2 * Hook output functions (like printf(3)) with LD_PRELOAD to color stderr (or
3 * other file descriptors).
5 * Copyright (C) 2013 Simon Ruderich
7 * This program is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program. If not, see <http://www.gnu.org/licenses/>.
23 /* Must be loaded before the following headers. */
24 #include "ldpreload.h"
37 /* Conflicting declaration in glibc. */
38 #undef fwrite_unlocked
41 /* Used by various functions, including debug(). */
42 static ssize_t (*real_write)(int, void const *, size_t);
43 static int (*real_close)(int);
44 static size_t (*real_fwrite)(void const *, size_t, size_t, FILE *);
46 /* Did we already (try to) parse the environment and setup the necessary
48 static int initialized;
49 /* Force hooked writes even when not writing to a tty. Used for tests. */
50 static int force_write_to_non_tty;
53 #include "constants.h"
59 #include "hookmacros.h"
64 /* See hookmacros.h for the decision if a function call is colored. */
67 /* Prevent inlining into hook functions because it may increase the number of
68 * spilled registers unnecessarily. As it's not called very often accept the
70 static int isatty_noinline(int fd) __noinline;
71 static int isatty_noinline(int fd) {
72 int saved_errno = errno;
73 int result = isatty(fd);
80 static void dup_fd(int oldfd, int newfd) {
82 debug("%3d -> %3d\t\t\t[%d]\n", oldfd, newfd, getpid());
85 if (unlikely(!initialized)) {
86 init_from_environment();
89 /* We are already tracking this file descriptor, add newfd to the list as
90 * it will reference the same descriptor. */
91 if (tracked_fds_find(oldfd)) {
92 if (!tracked_fds_find(newfd)) {
93 tracked_fds_add(newfd);
95 /* We are not tracking this file descriptor, remove newfd from the list
98 tracked_fds_remove(newfd);
102 static void close_fd(int fd) {
104 debug("%3d -> .\t\t\t[%d]\n", fd, getpid());
107 if (unlikely(!initialized)) {
108 init_from_environment();
111 tracked_fds_remove(fd);
115 /* "Action" handlers called when a file descriptor is matched. */
117 static char const *pre_string;
118 static size_t pre_string_size;
119 static char const *post_string;
120 static size_t post_string_size;
122 /* Load alternative pre/post strings from the environment if available, fall
123 * back to default values. */
124 inline static void init_pre_post_string(void) {
125 pre_string = getenv(ENV_NAME_PRE_STRING);
127 pre_string = DEFAULT_PRE_STRING;
129 pre_string_size = strlen(pre_string);
131 post_string = getenv(ENV_NAME_POST_STRING);
133 post_string = DEFAULT_POST_STRING;
135 post_string_size = strlen(post_string);
138 static void handle_fd_pre(int fd) {
139 int saved_errno = errno;
141 if (unlikely(!pre_string || !post_string)) {
142 init_pre_post_string();
145 DLSYM_FUNCTION(real_write, "write");
146 real_write(fd, pre_string, pre_string_size);
150 static void handle_fd_post(int fd) {
151 int saved_errno = errno;
153 /* write() already loaded above in handle_fd_pre(). */
154 real_write(fd, post_string, post_string_size);
159 static void handle_file_pre(FILE *stream) {
160 int saved_errno = errno;
162 if (unlikely(!pre_string || !post_string)) {
163 init_pre_post_string();
166 DLSYM_FUNCTION(real_fwrite, "fwrite");
167 real_fwrite(pre_string, pre_string_size, 1, stream);
171 static void handle_file_post(FILE *stream) {
172 int saved_errno = errno;
174 /* fwrite() already loaded above in handle_file_pre(). */
175 real_fwrite(post_string, post_string_size, 1, stream);
182 /* Hook all important output functions to manipulate their output. */
184 HOOK_FD3(ssize_t, write, fd,
185 int, fd, void const *, buf, size_t, count)
186 HOOK_FILE4(size_t, fwrite, stream,
187 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
190 HOOK_FILE2(int, fputs, stream,
191 char const *, s, FILE *, stream)
192 HOOK_FILE2(int, fputc, stream,
193 int, c, FILE *, stream)
194 HOOK_FILE2(int, putc, stream,
195 int, c, FILE *, stream)
196 HOOK_FILE1(int, putchar, stdout,
198 HOOK_FILE1(int, puts, stdout,
201 /* printf(3), excluding all s*() and vs*() functions (no output) */
202 HOOK_VAR_FILE1(int, printf, stdout, vprintf,
203 char const *, format)
204 HOOK_VAR_FILE2(int, fprintf, stream, vfprintf,
205 FILE *, stream, char const *, format)
206 HOOK_FILE2(int, vprintf, stdout,
207 char const *, format, va_list, ap)
208 HOOK_FILE3(int, vfprintf, stream,
209 FILE *, stream, char const *, format, va_list, ap)
210 /* Hardening functions (-D_FORTIFY_SOURCE=2), only functions from above */
