1 /* go-callers.c -- get callers for Go.
2
3 Copyright 2012 The Go Authors. All rights reserved.
4 Use of this source code is governed by a BSD-style
5 license that can be found in the LICENSE file. */
6
7 #include "config.h"
8
9 #include "backtrace.h"
10
11 #include "runtime.h"
12 #include "array.h"
13
14 /* This is set to non-zero when calling backtrace_full. This is used
15 to avoid getting hanging on a recursive lock in dl_iterate_phdr on
16 older versions of glibc when a SIGPROF signal arrives while
17 collecting a backtrace. */
18
19 uint32 runtime_in_callers;
20
21 /* Argument passed to callback function. */
22
23 struct callers_data
24 {
25 Location *locbuf;
26 int skip;
27 int index;
28 int max;
29 int keep_thunks;
30 };
31
32 /* Callback function for backtrace_full. Just collect the locations.
33 Return zero to continue, non-zero to stop. */
34
35 static int
callback(void * data,uintptr_t pc,const char * filename,int lineno,const char * function)36 callback (void *data, uintptr_t pc, const char *filename, int lineno,
37 const char *function)
38 {
39 struct callers_data *arg = (struct callers_data *) data;
40 Location *loc;
41
42 /* Skip split stack functions. */
43 if (function != NULL)
44 {
45 const char *p;
46
47 p = function;
48 if (__builtin_strncmp (p, "___", 3) == 0)
49 ++p;
50 if (__builtin_strncmp (p, "__morestack_", 12) == 0)
51 return 0;
52 }
53 else if (filename != NULL)
54 {
55 const char *p;
56
57 p = strrchr (filename, '/');
58 if (p == NULL)
59 p = filename;
60 if (__builtin_strncmp (p, "/morestack.S", 12) == 0)
61 return 0;
62 }
63
64 /* Skip thunks and recover functions. There is no equivalent to
65 these functions in the gc toolchain, so returning them here means
66 significantly different results for runtime.Caller(N). */
67 if (function != NULL && !arg->keep_thunks)
68 {
69 const char *p;
70
71 p = __builtin_strchr (function, '.');
72 if (p != NULL && __builtin_strncmp (p + 1, "$thunk", 6) == 0)
73 return 0;
74 p = __builtin_strrchr (function, '$');
75 if (p != NULL && __builtin_strcmp(p, "$recover") == 0)
76 return 0;
77 if (p != NULL && __builtin_strncmp(p, "$stub", 5) == 0)
78 return 0;
79 }
80
81 if (arg->skip > 0)
82 {
83 --arg->skip;
84 return 0;
85 }
86
87 loc = &arg->locbuf[arg->index];
88
89 /* On the call to backtrace_full the pc value was most likely
90 decremented if there was a normal call, since the pc referred to
91 the instruction where the call returned and not the call itself.
92 This was done so that the line number referred to the call
93 instruction. To make sure the actual pc from the call stack is
94 used, it is incremented here.
95
96 In the case of a signal, the pc was not decremented by
97 backtrace_full but still incremented here. That doesn't really
98 hurt anything since the line number is right and the pc refers to
99 the same instruction. */
100
101 loc->pc = pc + 1;
102
103 /* The libbacktrace library says that these strings might disappear,
104 but with the current implementation they won't. We can't easily
105 allocate memory here, so for now assume that we can save a
106 pointer to the strings. */
107 loc->filename = runtime_gostringnocopy ((const byte *) filename);
108 loc->function = runtime_gostringnocopy ((const byte *) function);
109
110 loc->lineno = lineno;
111 ++arg->index;
112
113 /* There is no point to tracing past certain runtime functions.
114 Stopping the backtrace here can avoid problems on systems that
115 don't provide proper unwind information for makecontext, such as
116 Solaris (http://gcc.gnu.org/PR52583 comment #21). */
117 if (function != NULL)
118 {
119 if (__builtin_strcmp (function, "makecontext") == 0)
120 return 1;
121 if (filename != NULL)
122 {
123 const char *p;
124
125 p = strrchr (filename, '/');
126 if (p == NULL)
127 p = filename;
128 if (__builtin_strcmp (p, "/proc.c") == 0)
129 {
130 if (__builtin_strcmp (function, "kickoff") == 0
131 || __builtin_strcmp (function, "runtime_mstart") == 0
132 || __builtin_strcmp (function, "runtime_main") == 0)
133 return 1;
134 }
135 }
136 }
137
138 return arg->index >= arg->max;
139 }
140
141 /* Error callback. */
142
143 static void
error_callback(void * data,const char * msg,int errnum)144 error_callback (void *data __attribute__ ((unused)),
145 const char *msg, int errnum)
146 {
147 if (errnum == -1)
148 {
149 /* No debug info available. Carry on as best we can. */
150 return;
151 }
152 if (errnum != 0)
153 runtime_printf ("%s errno %d\n", msg, errnum);
154 runtime_throw (msg);
155 }
156
157 /* Gather caller PC's. */
158
159 int32
runtime_callers(int32 skip,Location * locbuf,int32 m,bool keep_thunks)160 runtime_callers (int32 skip, Location *locbuf, int32 m, bool keep_thunks)
161 {
162 struct callers_data data;
163
164 data.locbuf = locbuf;
165 data.skip = skip + 1;
166 data.index = 0;
167 data.max = m;
168 data.keep_thunks = keep_thunks;
169 runtime_xadd (&runtime_in_callers, 1);
170 backtrace_full (__go_get_backtrace_state (), 0, callback, error_callback,
171 &data);
172 runtime_xadd (&runtime_in_callers, -1);
173 return data.index;
174 }
175
176 int Callers (int, struct __go_open_array)
177 __asm__ (GOSYM_PREFIX "runtime.Callers");
178
179 int
Callers(int skip,struct __go_open_array pc)180 Callers (int skip, struct __go_open_array pc)
181 {
182 Location *locbuf;
183 int ret;
184 int i;
185
186 locbuf = (Location *) runtime_mal (pc.__count * sizeof (Location));
187
188 /* In the Go 1 release runtime.Callers has an off-by-one error,
189 which we can not correct because it would break backward
190 compatibility. Normally we would add 1 to SKIP here, but we
191 don't so that we are compatible. */
192 ret = runtime_callers (skip, locbuf, pc.__count, false);
193
194 for (i = 0; i < ret; i++)
195 ((uintptr *) pc.__values)[i] = locbuf[i].pc;
196
197 return ret;
198 }
199