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Use register %ebp (instead of %esp) when calculating the value of

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.raSearchStart in the cases where there are alignment operators in
the program string.

If alignment operators are found in the program string, the current
value of %ebp must be valid and it is the only reliable data point
that can be used for getting to the previous frame.  Previously, the
.raSearchStart calculation was based on %esp and when %esp is aligned
in the current frame (which is a lossy operation) the resulting
.raSearchStart cannot was incorrect.  There is code that is trying to
work around this problem (scanning of up to 3 words for a return
address) which is unreliable and it doesn't work in many cases (e.g.
when the alignment is on a 64-byte boundary).

This fix is already deployed in Google and it was measured to reduce
the number of wrong stack traces (for Windows crashes) by 45%. No
regressions have been found so far.

Here is an example of an issue that was fixed by this change (where
register %esp is aligned on the 64-byte boundary and the workarounds
that we already had didn't work):

https://code.google.com/p/chromium/issues/detail?id=311359

0:013> uf chrome_59630000!base::MessagePumpForIO::DoRunLoop
  518 59685c39 55      push    ebp
  518 59685c3a 8bec    mov     ebp,esp
  518 59685c3c 83e4c0  and     esp,0FFFFFFC0h  <== 64-byte boundary
  518 59685c3f 83ec34  sub     esp,34h
  518 59685c42 53      push    ebx
  518 59685c43 56      push    esi

Program string contains 64-byte alignment:
$T1 .raSearch = $T0 $T1 4 - 64 @ = $ebp $T1 4 - ^ = $eip $T1 ^ = 
$esp $T1 4 + = $20 $T0 56 - ^ =  $23 $T0 60 - ^ =  $24 $T0 64 - ^ =
Review URL: https://breakpad.appspot.com/694002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1232 4c0a9323-5329-0410-9bdc-e9ce6186880e
This commit is contained in:
ivan.penkov@gmail.com 2013-11-05 23:50:49 +00:00
parent c7a1674f16
commit fd9f3d8b17
2 changed files with 245 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
src/processor/stackwalker_x86.cc
View File

@ -225,6 +225,19 @@ StackFrameX86* StackwalkerX86::GetCallerByWindowsFrameInfo(
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 &&
@ -241,11 +254,6 @@ StackFrameX86* StackwalkerX86::GetCallerByWindowsFrameInfo(
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[".raSearchStart"] = raSearchStart;
dictionary[".raSearch"] = raSearchStart;
dictionary[".cbParams"] = last_frame_info->parameter_size;
// Decide what type of program string to use. The program string is in
@ -330,6 +338,27 @@ StackFrameX86* StackwalkerX86::GetCallerByWindowsFrameInfo(
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 =

