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 /* The following functions may be macros. Undefine them or they cause build
53 * failures when used in our hook macros below. */
55 /* In glibc, real fwrite_unlocked() is called in macro. */
56 #ifdef HAVE_FWRITE_UNLOCKED
57 # undef fwrite_unlocked
59 /* In Clang when compiling with hardening flags (fortify) on Debian Wheezy. */
64 /* Used by various functions, including debug(). */
65 static ssize_t (*real_write)(int, void const *, size_t);
66 static int (*real_close)(int);
67 static size_t (*real_fwrite)(void const *, size_t, size_t, FILE *);
69 /* Did we already (try to) parse the environment and setup the necessary
71 static int initialized;
72 /* Force hooked writes even when not writing to a tty. Used for tests. */
73 static int force_write_to_non_tty;
76 #include "constants.h"
81 #include "hookmacros.h"
86 /* See hookmacros.h for the decision if a function call is colored. */
89 /* Prevent inlining into hook functions because it may increase the number of
90 * spilled registers unnecessarily. As it's not called very often accept the
92 static int isatty_noinline(int fd) noinline;
93 static int isatty_noinline(int fd) {
96 int saved_errno = errno;
97 int result = isatty(fd);
104 static void dup_fd(int oldfd, int newfd) {
106 debug("%3d -> %3d\t\t\t[%d]\n", oldfd, newfd, getpid());
109 assert(oldfd >= 0 && newfd >= 0);
111 if (unlikely(!initialized)) {
112 init_from_environment();
115 /* We are already tracking this file descriptor, add newfd to the list as
116 * it will reference the same descriptor. */
117 if (tracked_fds_find(oldfd)) {
118 if (!tracked_fds_find(newfd)) {
119 tracked_fds_add(newfd);
121 /* We are not tracking this file descriptor, remove newfd from the list
124 tracked_fds_remove(newfd);
128 static void close_fd(int fd) {
130 debug("%3d -> .\t\t\t[%d]\n", fd, getpid());
135 if (unlikely(!initialized)) {
136 init_from_environment();
139 tracked_fds_remove(fd);
143 /* "Action" handlers called when a file descriptor is matched. */
145 static char const *pre_string;
146 static size_t pre_string_size;
147 static char const *post_string;
148 static size_t post_string_size;
150 /* Load alternative pre/post strings from the environment if available, fall
151 * back to default values. */
152 static void init_pre_post_string(void) {
153 pre_string = getenv(ENV_NAME_PRE_STRING);
155 pre_string = DEFAULT_PRE_STRING;
157 pre_string_size = strlen(pre_string);
159 post_string = getenv(ENV_NAME_POST_STRING);
161 post_string = DEFAULT_POST_STRING;
163 post_string_size = strlen(post_string);
166 /* Don't inline any of the pre/post functions. Keep the hook function as small
167 * as possible for speed reasons. */
168 static void handle_fd_pre(int fd) noinline;
169 static void handle_fd_post(int fd) noinline;
170 static void handle_file_pre(FILE *stream) noinline;
171 static void handle_file_post(FILE *stream) noinline;
173 static void handle_fd_pre(int fd) {
174 int saved_errno = errno;
176 if (unlikely(!pre_string || !post_string)) {
177 init_pre_post_string();
180 DLSYM_FUNCTION(real_write, "write");
181 real_write(fd, pre_string, pre_string_size);
185 static void handle_fd_post(int fd) {
186 int saved_errno = errno;
188 /* write() already loaded above in handle_fd_pre(). */
189 real_write(fd, post_string, post_string_size);
194 static void handle_file_pre(FILE *stream) {
195 int saved_errno = errno;
197 if (unlikely(!pre_string || !post_string)) {
198 init_pre_post_string();
201 DLSYM_FUNCTION(real_fwrite, "fwrite");
202 real_fwrite(pre_string, pre_string_size, 1, stream);
206 static void handle_file_post(FILE *stream) {
