[thirdparty/git.git] / tempfile.c

/*
 * State diagram and cleanup
 * -------------------------
 *
 * If the program exits while a temporary file is active, we want to
 * make sure that we remove it. This is done by remembering the active
 * temporary files in a linked list, `tempfile_list`. An `atexit(3)`
 * handler and a signal handler are registered, to clean up any active
 * temporary files.
 *
 * Because the signal handler can run at any time, `tempfile_list` and
 * the `tempfile` objects that comprise it must be kept in
 * self-consistent states at all times.
 *
 * The possible states of a `tempfile` object are as follows:
 *
 * - Uninitialized. In this state the object's `on_list` field must be
 *   zero but the rest of its contents need not be initialized. As
 *   soon as the object is used in any way, it is irrevocably
 *   registered in `tempfile_list`, and `on_list` is set.
 *
 * - Active, file open (after `create_tempfile()` or
 *   `reopen_tempfile()`). In this state:
 *
 *   - the temporary file exists
 *   - `active` is set
 *   - `filename` holds the filename of the temporary file
 *   - `fd` holds a file descriptor open for writing to it
 *   - `fp` holds a pointer to an open `FILE` object if and only if
 *     `fdopen_tempfile()` has been called on the object
 *   - `owner` holds the PID of the process that created the file
 *
 * - Active, file closed (after `close_tempfile_gently()`). Same
 *   as the previous state, except that the temporary file is closed,
 *   `fd` is -1, and `fp` is `NULL`.
 *
 * - Inactive (after `delete_tempfile()`, `rename_tempfile()`, or a
 *   failed attempt to create a temporary file). In this state:
 *
 *   - `active` is unset
 *   - `filename` is empty (usually, though there are transitory
 *     states in which this condition doesn't hold). Client code should
 *     *not* rely on the filename being empty in this state.
 *   - `fd` is -1 and `fp` is `NULL`
 *   - the object is left registered in the `tempfile_list`, and
 *     `on_list` is set.
 *
 * A temporary file is owned by the process that created it. The
 * `tempfile` has an `owner` field that records the owner's PID. This
 * field is used to prevent a forked process from deleting a temporary
 * file created by its parent.
 */

#include "cache.h"
#include "tempfile.h"
#include "sigchain.h"

static VOLATILE_LIST_HEAD(tempfile_list);

static void remove_tempfiles(int in_signal_handler)
{
	pid_t me = getpid();
	volatile struct volatile_list_head *pos;

	list_for_each(pos, &tempfile_list) {
		struct tempfile *p = list_entry(pos, struct tempfile, list);

		if (!is_tempfile_active(p) || p->owner != me)
			continue;

		if (p->fd >= 0)
			close(p->fd);

		if (in_signal_handler)
			unlink(p->filename.buf);
		else
			unlink_or_warn(p->filename.buf);

		p->active = 0;
	}
}

static void remove_tempfiles_on_exit(void)
{
	remove_tempfiles(0);
}

static void remove_tempfiles_on_signal(int signo)
{
	remove_tempfiles(1);
	sigchain_pop(signo);
	raise(signo);
}

/*
 * Initialize *tempfile if necessary and add it to tempfile_list.
 */
static void prepare_tempfile_object(struct tempfile *tempfile)
{
	if (volatile_list_empty(&tempfile_list)) {
		/* One-time initialization */
		sigchain_push_common(remove_tempfiles_on_signal);
		atexit(remove_tempfiles_on_exit);
	}

	if (is_tempfile_active(tempfile))
		BUG("prepare_tempfile_object called for active object");
	if (!tempfile->on_list) {
		/* Initialize *tempfile and add it to tempfile_list: */
		tempfile->fd = -1;
		tempfile->fp = NULL;
		tempfile->active = 0;
		tempfile->owner = 0;
		strbuf_init(&tempfile->filename, 0);
		volatile_list_add(&tempfile->list, &tempfile_list);
		tempfile->on_list = 1;
	} else if (tempfile->filename.len) {
		/* This shouldn't happen, but better safe than sorry. */
		BUG("prepare_tempfile_object called for improperly-reset object");
	}
}

static void activate_tempfile(struct tempfile *tempfile)
{
	tempfile->owner = getpid();
	tempfile->active = 1;
}

static void deactivate_tempfile(struct tempfile *tempfile)
{
	tempfile->active = 0;
	strbuf_release(&tempfile->filename);
}

