registers and provide pointers to local variables and
+// parameters.  In some cases, particularly with program strings that use
+// .raSearchStart, the stack may need to be scanned afterward.
+program_string = last_frame_info->program_string;
+} else if (last_frame_info->allocates_base_pointer) {
+// The function corresponding to the last frame doesn't use the frame
+// pointer for conventional purposes, but it does allocate a new
+// frame pointer and use it for its own purposes.  Its callee's
+// information is still accessed relative to %esp, and the previous
+// value of %ebp can be recovered from a location in its stack frame,
+// within the saved-register area.
+//
+// Functions that fall into this category use the %ebp register for
+// a purpose other than the frame pointer.  They restore the caller's
+// %ebp before returning.  These functions create their stack frame
+// after a CALL by decrementing the stack pointer in an amount
+// sufficient to store local variables, and then PUSHing saved
+// registers onto the stack.  Arguments to a callee function, if any,
+// are PUSHed after that.  Walking up to the caller, therefore,
+// can be done solely with calculations relative to the stack pointer
+// (%esp).  The return address is recovered from the memory location
+// above the known sizes of the callee's parameters, saved registers,
+// and locals.  The caller's stack pointer (the value of %esp when
+// the caller executed CALL) is the location immediately above the
+// saved return address.  The saved value of %ebp to be restored for
+// the caller is at a known location in the saved-register area of
+// the stack frame.
+//
+// For this type of frame, MSVC 14 (from Visual Studio 8/2005) in
+// link-time code generation mode (/LTCG and /GL) can generate erroneous
+// debugging data.  The reported size of saved registers can be 0,
+// which is clearly an error because these frames must, at the very
+// least, save %ebp.  For this reason, in addition to those given above
+// about the use of .raSearchStart, the stack may need to be scanned
+// for a better return address and a better frame pointer after the
+// program string is evaluated.
+//
+// %eip_new = *(%esp_old + callee_params + saved_regs + locals)
+// %ebp_new = *(%esp_old + callee_params + saved_regs - 8)
+// %esp_new = %esp_old + callee_params + saved_regs + locals + 4
+program_string = "$eip .raSearchStart ^ = "
+"$ebp $esp .cbCalleeParams + .cbSavedRegs + 8 - ^ = "
+"$esp .raSearchStart 4 + =";
+} else {
+// The function corresponding to the last frame doesn't use %ebp at
+// all.  The callee frame is located relative to %esp.
+//
+// The called procedure's instruction pointer and stack pointer are
+// recovered in the same way as the case above, except that no
+// frame pointer (%ebp) is used at all, so it is not saved anywhere
+// in the callee's stack frame and does not need to be recovered.
+// Because %ebp wasn't used in the callee, whatever value it has
+// is the value that it had in the caller, so it can be carried
+// straight through without bringing its validity into question.
+//
+// Because of the use of .raSearchStart, the stack will possibly be
+// examined to locate a better return address after program string
+// evaluation.  The stack will not be examined to locate a saved
+// %ebp value, because these frames do not save (or use) %ebp.
+//
+// %eip_new = *(%esp_old + callee_params + saved_regs + locals)
+// %esp_new = %esp_old + callee_params + saved_regs + locals + 4
+// %ebp_new = %ebp_old
+program_string = "$eip .raSearchStart ^ = "
+"$esp .raSearchStart 4 + =";
+recover_ebp = false;
+}
+// Now crank it out, making sure that the program string set at least the
+// two required variables.
+PostfixEvaluator<uint32_t> evaluator =
+PostfixEvaluator<uint32_t>(&dictionary, memory_);
+PostfixEvaluator<uint32_t>::DictionaryValidityType dictionary_validity;
+if (!evaluator.Evaluate(program_string, &dictionary_validity) ||
+!dictionary_validity.have(ustr__ZSeip()) ||
+!dictionary_validity.have(ustr__ZSesp())) {
+// Program string evaluation failed. It may be that %eip is not somewhere
+// with stack frame info, and %ebp is pointing to non-stack memory, so
+// our evaluation couldn't succeed. We'll scan the stack for a return
+// address. This can happen if the stack is in a module for which
+// we don't have symbols, and that module is compiled without a
+// frame pointer.