207 int saved_errno = errno;
209 /* fwrite() already loaded above in handle_file_pre(). */
210 real_fwrite(post_string, post_string_size, 1, stream);
217 /* Hook all important output functions to manipulate their output. */
219 HOOK_FD3(ssize_t, write, fd,
220 int, fd, void const *, buf, size_t, count)
221 HOOK_FILE4(size_t, fwrite, stream,
222 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
225 HOOK_FILE2(int, fputs, stream,
226 char const *, s, FILE *, stream)
227 HOOK_FILE2(int, fputc, stream,
228 int, c, FILE *, stream)
229 HOOK_FILE2(int, putc, stream,
230 int, c, FILE *, stream)
231 HOOK_FILE1(int, putchar, stdout,
233 HOOK_FILE1(int, puts, stdout,
236 /* printf(3), excluding all s*() and vs*() functions (no output) */
237 HOOK_VAR_FILE1(int, printf, stdout, vprintf,
238 char const *, format)
239 HOOK_VAR_FILE2(int, fprintf, stream, vfprintf,
240 FILE *, stream, char const *, format)
241 HOOK_FILE2(int, vprintf, stdout,
242 char const *, format, va_list, ap)
243 HOOK_FILE3(int, vfprintf, stream,
244 FILE *, stream, char const *, format, va_list, ap)
245 /* Hardening functions (-D_FORTIFY_SOURCE=2), only functions from above */
246 HOOK_VAR_FILE2(int, __printf_chk, stdout, __vprintf_chk,
247 int, flag, char const *, format)
248 HOOK_VAR_FILE3(int, __fprintf_chk, fp, __vfprintf_chk,
249 FILE *, fp, int, flag, char const *, format)
250 HOOK_FILE3(int, __vprintf_chk, stdout,
251 int, flag, char const *, format, va_list, ap)
252 HOOK_FILE4(int, __vfprintf_chk, stream,
253 FILE *, stream, int, flag, char const *, format, va_list, ap)
255 /* unlocked_stdio(3), only functions from above are hooked */
256 #ifdef HAVE_FWRITE_UNLOCKED
257 HOOK_FILE4(size_t, fwrite_unlocked, stream,
258 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
260 #ifdef HAVE_FPUTS_UNLOCKED
261 HOOK_FILE2(int, fputs_unlocked, stream,
262 char const *, s, FILE *, stream)
264 #ifdef HAVE_FPUTC_UNLOCKED
265 HOOK_FILE2(int, fputc_unlocked, stream,
266 int, c, FILE *, stream)
268 HOOK_FILE2(int, putc_unlocked, stream,
269 int, c, FILE *, stream)
270 HOOK_FILE1(int, putchar_unlocked, stdout,
272 /* glibc defines (_IO_)putc_unlocked() to a macro which either updates the
273 * output buffer or calls __overflow(). As this code is inlined we can't
274 * handle the first case, but if __overflow() is called we can color that
275 * part. As writes to stderr are never buffered, __overflow() is always called
276 * and everything works fine. This is only a problem if stdout is dupped to
277 * stderr (which shouldn't be the case too often). */
278 #if defined(HAVE_STRUCT__IO_FILE__FILENO) && defined(HAVE___OVERFLOW)
279 /* _IO_FILE is glibc's representation of FILE. */
280 HOOK_FILE2(int, __overflow, f, _IO_FILE *, f, int, ch)
284 HOOK_VOID1(void, perror, STDERR_FILENO,
287 /* err(3), non standard BSD extension */
289 HOOK_VAR_VOID2(void, err, STDERR_FILENO, verr,
290 int, eval, char const *, fmt)
291 HOOK_VAR_VOID2(void, errx, STDERR_FILENO, verrx,
292 int, eval, char const *, fmt)
293 HOOK_VAR_VOID1(void, warn, STDERR_FILENO, vwarn,
295 HOOK_VAR_VOID1(void, warnx, STDERR_FILENO, vwarnx,
297 HOOK_FUNC_SIMPLE3(void, verr, int, eval, const char *, fmt, va_list, args) {
298 /* Can't use verr() directly as it terminates the process which prevents
299 * the post string from being printed. */
303 HOOK_FUNC_SIMPLE3(void, verrx, int, eval, const char *, fmt, va_list, args) {
308 HOOK_VOID2(void, vwarn, STDERR_FILENO,
309 char const *, fmt, va_list, args)
310 HOOK_VOID2(void, vwarnx, STDERR_FILENO,
311 char const *, fmt, va_list, args)
314 /* error(3), non-standard GNU extension */
316 static void error_vararg(int status, int errnum,
