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. */
48 #ifdef HAVE_STRUCT__IO_FILE__FILENO
52 /* Conflicting declaration in glibc. */
53 #undef fwrite_unlocked
54 /* These functions may be macros when compiling with hardening flags (fortify)
55 * which cause build failures when used in our hook macros below. Observed
56 * with Clang on Debian Wheezy. */
61 /* Used by various functions, including debug(). */
62 static ssize_t (*real_write)(int, void const *, size_t);
63 static int (*real_close)(int);
64 static size_t (*real_fwrite)(void const *, size_t, size_t, FILE *);
66 /* Did we already (try to) parse the environment and setup the necessary
68 static int initialized;
69 /* Force hooked writes even when not writing to a tty. Used for tests. */
70 static int force_write_to_non_tty;
73 #include "constants.h"
78 #include "hookmacros.h"
83 /* See hookmacros.h for the decision if a function call is colored. */
86 /* Prevent inlining into hook functions because it may increase the number of
87 * spilled registers unnecessarily. As it's not called very often accept the
89 static int isatty_noinline(int fd) noinline;
90 static int isatty_noinline(int fd) {
93 int saved_errno = errno;
94 int result = isatty(fd);
101 static void dup_fd(int oldfd, int newfd) {
103 debug("%3d -> %3d\t\t\t[%d]\n", oldfd, newfd, getpid());
106 assert(oldfd >= 0 && newfd >= 0);
108 if (unlikely(!initialized)) {
109 init_from_environment();
112 /* We are already tracking this file descriptor, add newfd to the list as
113 * it will reference the same descriptor. */
114 if (tracked_fds_find(oldfd)) {
115 if (!tracked_fds_find(newfd)) {
116 tracked_fds_add(newfd);
118 /* We are not tracking this file descriptor, remove newfd from the list
121 tracked_fds_remove(newfd);
125 static void close_fd(int fd) {
127 debug("%3d -> .\t\t\t[%d]\n", fd, getpid());
132 if (unlikely(!initialized)) {
133 init_from_environment();
136 tracked_fds_remove(fd);
140 /* "Action" handlers called when a file descriptor is matched. */
142 static char const *pre_string;
143 static size_t pre_string_size;
144 static char const *post_string;
145 static size_t post_string_size;
147 /* Load alternative pre/post strings from the environment if available, fall
148 * back to default values. */
149 static void init_pre_post_string(void) {
150 pre_string = getenv(ENV_NAME_PRE_STRING);
152 pre_string = DEFAULT_PRE_STRING;
154 pre_string_size = strlen(pre_string);
156 post_string = getenv(ENV_NAME_POST_STRING);
158 post_string = DEFAULT_POST_STRING;
160 post_string_size = strlen(post_string);
163 /* Don't inline any of the pre/post functions. Keep the hook function as small
164 * as possible for speed reasons. */
165 static void handle_fd_pre(int fd) noinline;
166 static void handle_fd_post(int fd) noinline;
167 static void handle_file_pre(FILE *stream) noinline;
168 static void handle_file_post(FILE *stream) noinline;
170 static void handle_fd_pre(int fd) {
171 int saved_errno = errno;
173 if (unlikely(!pre_string || !post_string)) {
174 init_pre_post_string();
177 DLSYM_FUNCTION(real_write, "write");
178 real_write(fd, pre_string, pre_string_size);
182 static void handle_fd_post(int fd) {
183 int saved_errno = errno;
185 /* write() already loaded above in handle_fd_pre(). */
186 real_write(fd, post_string, post_string_size);
191 static void handle_file_pre(FILE *stream) {
192 int saved_errno = errno;
194 if (unlikely(!pre_string || !post_string)) {