/* Make sure errno contains a meaningful value on error */
int create_tempfile(struct tempfile *tempfile, const char *path)
{
	prepare_tempfile_object(tempfile);

	strbuf_add_absolute_path(&tempfile->filename, path);
	tempfile->fd = open(tempfile->filename.buf,
			    O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0666);
	if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
		/* Try again w/o O_CLOEXEC: the kernel might not support it */
		tempfile->fd = open(tempfile->filename.buf,
				    O_RDWR | O_CREAT | O_EXCL, 0666);
	if (tempfile->fd < 0) {
		deactivate_tempfile(tempfile);
		return -1;
	}
	activate_tempfile(tempfile);
	if (adjust_shared_perm(tempfile->filename.buf)) {
		int save_errno = errno;
		error("cannot fix permission bits on %s", tempfile->filename.buf);
		delete_tempfile(tempfile);
		errno = save_errno;
		return -1;
	}
	return tempfile->fd;
}

void register_tempfile(struct tempfile *tempfile, const char *path)
{
	prepare_tempfile_object(tempfile);
	strbuf_add_absolute_path(&tempfile->filename, path);
	activate_tempfile(tempfile);
}

int mks_tempfile_sm(struct tempfile *tempfile,
		    const char *template, int suffixlen, int mode)
{
	prepare_tempfile_object(tempfile);

	strbuf_add_absolute_path(&tempfile->filename, template);
	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	if (tempfile->fd < 0) {
		deactivate_tempfile(tempfile);
		return -1;
	}
	activate_tempfile(tempfile);
	return tempfile->fd;
}

int mks_tempfile_tsm(struct tempfile *tempfile,
		     const char *template, int suffixlen, int mode)
{
	const char *tmpdir;

	prepare_tempfile_object(tempfile);

	tmpdir = getenv("TMPDIR");
	if (!tmpdir)
		tmpdir = "/tmp";

	strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	if (tempfile->fd < 0) {
		deactivate_tempfile(tempfile);
		return -1;
	}
	activate_tempfile(tempfile);
	return tempfile->fd;
}

int xmks_tempfile_m(struct tempfile *tempfile, const char *template, int mode)
{
	int fd;
	struct strbuf full_template = STRBUF_INIT;

	strbuf_add_absolute_path(&full_template, template);
	fd = mks_tempfile_m(tempfile, full_template.buf, mode);
	if (fd < 0)
		die_errno("Unable to create temporary file '%s'",
			  full_template.buf);

	strbuf_release(&full_template);
	return fd;
}

FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
{
	if (!is_tempfile_active(tempfile))
		BUG("fdopen_tempfile() called for inactive object");
	if (tempfile->fp)
		BUG("fdopen_tempfile() called for open object");

	tempfile->fp = fdopen(tempfile->fd, mode);
	return tempfile->fp;
}

const char *get_tempfile_path(struct tempfile *tempfile)
{
	if (!is_tempfile_active(tempfile))
		BUG("get_tempfile_path() called for inactive object");
	return tempfile->filename.buf;
}

int get_tempfile_fd(struct tempfile *tempfile)
{
	if (!is_tempfile_active(tempfile))
		BUG("get_tempfile_fd() called for inactive object");
	return tempfile->fd;
}

FILE *get_tempfile_fp(struct tempfile *tempfile)
{
	if (!is_tempfile_active(tempfile))
		BUG("get_tempfile_fp() called for inactive object");
	return tempfile->fp;
}

int close_tempfile_gently(struct tempfile *tempfile)
{
	int fd;
	FILE *fp;
	int err;

	if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
		return 0;

	fd = tempfile->fd;
	fp = tempfile->fp;
	tempfile->fd = -1;
	if (fp) {
		tempfile->fp = NULL;
		if (ferror(fp)) {
			err = -1;
			if (!fclose(fp))
				errno = EIO;
		} else {
			err = fclose(fp);
		}
	} else {
		err = close(fd);
	}

	return err ? -1 : 0;
}

int reopen_tempfile(struct tempfile *tempfile)
{
	if (!is_tempfile_active(tempfile))
		BUG("reopen_tempfile called for an inactive object");
	if (0 <= tempfile->fd)
		BUG("reopen_tempfile called for an open object");
	tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
	return tempfile->fd;
}

int rename_tempfile(struct tempfile *tempfile, const char *path)
{
	if (!is_tempfile_active(tempfile))
		BUG("rename_tempfile called for inactive object");

