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Breakpad processor: Segregate STACK WIN vs. traditional stack walking.

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This patch moves the code for finding caller frames using STACK WIN
data and the code to do so using the traditional frame layout (%ebp
points at saved %ebp, pushed just after return address) into their own
functions. In addition to making things a little clearer, this is
preparation for adding support for STACK CFI records into the mix.

a=jimblandy, r=mmentovai


git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@512 4c0a9323-5329-0410-9bdc-e9ce6186880e
This commit is contained in:
jimblandy 2010-02-05 18:04:56 +00:00
parent 89e07bf2c7
commit 7f1455601d
2 changed files with 245 additions and 169 deletions
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243
src/processor/stackwalker_x86.cc
View file

@ -36,13 +36,14 @@
#include "processor/postfix_evaluator-inl.h"
#include "processor/stackwalker_x86.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/stack_frame_cpu.h"
#include "google_breakpad/processor/source_line_resolver_interface.h"
#include "google_breakpad/processor/stack_frame_cpu.h"
#include "processor/logging.h"
#include "processor/scoped_ptr.h"
#include "processor/stackwalker_x86.h"
#include "processor/windows_frame_info.h"
namespace google_breakpad {
@ -90,23 +91,23 @@ StackFrame* StackwalkerX86::GetContextFrame() {
return frame;
}
StackFrame* StackwalkerX86::GetCallerFrame(const CallStack *stack) {
if (!memory_ || !stack) {
BPLOG(ERROR) << "Can't get caller frame without memory or stack";
return NULL;
}
StackFrameX86 *StackwalkerX86::GetCallerByWindowsFrameInfo(
const vector<StackFrame *> &frames,
WindowsFrameInfo *last_frame_info) {
StackFrameX86::FrameTrust trust = StackFrameX86::FRAME_TRUST_NONE;
StackFrameX86 *last_frame = static_cast<StackFrameX86*>(
stack->frames()->back());
WindowsFrameInfo *last_frame_info
= resolver_->FindWindowsFrameInfo(last_frame);
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
@ -139,12 +140,11 @@ StackFrame* StackwalkerX86::GetCallerFrame(const CallStack *stack) {
// 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.
int frames_already_walked = stack->frames()->size();
u_int32_t last_frame_callee_parameter_size = 0;
int frames_already_walked = frames.size();
if (frames_already_walked >= 2) {
StackFrameX86 *last_frame_callee
= static_cast<StackFrameX86 *>((*stack->frames())
[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 &&
@ -157,46 +157,35 @@ StackFrame* StackwalkerX86::GetCallerFrame(const CallStack *stack) {
// 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. .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.
// here.
PostfixEvaluator<u_int32_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;
if (last_frame_info && last_frame_info->valid == WindowsFrameInfo::VALID_ALL) {
// FPO debugging data is available. Initialize constants.
dictionary[".cbSavedRegs"] = last_frame_info->saved_register_size;
dictionary[".cbLocals"] = last_frame_info->local_size;
dictionary[".raSearchStart"] = last_frame->context.esp +
last_frame_callee_parameter_size +
last_frame_info->local_size +
last_frame_info->saved_register_size;
}
if (last_frame_info &&
last_frame_info->valid & WindowsFrameInfo::VALID_PARAMETER_SIZE) {
// This is treated separately because it can either come from FPO data or
// from other debugging data.
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. When encountering a nontraditional frame (one which takes
// advantage of FPO), the stack may need to be scanned for these values.
// For traditional frames, simple deterministic dereferencing suffices
// without any need for scanning. The results of program string evaluation
// 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 traditional_frame = true;
bool recover_ebp = true;
if (last_frame_info && last_frame_info->valid == WindowsFrameInfo::VALID_ALL) {
// FPO data available.
traditional_frame = false;
trust = StackFrameX86::FRAME_TRUST_CFI;
if (!last_frame_info->program_string.empty()) {
// The FPO data has its own program string, which will tell us how to
@ -268,38 +257,6 @@ StackFrame* StackwalkerX86::GetCallerFrame(const CallStack *stack) {
"$esp .raSearchStart 4 + =";
recover_ebp = false;
}
} else {
// No FPO information is available for the last frame. Assume that the
// standard %ebp-using x86 calling convention is in use.
//
// The typical x86 calling convention, when frame pointers are present,
// is for the calling procedure to use CALL, which pushes the return
// address onto the stack and sets the instruction pointer (%eip) to
// the entry point of the called routine. The called routine then
// PUSHes the calling routine's frame pointer (%ebp) onto the stack
// before copying the stack pointer (%esp) to the frame pointer (%ebp).
// Therefore, the calling procedure's frame pointer is always available
// by dereferencing the called procedure's frame pointer, and the return
// address is always available at the memory location immediately above
// the address pointed to by the called procedure's frame pointer. The
// calling procedure's stack pointer (%esp) is 8 higher than the value
// of the called procedure's frame pointer at the time the calling
// procedure made the CALL: 4 bytes for the return address pushed by the
// CALL itself, and 4 bytes for the callee's PUSH of the caller's frame
// pointer.
//
// Instruction and frame pointer recovery for these traditional frames is
// entirely deterministic, and the stack will not be scanned after
// recovering these values.
//
// %eip_new = *(%ebp_old + 4)
// %esp_new = %ebp_old + 8
// %ebp_new = *(%ebp_old)
trust = StackFrameX86::FRAME_TRUST_FP;
program_string = "$eip $ebp 4 + ^ = "
"$esp $ebp 8 + = "
"$ebp $ebp ^ =";
}
// Now crank it out, making sure that the program string set at least the
// two required variables.
@ -331,15 +288,14 @@ StackFrame* StackwalkerX86::GetCallerFrame(const CallStack *stack) {
trust = StackFrameX86::FRAME_TRUST_SCAN;
}
// If this stack frame did not use %ebp in a traditional way, locating the
// return address isn't entirely deterministic. In that case, the stack
// can be scanned to locate the return address.
// Since this stack frame did not use %ebp in a traditional way,
// locating the return address isn't entirely deterministic. In that
// case, the stack can be scanned to locate the return address.
//
// Even in nontraditional frames, if program string evaluation resulted in
// both %eip and %ebp values of 0, trust that the end of the stack has been
// However, if program string evaluation resulted in both %eip and
// %ebp values of 0, trust that the end of the stack has been
// reached and don't scan for anything else.
if (!traditional_frame &&
(dictionary["$eip"] != 0 || dictionary["$ebp"] != 0)) {
if (dictionary["$eip"] != 0 || dictionary["$ebp"] != 0) {
int offset = 0;
// This scan can only be done if a CodeModules object is available, to
@ -401,13 +357,6 @@ StackFrame* StackwalkerX86::GetCallerFrame(const CallStack *stack) {
}
}
// Treat an instruction address of 0 as end-of-stack. Treat incorrect stack
// direction as end-of-stack to enforce progress and avoid infinite loops.
if (dictionary["$eip"] == 0 ||
dictionary["$esp"] <= last_frame->context.esp) {
return NULL;
}
// Create a new stack frame (ownership will be transferred to the caller)
// and fill it in.
StackFrameX86 *frame = new StackFrameX86();
@ -436,19 +385,129 @@ StackFrame* StackwalkerX86::GetCallerFrame(const CallStack *stack) {
frame->context_validity |= StackFrameX86::CONTEXT_VALID_EDI;
}
// frame->context.eip is the return address, which is one instruction
// past the CALL that caused us to arrive at the callee. Set
// frame->instruction to one less than that. This won't reference the
// beginning of the CALL instruction, but it's guaranteed to be within the
// CALL, which is sufficient to get the source line information to match up
// with the line that contains a function call. Callers that require the
// exact return address value may access the context.eip field of
// StackFrameX86.
frame->instruction = frame->context.eip - 1;
return frame;
}
StackFrameX86 *StackwalkerX86::GetCallerByEBPAtBase(
const vector<StackFrame *> &frames) {
StackFrameX86::FrameTrust trust;
StackFrameX86 *last_frame = static_cast<StackFrameX86 *>(frames.back());
u_int32_t last_esp = last_frame->context.esp;
u_int32_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)
u_int32_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 = StackFrameX86::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 (!ScanForReturnAddress(last_esp, &caller_esp, &caller_eip)) {
// if we can't find an instruction pointer even with stack scanning,
// give up.
return false;
}
// 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 = StackFrameX86::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) {
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 we have Windows stack walking information, use that.
WindowsFrameInfo *windows_frame_info
= resolver_->FindWindowsFrameInfo(last_frame);
if (windows_frame_info)
new_frame.reset(GetCallerByWindowsFrameInfo(frames, windows_frame_info));
// Otherwise, hope that we're using a traditional frame structure.
if (!new_frame.get())
new_frame.reset(GetCallerByEBPAtBase(frames));
// 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 one instruction
// past the CALL that caused us to arrive at the callee. Set
// new_frame->instruction to one less than that. This won't reference the
// beginning of the CALL instruction, but it's guaranteed to be within
// the CALL, which is sufficient to get the source line information to
// match up with the line that contains a function call. Callers that
// require the exact return address value may access the context.eip
// field of StackFrameX86.
new_frame->instruction = new_frame->context.eip - 1;
return new_frame.release();
}
bool StackwalkerX86::ScanForReturnAddress(u_int32_t location_start,
u_int32_t *location_found,
u_int32_t *eip_found) {

