libvtv/vtv_utils.cc

   1 /* Copyright (C) 2012-2013
   2    Free Software Foundation
   3
   4    This file is part of GCC.
   5
   6    GCC is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    GCC is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 /* This file is part of the vtable verication runtime library (see
  26    comments in vtv_rts.cc for more information about vtable
  27    verification).  This file contains log file utilities.  */
  28
  29 #include <sys/types.h>
  30 #include <sys/stat.h>
  31 #include <fcntl.h>
  32 #include <stdarg.h>
  33 #include <stdio.h>
  34 #include <stdlib.h>
  35 #include <string.h>
  36 #include <execinfo.h>
  37 #include <unistd.h>
  38 #include <errno.h>
  39
  40 #include "vtv_utils.h"
  41
  42 #ifndef HAVE_SECURE_GETENV
  43 #  ifdef HAVE___SECURE_GETENV
  44 #    define secure_getenv __secure_getenv
  45 #  else
  46 #    define secure_getenv getenv
  47 #  endif
  48 #endif
  49
  50 static int vtv_failures_log_fd = -1;
  51
  52 /* This function takes the NAME of a log file to open, attempts to
  53    open it in the logs_dir directory, and returns the resulting file
  54    descriptor.
  55
  56    This function first checks to see if the user has specifed (via
  57    the environment variable VTV_LOGS_DIR) a directory to use for the
  58    vtable verification logs.  If that fails, the function will open
  59    the logs in the current directory.
  60 */
  61
  62 int
  63 __vtv_open_log (const char *name)
  64 {
  65   char log_name[1024];
  66   char log_dir[512];
  67   uid_t user_id = getuid ();
  68   pid_t process_id = getpid ();
  69   char *logs_prefix;
  70   bool logs_dir_specified = false;
  71   int fd = -1;
  72
  73   logs_prefix = secure_getenv ("VTV_LOGS_DIR");
  74   if (logs_prefix && strlen (logs_prefix) > 0)
  75     {
  76       logs_dir_specified = true;
  77       mkdir (logs_prefix, S_IRWXU);
  78       snprintf (log_dir, sizeof (log_dir), "%s/vtv_logs", logs_prefix);
  79       mkdir (log_dir, S_IRWXU);
  80
  81       snprintf (log_name, sizeof (log_name), "%s/%d_%d_%s", log_dir,
  82                 (unsigned) user_id, (unsigned) process_id, name);
  83       fd = open (log_name, O_WRONLY | O_APPEND | O_CREAT | O_NOFOLLOW,
  84                  S_IRWXU);
  85     }
  86   else
  87     fd = dup (2);
  88
  89   if (fd == -1)
  90     __vtv_add_to_log (2, "Cannot open log file %s %s\n", name,
  91                     strerror (errno));
  92   return fd;
  93 }
  94
  95 /* This function takes a file descriptor (FD) and a string (STR) and
  96    tries to write the string to the file.  */
  97
  98 static int
  99 vtv_log_write (int fd, const char *str)
 100 {
 101   if (write (fd, str, strlen (str)) != -1)
 102     return 0;
 103
 104   if (fd != 2) /* Make sure we dont get in a loop.  */
 105     __vtv_add_to_log (2, "Error writing to log: %s\n", strerror (errno));
 106   return -1;
 107 }
 108
 109
 110 /* This function takes a file decriptor (LOG_FILE) and an output
 111  format string (FORMAT), followed by zero or more print format
 112  arguments (the same as fprintf, for example).  It gets the current
 113  process ID and PPID, pre-pends them to the formatted message, and
 114  writes write it out to the log file referenced by LOG_FILE via calles
 115  to vtv_log_write.  */
 116
 117 int
 118 __vtv_add_to_log (int log_file, const char * format, ...)
 119 {
 120   /* We dont want to dynamically allocate this buffer. This should be
 121      more than enough in most cases. It if isn't we are careful not to
 122      do a buffer overflow.  */
 123   char output[1024];
 124
 125   va_list ap;
 126   va_start (ap, format);
 127
 128   snprintf (output, sizeof (output), "VTV: PID=%d PPID=%d ", getpid (),
 129             getppid ());
 130   vtv_log_write (log_file, output);
 131   vsnprintf (output, sizeof (output), format, ap);
 132   vtv_log_write (log_file, output);
 133   va_end (ap);
 134
 135   return 0;
 136 }
 137
 138 /* Open error logging file, if not already open, and write vtable
 139    verification failure messages (LOG_MSG) to the log file.  Also
 140    generate a backtrace in the log file, if GENERATE_BACKTRACE is
 141    set.  */
 142
 143 void
 144 __vtv_log_verification_failure (const char *log_msg, bool generate_backtrace)
 145 {
 146   if (vtv_failures_log_fd == -1)
 147     vtv_failures_log_fd = __vtv_open_log ("vtable_verification_failures.log");
 148
 149   if (vtv_failures_log_fd == -1)
 150     return;
 151
 152   __vtv_add_to_log (vtv_failures_log_fd, "%s", log_msg);
 153
 154   if (generate_backtrace)
 155     {
 156 #define STACK_DEPTH 20
 157       void *callers[STACK_DEPTH];
 158       int actual_depth = backtrace (callers, STACK_DEPTH);
 159       backtrace_symbols_fd (callers, actual_depth, vtv_failures_log_fd);
 160     }
 161 }