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/>.
25 /* Must be loaded before the following headers. */
26 #include "ldpreload.h"
39 /* Conflicting declaration in glibc. */
40 #undef fwrite_unlocked
43 /* Used by various functions, including debug(). */
44 static ssize_t (*real_write)(int, void const *, size_t);
45 static int (*real_close)(int);
46 static size_t (*real_fwrite)(void const *, size_t, size_t, FILE *);
48 /* Did we already (try to) parse the environment and setup the necessary
50 static int initialized;
51 /* Force hooked writes even when not writing to a tty. Used for tests. */
52 static int force_write_to_non_tty;
55 #include "constants.h"
60 #include "hookmacros.h"
65 /* See hookmacros.h for the decision if a function call is colored. */
68 /* Prevent inlining into hook functions because it may increase the number of
69 * spilled registers unnecessarily. As it's not called very often accept the
71 static int isatty_noinline(int fd) noinline;
72 static int isatty_noinline(int fd) {
73 int saved_errno = errno;
74 int result = isatty(fd);
81 static void dup_fd(int oldfd, int newfd) {
83 debug("%3d -> %3d\t\t\t[%d]\n", oldfd, newfd, getpid());
86 if (unlikely(!initialized)) {
87 init_from_environment();
90 /* We are already tracking this file descriptor, add newfd to the list as
91 * it will reference the same descriptor. */
92 if (tracked_fds_find(oldfd)) {
93 if (!tracked_fds_find(newfd)) {
94 tracked_fds_add(newfd);
96 /* We are not tracking this file descriptor, remove newfd from the list
99 tracked_fds_remove(newfd);
103 static void close_fd(int fd) {
105 debug("%3d -> .\t\t\t[%d]\n", fd, getpid());
108 if (unlikely(!initialized)) {
109 init_from_environment();
112 tracked_fds_remove(fd);
116 /* "Action" handlers called when a file descriptor is matched. */
118 static char const *pre_string;
119 static size_t pre_string_size;
120 static char const *post_string;
121 static size_t post_string_size;
123 /* Load alternative pre/post strings from the environment if available, fall
124 * back to default values. */
125 static void init_pre_post_string(void) {
126 pre_string = getenv(ENV_NAME_PRE_STRING);
128 pre_string = DEFAULT_PRE_STRING;
130 pre_string_size = strlen(pre_string);
132 post_string = getenv(ENV_NAME_POST_STRING);
134 post_string = DEFAULT_POST_STRING;
136 post_string_size = strlen(post_string);
139 /* Don't inline any of the pre/post functions. Keep the hook function as small
140 * as possible for speed reasons. */
141 static void handle_fd_pre(int fd) noinline;
142 static void handle_fd_post(int fd) noinline;
143 static void handle_file_pre(FILE *stream) noinline;
144 static void handle_file_post(FILE *stream) noinline;
146 static void handle_fd_pre(int fd) {
147 int saved_errno = errno;
149 if (unlikely(!pre_string || !post_string)) {
150 init_pre_post_string();
153 DLSYM_FUNCTION(real_write, "write");
154 real_write(fd, pre_string, pre_string_size);
158 static void handle_fd_post(int fd) {
159 int saved_errno = errno;
161 /* write() already loaded above in handle_fd_pre(). */
162 real_write(fd, post_string, post_string_size);
167 static void handle_file_pre(FILE *stream) {
168 int saved_errno = errno;
170 if (unlikely(!pre_string || !post_string)) {
171 init_pre_post_string();
174 DLSYM_FUNCTION(real_fwrite, "fwrite");
175 real_fwrite(pre_string, pre_string_size, 1, stream);
179 static void handle_file_post(FILE *stream) {
180 int saved_errno = errno;
182 /* fwrite() already loaded above in handle_file_pre(). */
183 real_fwrite(post_string, post_string_size, 1, stream);
190 /* Hook all important output functions to manipulate their output. */
192 HOOK_FD3(ssize_t, write, fd,
193 int, fd, void const *, buf, size_t, count)
194 HOOK_FILE4(size_t, fwrite, stream,
195 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
198 HOOK_FILE2(int, fputs, stream,
199 char const *, s, FILE *, stream)
200 HOOK_FILE2(int, fputc, stream,
201 int, c, FILE *, stream)
202 HOOK_FILE2(int, putc, stream,
203 int, c, FILE *, stream)
204 HOOK_FILE1(int, putchar, stdout,
206 HOOK_FILE1(int, puts, stdout,
209 /* printf(3), excluding all s*() and vs*() functions (no output) */
210 HOOK_VAR_FILE1(int, printf, stdout, vprintf,
211 char const *, format)
212 HOOK_VAR_FILE2(int, fprintf, stream, vfprintf,
213 FILE *, stream, char const *, format)
214 HOOK_FILE2(int, vprintf, stdout,
215 char const *, format, va_list, ap)
216 HOOK_FILE3(int, vfprintf, stream,
217 FILE *, stream, char const *, format, va_list, ap)