	if (close_tempfile_gently(tempfile)) {
		delete_tempfile(tempfile);
		return -1;
	}

	if (rename(tempfile->filename.buf, path)) {
		int save_errno = errno;
		delete_tempfile(tempfile);
		errno = save_errno;
		return -1;
	}

	deactivate_tempfile(tempfile);
	return 0;
}

void delete_tempfile(struct tempfile *tempfile)
{
	if (!is_tempfile_active(tempfile))
		return;

	close_tempfile_gently(tempfile);
	unlink_or_warn(tempfile->filename.buf);
	deactivate_tempfile(tempfile);
}
Commit	Line	Data
1a9d15db MH	1	/*
	2	* State diagram and cleanup
	3	* -------------------------
	4	*
	5	* If the program exits while a temporary file is active, we want to
	6	* make sure that we remove it. This is done by remembering the active
	7	* temporary files in a linked list, `tempfile_list`. An `atexit(3)`
	8	* handler and a signal handler are registered, to clean up any active
	9	* temporary files.
	10	*
	11	* Because the signal handler can run at any time, `tempfile_list` and
	12	* the `tempfile` objects that comprise it must be kept in
	13	* self-consistent states at all times.
	14	*
	15	* The possible states of a `tempfile` object are as follows:
	16	*
	17	* - Uninitialized. In this state the object's `on_list` field must be
	18	* zero but the rest of its contents need not be initialized. As
	19	* soon as the object is used in any way, it is irrevocably
	20	* registered in `tempfile_list`, and `on_list` is set.
	21	*
	22	* - Active, file open (after `create_tempfile()` or
	23	* `reopen_tempfile()`). In this state:
	24	*
	25	* - the temporary file exists
	26	* - `active` is set
	27	* - `filename` holds the filename of the temporary file
	28	* - `fd` holds a file descriptor open for writing to it
	29	* - `fp` holds a pointer to an open `FILE` object if and only if
	30	* `fdopen_tempfile()` has been called on the object
	31	* - `owner` holds the PID of the process that created the file
	32	*
49bd0fc2	33	* - Active, file closed (after `close_tempfile_gently()`). Same
1a9d15db MH	34	* as the previous state, except that the temporary file is closed,
	35	* `fd` is -1, and `fp` is `NULL`.
	36	*
49bd0fc2 JK	37	* - Inactive (after `delete_tempfile()`, `rename_tempfile()`, or a
49bd0fc2 JK	38	* failed attempt to create a temporary file). In this state:
1a9d15db MH	39	*
	40	* - `active` is unset
	41	* - `filename` is empty (usually, though there are transitory
	42	* states in which this condition doesn't hold). Client code should
	43	* not rely on the filename being empty in this state.
	44	* - `fd` is -1 and `fp` is `NULL`
	45	* - the object is left registered in the `tempfile_list`, and
	46	* `on_list` is set.
	47	*
	48	* A temporary file is owned by the process that created it. The
	49	* `tempfile` has an `owner` field that records the owner's PID. This
	50	* field is used to prevent a forked process from deleting a temporary
	51	* file created by its parent.
	52	*/
	53
	54	#include "cache.h"
	55	#include "tempfile.h"
	56	#include "sigchain.h"
	57
24d82185	58	static VOLATILE_LIST_HEAD(tempfile_list);
1a9d15db	59
6b935066	60	static void remove_tempfiles(int in_signal_handler)
1a9d15db MH	61	{
1a9d15db MH	62	pid_t me = getpid();
24d82185 JK	63	volatile struct volatile_list_head *pos;
	64
	65	list_for_each(pos, &tempfile_list) {
	66	struct tempfile *p = list_entry(pos, struct tempfile, list);
1a9d15db	67
6b935066 JK	68	if (!is_tempfile_active(p) \|\| p->owner != me)
	69	continue;
	70
	71	if (p->fd >= 0)
	72	close(p->fd);
	73
	74	if (in_signal_handler)
	75	unlink(p->filename.buf);
	76	else