195 init_pre_post_string();
198 DLSYM_FUNCTION(real_fwrite, "fwrite");
199 real_fwrite(pre_string, pre_string_size, 1, stream);
203 static void handle_file_post(FILE *stream) {
204 int saved_errno = errno;
206 /* fwrite() already loaded above in handle_file_pre(). */
207 real_fwrite(post_string, post_string_size, 1, stream);
214 /* Hook all important output functions to manipulate their output. */
216 HOOK_FD3(ssize_t, write, fd,
217 int, fd, void const *, buf, size_t, count)
218 HOOK_FILE4(size_t, fwrite, stream,
219 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
222 HOOK_FILE2(int, fputs, stream,
223 char const *, s, FILE *, stream)
224 HOOK_FILE2(int, fputc, stream,
225 int, c, FILE *, stream)
226 HOOK_FILE2(int, putc, stream,
227 int, c, FILE *, stream)
228 HOOK_FILE1(int, putchar, stdout,
230 HOOK_FILE1(int, puts, stdout,
233 /* printf(3), excluding all s*() and vs*() functions (no output) */
234 HOOK_VAR_FILE1(int, printf, stdout, vprintf,
235 char const *, format)
236 HOOK_VAR_FILE2(int, fprintf, stream, vfprintf,
237 FILE *, stream, char const *, format)
238 HOOK_FILE2(int, vprintf, stdout,
239 char const *, format, va_list, ap)
240 HOOK_FILE3(int, vfprintf, stream,
241 FILE *, stream, char const *, format, va_list, ap)
242 /* Hardening functions (-D_FORTIFY_SOURCE=2), only functions from above */
243 HOOK_VAR_FILE2(int, __printf_chk, stdout, __vprintf_chk,
244 int, flag, char const *, format)
245 HOOK_VAR_FILE3(int, __fprintf_chk, fp, __vfprintf_chk,
246 FILE *, fp, int, flag, char const *, format)
247 HOOK_FILE3(int, __vprintf_chk, stdout,
248 int, flag, char const *, format, va_list, ap)
249 HOOK_FILE4(int, __vfprintf_chk, stream,
250 FILE *, stream, int, flag, char const *, format, va_list, ap)
252 /* unlocked_stdio(3), only functions from above are hooked */
253 HOOK_FILE4(size_t, fwrite_unlocked, stream,
254 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
255 HOOK_FILE2(int, fputs_unlocked, stream,
256 char const *, s, FILE *, stream)
257 HOOK_FILE2(int, fputc_unlocked, stream,
258 int, c, FILE *, stream)
259 HOOK_FILE2(int, putc_unlocked, stream,
260 int, c, FILE *, stream)
261 HOOK_FILE1(int, putchar_unlocked, stdout,
263 /* glibc defines (_IO_)putc_unlocked() to __overflow() in some cases. */
264 #ifdef HAVE_STRUCT__IO_FILE__FILENO
265 HOOK_FD2(int, __overflow, f->_fileno, _IO_FILE *, f, int, ch)
269 HOOK_VOID1(void, perror, STDERR_FILENO,
272 /* err(3), non standard BSD extension */
274 HOOK_VAR_VOID2(void, err, STDERR_FILENO, verr,
275 int, eval, char const *, fmt)
276 HOOK_VAR_VOID2(void, errx, STDERR_FILENO, verrx,
277 int, eval, char const *, fmt)
278 HOOK_VAR_VOID1(void, warn, STDERR_FILENO, vwarn,
280 HOOK_VAR_VOID1(void, warnx, STDERR_FILENO, vwarnx,
282 HOOK_FUNC_SIMPLE3(void, verr, int, eval, const char *, fmt, va_list, args) {
283 /* Can't use verr() directly as it terminates the process which prevents
284 * the post string from being printed. */
288 HOOK_FUNC_SIMPLE3(void, verrx, int, eval, const char *, fmt, va_list, args) {
293 HOOK_VOID2(void, vwarn, STDERR_FILENO,
294 char const *, fmt, va_list, args)
295 HOOK_VOID2(void, vwarnx, STDERR_FILENO,
296 char const *, fmt, va_list, args)
299 /* error(3), non-standard GNU extension */
301 static void error_vararg(int status, int errnum,
302 char const *filename, unsigned int linenum,
303 char const *format, va_list ap) {
304 static char const *last_filename;
305 static unsigned int last_linenum;