17
src/processor/stackwalker_x86.h
View file

@ -1,3 +1,5 @@
// -*- mode: c++ -*-
// Copyright (c) 2006, Google Inc.
// All rights reserved.
//
@ -42,6 +44,7 @@
#include "google_breakpad/common/breakpad_types.h"
#include "google_breakpad/common/minidump_format.h"
#include "google_breakpad/processor/stackwalker.h"
#include "google_breakpad/processor/stack_frame_cpu.h"
namespace google_breakpad {
@ -69,6 +72,20 @@ class StackwalkerX86 : public Stackwalker {
virtual StackFrame *GetContextFrame();
virtual StackFrame *GetCallerFrame(const CallStack *stack);
// Use windows_frame_info (derived from STACK WIN and FUNC records)
// to construct the frame that called frames.back(). The caller
// takes ownership of the returned frame. Return NULL on failure.
StackFrameX86 *GetCallerByWindowsFrameInfo(
const vector<StackFrame*> &frames,
WindowsFrameInfo *windows_frame_info);
// Assuming a traditional frame layout --- where the caller's %ebp
// has been pushed just after the return address and the callee's
// %ebp points to the saved %ebp --- construct the frame that called
// frames.back(). The caller takes ownership of the returned frame.
// Return NULL on failure.
StackFrameX86 *GetCallerByEBPAtBase(const vector<StackFrame*> &frames);
// Scan the stack starting at location_start, looking for an address
// that looks like a valid instruction pointer. Addresses must
// 1) be contained in the current stack memory