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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
|
/* ===-- gcc_personality_v0.c - Implement __gcc_personality_v0 -------------===
*
* The LLVM Compiler Infrastructure
*
* This file is dual licensed under the MIT and the University of Illinois Open
* Source Licenses. See LICENSE.TXT for details.
*
* ===----------------------------------------------------------------------===
*
*/
#include "int_lib.h"
#include <unwind.h>
/*
* Pointer encodings documented at:
* http://refspecs.freestandards.org/LSB_1.3.0/gLSB/gLSB/ehframehdr.html
*/
#define DW_EH_PE_omit 0xff /* no data follows */
#define DW_EH_PE_absptr 0x00
#define DW_EH_PE_uleb128 0x01
#define DW_EH_PE_udata2 0x02
#define DW_EH_PE_udata4 0x03
#define DW_EH_PE_udata8 0x04
#define DW_EH_PE_sleb128 0x09
#define DW_EH_PE_sdata2 0x0A
#define DW_EH_PE_sdata4 0x0B
#define DW_EH_PE_sdata8 0x0C
#define DW_EH_PE_pcrel 0x10
#define DW_EH_PE_textrel 0x20
#define DW_EH_PE_datarel 0x30
#define DW_EH_PE_funcrel 0x40
#define DW_EH_PE_aligned 0x50
#define DW_EH_PE_indirect 0x80 /* gcc extension */
/* read a uleb128 encoded value and advance pointer */
static uintptr_t readULEB128(const uint8_t** data)
{
uintptr_t result = 0;
uintptr_t shift = 0;
unsigned char byte;
const uint8_t* p = *data;
do {
byte = *p++;
result |= (byte & 0x7f) << shift;
shift += 7;
} while (byte & 0x80);
*data = p;
return result;
}
/* read a pointer encoded value and advance pointer */
static uintptr_t readEncodedPointer(const uint8_t** data, uint8_t encoding)
{
const uint8_t* p = *data;
uintptr_t result = 0;
if ( encoding == DW_EH_PE_omit )
return 0;
/* first get value */
switch (encoding & 0x0F) {
case DW_EH_PE_absptr:
result = *((const uintptr_t*)p);
p += sizeof(uintptr_t);
break;
case DW_EH_PE_uleb128:
result = readULEB128(&p);
break;
case DW_EH_PE_udata2:
result = *((const uint16_t*)p);
p += sizeof(uint16_t);
break;
case DW_EH_PE_udata4:
result = *((const uint32_t*)p);
p += sizeof(uint32_t);
break;
case DW_EH_PE_udata8:
result = *((const uint64_t*)p);
p += sizeof(uint64_t);
break;
case DW_EH_PE_sdata2:
result = *((const int16_t*)p);
p += sizeof(int16_t);
break;
case DW_EH_PE_sdata4:
result = *((const int32_t*)p);
p += sizeof(int32_t);
break;
case DW_EH_PE_sdata8:
result = *((const int64_t*)p);
p += sizeof(int64_t);
break;
case DW_EH_PE_sleb128:
default:
/* not supported */
compilerrt_abort();
break;
}
/* then add relative offset */
switch ( encoding & 0x70 ) {
case DW_EH_PE_absptr:
/* do nothing */
break;
case DW_EH_PE_pcrel:
result += (uintptr_t)(*data);
break;
case DW_EH_PE_textrel:
case DW_EH_PE_datarel:
case DW_EH_PE_funcrel:
case DW_EH_PE_aligned:
default:
/* not supported */
compilerrt_abort();
break;
}
/* then apply indirection */
if (encoding & DW_EH_PE_indirect) {
result = *((const uintptr_t*)result);
}
*data = p;
return result;
}
/*
* The C compiler makes references to __gcc_personality_v0 in
* the dwarf unwind information for translation units that use
* __attribute__((cleanup(xx))) on local variables.
* This personality routine is called by the system unwinder
* on each frame as the stack is unwound during a C++ exception
* throw through a C function compiled with -fexceptions.
*/
#if __USING_SJLJ_EXCEPTIONS__
// the setjump-longjump based exceptions personality routine has a different name
COMPILER_RT_ABI _Unwind_Reason_Code
__gcc_personality_sj0(int version, _Unwind_Action actions,
uint64_t exceptionClass, struct _Unwind_Exception* exceptionObject,
struct _Unwind_Context *context)
#else
COMPILER_RT_ABI _Unwind_Reason_Code
__gcc_personality_v0(int version, _Unwind_Action actions,
uint64_t exceptionClass, struct _Unwind_Exception* exceptionObject,
struct _Unwind_Context *context)
#endif
{
/* Since C does not have catch clauses, there is nothing to do during */
/* phase 1 (the search phase). */
if ( actions & _UA_SEARCH_PHASE )
return _URC_CONTINUE_UNWIND;
/* There is nothing to do if there is no LSDA for this frame. */
const uint8_t* lsda = (uint8_t*)_Unwind_GetLanguageSpecificData(context);
if ( lsda == (uint8_t*) 0 )
return _URC_CONTINUE_UNWIND;
uintptr_t pc = _Unwind_GetIP(context)-1;
uintptr_t funcStart = _Unwind_GetRegionStart(context);
uintptr_t pcOffset = pc - funcStart;
/* Parse LSDA header. */
uint8_t lpStartEncoding = *lsda++;
if (lpStartEncoding != DW_EH_PE_omit) {
readEncodedPointer(&lsda, lpStartEncoding);
}
uint8_t ttypeEncoding = *lsda++;
if (ttypeEncoding != DW_EH_PE_omit) {
readULEB128(&lsda);
}
/* Walk call-site table looking for range that includes current PC. */
uint8_t callSiteEncoding = *lsda++;
uint32_t callSiteTableLength = readULEB128(&lsda);
const uint8_t* callSiteTableStart = lsda;
const uint8_t* callSiteTableEnd = callSiteTableStart + callSiteTableLength;
const uint8_t* p=callSiteTableStart;
while (p < callSiteTableEnd) {
uintptr_t start = readEncodedPointer(&p, callSiteEncoding);
uintptr_t length = readEncodedPointer(&p, callSiteEncoding);
uintptr_t landingPad = readEncodedPointer(&p, callSiteEncoding);
readULEB128(&p); /* action value not used for C code */
if ( landingPad == 0 )
continue; /* no landing pad for this entry */
if ( (start <= pcOffset) && (pcOffset < (start+length)) ) {
/* Found landing pad for the PC.
* Set Instruction Pointer to so we re-enter function
* at landing pad. The landing pad is created by the compiler
* to take two parameters in registers.
*/
_Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
(uintptr_t)exceptionObject);
_Unwind_SetGR(context, __builtin_eh_return_data_regno(1), 0);
_Unwind_SetIP(context, funcStart+landingPad);
return _URC_INSTALL_CONTEXT;
}
}
/* No landing pad found, continue unwinding. */
return _URC_CONTINUE_UNWIND;
}
|