218 /* Hardening functions (-D_FORTIFY_SOURCE=2), only functions from above */
219 HOOK_VAR_FILE2(int, __printf_chk, stdout, __vprintf_chk,
220 int, flag, char const *, format)
221 HOOK_VAR_FILE3(int, __fprintf_chk, fp, __vfprintf_chk,
222 FILE *, fp, int, flag, char const *, format)
223 HOOK_FILE3(int, __vprintf_chk, stdout,
224 int, flag, char const *, format, va_list, ap)
225 HOOK_FILE4(int, __vfprintf_chk, stream,
226 FILE *, stream, int, flag, char const *, format, va_list, ap)
228 /* unlocked_stdio(3), only functions from above are hooked */
229 HOOK_FILE4(size_t, fwrite_unlocked, stream,
230 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
231 HOOK_FILE2(int, fputs_unlocked, stream,
232 char const *, s, FILE *, stream)
233 HOOK_FILE2(int, fputc_unlocked, stream,
234 int, c, FILE *, stream)
235 HOOK_FILE2(int, putc_unlocked, stream,
236 int, c, FILE *, stream)
237 HOOK_FILE1(int, putchar_unlocked, stdout,
241 HOOK_VOID1(void, perror, STDERR_FILENO,
246 static void error_vararg(int status, int errnum,
247 char const *filename, unsigned int linenum,
248 char const *format, va_list ap) {
249 static char const *last_filename;
250 static unsigned int last_linenum;
252 /* Skip this error message if requested and if there was already an error
253 * in the same file/line. */
254 if (error_one_per_line
255 && filename != NULL && linenum != 0
256 && filename == last_filename && linenum == last_linenum) {
259 last_filename = filename;
260 last_linenum = linenum;
262 error_message_count++;
266 if (error_print_progname) {
267 error_print_progname();
269 fprintf(stderr, "%s:", program_invocation_name);
271 if (filename != NULL && linenum != 0) {
272 fprintf(stderr, "%s:%u:", filename, linenum);
273 if (error_print_progname) {
274 fprintf(stderr, " ");
277 if (!error_print_progname) {
278 fprintf(stderr, " ");
282 vfprintf(stderr, format, ap);
285 fprintf(stderr, ": %s", strerror(errnum));
288 fprintf(stderr, "\n");
294 void error_at_line(int status, int errnum,
295 char const *filename, unsigned int linenum,
296 char const *format, ...) {
299 va_start(ap, format);
300 error_vararg(status, errnum, filename, linenum, format, ap);
303 void error(int status, int errnum, char const *format, ...) {
306 va_start(ap, format);
307 error_vararg(status, errnum, NULL, 0, format, ap);
313 /* Hook functions which duplicate file descriptors to track them. */
315 static int (*real_dup)(int);
316 static int (*real_dup2)(int, int);
317 static int (*real_dup3)(int, int, int);
321 DLSYM_FUNCTION(real_dup, "dup");
323 newfd = real_dup(oldfd);
325 dup_fd(oldfd, newfd);
330 int dup2(int oldfd, int newfd) {
331 DLSYM_FUNCTION(real_dup2, "dup2");
333 newfd = real_dup2(oldfd, newfd);
335 dup_fd(oldfd, newfd);
340 int dup3(int oldfd, int newfd, int flags) {
341 DLSYM_FUNCTION(real_dup3, "dup3");
343 newfd = real_dup3(oldfd, newfd, flags);
345 dup_fd(oldfd, newfd);
351 static int (*real_fcntl)(int, int, ...);
352 int fcntl(int fd, int cmd, ...) {
356 DLSYM_FUNCTION(real_fcntl, "fcntl");
358 /* fcntl() takes different types of arguments depending on the cmd type
359 * (int, void and pointers are used at the moment). Handling these
360 * arguments for different systems and with possible changes in the future
363 * Therefore always retrieve a void-pointer from our arguments (even if it
364 * wasn't there) and pass it to real_fcntl(). This shouldn't cause any
365 * problems because a void-pointer is most-likely bigger than an int
366 * (something which is not true in reverse) and shouldn't cause
367 * truncation. For register based calling conventions an invalid register
368 * content is passed, but ignored by real_fcntl(). Not perfect, but should
372 result = real_fcntl(fd, cmd, va_arg(ap, void *));
375 /* We only care about duping fds. */
376 if (cmd == F_DUPFD && result != -1) {
383 static int (*real_close)(int);
385 DLSYM_FUNCTION(real_close, "close");
388 return real_close(fd);
390 static int (*real_fclose)(FILE *);
391 int fclose(FILE *fp) {
392 DLSYM_FUNCTION(real_fclose, "fclose");
394 close_fd(fileno(fp));
395 return real_fclose(fp);
399 /* Hook functions which are necessary for correct tracking. */
401 #if defined(HAVE_VFORK) && defined(HAVE_FORK)
403 /* vfork() is similar to fork() but the address space is shared between
404 * father and child. It's designed for fork()/exec() usage because it's
405 * faster than fork(). However according to the POSIX standard the "child"
406 * isn't allowed to perform any memory-modifications before the exec()
407 * (except the pid_t result variable of vfork()).