+uint32_t location_start = last_frame->context.esp;
+uint32_t location, eip;
+if (!stack_scan_allowed
+|| !ScanForReturnAddress(location_start, &location, &eip)) {
+// if we can't find an instruction pointer even with stack scanning,
+// give up.
+return NULL;
+}
+// This seems like a reasonable return address. Since program string
+// evaluation failed, use it and set %esp to the location above the
+// one where the return address was found.
+dictionary.set(ustr__ZSeip(), eip);
+dictionary.set(ustr__ZSesp(), location + 4);
+trust = StackFrame::FRAME_TRUST_SCAN;
+}
+// Since this stack frame did not use %ebp in a traditional way,
+// locating the return address isn't entirely deterministic. In that
+// case, the stack can be scanned to locate the return address.
+//
+// However, if program string evaluation resulted in both %eip and
+// %ebp values of 0, trust that the end of the stack has been
+// reached and don't scan for anything else.
+if (dictionary.get(ustr__ZSeip()) != 0 ||
+dictionary.get(ustr__ZSebp()) != 0) {
+int offset = 0;
+// This scan can only be done if a CodeModules object is available, to
+// check that candidate return addresses are in fact inside a module.
+//
+// TODO(mmentovai): This ignores dynamically-generated code.  One possible
+// solution is to check the minidump's memory map to see if the candidate
+// %eip value comes from a mapped executable page, although this would
+// require dumps that contain MINIDUMP_MEMORY_INFO, which the Breakpad
+// client doesn't currently write (it would need to call MiniDumpWriteDump
+// with the MiniDumpWithFullMemoryInfo type bit set).  Even given this
+// ability, older OSes (pre-XP SP2) and CPUs (pre-P4) don't enforce
+// an independent execute privilege on memory pages.
+uint32_t eip = dictionary.get(ustr__ZSeip());
+if (modules_ && !modules_->GetModuleForAddress(eip)) {
+// The instruction pointer at .raSearchStart was invalid, so start
+// looking one 32-bit word above that location.
+uint32_t location_start = dictionary.get(ustr__ZDraSearchStart()) + 4;
+uint32_t location;
+if (stack_scan_allowed
+&& ScanForReturnAddress(location_start, &location, &eip)) {
+// This is a better return address that what program string
+// evaluation found.  Use it, and set %esp to the location above the
+// one where the return address was found.
+dictionary.set(ustr__ZSeip(), eip);
+dictionary.set(ustr__ZSesp(), location + 4);
+offset = location - location_start;
+trust = StackFrame::FRAME_TRUST_CFI_SCAN;
+}
+}
+if (recover_ebp) {
+// When trying to recover the previous value of the frame pointer (%ebp),
+// start looking at the lowest possible address in the saved-register
+// area, and look at the entire saved register area, increased by the
+// size of |offset| to account for additional data that may be on the
+// stack.  The scan is performed from the highest possible address to
+// the lowest, because the expectation is that the function's prolog
+// would have saved %ebp early.
+uint32_t ebp = dictionary.get(ustr__ZSebp());
+// When a scan for return address is used, it is possible to skip one or
+// more frames (when return address is not in a known module).  One
+// indication for skipped frames is when the value of %ebp is lower than
+// the location of the return address on the stack
+bool has_skipped_frames =
+(trust != StackFrame::FRAME_TRUST_CFI && ebp <= raSearchStart + offset);
+uint32_t value;  // throwaway variable to check pointer validity
+if (has_skipped_frames || !memory_->GetMemoryAtAddress(ebp, &value)) {
+int fp_search_bytes = last_frame_info->saved_register_size + offset;
+uint32_t location_end = last_frame->context.esp +
+last_frame_callee_parameter_size;
+for (uint32_t location = location_end + fp_search_bytes;
+location >= location_end;
+location -= 4) {
+if (!memory_->GetMemoryAtAddress(location, &ebp))
+break;
+if (memory_->GetMemoryAtAddress(ebp, &value)) {
+// The candidate value is a pointer to the same memory region
+// (the stack).  Prefer it as a recovered %ebp result.