213
src/processor/stackwalker_x86_unittest.cc
View File

@ -565,15 +565,18 @@ TEST_F(GetCallerFrame, WindowsFrameDataAligned) {
" $ebp $T1 4 - ^ ="
" $eip $T1 ^ ="
" $esp $T1 4 + =");
Label frame0_esp, frame0_ebp;
Label frame1_esp, frame1_ebp;
stack_section.start() = 0x80000000;
stack_section
// frame 0
.Mark(&frame0_esp)
.D32(0x0ffa0ffa) // unused saved register
.D32(0xdeaddead) // locals
.D32(0xbeefbeef)
.D32(0) // 8-byte alignment
.D32(frame1_ebp)
.Mark(&frame0_ebp)
.D32(frame1_ebp) // saved %ebp
.D32(0x5000129d) // return address
// frame 1
.Mark(&frame1_esp)
@ -584,8 +587,8 @@ TEST_F(GetCallerFrame, WindowsFrameDataAligned) {
RegionFromSection();
raw_context.eip = 0x4000aa85;
raw_context.esp = stack_section.start().Value();
raw_context.ebp = 0xf052c1de; // should not be needed to walk frame
raw_context.esp = frame0_esp.Value();
raw_context.ebp = frame0_ebp.Value();
StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
StackwalkerX86 walker(&system_info, &raw_context, &stack_region, &modules,
@ -606,8 +609,8 @@ TEST_F(GetCallerFrame, WindowsFrameDataAligned) {
ASSERT_EQ(StackFrameX86::CONTEXT_VALID_ALL, frame0->context_validity);
EXPECT_EQ(0x4000aa85U, frame0->instruction);
EXPECT_EQ(0x4000aa85U, frame0->context.eip);
EXPECT_EQ(stack_section.start().Value(), frame0->context.esp);
EXPECT_EQ(0xf052c1deU, frame0->context.ebp);
EXPECT_EQ(frame0_esp.Value(), frame0->context.esp);
EXPECT_EQ(frame0_ebp.Value(), frame0->context.ebp);
EXPECT_TRUE(frame0->windows_frame_info != NULL);
}
@ -1462,6 +1465,206 @@ TEST_F(GetCallerFrame, ReturnAddressIsNotInKnownModule) {
}
}
// Test the .raSearchStart/.raSearch calculation when alignment operators are
// used in the program string. The current %ebp must be valid and it is the
// only reliable data point that can be used for that calculation.
TEST_F(GetCallerFrame, HandleAlignmentInProgramString) {
MockCodeModule chrome_dll(0x59630000, 0x19e3000, "chrome.dll", "version1");
SetModuleSymbols(&chrome_dll, // chrome.dll
"FUNC 56422 50c 8 base::MessageLoop::RunTask"
"(base::PendingTask const &)\n"
"56422 e 458 4589\n"
"STACK WIN 4 56422 50c 11 0 8 c ac 0 1 $T1 .raSearch = $T0 "
"$T1 4 - 8 @ = $ebp $T1 4 - ^ = $eip $T1 ^ = $esp $T1 4 + = "
"$20 $T0 176 - ^ = $23 $T0 180 - ^ = $24 $T0 184 - ^ =\n"
"FUNC 55d34 34a 0 base::MessageLoop::DoWork()\n"
"55d34 11 596 4589\n"
"STACK WIN 4 55d34 34a 19 0 0 c 134 0 1 $T1 .raSearch = "
"$T0 $T1 4 - 8 @ = $ebp $T1 4 - ^ = $eip $T1 ^ = $esp "
"$T1 4 + = $20 $T0 312 - ^ = $23 $T0 316 - ^ = $24 $T0 "
"320 - ^ =\n"
"FUNC 55c39 fb 0 base::MessagePumpForIO::DoRunLoop()\n"
"55c39 d 518 19962\n"
"STACK WIN 4 55c39 fb d 0 0 c 34 0 1 $T1 .raSearch = $T0 "
"$T1 4 - 64 @ = $ebp $T1 4 - ^ = $eip $T1 ^ = $esp $T1 4 + "
"= $20 $T0 56 - ^ = $23 $T0 60 - ^ = $24 $T0 64 - ^ =\n"
"FUNC 55bf0 49 4 base::MessagePumpWin::Run(base::"
"MessagePump::Delegate *)\n"
"55bf0 49 48 4724\n"
"STACK WIN 4 55bf0 49 c 0 4 0 10 0 1 $T0 $ebp = $eip $T0 4 "
"+ ^ = $ebp $T0 ^ = $esp $T0 8 + =\n"
"FUNC 165d de 4 malloc\n"
