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 <string.h>
  35 #include <execinfo.h>
  36 #include <unistd.h>
  37 #include <errno.h>
  38
  39 #include "vtv_utils.h"
  40
  41 /* This is the directory into which all vtable verication log files
  42    get written.  */
  43 static const char * const logs_dir = "/tmp/vtv_logs";
  44 static int vtv_failures_log_fd = -1;
  45
  46
  47
  48 /* This function takes the NAME of a log file to open, attempts to
  49    open it in the logs_dir directory, and returns the resulting file
  50    decriptor.  */
  51
  52 int
  53 __vtv_open_log (const char *name)
  54 {
  55   char log_name[256];
  56   snprintf (log_name, sizeof (log_name), "%s/%s", logs_dir, name);
  57   mkdir (logs_dir, S_IRWXU);
  58   int fd = open (log_name, O_WRONLY | O_APPEND | O_CREAT, S_IRWXU);
  59   if (fd == -1)
  60     __vtv_add_to_log (2, "Cannot open log file %s %s\n", name,
  61                     strerror (errno));
  62   return fd;
  63 }
  64
  65 /* This function takes a file descriptor (FD) and a string (STR) and
  66    tries to write the string to the file.  */
  67
  68 static int
  69 vtv_log_write (int fd, const char *str)
  70 {
  71   if (write (fd, str, strlen (str)) != -1)
  72     return 0;
  73
  74   if (fd != 2) /* Make sure we dont get in a loop.  */
  75     __vtv_add_to_log (2, "Error writing to log: %s\n", strerror (errno));
  76   return -1;
  77 }
  78
  79
  80 /* This function takes a file decriptor (LOG_FILE) and an output
  81  format string (FORMAT), followed by zero or more print format
  82  arguments (the same as fprintf, for example).  It gets the current
  83  process ID and PPID, pre-pends them to the formatted message, and
  84  writes write it out to the log file referenced by LOG_FILE via calles
  85  to vtv_log_write.  */
  86
  87 int
  88 __vtv_add_to_log (int log_file, const char * format, ...)
  89 {
  90   /* We dont want to dynamically allocate this buffer. This should be
  91      more than enough in most cases. It if isn't we are careful not to
  92      do a buffer overflow.  */
  93   char output[1024];
  94
  95   va_list ap;
  96   va_start (ap, format);
  97
  98   snprintf (output, sizeof (output), "VTV: PID=%d PPID=%d ", getpid (),
  99             getppid ());
 100   vtv_log_write (log_file, output);
 101   vsnprintf (output, sizeof (output), format, ap);
 102   vtv_log_write (log_file, output);
 103   va_end (ap);
 104
 105   return 0;
 106 }
 107
 108 /* Open error logging file, if not already open, and write vtable
 109    verification failure messages (LOG_MSG) to the log file.  Also
 110    generate a backtrace in the log file, if GENERATE_BACKTRACE is
 111    set.  */
 112
 113 void
 114 __vtv_log_verification_failure (const char *log_msg, bool generate_backtrace)
 115 {
 116   if (vtv_failures_log_fd == -1)
 117     vtv_failures_log_fd = __vtv_open_log ("vtable_verification_failures.log");
 118
 119   if (vtv_failures_log_fd == -1)
 120     return;
 121
 122   __vtv_add_to_log (vtv_failures_log_fd, "%s", log_msg);
 123
 124   if (generate_backtrace)
 125     {
 126 #define STACK_DEPTH 20
 127       void *callers[STACK_DEPTH];
 128       int actual_depth = backtrace (callers, STACK_DEPTH);
 129       backtrace_symbols_fd (callers, actual_depth, vtv_failures_log_fd);
 130     }
 131 }