+dictionary.set(ustr__ZSebp(), ebp);
+break;
+}
+}
+}
+}
+}
+// Create a new stack frame (ownership will be transferred to the caller)
+// and fill it in.
+StackFrameX86* frame = new StackFrameX86();
+frame->trust = trust;
+frame->context = last_frame->context;
+frame->context.eip = dictionary.get(ustr__ZSeip());
+frame->context.esp = dictionary.get(ustr__ZSesp());
+frame->context.ebp = dictionary.get(ustr__ZSebp());
+frame->context_validity = StackFrameX86::CONTEXT_VALID_EIP |
+StackFrameX86::CONTEXT_VALID_ESP |
+StackFrameX86::CONTEXT_VALID_EBP;
+// These are nonvolatile (callee-save) registers, and the program string
+// may have filled them in.
+if (dictionary_validity.have(ustr__ZSebx())) {
+frame->context.ebx = dictionary.get(ustr__ZSebx());
+frame->context_validity |= StackFrameX86::CONTEXT_VALID_EBX;
+}
+if (dictionary_validity.have(ustr__ZSesi())) {
+frame->context.esi = dictionary.get(ustr__ZSesi());
+frame->context_validity |= StackFrameX86::CONTEXT_VALID_ESI;
+}
+if (dictionary_validity.have(ustr__ZSedi())) {
+frame->context.edi = dictionary.get(ustr__ZSedi());
+frame->context_validity |= StackFrameX86::CONTEXT_VALID_EDI;
+}
+return frame;
+}
+StackFrameX86* StackwalkerX86::GetCallerByCFIFrameInfo(
+const vector<StackFrame*> &frames,
+CFIFrameInfo* cfi_frame_info) {
+StackFrameX86* last_frame = static_cast<StackFrameX86*>(frames.back());
+last_frame->cfi_frame_info = cfi_frame_info;
+scoped_ptr<StackFrameX86> frame(new StackFrameX86());
+if (!cfi_walker_
+.FindCallerRegisters(*memory_, *cfi_frame_info,
+last_frame->context, last_frame->context_validity,
+&frame->context, &frame->context_validity))
+return NULL;
+// Make sure we recovered all the essentials.
+static const int essentials = (StackFrameX86::CONTEXT_VALID_EIP
+| StackFrameX86::CONTEXT_VALID_ESP
+| StackFrameX86::CONTEXT_VALID_EBP);
+if ((frame->context_validity & essentials) != essentials)
+return NULL;
+frame->trust = StackFrame::FRAME_TRUST_CFI;
+return frame.release();
+}
+StackFrameX86* StackwalkerX86::GetCallerByEBPAtBase(
+const vector<StackFrame*> &frames,
+bool stack_scan_allowed) {
+StackFrame::FrameTrust trust;
+StackFrameX86* last_frame = static_cast<StackFrameX86*>(frames.back());
+uint32_t last_esp = last_frame->context.esp;
+uint32_t last_ebp = last_frame->context.ebp;
+// Assume that the standard %ebp-using x86 calling convention is in
+// use.
+//
+// The typical x86 calling convention, when frame pointers are present,
+// is for the calling procedure to use CALL, which pushes the return
+// address onto the stack and sets the instruction pointer (%eip) to
+// the entry point of the called routine.  The called routine then
+// PUSHes the calling routine's frame pointer (%ebp) onto the stack
+// before copying the stack pointer (%esp) to the frame pointer (%ebp).
+// Therefore, the calling procedure's frame pointer is always available
+// by dereferencing the called procedure's frame pointer, and the return
+// address is always available at the memory location immediately above
+// the address pointed to by the called procedure's frame pointer.  The
+// calling procedure's stack pointer (%esp) is 8 higher than the value
+// of the called procedure's frame pointer at the time the calling
+// procedure made the CALL: 4 bytes for the return address pushed by the
+// CALL itself, and 4 bytes for the callee's PUSH of the caller's frame
+// pointer.