"165d 6 119 54\n"
"STACK WIN 4 165d de d 0 4 8 0 0 1 $T1 .raSearch = $T0 "
"$T1 4 - 8 @ = $ebp $T1 4 - ^ = $eip $T1 ^ = $esp $T1 4 "
"+ = $23 $T0 4 - ^ = $24 $T0 8 - ^ =\n"
"FUNC 55ac9 79 0 base::MessageLoop::RunInternal()\n"
"55ac9 d 427 4589\n"
"STACK WIN 4 55ac9 79 d 0 0 8 10 0 1 $T1 .raSearch = $T0 "
"$T1 4 - 8 @ = $ebp $T1 4 - ^ = $eip $T1 ^ = $esp $T1 4 + = "
"$23 $T0 20 - ^ = $24 $T0 24 - ^ =\n");
// Create some modules with some stock debugging information.
MockCodeModules local_modules;
local_modules.Add(&chrome_dll);
Label frame0_esp;
Label frame0_ebp;
Label frame1_esp;
Label frame1_ebp;
Label frame2_esp;
Label frame2_ebp;
Label frame3_esp;
Label frame3_ebp;
stack_section.start() = 0x046bfc80;
stack_section
.D32(0)
.Mark(&frame0_esp)
.D32(0x01e235a0)
.D32(0x00000000)
.D32(0x01e9f580)
.D32(0x01e9f580)
.D32(0x00000020)
.D32(0x00000000)
.D32(0x00463674)
.D32(0x00000020)
.D32(0x00000000)
.D32(0x046bfcd8)
.D32(0x046bfcd8)
.D32(0x0001204b)
.D32(0x00000000)
.D32(0xfdddb523)
.D32(0x00000000)
.D32(0x00000007)
.D32(0x00000040)
.D32(0x00000000)
.D32(0x59631693) // chrome_59630000!malloc+0x36
.D32(0x01e9f580)
.D32(0x01e9f580)
.D32(0x046bfcf8)
.D32(0x77da6704) // ntdll!NtSetIoCompletion+0xc
.D32(0x046bfd4c)
.D32(0x59685bec) // chrome_59630000!base::MessageLoop::StartHistogrammer..
.D32(0x01e235a0)
.Mark(&frame0_ebp)
.D32(frame1_ebp) // Child EBP .D32(0x046bfd0c)
.D32(0x59685c2e) // Return address in
// chrome_59630000!base::MessagePumpWin::Run+0x3e
.Mark(&frame1_esp)
.D32(0x01e75a90)
.D32(0x046bfd4c)
.D32(0x01e75a90)
.D32(0x00000000)
.D32(0x00000300)
.D32(0x00000001)
.Mark(&frame1_ebp)
.D32(frame2_ebp) // Child EBP .D32(0x046bfd30)
.D32(0x59685b3c) // Return address in
// chrome_59630000!base::MessageLoop::RunInternal+0x73
.Mark(&frame2_esp)
.D32(0x01e75a90)
.D32(0x00000000)
.D32(0x046bfd4c)
.D32(0x59658123) // chrome_59630000!std::deque..
.D32(0x046bfda0)
.D32(0x01e79d70)
.D32(0x046bfda0)
.Mark(&frame2_ebp) // .D32(0x046bfd40)
.D32(0) // saved %ebp (stack end)
.D32(0); // saved %eip (stack end)
RegionFromSection();
raw_context.eip = 0x59685c46; // Context frame in
// base::MessagePumpForIO::DoRunLoop
raw_context.esp = frame0_esp.Value();
raw_context.ebp = frame0_ebp.Value();
StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
StackwalkerX86 walker(&system_info, &raw_context, &stack_region,
&local_modules, &frame_symbolizer);
vector<const CodeModule*> modules_without_symbols;
vector<const CodeModule*> modules_with_corrupt_symbols;
ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
&modules_with_corrupt_symbols));
ASSERT_EQ(0U, modules_without_symbols.size());
ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
frames = call_stack.frames();
ASSERT_EQ(3U, frames->size());
{ // To avoid reusing locals by mistake
StackFrameX86 *frame = static_cast<StackFrameX86 *>(frames->at(0));
EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame->trust);
ASSERT_EQ(StackFrameX86::CONTEXT_VALID_ALL, frame->context_validity);
EXPECT_EQ("base::MessagePumpForIO::DoRunLoop()", frame->function_name);