211 HOOK_VAR_FILE2(int, __printf_chk, stdout, __vprintf_chk,
212 int, flag, char const *, format)
213 HOOK_VAR_FILE3(int, __fprintf_chk, fp, __vfprintf_chk,
214 FILE *, fp, int, flag, char const *, format)
215 HOOK_FILE3(int, __vprintf_chk, stdout,
216 int, flag, char const *, format, va_list, ap)
217 HOOK_FILE4(int, __vfprintf_chk, stream,
218 FILE *, stream, int, flag, char const *, format, va_list, ap)
220 /* unlocked_stdio(3), only functions from above are hooked */
221 HOOK_FILE4(size_t, fwrite_unlocked, stream,
222 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
223 HOOK_FILE2(int, fputs_unlocked, stream,
224 char const *, s, FILE *, stream)
225 HOOK_FILE2(int, fputc_unlocked, stream,
226 int, c, FILE *, stream)
227 HOOK_FILE2(int, putc_unlocked, stream,
228 int, c, FILE *, stream)
229 HOOK_FILE1(int, putchar_unlocked, stdout,
233 HOOK_VOID1(void, perror, STDERR_FILENO,
238 static void error_vararg(int status, int errnum,
239 char const *filename, unsigned int linenum,
240 char const *format, va_list ap) {
241 static char const *last_filename;
242 static unsigned int last_linenum;
244 /* Skip this error message if requested and if there was already an error
245 * in the same file/line. */
246 if (error_one_per_line
247 && filename != NULL && linenum != 0
248 && filename == last_filename && linenum == last_linenum) {
251 last_filename = filename;
252 last_linenum = linenum;
254 error_message_count++;
258 if (error_print_progname) {
259 error_print_progname();
261 fprintf(stderr, "%s:", program_invocation_name);
263 if (filename != NULL && linenum != 0) {
264 fprintf(stderr, "%s:%u:", filename, linenum);
265 if (error_print_progname) {
266 fprintf(stderr, " ");
269 if (!error_print_progname) {
270 fprintf(stderr, " ");
274 vfprintf(stderr, format, ap);
277 fprintf(stderr, ": %s", strerror(errnum));
280 fprintf(stderr, "\n");
286 void error_at_line(int status, int errnum,
287 char const *filename, unsigned int linenum,
288 char const *format, ...) {
291 va_start(ap, format);
292 error_vararg(status, errnum, filename, linenum, format, ap);
295 void error(int status, int errnum, char const *format, ...) {
298 va_start(ap, format);
299 error_vararg(status, errnum, NULL, 0, format, ap);
305 /* Hook functions which duplicate file descriptors to track them. */
307 static int (*real_dup)(int);
308 static int (*real_dup2)(int, int);
309 static int (*real_dup3)(int, int, int);
313 DLSYM_FUNCTION(real_dup, "dup");
315 newfd = real_dup(oldfd);
317 dup_fd(oldfd, newfd);
322 int dup2(int oldfd, int newfd) {
323 DLSYM_FUNCTION(real_dup2, "dup2");
325 newfd = real_dup2(oldfd, newfd);
327 dup_fd(oldfd, newfd);
332 int dup3(int oldfd, int newfd, int flags) {
333 DLSYM_FUNCTION(real_dup3, "dup3");
335 newfd = real_dup3(oldfd, newfd, flags);
337 dup_fd(oldfd, newfd);
343 static int (*real_fcntl)(int, int, ...);
344 int fcntl(int fd, int cmd, ...) {
348 DLSYM_FUNCTION(real_fcntl, "fcntl");
350 /* fcntl() takes different types of arguments depending on the cmd type
351 * (int, void and pointers are used at the moment). Handling these
352 * arguments for different systems and with possible changes in the future
355 * Therefore always retrieve a void-pointer from our arguments (even if it
356 * wasn't there) and pass it to real_fcntl(). This shouldn't cause any
357 * problems because a void-pointer is most-likely bigger than an int
358 * (something which is not true in reverse) and shouldn't cause
359 * truncation. For register based calling conventions an invalid register
360 * content is passed, but ignored by real_fcntl(). Not perfect, but should
364 result = real_fcntl(fd, cmd, va_arg(ap, void *));
367 /* We only care about duping fds. */
368 if (cmd == F_DUPFD && result != -1) {
375 static int (*real_close)(int);
377 DLSYM_FUNCTION(real_close, "close");
380 return real_close(fd);
382 static int (*real_fclose)(FILE *);
383 int fclose(FILE *fp) {
384 DLSYM_FUNCTION(real_fclose, "fclose");
386 close_fd(fileno(fp));
387 return real_fclose(fp);
391 /* Hook functions which are necessary for correct tracking. */
393 #if defined(HAVE_VFORK) && defined(HAVE_FORK)
395 /* vfork() is similar to fork() but the address space is shared between
396 * father and child. It's designed for fork()/exec() usage because it's
397 * faster than fork(). However according to the POSIX standard the "child"
398 * isn't allowed to perform any memory-modifications before the exec()
399 * (except the pid_t result variable of vfork()).
