libgo/runtime/go-caller.c

   1 /* go-caller.c -- runtime.Caller and runtime.FuncForPC for Go.
   2
   3    Copyright 2009 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 /* Implement runtime.Caller.  */
   8
   9 #include <stdint.h>
  10
  11 #include "backtrace.h"
  12
  13 #include "runtime.h"
  14
  15 /* Get the function name, file name, and line number for a PC value.
  16    We use the backtrace library to get this.  */
  17
  18 /* Data structure to gather file/line information.  */
  19
  20 struct caller
  21 {
  22   String fn;
  23   String file;
  24   intgo line;
  25 };
  26
  27 /* Collect file/line information for a PC value.  If this is called
  28    more than once, due to inlined functions, we use the last call, as
  29    that is usually the most useful one.  */
  30
  31 static int
  32 callback (void *data, uintptr_t pc __attribute__ ((unused)),
  33           const char *filename, int lineno, const char *function)
  34 {
  35   struct caller *c = (struct caller *) data;
  36
  37   if (function == NULL)
  38     {
  39       c->fn.str = NULL;
  40       c->fn.len = 0;
  41     }
  42   else
  43     {
  44       byte *s;
  45
  46       c->fn.len = __builtin_strlen (function);
  47       s = runtime_malloc (c->fn.len);
  48       __builtin_memcpy (s, function, c->fn.len);
  49       c->fn.str = s;
  50     }
  51
  52   if (filename == NULL)
  53     {
  54       c->file.str = NULL;
  55       c->file.len = 0;
  56     }
  57   else
  58     {
  59       byte *s;
  60
  61       c->file.len = __builtin_strlen (filename);
  62       s = runtime_malloc (c->file.len);
  63       __builtin_memcpy (s, filename, c->file.len);
  64       c->file.str = s;
  65     }
  66
  67   c->line = lineno;
  68
  69   return 0;
  70 }
  71
  72 /* The error callback for backtrace_pcinfo and backtrace_syminfo.  */
  73
  74 static void
  75 error_callback (void *data __attribute__ ((unused)),
  76                 const char *msg, int errnum)
  77 {
  78   if (errnum == -1)
  79     return;
  80   if (errnum > 0)
  81     runtime_printf ("%s errno %d\n", msg, errnum);
  82   runtime_throw (msg);
  83 }
  84
  85 /* The backtrace library state.  */
  86
  87 static void *back_state;
  88
  89 /* A lock to control creating back_state.  */
  90
  91 static Lock back_state_lock;
  92
  93 /* Fetch back_state, creating it if necessary.  */
  94
  95 struct backtrace_state *
  96 __go_get_backtrace_state ()
  97 {
  98   runtime_lock (&back_state_lock);
  99   if (back_state == NULL)
 100     {
 101       const char *filename;
 102
 103       filename = (const char *) runtime_progname ();
 104       back_state = backtrace_create_state (filename, 1, error_callback, NULL);
 105     }
 106   runtime_unlock (&back_state_lock);
 107   return back_state;
 108 }
 109
 110 /* Return function/file/line information for PC.  */
 111
 112 _Bool
 113 __go_file_line (uintptr pc, String *fn, String *file, intgo *line)
 114 {
 115   struct caller c;
 116
 117   runtime_memclr (&c, sizeof c);
 118   backtrace_pcinfo (__go_get_backtrace_state (), pc, callback,
 119                     error_callback, &c);
 120   *fn = c.fn;
 121   *file = c.file;
 122   *line = c.line;
 123   return c.file.len > 0;
 124 }
 125
 126 /* Collect symbol information.  */
 127
 128 static void
 129 syminfo_callback (void *data, uintptr_t pc __attribute__ ((unused)),
 130                   const char *symname __attribute__ ((unused)),
 131                   uintptr_t address)
 132 {
 133   uintptr_t *pval = (uintptr_t *) data;
 134
 135   *pval = address;
 136 }
 137
 138 /* Set *VAL to the value of the symbol for PC.  */
 139
 140 static _Bool
 141 __go_symbol_value (uintptr_t pc, uintptr_t *val)
 142 {
 143   *val = 0;
 144   backtrace_syminfo (__go_get_backtrace_state (), pc, syminfo_callback,
 145                      error_callback, val);
 146   return *val != 0;
 147 }
 148
 149 /* The values returned by runtime.Caller.  */
 150
 151 struct caller_ret
 152 {
 153   uintptr_t pc;
 154   String file;
 155   intgo line;
 156   _Bool ok;
 157 };
 158
 159 struct caller_ret Caller (int n) __asm__ (GOSYM_PREFIX "runtime.Caller");
 160
 161 Func *FuncForPC (uintptr_t) __asm__ (GOSYM_PREFIX "runtime.FuncForPC");
 162
 163 /* Implement runtime.Caller.  */
 164
 165 struct caller_ret
 166 Caller (int skip)
 167 {
 168   struct caller_ret ret;
 169   Location loc;
 170   int32 n;
 171
 172   runtime_memclr (&ret, sizeof ret);
 173   n = runtime_callers (skip + 1, &loc, 1);
 174   if (n < 1)
 175     return ret;
 176   ret.pc = loc.pc;
 177   ret.file = loc.filename;
 178   ret.line = loc.lineno;
 179   ret.ok = 1;
 180   return ret;
 181 }
 182
 183 /* Implement runtime.FuncForPC.  */
 184
 185 Func *
 186 FuncForPC (uintptr_t pc)
 187 {
 188   Func *ret;
 189   String fn;
 190   String file;
 191   intgo line;
 192   uintptr_t val;
 193
 194   if (!__go_file_line (pc, &fn, &file, &line))
 195     return NULL;
 196
 197   ret = (Func *) runtime_malloc (sizeof (*ret));
 198   ret->name = fn;
 199
 200   if (__go_symbol_value (pc, &val))
 201     ret->entry = val;
 202   else
 203     ret->entry = 0;
 204
 205   return ret;
 206 }
 207
 208 /* Look up the file and line information for a PC within a
 209    function.  */
 210
 211 struct funcline_go_return
 212 {
 213   String retfile;
 214   intgo retline;
 215 };
 216
 217 struct funcline_go_return
 218 runtime_funcline_go (Func *f, uintptr targetpc)
 219   __asm__ (GOSYM_PREFIX "runtime.funcline_go");
 220
 221 struct funcline_go_return
 222 runtime_funcline_go (Func *f __attribute__((unused)), uintptr targetpc)
 223 {
 224   struct funcline_go_return ret;
 225   String fn;
 226
 227   if (!__go_file_line (targetpc, &fn, &ret.retfile,  &ret.retline))
 228     runtime_memclr (&ret, sizeof ret);
 229   return ret;
 230 }