EXPECT_EQ(0x59685c46U, frame->instruction);
EXPECT_EQ(0x59685c46U, frame->context.eip);
EXPECT_EQ(frame0_esp.Value(), frame->context.esp);
EXPECT_EQ(frame0_ebp.Value(), frame->context.ebp);
EXPECT_EQ(&chrome_dll, frame->module);
ASSERT_TRUE(frame->windows_frame_info != NULL);
EXPECT_EQ(WindowsFrameInfo::VALID_ALL, frame->windows_frame_info->valid);
EXPECT_EQ(WindowsFrameInfo::STACK_INFO_FRAME_DATA,
frame->windows_frame_info->type_);
EXPECT_EQ("$T1 .raSearch = $T0 "
"$T1 4 - 64 @ = $ebp $T1 4 - ^ = $eip $T1 ^ = $esp $T1 4 + "
"= $20 $T0 56 - ^ = $23 $T0 60 - ^ = $24 $T0 64 - ^ =",
frame->windows_frame_info->program_string);
EXPECT_FALSE(frame->windows_frame_info->allocates_base_pointer);
}
{ // To avoid reusing locals by mistake
StackFrameX86 *frame = static_cast<StackFrameX86 *>(frames->at(1));
EXPECT_EQ(StackFrame::FRAME_TRUST_CFI, frame->trust);
ASSERT_EQ((StackFrameX86::CONTEXT_VALID_EIP |
StackFrameX86::CONTEXT_VALID_ESP |
StackFrameX86::CONTEXT_VALID_EBP),
frame->context_validity);
EXPECT_EQ("base::MessagePumpWin::Run(base::MessagePump::Delegate *)",
frame->function_name);
EXPECT_EQ(1500011566U, frame->instruction + 1);
EXPECT_EQ(1500011566U, frame->context.eip);
EXPECT_EQ(frame1_esp.Value(), frame->context.esp);
EXPECT_EQ(frame1_ebp.Value(), frame->context.ebp);
EXPECT_EQ(&chrome_dll, frame->module);
ASSERT_TRUE(frame->windows_frame_info != NULL);
EXPECT_EQ(WindowsFrameInfo::VALID_ALL, frame->windows_frame_info->valid);
EXPECT_EQ(WindowsFrameInfo::STACK_INFO_FRAME_DATA,
frame->windows_frame_info->type_);
EXPECT_EQ("$T0 $ebp = $eip $T0 4 + ^ = $ebp $T0 ^ = $esp $T0 8 + =",
frame->windows_frame_info->program_string);
EXPECT_FALSE(frame->windows_frame_info->allocates_base_pointer);
}
{ // To avoid reusing locals by mistake
StackFrameX86 *frame = static_cast<StackFrameX86 *>(frames->at(2));
EXPECT_EQ(StackFrame::FRAME_TRUST_CFI, frame->trust);
ASSERT_EQ((StackFrameX86::CONTEXT_VALID_EIP |
StackFrameX86::CONTEXT_VALID_ESP |
StackFrameX86::CONTEXT_VALID_EBP),
frame->context_validity);
EXPECT_EQ("base::MessageLoop::RunInternal()", frame->function_name);
EXPECT_EQ(1500011324U, frame->instruction + 1);
EXPECT_EQ(1500011324U, frame->context.eip);
EXPECT_EQ(frame2_esp.Value(), frame->context.esp);
EXPECT_EQ(frame2_ebp.Value(), frame->context.ebp);
EXPECT_EQ(&chrome_dll, frame->module);
ASSERT_TRUE(frame->windows_frame_info != NULL);
EXPECT_EQ(WindowsFrameInfo::VALID_ALL, frame->windows_frame_info->valid);
EXPECT_EQ(WindowsFrameInfo::STACK_INFO_FRAME_DATA,
frame->windows_frame_info->type_);
EXPECT_EQ("$T1 .raSearch = $T0 "
"$T1 4 - 8 @ = $ebp $T1 4 - ^ = $eip $T1 ^ = $esp $T1 4 + = "
"$23 $T0 20 - ^ = $24 $T0 24 - ^ =",
frame->windows_frame_info->program_string);
EXPECT_FALSE(frame->windows_frame_info->allocates_base_pointer);
}
}
// Scan the stack for a return address and potentially skip frames when the
// current IP address is not in a known module. Note, that that the span of
// this scan is limited to 120 search words for the context frame and 30