gdb/bt-utils.c

   1 /* Copyright (C) 2021-2022 Free Software Foundation, Inc.
   2
   3    This file is part of GDB.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include "defs.h"
  19 #include "bt-utils.h"
  20 #include "command.h"
  21 #include "gdbcmd.h"
  22 #include "top.h"
  23 #include "cli/cli-decode.h"
  24
  25 /* See bt-utils.h.  */
  26
  27 void
  28 gdb_internal_backtrace_set_cmd (const char *args, int from_tty,
  29                                 cmd_list_element *c)
  30 {
  31   gdb_assert (c->type == set_cmd);
  32   gdb_assert (c->var.has_value ());
  33   gdb_assert (c->var->type () == var_boolean);
  34
  35 #ifndef GDB_PRINT_INTERNAL_BACKTRACE
  36   if (c->var->get<bool> ())
  37     {
  38       c->var->set<bool> (false);
  39       error (_("support for this feature is not compiled into GDB"));
  40     }
  41 #endif
  42 }
  43
  44 #ifdef GDB_PRINT_INTERNAL_BACKTRACE
  45 #ifdef GDB_PRINT_INTERNAL_BACKTRACE_USING_LIBBACKTRACE
  46
  47 /* Callback used by libbacktrace if it encounters an error.  */
  48
  49 static void
  50 libbacktrace_error (void *data, const char *errmsg, int errnum)
  51 {
  52   /* A negative errnum indicates no debug info was available, just
  53      skip printing a backtrace in this case.  */
  54   if (errnum < 0)
  55     return;
  56
  57   const auto sig_write = [] (const char *msg) -> void
  58   {
  59     gdb_stderr->write_async_safe (msg, strlen (msg));
  60   };
  61
  62   sig_write ("error creating backtrace: ");
  63   sig_write (errmsg);
  64   if (errnum > 0)
  65     {
  66       char buf[20];
  67       snprintf (buf, sizeof (buf), ": %d", errnum);
  68       buf[sizeof (buf) - 1] = '\0';
  69
  70       sig_write (buf);
  71     }
  72   sig_write ("\n");
  73 }
  74
  75 /* Callback used by libbacktrace to print a single stack frame.  */
  76
  77 static int
  78 libbacktrace_print (void *data, uintptr_t pc, const char *filename,
  79                     int lineno, const char *function)
  80 {
  81   const auto sig_write = [] (const char *msg) -> void
  82   {
  83     gdb_stderr->write_async_safe (msg, strlen (msg));
  84   };
  85
  86   /* Buffer to print addresses and line numbers into.  An 8-byte address
  87      with '0x' prefix and a null terminator requires 20 characters.  This
  88      also feels like it should be enough to represent line numbers in most
  89      files.  We are also careful to ensure we don't overflow this buffer.  */
  90   char buf[20];
  91
  92   snprintf (buf, sizeof (buf), "0x%" PRIxPTR " ", pc);
  93   buf[sizeof (buf) - 1] = '\0';
  94   sig_write (buf);
  95   sig_write (function == nullptr ? "???" : function);
  96   if (filename != nullptr)
  97     {
  98       sig_write ("\n\t");
  99       sig_write (filename);
 100       sig_write (":");
 101       snprintf (buf, sizeof (buf), "%d", lineno);
 102       buf[sizeof (buf) - 1] = '\0';
 103       sig_write (buf);
 104     }
 105   sig_write ("\n");
 106
 107   return function != nullptr && strcmp (function, "main") == 0;
 108 }
 109
 110 /* Write a backtrace to GDB's stderr in an async safe manner.  This is a
 111    backtrace of GDB, not any running inferior, and is to be used when GDB
 112    crashes or hits some other error condition.  */
 113
 114 static void
 115 gdb_internal_backtrace_1 ()
 116 {
 117   static struct backtrace_state *state = nullptr;
 118
 119   if (state == nullptr)
 120     state = backtrace_create_state (nullptr, 0, libbacktrace_error, nullptr);
 121
 122   backtrace_full (state, 0, libbacktrace_print, libbacktrace_error, nullptr);
 123 }
 124
 125 #elif defined GDB_PRINT_INTERNAL_BACKTRACE_USING_EXECINFO
 126
 127 /* See the comment on previous version of this function.  */
 128
 129 static void
 130 gdb_internal_backtrace_1 ()
 131 {
 132   const auto sig_write = [] (const char *msg) -> void
 133   {
 134     gdb_stderr->write_async_safe (msg, strlen (msg));
 135   };
 136
 137   /* Allow up to 25 frames of backtrace.  */
 138   void *buffer[25];
 139   int frames = backtrace (buffer, ARRAY_SIZE (buffer));
 140
 141   backtrace_symbols_fd (buffer, frames, gdb_stderr->fd ());
 142   if (frames == ARRAY_SIZE (buffer))
 143     sig_write (_("Backtrace might be incomplete.\n"));
 144 }
 145
 146 #else
 147 #error "unexpected internal backtrace policy"
 148 #endif
 149 #endif /* GDB_PRINT_INTERNAL_BACKTRACE */
 150
 151 /* See bt-utils.h.  */
 152
 153 void
 154 gdb_internal_backtrace ()
 155 {
 156   if (current_ui == nullptr)
 157     return;
 158
 159 #ifdef GDB_PRINT_INTERNAL_BACKTRACE
 160   const auto sig_write = [] (const char *msg) -> void
 161   {
 162     gdb_stderr->write_async_safe (msg, strlen (msg));
 163   };
 164
 165   sig_write (_("----- Backtrace -----\n"));
 166
 167   if (gdb_stderr->fd () > -1)
 168     gdb_internal_backtrace_1 ();
 169   else
 170     sig_write (_("Backtrace unavailable\n"));
 171
 172   sig_write ("---------------------\n");
 173 #endif
 174 }