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Diffstat (limited to 'toolkit/crashreporter/google-breakpad/src/processor/stackwalker_x86.cc')
| -rw-r--r-- | toolkit/crashreporter/google-breakpad/src/processor/stackwalker_x86.cc | 672 |
1 files changed, 0 insertions, 672 deletions
diff --git a/toolkit/crashreporter/google-breakpad/src/processor/stackwalker_x86.cc b/toolkit/crashreporter/google-breakpad/src/processor/stackwalker_x86.cc deleted file mode 100644 index 29d98e4b8..000000000 --- a/toolkit/crashreporter/google-breakpad/src/processor/stackwalker_x86.cc +++ /dev/null @@ -1,672 +0,0 @@ -// 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 "processor/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 { - -// Max reasonable size for a single x86 frame is 128 KB. This value is used in -// a heuristic for recovering of the EBP chain after a scan for return address. -// This value is based on a stack frame size histogram built for a set of -// popular third party libraries which suggests that 99.5% of all frames are -// smaller than 128 KB. -static const uint32_t kMaxReasonableGapBetweenFrames = 128 * 1024; - -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 $esp. - { "$eip", ".ra", false, - StackFrameX86::CONTEXT_VALID_EIP, &MDRawContextX86::eip }, - { "$esp", ".cfa", false, - StackFrameX86::CONTEXT_VALID_ESP, &MDRawContextX86::esp }, - { "$ebp", NULL, true, - StackFrameX86::CONTEXT_VALID_EBP, &MDRawContextX86::ebp }, - { "$eax", NULL, false, - StackFrameX86::CONTEXT_VALID_EAX, &MDRawContextX86::eax }, - { "$ebx", NULL, true, - StackFrameX86::CONTEXT_VALID_EBX, &MDRawContextX86::ebx }, - { "$ecx", NULL, false, - StackFrameX86::CONTEXT_VALID_ECX, &MDRawContextX86::ecx }, - { "$edx", NULL, false, - StackFrameX86::CONTEXT_VALID_EDX, &MDRawContextX86::edx }, - { "$esi", NULL, true, - StackFrameX86::CONTEXT_VALID_ESI, &MDRawContextX86::esi }, - { "$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["$ebp"] = last_frame->context.ebp; - dictionary["$esp"] = 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[".cbCalleeParams"] = last_frame_callee_parameter_size; - dictionary[".cbSavedRegs"] = last_frame_info->saved_register_size; - dictionary[".cbLocals"] = 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. - // - // TODO(ivan.penkov): Consider cleaning up the scan for return address that - // follows. The purpose of this scan is to adjust the .raSearchStart - // calculation (which is based on register %esp) in the cases where register - // %esp may have been aligned (up to a quadword). There are two problems - // with this approach: - // 1) In practice, 64 byte boundary alignment is seen which clearly can not - // be handled by a three word scan. - // 2) A search for a return address is "guesswork" by definition because - // the results will be different depending on what is left on the stack - // from previous executions. - // So, basically, the results from this scan should be ignored if other means - // for calculation of the value of .raSearchStart are available. - 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); - } - - dictionary[".cbParams"] = 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; - } - - // Check for alignment operators in the program string. If alignment - // operators are found, then current %ebp must be valid and it is the only - // reliable data point that can be used for getting to the previous frame. - // E.g. the .raSearchStart calculation (above) is based on %esp and since - // %esp was aligned in the current frame (which is a lossy operation) the - // calculated value of .raSearchStart cannot be correct and should not be - // used. Instead .raSearchStart must be calculated based on %ebp. - // The code that follows assumes that .raSearchStart is supposed to point - // at the saved return address (ebp + 4). - // For some more details on this topic, take a look at the following thread: - // https://groups.google.com/forum/#!topic/google-breakpad-dev/ZP1FA9B1JjM - if ((StackFrameX86::CONTEXT_VALID_EBP & last_frame->context_validity) != 0 && - program_string.find('@') != string::npos) { - raSearchStart = last_frame->context.ebp + 4; - } - - // The difference between raSearch and raSearchStart is unknown, - // but making them the same seems to work well in practice. - dictionary[".raSearchStart"] = raSearchStart; - dictionary[".raSearch"] = raSearchStart; - - // 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.find("$eip") == dictionary_validity.end() || - dictionary_validity.find("$esp") == dictionary_validity.end()) { - // 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, - frames.size() == 1 /* is_context_frame */)) { - // 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["$eip"] = eip; - dictionary["$esp"] = 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["$eip"] != 0 || dictionary["$ebp"] != 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["$eip"]; - if (modules_ && !modules_->GetModuleForAddress(eip)) { - // The instruction pointer at .raSearchStart was invalid, so start - // looking one 32-bit word above that location. - uint32_t location_start = dictionary[".raSearchStart"] + 4; - uint32_t location; - if (stack_scan_allowed - && ScanForReturnAddress(location_start, &location, &eip, - frames.size() == 1 /* is_context_frame */)) { - // This is a better return address that what program string - // evaluation found. Use it, and set %esp to the location above the - // one where the return address was found. - dictionary["$eip"] = eip; - dictionary["$esp"] = location + 4; - offset = location - location_start; - trust = StackFrame::FRAME_TRUST_CFI_SCAN; - } - } - - if (recover_ebp) { - // When trying to recover the previous value of the frame pointer (%ebp), - // start looking at the lowest possible address in the saved-register - // area, and look at the entire saved register area, increased by the - // size of |offset| to account for additional data that may be on the - // stack. The scan is performed from the highest possible address to - // the lowest, because the expectation is that the function's prolog - // would have saved %ebp early. - uint32_t ebp = dictionary["$ebp"]; - - // 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["$ebp"] = ebp; - break; - } - } - } - } - } - - // Create a new stack frame (ownership will be transferred to the caller) - // and fill it in. - StackFrameX86* frame = new StackFrameX86(); - - frame->trust = trust; - frame->context = last_frame->context; - frame->context.eip = dictionary["$eip"]; - frame->context.esp = dictionary["$esp"]; - frame->context.ebp = dictionary["$ebp"]; - 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.find("$ebx") != dictionary_validity.end()) { - frame->context.ebx = dictionary["$ebx"]; - frame->context_validity |= StackFrameX86::CONTEXT_VALID_EBX; - } - if (dictionary_validity.find("$esi") != dictionary_validity.end()) { - frame->context.esi = dictionary["$esi"]; - frame->context_validity |= StackFrameX86::CONTEXT_VALID_ESI; - } - if (dictionary_validity.find("$edi") != dictionary_validity.end()) { - frame->context.edi = dictionary["$edi"]; - 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, - frames.size() == 1 /* is_context_frame */)) { - // 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 immediately above the one where the return address was - // found. - caller_esp += 4; - // Try to restore the %ebp chain. The caller %ebp should be stored at a - // location immediately below the one where the return address was found. - // A valid caller %ebp must be greater than the address where it is stored - // and the gap between the two adjacent frames should be reasonable. - uint32_t restored_ebp_chain = caller_esp - 8; - if (!memory_->GetMemoryAtAddress(restored_ebp_chain, &caller_ebp) || - caller_ebp <= restored_ebp_chain || - caller_ebp - restored_ebp_chain > kMaxReasonableGapBetweenFrames) { - // The restored %ebp chain doesn't appear to be valid. - // Assume that %ebp is unchanged. - 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 |