Add "bootstat --output-dir" option.

bootstat_log.c

-// Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+// Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Implementation of bootstat_log(), part of the Chromium OS 'bootstat'
 // facility.
 
 #include "bootstat.h"
 #include "bootstat_test.h"
 
 #include <assert.h>
+#include <errno.h>
 #include <stddef.h>
 #include <stdio.h>
+#include <string.h>
 
 #include <sys/fcntl.h>
 #include <sys/param.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 //
-// Default path to directory where output statistics will be stored.
+// Variables relating to the directory where output statistics will
+// be stored.
 //
+static char output_directory_buffer[PATH_MAX+1];
 static const char kDefaultOutputDirectoryName[] = "/tmp";
+static const char *output_directory_name = kDefaultOutputDirectoryName;
+
+// The longest path we allow to be stored in output_directory_buffer.
+// The buffer is filled by the snprintf() in append_logdata() (the
+// format string is "%s/%s-%.*s").
+//
+// The "+ 2" in the formula accounts for '\0' characters counted in
+// BOOTSTAT_MAX_EVENT_LEN and the 'sizeof' expression.
+//
+const int kMaxOutputDirectoryPath = (sizeof(output_directory_buffer) -
+  BOOTSTAT_MAX_EVENT_LEN - sizeof("/uptime-") + 1);
 
 //
 // Paths to the statistics files we snapshot as part of the data to
 // be logged.
 //
 static const char kDefaultUptimeStatisticsFileName[] = "/proc/uptime";
 
 #if defined (__amd64__) || defined (__x86_64__) || defined (__i386__)
 static const char kDefaultDiskStatisticsFileName[] = "/sys/block/sda/stat";
 #elif defined (__arm__)
 static const char kDefaultDiskStatisticsFileName[] = "/sys/block/mmcblk0/stat";
 #else
 #error "unknown processor type?"
 #endif
 
-static const char *output_directory_name = kDefaultOutputDirectoryName;
 static const char *uptime_statistics_file_name =
     kDefaultUptimeStatisticsFileName;
-static const char *disk_statistics_file_name = kDefaultDiskStatisticsFileName;
+static const char *disk_statistics_file_name =
+    kDefaultDiskStatisticsFileName;
 
 static void append_logdata(const char* input_path,
                            const char* output_name_prefix,
                            const char* event_name)
 {
   const mode_t kFileCreationMode =
       S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
   char output_path[PATH_MAX];
   char buffer[256];
   ssize_t num_read;
@@ skipping 37 matching lines @@
 }
 
 
 void bootstat_log(const char* event_name)
 {
   append_logdata(uptime_statistics_file_name, "uptime", event_name);
   append_logdata(disk_statistics_file_name, "disk", event_name);
 }
 
 
-void bootstat_set_output_directory(const char* dirname)
+int bootstat_set_output_directory(const char* dirname)
 {
-  if (dirname != NULL)
-    output_directory_name = dirname;
-  else
+  int rv;
+  char namebuffer[kMaxOutputDirectoryPath + 3];
+
+  if (dirname == NULL) {
     output_directory_name = kDefaultOutputDirectoryName;
+    return 0;
+  }
+
+  if (strlen(dirname) > kMaxOutputDirectoryPath) {
+    errno = ENAMETOOLONG;
+    return -1;
+  }
+
+  // We test for "%s/." rather than "%s" as a cheap way to force
+  // euidaccess() to confirm that the path is a directory, in
+  // addition to being writable and executable.
+  //
+  // sprintf() is safe, because we checked strlen() above.
+  sprintf(namebuffer, "%s/.", dirname);
+  rv = euidaccess(namebuffer, W_OK | X_OK);
+  if (rv < 0) {
+    return -1;
+  }
+
+  strcpy(output_directory_buffer, dirname);
+  output_directory_name = output_directory_buffer;
+  return 0;
 }
 
 
 void bootstat_set_uptime_file_name(const char* filename)
 {
   if (filename != NULL)
     uptime_statistics_file_name = filename;
   else
     uptime_statistics_file_name = kDefaultUptimeStatisticsFileName;
 }
 
 
 void bootstat_set_disk_file_name(const char* filename)
 {
   if (filename != NULL)
     disk_statistics_file_name = filename;
   else
     disk_statistics_file_name = kDefaultDiskStatisticsFileName;
 }