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

toolkit/crashreporter/google-breakpad/src/processor/stackwalker_x86.cc@6474c204b198 (annotated)

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

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 // 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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toolkit/crashreporter/google-breakpad/src/processor/stackwalker_x86.cc@6474c204b198 (annotated)

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