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"
28 /* Disable assert()s if not compiled with --enable-debug. */
44 #ifdef HAVE_STRUCT__IO_FILE__FILENO
48 /* Conflicting declaration in glibc. */
49 #undef fwrite_unlocked
50 /* These functions may be macros when compiling with hardening flags (fortify)
51 * which cause build failures when used in our hook macros below. Observed
52 * with Clang on Debian Wheezy. */
57 /* Used by various functions, including debug(). */
58 static ssize_t (*real_write)(int, void const *, size_t);
59 static int (*real_close)(int);
60 static size_t (*real_fwrite)(void const *, size_t, size_t, FILE *);
62 /* Did we already (try to) parse the environment and setup the necessary
64 static int initialized;
65 /* Force hooked writes even when not writing to a tty. Used for tests. */
66 static int force_write_to_non_tty;
69 #include "constants.h"
74 #include "hookmacros.h"
79 /* See hookmacros.h for the decision if a function call is colored. */
82 /* Prevent inlining into hook functions because it may increase the number of
83 * spilled registers unnecessarily. As it's not called very often accept the
85 static int isatty_noinline(int fd) noinline;
86 static int isatty_noinline(int fd) {
89 int saved_errno = errno;
90 int result = isatty(fd);
97 static void dup_fd(int oldfd, int newfd) {
99 debug("%3d -> %3d\t\t\t[%d]\n", oldfd, newfd, getpid());
102 assert(oldfd >= 0 && newfd >= 0);
104 if (unlikely(!initialized)) {
105 init_from_environment();
108 /* We are already tracking this file descriptor, add newfd to the list as
109 * it will reference the same descriptor. */
110 if (tracked_fds_find(oldfd)) {
111 if (!tracked_fds_find(newfd)) {
112 tracked_fds_add(newfd);
114 /* We are not tracking this file descriptor, remove newfd from the list
117 tracked_fds_remove(newfd);
121 static void close_fd(int fd) {
123 debug("%3d -> .\t\t\t[%d]\n", fd, getpid());
128 if (unlikely(!initialized)) {
129 init_from_environment();
132 tracked_fds_remove(fd);
136 /* "Action" handlers called when a file descriptor is matched. */
138 static char const *pre_string;
139 static size_t pre_string_size;
140 static char const *post_string;
141 static size_t post_string_size;
143 /* Load alternative pre/post strings from the environment if available, fall
144 * back to default values. */
145 static void init_pre_post_string(void) {
146 pre_string = getenv(ENV_NAME_PRE_STRING);
148 pre_string = DEFAULT_PRE_STRING;
150 pre_string_size = strlen(pre_string);
152 post_string = getenv(ENV_NAME_POST_STRING);
154 post_string = DEFAULT_POST_STRING;
156 post_string_size = strlen(post_string);
159 /* Don't inline any of the pre/post functions. Keep the hook function as small
160 * as possible for speed reasons. */
161 static void handle_fd_pre(int fd) noinline;
162 static void handle_fd_post(int fd) noinline;
163 static void handle_file_pre(FILE *stream) noinline;
164 static void handle_file_post(FILE *stream) noinline;
166 static void handle_fd_pre(int fd) {
167 int saved_errno = errno;
169 if (unlikely(!pre_string || !post_string)) {
170 init_pre_post_string();
173 DLSYM_FUNCTION(real_write, "write");
174 real_write(fd, pre_string, pre_string_size);
178 static void handle_fd_post(int fd) {
179 int saved_errno = errno;
181 /* write() already loaded above in handle_fd_pre(). */
182 real_write(fd, post_string, post_string_size);
187 static void handle_file_pre(FILE *stream) {
188 int saved_errno = errno;
190 if (unlikely(!pre_string || !post_string)) {
191 init_pre_post_string();
194 DLSYM_FUNCTION(real_fwrite, "fwrite");
195 real_fwrite(pre_string, pre_string_size, 1, stream);
199 static void handle_file_post(FILE *stream) {
200 int saved_errno = errno;
202 /* fwrite() already loaded above in handle_file_pre(). */
203 real_fwrite(post_string, post_string_size, 1, stream);
210 /* Hook all important output functions to manipulate their output. */
212 HOOK_FD3(ssize_t, write, fd,
213 int, fd, void const *, buf, size_t, count)
214 HOOK_FILE4(size_t, fwrite, stream,
215 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
218 HOOK_FILE2(int, fputs, stream,
219 char const *, s, FILE *, stream)
220 HOOK_FILE2(int, fputc, stream,
221 int, c, FILE *, stream)
222 HOOK_FILE2(int, putc, stream,
223 int, c, FILE *, stream)
224 HOOK_FILE1(int, putchar, stdout,
226 HOOK_FILE1(int, puts, stdout,
229 /* printf(3), excluding all s*() and vs*() functions (no output) */
230 HOOK_VAR_FILE1(int, printf, stdout, vprintf,
231 char const *, format)
232 HOOK_VAR_FILE2(int, fprintf, stream, vfprintf,
233 FILE *, stream, char const *, format)
234 HOOK_FILE2(int, vprintf, stdout,
235 char const *, format, va_list, ap)
236 HOOK_FILE3(int, vfprintf, stream,
237 FILE *, stream, char const *, format, va_list, ap)