307 /* Skip this error message if requested and if there was already an error
308 * in the same file/line. */
309 if (error_one_per_line
310 && filename != NULL && linenum != 0
311 && filename == last_filename && linenum == last_linenum) {
314 last_filename = filename;
315 last_linenum = linenum;
317 error_message_count++;
321 if (error_print_progname) {
322 error_print_progname();
324 fprintf(stderr, "%s:", program_invocation_name);
326 if (filename != NULL && linenum != 0) {
327 fprintf(stderr, "%s:%u:", filename, linenum);
328 if (error_print_progname) {
329 fprintf(stderr, " ");
332 if (!error_print_progname) {
333 fprintf(stderr, " ");
337 vfprintf(stderr, format, ap);
340 fprintf(stderr, ": %s", strerror(errnum));
343 fprintf(stderr, "\n");
349 void error_at_line(int status, int errnum,
350 char const *filename, unsigned int linenum,
351 char const *format, ...) {
354 va_start(ap, format);
355 error_vararg(status, errnum, filename, linenum, format, ap);
358 void error(int status, int errnum, char const *format, ...) {
361 va_start(ap, format);
362 error_vararg(status, errnum, NULL, 0, format, ap);
368 /* Hook functions which duplicate file descriptors to track them. */
371 HOOK_FUNC_DEF1(int, dup, int, oldfd) {
374 DLSYM_FUNCTION(real_dup, "dup");
376 newfd = real_dup(oldfd);
378 dup_fd(oldfd, newfd);
383 /* int dup2(int, int) */
384 HOOK_FUNC_DEF2(int, dup2, int, oldfd, int, newfd) {
385 DLSYM_FUNCTION(real_dup2, "dup2");
387 newfd = real_dup2(oldfd, newfd);
389 dup_fd(oldfd, newfd);
394 /* int dup3(int, int, int) */
395 HOOK_FUNC_DEF3(int, dup3, int, oldfd, int, newfd, int, flags) {
396 DLSYM_FUNCTION(real_dup3, "dup3");
398 newfd = real_dup3(oldfd, newfd, flags);
400 dup_fd(oldfd, newfd);
406 /* int fcntl(int, int, ...) */
407 HOOK_FUNC_VAR_DEF2(int, fcntl, int, fd, int, cmd /*, ... */) {
411 DLSYM_FUNCTION(real_fcntl, "fcntl");
413 /* fcntl() takes different types of arguments depending on the cmd type
414 * (int, void and pointers are used at the moment). Handling these
415 * arguments for different systems and with possible changes in the future
418 * Therefore always retrieve a void-pointer from our arguments (even if it
419 * wasn't there) and pass it to real_fcntl(). This shouldn't cause any
420 * problems because a void-pointer is most-likely bigger than an int
421 * (something which is not true in reverse) and shouldn't cause
422 * truncation. For register based calling conventions an invalid register
423 * content is passed, but ignored by real_fcntl(). Not perfect, but should
427 result = real_fcntl(fd, cmd, va_arg(ap, void *));
430 /* We only care about duping fds. */
431 if (cmd == F_DUPFD && result != -1) {
439 HOOK_FUNC_DEF1(int, close, int, fd) {
440 DLSYM_FUNCTION(real_close, "close");
445 return real_close(fd);
447 /* int fclose(FILE *) */
448 HOOK_FUNC_DEF1(int, fclose, FILE *, fp) {
451 DLSYM_FUNCTION(real_fclose, "fclose");
453 if (fp != NULL && (fd = fileno(fp)) >= 0) {
456 return real_fclose(fp);
460 /* Hook functions which are necessary for correct tracking. */
462 #if defined(HAVE_VFORK) && defined(HAVE_FORK)
464 /* vfork() is similar to fork() but the address space is shared between
465 * father and child. It's designed for fork()/exec() usage because it's
466 * faster than fork(). However according to the POSIX standard the "child"
467 * isn't allowed to perform any memory-modifications before the exec()
468 * (except the pid_t result variable of vfork()).