	77	unlink_or_warn(p->filename.buf);
	78
	79	p->active = 0;
1a9d15db MH	80	}
	81	}
	82
	83	static void remove_tempfiles_on_exit(void)
	84	{
	85	remove_tempfiles(0);
	86	}
	87
	88	static void remove_tempfiles_on_signal(int signo)
	89	{
	90	remove_tempfiles(1);
	91	sigchain_pop(signo);
	92	raise(signo);
	93	}
	94
7eba6ce5 MH	95	/*
	96	* Initialize *tempfile if necessary and add it to tempfile_list.
	97	*/
	98	static void prepare_tempfile_object(struct tempfile *tempfile)
1a9d15db	99	{
24d82185	100	if (volatile_list_empty(&tempfile_list)) {
1a9d15db MH	101	/* One-time initialization */
	102	sigchain_push_common(remove_tempfiles_on_signal);
	103	atexit(remove_tempfiles_on_exit);
	104	}
	105
e6fc2673	106	if (is_tempfile_active(tempfile))
9b028aa4	107	BUG("prepare_tempfile_object called for active object");
1a9d15db MH	108	if (!tempfile->on_list) {
	109	/* Initialize tempfile and add it to tempfile_list: /
	110	tempfile->fd = -1;
	111	tempfile->fp = NULL;
	112	tempfile->active = 0;
	113	tempfile->owner = 0;
7eba6ce5	114	strbuf_init(&tempfile->filename, 0);
24d82185	115	volatile_list_add(&tempfile->list, &tempfile_list);
1a9d15db MH	116	tempfile->on_list = 1;
	117	} else if (tempfile->filename.len) {
	118	/* This shouldn't happen, but better safe than sorry. */
9b028aa4	119	BUG("prepare_tempfile_object called for improperly-reset object");
1a9d15db	120	}
7eba6ce5 MH	121	}
7eba6ce5 MH	122
2933ebba JK	123	static void activate_tempfile(struct tempfile *tempfile)
	124	{
	125	tempfile->owner = getpid();
	126	tempfile->active = 1;
	127	}
	128
b5f4dcb5 JK	129	static void deactivate_tempfile(struct tempfile *tempfile)
	130	{
	131	tempfile->active = 0;
102cf7a6	132	strbuf_release(&tempfile->filename);
b5f4dcb5 JK	133	}
b5f4dcb5 JK	134
7eba6ce5 MH	135	/* Make sure errno contains a meaningful value on error */
	136	int create_tempfile(struct tempfile tempfile, const char path)
	137	{
	138	prepare_tempfile_object(tempfile);
1a9d15db MH	139
1a9d15db MH	140	strbuf_add_absolute_path(&tempfile->filename, path);
05d1ed61 BW	141	tempfile->fd = open(tempfile->filename.buf,
	142	O_RDWR \| O_CREAT \| O_EXCL \| O_CLOEXEC, 0666);
	143	if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
	144	/* Try again w/o O_CLOEXEC: the kernel might not support it */
	145	tempfile->fd = open(tempfile->filename.buf,
	146	O_RDWR \| O_CREAT \| O_EXCL, 0666);
1a9d15db	147	if (tempfile->fd < 0) {
b5f4dcb5	148	deactivate_tempfile(tempfile);
1a9d15db MH	149	return -1;
1a9d15db MH	150	}
2933ebba	151	activate_tempfile(tempfile);
1a9d15db MH	152	if (adjust_shared_perm(tempfile->filename.buf)) {
	153	int save_errno = errno;
	154	error("cannot fix permission bits on %s", tempfile->filename.buf);
	155	delete_tempfile(tempfile);
	156	errno = save_errno;
	157	return -1;
	158	}
	159	return tempfile->fd;
	160	}
	161
99397152 MH	162	void register_tempfile(struct tempfile tempfile, const char path)
	163	{
	164	prepare_tempfile_object(tempfile);
	165	strbuf_add_absolute_path(&tempfile->filename, path);
2933ebba	166	activate_tempfile(tempfile);
99397152 MH	167	}
99397152 MH	168
354ab112 MH	169	int mks_tempfile_sm(struct tempfile *tempfile,
	170	const char *template, int suffixlen, int mode)
	171	{
	172	prepare_tempfile_object(tempfile);
	173
	174	strbuf_add_absolute_path(&tempfile->filename, template);
	175	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	176	if (tempfile->fd < 0) {
b5f4dcb5	177	deactivate_tempfile(tempfile);
354ab112 MH	178	return -1;
354ab112 MH	179	}
2933ebba	180	activate_tempfile(tempfile);