317 char const *filename, unsigned int linenum,
318 char const *format, va_list ap) {
319 static char const *last_filename;
320 static unsigned int last_linenum;
322 /* Skip this error message if requested and if there was already an error
323 * in the same file/line. */
324 if (error_one_per_line
325 && filename != NULL && linenum != 0
326 && filename == last_filename && linenum == last_linenum) {
329 last_filename = filename;
330 last_linenum = linenum;
332 error_message_count++;
336 if (error_print_progname) {
337 error_print_progname();
339 fprintf(stderr, "%s:", program_invocation_name);
341 if (filename != NULL && linenum != 0) {
342 fprintf(stderr, "%s:%u:", filename, linenum);
343 if (error_print_progname) {
344 fprintf(stderr, " ");
347 if (!error_print_progname) {
348 fprintf(stderr, " ");
352 vfprintf(stderr, format, ap);
355 fprintf(stderr, ": %s", strerror(errnum));
358 fprintf(stderr, "\n");
364 void error_at_line(int status, int errnum,
365 char const *filename, unsigned int linenum,
366 char const *format, ...) {
369 va_start(ap, format);
370 error_vararg(status, errnum, filename, linenum, format, ap);
373 void error(int status, int errnum, char const *format, ...) {
376 va_start(ap, format);
377 error_vararg(status, errnum, NULL, 0, format, ap);
383 /* Hook functions which duplicate file descriptors to track them. */
386 HOOK_FUNC_DEF1(int, dup, int, oldfd) {
389 DLSYM_FUNCTION(real_dup, "dup");
391 newfd = real_dup(oldfd);
393 dup_fd(oldfd, newfd);
398 /* int dup2(int, int) */
399 HOOK_FUNC_DEF2(int, dup2, int, oldfd, int, newfd) {
400 DLSYM_FUNCTION(real_dup2, "dup2");
402 newfd = real_dup2(oldfd, newfd);
404 dup_fd(oldfd, newfd);
409 /* int dup3(int, int, int) */
410 HOOK_FUNC_DEF3(int, dup3, int, oldfd, int, newfd, int, flags) {
411 DLSYM_FUNCTION(real_dup3, "dup3");
413 newfd = real_dup3(oldfd, newfd, flags);
415 dup_fd(oldfd, newfd);
421 /* int fcntl(int, int, ...) */
422 HOOK_FUNC_VAR_DEF2(int, fcntl, int, fd, int, cmd /*, ... */) {
426 DLSYM_FUNCTION(real_fcntl, "fcntl");
428 /* fcntl() takes different types of arguments depending on the cmd type
429 * (int, void and pointers are used at the moment). Handling these
430 * arguments for different systems and with possible changes in the future
433 * Therefore always retrieve a void-pointer from our arguments (even if it
434 * wasn't there) and pass it to real_fcntl(). This shouldn't cause any
435 * problems because a void-pointer is most-likely bigger than an int
436 * (something which is not true in reverse) and shouldn't cause
437 * truncation. For register based calling conventions an invalid register
438 * content is passed, but ignored by real_fcntl(). Not perfect, but should
442 result = real_fcntl(fd, cmd, va_arg(ap, void *));
445 /* We only care about duping fds. */
446 if (cmd == F_DUPFD && result != -1) {
454 HOOK_FUNC_DEF1(int, close, int, fd) {
455 DLSYM_FUNCTION(real_close, "close");
460 return real_close(fd);
462 /* int fclose(FILE *) */
463 HOOK_FUNC_DEF1(int, fclose, FILE *, fp) {
466 DLSYM_FUNCTION(real_fclose, "fclose");
468 if (fp != NULL && (fd = fileno(fp)) >= 0) {
471 return real_fclose(fp);
475 /* Hook functions which are necessary for correct tracking. */
477 #if defined(HAVE_VFORK) && defined(HAVE_FORK)
479 /* vfork() is similar to fork() but the address space is shared between
480 * father and child. It's designed for fork()/exec() usage because it's
481 * faster than fork(). However according to the POSIX standard the "child"
482 * isn't allowed to perform any memory-modifications before the exec()
483 * (except the pid_t result variable of vfork()).