409 * As some programs don't adhere to the standard (e.g. the "child" closes
410 * or dups a descriptor before the exec()) and this breaks our tracking of
411 * file descriptors (e.g. it gets closed in the parent as well), we just
412 * fork() instead. This is in compliance with the POSIX standard and as
413 * most systems use copy-on-write anyway not a performance issue. */
419 /* Hook execve() and the other exec*() functions. Some shells use exec*() with
420 * a custom environment which doesn't necessarily contain our updates to
421 * ENV_NAME_FDS. It's also faster to update the environment only when
422 * necessary, right before the exec() to pass it to the new process. */
424 static int (*real_execve)(char const *filename, char * const argv[], char * const env[]);
425 int execve(char const *filename, char * const argv[], char * const env[]) {
426 DLSYM_FUNCTION(real_execve, "execve");
431 /* Count arguments and search for existing ENV_NAME_FDS environment
434 char * const *x = env;
436 if (!strncmp(*x, ENV_NAME_FDS "=", strlen(ENV_NAME_FDS) + 1)) {
444 /* Terminating NULL. */
447 char *env_copy[count + 1 /* space for our new entry if necessary */];
448 memcpy(env_copy, env, count * sizeof(char *));
450 /* Make sure the information from the environment is loaded. We can't just
451 * do nothing (like update_environment()) because the caller might pass a
452 * different environment which doesn't include any of our settings. */
454 init_from_environment();
457 char fds_env[strlen(ENV_NAME_FDS) + 1 + update_environment_buffer_size()];
458 strcpy(fds_env, ENV_NAME_FDS "=");
459 update_environment_buffer(fds_env + strlen(ENV_NAME_FDS) + 1);
462 env_copy[index] = fds_env;
464 /* If the process removed ENV_NAME_FDS from the environment, re-add
466 env_copy[count-1] = fds_env;
467 env_copy[count] = NULL;
470 return real_execve(filename, argv, env_copy);
473 #define EXECL_COPY_VARARGS_START(args) \
477 /* Count arguments. */ \
478 size_t count = 1; /* arg */ \
480 while (va_arg(ap, char const *)) { \
485 /* Copy varargs. */ \
486 char *args[count + 1 /* terminating NULL */]; \
487 args[0] = (char *)arg; \
491 while ((x = va_arg(ap, char *))) { \
495 #define EXECL_COPY_VARARGS_END(args) \
497 #define EXECL_COPY_VARARGS(args) \
498 EXECL_COPY_VARARGS_START(args); \
499 EXECL_COPY_VARARGS_END(args);
501 int execl(char const *path, char const *arg, ...) {
502 EXECL_COPY_VARARGS(args);
504 update_environment();
505 return execv(path, args);
508 int execlp(char const *file, char const *arg, ...) {
509 EXECL_COPY_VARARGS(args);
511 update_environment();
512 return execvp(file, args);
515 int execle(char const *path, char const *arg, ... /*, char * const envp[] */) {
516 EXECL_COPY_VARARGS_START(args);
517 /* Get envp[] located after arguments. */
518 char * const *envp = va_arg(ap, char * const *);
519 EXECL_COPY_VARARGS_END(args);
521 return execve(path, args, envp);
524 static int (*real_execv)(char const *path, char * const argv[]);
525 int execv(char const *path, char * const argv[]) {
526 DLSYM_FUNCTION(real_execv, "execv");
528 update_environment();
529 return real_execv(path, argv);
532 static int (*real_execvp)(char const *path, char * const argv[]);
533 int execvp(char const *file, char * const argv[]) {
534 DLSYM_FUNCTION(real_execvp, "execvp");
536 update_environment();
537 return real_execvp(file, argv);