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
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
|
// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "textflag.h"
// The signals handled by sigHandler.
#define SIGBUS 7
#define SIGSEGV 11
// Offsets to the registers in context->uc_mcontext.gregs[].
#define REG_RDI 0x68
#define REG_RAX 0x90
#define REG_IP 0xa8
// Offset to the si_addr field of siginfo.
#define SI_CODE 0x08
#define SI_ADDR 0x10
// signalHandler is the signal handler for SIGSEGV and SIGBUS signals. It must
// not be set up as a handler to any other signals.
//
// If the instruction causing the signal is within a safecopy-protected
// function, the signal is handled such that execution resumes in the
// appropriate fault handling stub with AX containing the faulting address and
// DI containing the signal number. Otherwise control is transferred to the
// previously configured signal handler (savedSigSegvHandler or
// savedSigBusHandler).
//
// This function cannot be written in go because it runs whenever a signal is
// received by the thread (preempting whatever was running), which includes when
// garbage collector has stopped or isn't expecting any interactions (like
// barriers).
//
// The arguments are the following:
// DI - The signal number.
// SI - Pointer to siginfo_t structure.
// DX - Pointer to ucontext structure.
TEXT ·signalHandler(SB),NOSPLIT,$0
// Check if the signal is from the kernel.
MOVQ $0x0, CX
CMPL CX, SI_CODE(SI)
JGE original_handler
// Check if RIP is within the area we care about.
MOVQ REG_IP(DX), CX
CMPQ CX, ·memcpyBegin(SB)
JB not_memcpy
CMPQ CX, ·memcpyEnd(SB)
JAE not_memcpy
// Modify the context such that execution will resume in the fault
// handler.
LEAQ handleMemcpyFault(SB), CX
JMP handle_fault
not_memcpy:
CMPQ CX, ·memclrBegin(SB)
JB not_memclr
CMPQ CX, ·memclrEnd(SB)
JAE not_memclr
LEAQ handleMemclrFault(SB), CX
JMP handle_fault
not_memclr:
CMPQ CX, ·swapUint32Begin(SB)
JB not_swapuint32
CMPQ CX, ·swapUint32End(SB)
JAE not_swapuint32
LEAQ handleSwapUint32Fault(SB), CX
JMP handle_fault
not_swapuint32:
CMPQ CX, ·swapUint64Begin(SB)
JB not_swapuint64
CMPQ CX, ·swapUint64End(SB)
JAE not_swapuint64
LEAQ handleSwapUint64Fault(SB), CX
JMP handle_fault
not_swapuint64:
CMPQ CX, ·compareAndSwapUint32Begin(SB)
JB not_casuint32
CMPQ CX, ·compareAndSwapUint32End(SB)
JAE not_casuint32
LEAQ handleCompareAndSwapUint32Fault(SB), CX
JMP handle_fault
not_casuint32:
CMPQ CX, ·loadUint32Begin(SB)
JB not_loaduint32
CMPQ CX, ·loadUint32End(SB)
JAE not_loaduint32
LEAQ handleLoadUint32Fault(SB), CX
JMP handle_fault
not_loaduint32:
original_handler:
// Jump to the previous signal handler, which is likely the golang one.
XORQ CX, CX
MOVQ ·savedSigBusHandler(SB), AX
CMPL DI, $SIGSEGV
CMOVQEQ ·savedSigSegVHandler(SB), AX
JMP AX
handle_fault:
// Entered with the address of the fault handler in RCX; store it in
// RIP.
MOVQ CX, REG_IP(DX)
// Store the faulting address in RAX.
MOVQ SI_ADDR(SI), CX
MOVQ CX, REG_RAX(DX)
// Store the signal number in EDI.
MOVL DI, REG_RDI(DX)
RET
|