238 /* Hardening functions (-D_FORTIFY_SOURCE=2), only functions from above */
239 HOOK_VAR_FILE2(int, __printf_chk, stdout, __vprintf_chk,
240 int, flag, char const *, format)
241 HOOK_VAR_FILE3(int, __fprintf_chk, fp, __vfprintf_chk,
242 FILE *, fp, int, flag, char const *, format)
243 HOOK_FILE3(int, __vprintf_chk, stdout,
244 int, flag, char const *, format, va_list, ap)
245 HOOK_FILE4(int, __vfprintf_chk, stream,
246 FILE *, stream, int, flag, char const *, format, va_list, ap)
248 /* unlocked_stdio(3), only functions from above are hooked */
249 HOOK_FILE4(size_t, fwrite_unlocked, stream,
250 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
251 HOOK_FILE2(int, fputs_unlocked, stream,
252 char const *, s, FILE *, stream)
253 HOOK_FILE2(int, fputc_unlocked, stream,
254 int, c, FILE *, stream)
255 HOOK_FILE2(int, putc_unlocked, stream,
256 int, c, FILE *, stream)
257 HOOK_FILE1(int, putchar_unlocked, stdout,
259 /* glibc defines (_IO_)putc_unlocked() to __overflow() in some cases. */
260 #ifdef HAVE_STRUCT__IO_FILE__FILENO
261 HOOK_FD2(int, __overflow, f->_fileno, _IO_FILE *, f, int, ch)
265 HOOK_VOID1(void, perror, STDERR_FILENO,
270 static void error_vararg(int status, int errnum,
271 char const *filename, unsigned int linenum,
272 char const *format, va_list ap) {
273 static char const *last_filename;
274 static unsigned int last_linenum;
276 /* Skip this error message if requested and if there was already an error
277 * in the same file/line. */
278 if (error_one_per_line
279 && filename != NULL && linenum != 0
280 && filename == last_filename && linenum == last_linenum) {
283 last_filename = filename;
284 last_linenum = linenum;
286 error_message_count++;
290 if (error_print_progname) {
291 error_print_progname();
293 fprintf(stderr, "%s:", program_invocation_name);
295 if (filename != NULL && linenum != 0) {
296 fprintf(stderr, "%s:%u:", filename, linenum);
297 if (error_print_progname) {
298 fprintf(stderr, " ");
301 if (!error_print_progname) {
302 fprintf(stderr, " ");
306 vfprintf(stderr, format, ap);
309 fprintf(stderr, ": %s", strerror(errnum));
312 fprintf(stderr, "\n");
318 void error_at_line(int status, int errnum,
319 char const *filename, unsigned int linenum,
320 char const *format, ...) {
323 va_start(ap, format);
324 error_vararg(status, errnum, filename, linenum, format, ap);
327 void error(int status, int errnum, char const *format, ...) {
330 va_start(ap, format);
331 error_vararg(status, errnum, NULL, 0, format, ap);
337 /* Hook functions which duplicate file descriptors to track them. */
339 static int (*real_dup)(int);
340 static int (*real_dup2)(int, int);
341 static int (*real_dup3)(int, int, int);
345 DLSYM_FUNCTION(real_dup, "dup");
347 newfd = real_dup(oldfd);
349 dup_fd(oldfd, newfd);
354 int dup2(int oldfd, int newfd) {
355 DLSYM_FUNCTION(real_dup2, "dup2");
357 newfd = real_dup2(oldfd, newfd);
359 dup_fd(oldfd, newfd);
364 int dup3(int oldfd, int newfd, int flags) {
365 DLSYM_FUNCTION(real_dup3, "dup3");
367 newfd = real_dup3(oldfd, newfd, flags);
369 dup_fd(oldfd, newfd);
375 static int (*real_fcntl)(int, int, ...);
376 int fcntl(int fd, int cmd, ...) {
380 DLSYM_FUNCTION(real_fcntl, "fcntl");
382 /* fcntl() takes different types of arguments depending on the cmd type
383 * (int, void and pointers are used at the moment). Handling these
384 * arguments for different systems and with possible changes in the future
387 * Therefore always retrieve a void-pointer from our arguments (even if it
388 * wasn't there) and pass it to real_fcntl(). This shouldn't cause any
389 * problems because a void-pointer is most-likely bigger than an int
390 * (something which is not true in reverse) and shouldn't cause
391 * truncation. For register based calling conventions an invalid register
392 * content is passed, but ignored by real_fcntl(). Not perfect, but should
396 result = real_fcntl(fd, cmd, va_arg(ap, void *));
399 /* We only care about duping fds. */
400 if (cmd == F_DUPFD && result != -1) {
407 static int (*real_close)(int);
409 DLSYM_FUNCTION(real_close, "close");
414 return real_close(fd);
416 static int (*real_fclose)(FILE *);
417 int fclose(FILE *fp) {
420 DLSYM_FUNCTION(real_fclose, "fclose");
422 if (fp != NULL && (fd = fileno(fp)) >= 0) {
425 return real_fclose(fp);
429 /* Hook functions which are necessary for correct tracking. */
431 #if defined(HAVE_VFORK) && defined(HAVE_FORK)
433 /* vfork() is similar to fork() but the address space is shared between
434 * father and child. It's designed for fork()/exec() usage because it's
435 * faster than fork(). However according to the POSIX standard the "child"
436 * isn't allowed to perform any memory-modifications before the exec()
437 * (except the pid_t result variable of vfork()).