470 * As some programs don't adhere to the standard (e.g. the "child" closes
471 * or dups a descriptor before the exec()) and this breaks our tracking of
472 * file descriptors (e.g. it gets closed in the parent as well), we just
473 * fork() instead. This is in compliance with the POSIX standard and as
474 * most systems use copy-on-write anyway not a performance issue. */
480 /* Hook execve() and the other exec*() functions. Some shells use exec*() with
481 * a custom environment which doesn't necessarily contain our updates to
482 * ENV_NAME_FDS. It's also faster to update the environment only when
483 * necessary, right before the exec() to pass it to the new process. */
485 /* int execve(char const *, char * const [], char * const []) */
486 HOOK_FUNC_DEF3(int, execve, char const *, filename, char * const *, argv, char * const *, env) {
487 DLSYM_FUNCTION(real_execve, "execve");
492 /* Count arguments and search for existing ENV_NAME_FDS environment
495 char * const *x = env;
497 if (!strncmp(*x, ENV_NAME_FDS "=", strlen(ENV_NAME_FDS) + 1)) {
505 /* Terminating NULL. */
508 char *env_copy[count + 1 /* space for our new entry if necessary */];
509 memcpy(env_copy, env, count * sizeof(char *));
511 /* Make sure the information from the environment is loaded. We can't just
512 * do nothing (like update_environment()) because the caller might pass a
513 * different environment which doesn't include any of our settings. */
515 init_from_environment();
518 char fds_env[strlen(ENV_NAME_FDS) + 1 + update_environment_buffer_size()];
519 strcpy(fds_env, ENV_NAME_FDS "=");
520 update_environment_buffer(fds_env + strlen(ENV_NAME_FDS) + 1);
523 env_copy[index] = fds_env;
525 /* If the process removed ENV_NAME_FDS from the environment, re-add
527 env_copy[count-1] = fds_env;
528 env_copy[count] = NULL;
531 return real_execve(filename, argv, env_copy);
534 #define EXECL_COPY_VARARGS_START(args) \
538 /* Count arguments. */ \
539 size_t count = 1; /* arg */ \
541 while (va_arg(ap, char *)) { \
546 /* Copy varargs. */ \
547 char *args[count + 1 /* terminating NULL */]; \
548 args[0] = (char *)arg; /* there's no other way around the cast */ \
552 while ((x = va_arg(ap, char *))) { \
556 #define EXECL_COPY_VARARGS_END(args) \
558 #define EXECL_COPY_VARARGS(args) \
559 EXECL_COPY_VARARGS_START(args); \
560 EXECL_COPY_VARARGS_END(args);
562 int execl(char const *path, char const *arg, ...) {
563 EXECL_COPY_VARARGS(args);
565 /* execv() updates the environment. */
566 return execv(path, args);
568 int execlp(char const *file, char const *arg, ...) {
569 EXECL_COPY_VARARGS(args);
571 /* execvp() updates the environment. */
572 return execvp(file, args);
574 int execle(char const *path, char const *arg, ... /*, char * const envp[] */) {
577 EXECL_COPY_VARARGS_START(args);
578 /* Get envp[] located after arguments. */
579 envp = va_arg(ap, char * const *);
580 EXECL_COPY_VARARGS_END(args);
582 /* execve() updates the environment. */
583 return execve(path, args, envp);
586 /* int execv(char const *, char * const []) */
587 HOOK_FUNC_DEF2(int, execv, char const *, path, char * const *, argv) {
588 DLSYM_FUNCTION(real_execv, "execv");
590 update_environment();
591 return real_execv(path, argv);
594 /* int execvp(char const *, char * const []) */
595 HOOK_FUNC_DEF2(int, execvp, char const *, file, char * const *, argv) {
596 DLSYM_FUNCTION(real_execvp, "execvp");
598 update_environment();
599 return real_execvp(file, argv);
603 extern char **environ;
604 int execvpe(char const *file, char * const argv[], char * const envp[]) {
605 /* Fake the environment so we can reuse execvp(). */
606 environ = (char **)envp;
608 /* execvp() updates the environment. */
609 return execvp(file, argv);