485 * As some programs don't adhere to the standard (e.g. the "child" closes
486 * or dups a descriptor before the exec()) and this breaks our tracking of
487 * file descriptors (e.g. it gets closed in the parent as well), we just
488 * fork() instead. This is in compliance with the POSIX standard and as
489 * most systems use copy-on-write anyway not a performance issue. */
495 /* Hook execve() and the other exec*() functions. Some shells use exec*() with
496 * a custom environment which doesn't necessarily contain our updates to
497 * ENV_NAME_FDS. It's also faster to update the environment only when
498 * necessary, right before the exec() to pass it to the new process. */
500 /* int execve(char const *, char * const [], char * const []) */
501 HOOK_FUNC_DEF3(int, execve, char const *, filename, char * const *, argv, char * const *, env) {
502 DLSYM_FUNCTION(real_execve, "execve");
507 /* Count arguments and search for existing ENV_NAME_FDS environment
510 char * const *x = env;
512 if (!strncmp(*x, ENV_NAME_FDS "=", strlen(ENV_NAME_FDS) + 1)) {
520 /* Terminating NULL. */
523 char *env_copy[count + 1 /* space for our new entry if necessary */];
524 memcpy(env_copy, env, count * sizeof(char *));
526 /* Make sure the information from the environment is loaded. We can't just
527 * do nothing (like update_environment()) because the caller might pass a
528 * different environment which doesn't include any of our settings. */
530 init_from_environment();
533 char fds_env[strlen(ENV_NAME_FDS) + 1 + update_environment_buffer_size()];
534 strcpy(fds_env, ENV_NAME_FDS "=");
535 update_environment_buffer(fds_env + strlen(ENV_NAME_FDS) + 1);
538 env_copy[index] = fds_env;
540 /* If the process removed ENV_NAME_FDS from the environment, re-add
542 env_copy[count-1] = fds_env;
543 env_copy[count] = NULL;
546 return real_execve(filename, argv, env_copy);
549 #define EXECL_COPY_VARARGS_START(args) \
553 /* Count arguments. */ \
554 size_t count = 1; /* arg */ \
556 while (va_arg(ap, char *)) { \
561 /* Copy varargs. */ \
562 char *args[count + 1 /* terminating NULL */]; \
563 args[0] = (char *)arg; /* there's no other way around the cast */ \
567 while ((x = va_arg(ap, char *))) { \
571 #define EXECL_COPY_VARARGS_END(args) \
573 #define EXECL_COPY_VARARGS(args) \
574 EXECL_COPY_VARARGS_START(args); \
575 EXECL_COPY_VARARGS_END(args);
577 int execl(char const *path, char const *arg, ...) {
578 EXECL_COPY_VARARGS(args);
580 /* execv() updates the environment. */
581 return execv(path, args);
583 int execlp(char const *file, char const *arg, ...) {
584 EXECL_COPY_VARARGS(args);
586 /* execvp() updates the environment. */
587 return execvp(file, args);
589 int execle(char const *path, char const *arg, ... /*, char * const envp[] */) {
592 EXECL_COPY_VARARGS_START(args);
593 /* Get envp[] located after arguments. */
594 envp = va_arg(ap, char * const *);
595 EXECL_COPY_VARARGS_END(args);
597 /* execve() updates the environment. */
598 return execve(path, args, envp);
601 /* int execv(char const *, char * const []) */
602 HOOK_FUNC_DEF2(int, execv, char const *, path, char * const *, argv) {
603 DLSYM_FUNCTION(real_execv, "execv");
605 update_environment();
606 return real_execv(path, argv);
609 /* int execvp(char const *, char * const []) */
610 HOOK_FUNC_DEF2(int, execvp, char const *, file, char * const *, argv) {
611 DLSYM_FUNCTION(real_execvp, "execvp");
613 update_environment();
614 return real_execvp(file, argv);
618 extern char **environ;
619 int execvpe(char const *file, char * const argv[], char * const envp[]) {
620 /* Fake the environment so we can reuse execvp(). */
621 environ = (char **)envp;
623 /* execvp() updates the environment. */
624 return execvp(file, argv);