439 * As some programs don't adhere to the standard (e.g. the "child" closes
440 * or dups a descriptor before the exec()) and this breaks our tracking of
441 * file descriptors (e.g. it gets closed in the parent as well), we just
442 * fork() instead. This is in compliance with the POSIX standard and as
443 * most systems use copy-on-write anyway not a performance issue. */
449 /* Hook execve() and the other exec*() functions. Some shells use exec*() with
450 * a custom environment which doesn't necessarily contain our updates to
451 * ENV_NAME_FDS. It's also faster to update the environment only when
452 * necessary, right before the exec() to pass it to the new process. */
454 static int (*real_execve)(char const *filename, char * const argv[], char * const env[]);
455 int execve(char const *filename, char * const argv[], char * const env[]) {
456 DLSYM_FUNCTION(real_execve, "execve");
461 /* Count arguments and search for existing ENV_NAME_FDS environment
464 char * const *x = env;
466 if (!strncmp(*x, ENV_NAME_FDS "=", strlen(ENV_NAME_FDS) + 1)) {
474 /* Terminating NULL. */
477 char *env_copy[count + 1 /* space for our new entry if necessary */];
478 memcpy(env_copy, env, count * sizeof(char *));
480 /* Make sure the information from the environment is loaded. We can't just
481 * do nothing (like update_environment()) because the caller might pass a
482 * different environment which doesn't include any of our settings. */
484 init_from_environment();
487 char fds_env[strlen(ENV_NAME_FDS) + 1 + update_environment_buffer_size()];
488 strcpy(fds_env, ENV_NAME_FDS "=");
489 update_environment_buffer(fds_env + strlen(ENV_NAME_FDS) + 1);
492 env_copy[index] = fds_env;
494 /* If the process removed ENV_NAME_FDS from the environment, re-add
496 env_copy[count-1] = fds_env;
497 env_copy[count] = NULL;
500 return real_execve(filename, argv, env_copy);
503 #define EXECL_COPY_VARARGS_START(args) \
507 /* Count arguments. */ \
508 size_t count = 1; /* arg */ \
510 while (va_arg(ap, char const *)) { \
515 /* Copy varargs. */ \
516 char *args[count + 1 /* terminating NULL */]; \
517 args[0] = (char *)arg; \
521 while ((x = va_arg(ap, char *))) { \
525 #define EXECL_COPY_VARARGS_END(args) \
527 #define EXECL_COPY_VARARGS(args) \
528 EXECL_COPY_VARARGS_START(args); \
529 EXECL_COPY_VARARGS_END(args);
531 int execl(char const *path, char const *arg, ...) {
532 EXECL_COPY_VARARGS(args);
534 /* execv() updates the environment. */
535 return execv(path, args);
537 int execlp(char const *file, char const *arg, ...) {
538 EXECL_COPY_VARARGS(args);
540 /* execvp() updates the environment. */
541 return execvp(file, args);
543 int execle(char const *path, char const *arg, ... /*, char * const envp[] */) {
546 EXECL_COPY_VARARGS_START(args);
547 /* Get envp[] located after arguments. */
548 envp = va_arg(ap, char * const *);
549 EXECL_COPY_VARARGS_END(args);
551 /* execve() updates the environment. */
552 return execve(path, args, envp);
555 static int (*real_execv)(char const *path, char * const argv[]);
556 int execv(char const *path, char * const argv[]) {
557 DLSYM_FUNCTION(real_execv, "execv");
559 update_environment();
560 return real_execv(path, argv);
563 static int (*real_execvp)(char const *path, char * const argv[]);
564 int execvp(char const *file, char * const argv[]) {
565 DLSYM_FUNCTION(real_execvp, "execvp");
567 update_environment();
568 return real_execvp(file, argv);
572 extern char **environ;
573 int execvpe(char const *file, char * const argv[], char * const envp[]) {
574 /* Fake the environment so we can reuse execvp(). */
575 environ = (char **)envp;
577 /* execvp() updates the environment. */
578 return execvp(file, argv);