401 * As some programs don't adhere to the standard (e.g. the "child" closes
402 * or dups a descriptor before the exec()) and this breaks our tracking of
403 * file descriptors (e.g. it gets closed in the parent as well), we just
404 * fork() instead. This is in compliance with the POSIX standard and as
405 * most systems use copy-on-write anyway not a performance issue. */
411 /* Hook execve() and the other exec*() functions. Some shells use exec*() with
412 * a custom environment which doesn't necessarily contain our updates to
413 * ENV_NAME_FDS. It's also faster to update the environment only when
414 * necessary, right before the exec() to pass it to the new process. */
416 static int (*real_execve)(char const *filename, char * const argv[], char * const env[]);
417 int execve(char const *filename, char * const argv[], char * const env[]) {
418 DLSYM_FUNCTION(real_execve, "execve");
423 /* Count arguments and search for existing ENV_NAME_FDS environment
426 char * const *x = env;
428 if (!strncmp(*x, ENV_NAME_FDS "=", strlen(ENV_NAME_FDS) + 1)) {
436 /* Terminating NULL. */
439 char *env_copy[count + 1 /* space for our new entry if necessary */];
440 memcpy(env_copy, env, count * sizeof(char *));
442 /* Make sure the information from the environment is loaded. We can't just
443 * do nothing (like update_environment()) because the caller might pass a
444 * different environment which doesn't include any of our settings. */
446 init_from_environment();
449 char fds_env[strlen(ENV_NAME_FDS) + 1 + update_environment_buffer_size()];
450 strcpy(fds_env, ENV_NAME_FDS "=");
451 update_environment_buffer(fds_env + strlen(ENV_NAME_FDS) + 1);
454 env_copy[index] = fds_env;
456 /* If the process removed ENV_NAME_FDS from the environment, re-add
458 env_copy[count-1] = fds_env;
459 env_copy[count] = NULL;
462 return real_execve(filename, argv, env_copy);
465 #define EXECL_COPY_VARARGS_START(args) \
469 /* Count arguments. */ \
470 size_t count = 1; /* arg */ \
472 while (va_arg(ap, char const *)) { \
477 /* Copy varargs. */ \
478 char *args[count + 1 /* terminating NULL */]; \
479 args[0] = (char *)arg; \
483 while ((x = va_arg(ap, char *))) { \
487 #define EXECL_COPY_VARARGS_END(args) \
489 #define EXECL_COPY_VARARGS(args) \
490 EXECL_COPY_VARARGS_START(args); \
491 EXECL_COPY_VARARGS_END(args);
493 int execl(char const *path, char const *arg, ...) {
494 EXECL_COPY_VARARGS(args);
496 update_environment();
497 return execv(path, args);
500 int execlp(char const *file, char const *arg, ...) {
501 EXECL_COPY_VARARGS(args);
503 update_environment();
504 return execvp(file, args);
507 int execle(char const *path, char const *arg, ... /*, char * const envp[] */) {
508 EXECL_COPY_VARARGS_START(args);
509 /* Get envp[] located after arguments. */
510 char * const *envp = va_arg(ap, char * const *);
511 EXECL_COPY_VARARGS_END(args);
513 return execve(path, args, envp);
516 static int (*real_execv)(char const *path, char * const argv[]);
517 int execv(char const *path, char * const argv[]) {
518 DLSYM_FUNCTION(real_execv, "execv");
520 update_environment();
521 return real_execv(path, argv);
524 static int (*real_execvp)(char const *path, char * const argv[]);
525 int execvp(char const *path, char * const argv[]) {
526 DLSYM_FUNCTION(real_execvp, "execvp");
528 update_environment();
529 return real_execvp(path, argv);