+//
+// %eip_new = *(%ebp_old + 4)
+// %esp_new = %ebp_old + 8
+// %ebp_new = *(%ebp_old)
+uint32_t caller_eip, caller_esp, caller_ebp;
+if (memory_->GetMemoryAtAddress(last_ebp + 4, &caller_eip) &&
+memory_->GetMemoryAtAddress(last_ebp, &caller_ebp)) {
+caller_esp = last_ebp + 8;
+trust = StackFrame::FRAME_TRUST_FP;
+} else {
+// We couldn't read the memory %ebp refers to. It may be that %ebp
+// is pointing to non-stack memory. We'll scan the stack for a
+// return address. This can happen if last_frame is executing code
+// for a module for which we don't have symbols, and that module
+// is compiled without a frame pointer.
+if (!stack_scan_allowed
+|| !ScanForReturnAddress(last_esp, &caller_esp, &caller_eip)) {
+// if we can't find an instruction pointer even with stack scanning,
+// give up.
+return NULL;
+}
+// ScanForReturnAddress found a reasonable return address. Advance
+// %esp to the location above the one where the return address was
+// found. Assume that %ebp is unchanged.
+caller_esp += 4;
+caller_ebp = last_ebp;
+trust = StackFrame::FRAME_TRUST_SCAN;
+}
+// Create a new stack frame (ownership will be transferred to the caller)
+// and fill it in.
+StackFrameX86* frame = new StackFrameX86();
+frame->trust = trust;
+frame->context = last_frame->context;
+frame->context.eip = caller_eip;
+frame->context.esp = caller_esp;
+frame->context.ebp = caller_ebp;
+frame->context_validity = StackFrameX86::CONTEXT_VALID_EIP |
+StackFrameX86::CONTEXT_VALID_ESP |
+StackFrameX86::CONTEXT_VALID_EBP;
+return frame;
+}
+StackFrame* StackwalkerX86::GetCallerFrame(const CallStack* stack,
+bool stack_scan_allowed) {
+if (!memory_ || !stack) {
+BPLOG(ERROR) << "Can't get caller frame without memory or stack";
+return NULL;
+}
+const vector<StackFrame*> &frames = *stack->frames();
+StackFrameX86* last_frame = static_cast<StackFrameX86*>(frames.back());
+scoped_ptr<StackFrameX86> new_frame;
+// If the resolver has Windows stack walking information, use that.
+WindowsFrameInfo* windows_frame_info
+= frame_symbolizer_->FindWindowsFrameInfo(last_frame);
+if (windows_frame_info)
+new_frame.reset(GetCallerByWindowsFrameInfo(frames, windows_frame_info,
+stack_scan_allowed));
+// If the resolver has DWARF CFI information, use that.
+if (!new_frame.get()) {
+CFIFrameInfo* cfi_frame_info =
+frame_symbolizer_->FindCFIFrameInfo(last_frame);
+if (cfi_frame_info)
+new_frame.reset(GetCallerByCFIFrameInfo(frames, cfi_frame_info));
+}
+// Otherwise, hope that the program was using a traditional frame structure.
+if (!new_frame.get())
+new_frame.reset(GetCallerByEBPAtBase(frames, stack_scan_allowed));
+// If nothing worked, tell the caller.
+if (!new_frame.get())
+return NULL;
+// Treat an instruction address of 0 as end-of-stack.
+if (new_frame->context.eip == 0)
+return NULL;
+// If the new stack pointer is at a lower address than the old, then
+// that's clearly incorrect. Treat this as end-of-stack to enforce
+// progress and avoid infinite loops.
+if (new_frame->context.esp <= last_frame->context.esp)
+return NULL;
+// new_frame->context.eip is the return address, which is the instruction
+// after the CALL that caused us to arrive at the callee. Set
+// new_frame->instruction to one less than that, so it points within the
+// CALL instruction. See StackFrame::instruction for details, and
+// StackFrameAMD64::ReturnAddress.
+new_frame->instruction = new_frame->context.eip - 1;
+return new_frame.release();
+}
+}  // namespace google_breakpad

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comparison: toolkit/crashreporter/google-breakpad/src/processor/stackwalker_x86.cc

toolkit/crashreporter/google-breakpad/src/processor/stackwalker_x86.cc