1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
|
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "mozilla/WindowsDiagnostics.h"
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/Types.h"
#include <windows.h>
#include <winternl.h>
#if defined(_M_AMD64)
namespace mozilla {
MOZ_RUNINIT static OnSingleStepCallback sOnSingleStepCallback{};
static void* sOnSingleStepCallbackState = nullptr;
static bool sIsSingleStepping = false;
MFBT_API AutoOnSingleStepCallback::AutoOnSingleStepCallback(
OnSingleStepCallback aOnSingleStepCallback, void* aState) {
MOZ_RELEASE_ASSERT(!sIsSingleStepping && !sOnSingleStepCallback &&
!sOnSingleStepCallbackState,
"Single-stepping is already active");
sOnSingleStepCallback = std::move(aOnSingleStepCallback);
sOnSingleStepCallbackState = aState;
sIsSingleStepping = true;
}
MFBT_API AutoOnSingleStepCallback::~AutoOnSingleStepCallback() {
sOnSingleStepCallback = OnSingleStepCallback();
sOnSingleStepCallbackState = nullptr;
sIsSingleStepping = false;
}
// Going though this assembly code turns on the trap flag, which will trigger
// a first single-step exception. It is then up to the exception handler to
// keep the trap flag enabled so that a new single step exception gets
// triggered with the following instruction.
MFBT_API MOZ_NEVER_INLINE MOZ_NAKED void EnableTrapFlag() {
asm volatile(
"pushfq;"
"orw $0x100,(%rsp);"
"popfq;"
"retq;");
}
// This function does not do anything special, but when we reach its address
// while single-stepping the exception handler will know that it is now time to
// leave the trap flag turned off.
MFBT_API MOZ_NEVER_INLINE MOZ_NAKED void DisableTrapFlag() {
asm volatile("retq;");
}
MFBT_API LONG SingleStepExceptionHandler(_EXCEPTION_POINTERS* aExceptionInfo) {
if (sIsSingleStepping && sOnSingleStepCallback &&
aExceptionInfo->ExceptionRecord->ExceptionCode == EXCEPTION_SINGLE_STEP) {
auto instructionPointer = aExceptionInfo->ContextRecord->Rip;
bool keepOnSingleStepping = false;
if (instructionPointer != reinterpret_cast<uintptr_t>(&DisableTrapFlag)) {
keepOnSingleStepping = sOnSingleStepCallback(
sOnSingleStepCallbackState, aExceptionInfo->ContextRecord);
}
if (keepOnSingleStepping) {
aExceptionInfo->ContextRecord->EFlags |= 0x100;
} else {
sIsSingleStepping = false;
}
return EXCEPTION_CONTINUE_EXECUTION;
}
return EXCEPTION_CONTINUE_SEARCH;
}
} // namespace mozilla
#endif // _M_AMD64
|