354ab112 MH	181	return tempfile->fd;
	182	}
	183
	184	int mks_tempfile_tsm(struct tempfile *tempfile,
	185	const char *template, int suffixlen, int mode)
	186	{
	187	const char *tmpdir;
	188
	189	prepare_tempfile_object(tempfile);
	190
	191	tmpdir = getenv("TMPDIR");
	192	if (!tmpdir)
	193	tmpdir = "/tmp";
	194
	195	strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
	196	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	197	if (tempfile->fd < 0) {
b5f4dcb5	198	deactivate_tempfile(tempfile);
354ab112 MH	199	return -1;
354ab112 MH	200	}
2933ebba	201	activate_tempfile(tempfile);
354ab112 MH	202	return tempfile->fd;
	203	}
	204
	205	int xmks_tempfile_m(struct tempfile tempfile, const char template, int mode)
	206	{
	207	int fd;
	208	struct strbuf full_template = STRBUF_INIT;
	209
	210	strbuf_add_absolute_path(&full_template, template);
	211	fd = mks_tempfile_m(tempfile, full_template.buf, mode);
	212	if (fd < 0)
	213	die_errno("Unable to create temporary file '%s'",
	214	full_template.buf);
	215
	216	strbuf_release(&full_template);
	217	return fd;
	218	}
	219
1a9d15db MH	220	FILE fdopen_tempfile(struct tempfile tempfile, const char *mode)
1a9d15db MH	221	{
e6fc2673	222	if (!is_tempfile_active(tempfile))
9b028aa4	223	BUG("fdopen_tempfile() called for inactive object");
1a9d15db	224	if (tempfile->fp)
9b028aa4	225	BUG("fdopen_tempfile() called for open object");
1a9d15db MH	226
	227	tempfile->fp = fdopen(tempfile->fd, mode);
	228	return tempfile->fp;
	229	}
	230
	231	const char get_tempfile_path(struct tempfile tempfile)
	232	{
e6fc2673	233	if (!is_tempfile_active(tempfile))
9b028aa4	234	BUG("get_tempfile_path() called for inactive object");
1a9d15db MH	235	return tempfile->filename.buf;
	236	}
	237
	238	int get_tempfile_fd(struct tempfile *tempfile)
	239	{
e6fc2673	240	if (!is_tempfile_active(tempfile))
9b028aa4	241	BUG("get_tempfile_fd() called for inactive object");
1a9d15db MH	242	return tempfile->fd;
	243	}
	244
	245	FILE get_tempfile_fp(struct tempfile tempfile)
	246	{
e6fc2673	247	if (!is_tempfile_active(tempfile))
9b028aa4	248	BUG("get_tempfile_fp() called for inactive object");
1a9d15db MH	249	return tempfile->fp;
	250	}
	251
49bd0fc2	252	int close_tempfile_gently(struct tempfile *tempfile)
1a9d15db	253	{
f5b4dc76 JK	254	int fd;
f5b4dc76 JK	255	FILE *fp;
1a9d15db MH	256	int err;
1a9d15db MH	257
f5b4dc76	258	if (!is_tempfile_active(tempfile) \|\| tempfile->fd < 0)
1a9d15db MH	259	return 0;
1a9d15db MH	260
f5b4dc76 JK	261	fd = tempfile->fd;
f5b4dc76 JK	262	fp = tempfile->fp;
1a9d15db MH	263	tempfile->fd = -1;
	264	if (fp) {
	265	tempfile->fp = NULL;
7e8c9355 JK	266	if (ferror(fp)) {
	267	err = -1;
	268	if (!fclose(fp))
	269	errno = EIO;
	270	} else {
	271	err = fclose(fp);
	272	}
1a9d15db MH	273	} else {
	274	err = close(fd);
	275	}
	276
49bd0fc2	277	return err ? -1 : 0;
1a9d15db MH	278	}
	279
	280	int reopen_tempfile(struct tempfile *tempfile)
	281	{
e6fc2673	282	if (!is_tempfile_active(tempfile))
9b028aa4	283	BUG("reopen_tempfile called for an inactive object");
f5b4dc76	284	if (0 <= tempfile->fd)
9b028aa4	285	BUG("reopen_tempfile called for an open object");
1a9d15db MH	286	tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
	287	return tempfile->fd;
	288	}
	289
	290	int rename_tempfile(struct tempfile tempfile, const char path)
	291	{
e6fc2673	292	if (!is_tempfile_active(tempfile))
9b028aa4	293	BUG("rename_tempfile called for inactive object");
1a9d15db	294
49bd0fc2 JK	295	if (close_tempfile_gently(tempfile)) {
49bd0fc2 JK	296	delete_tempfile(tempfile);
1a9d15db	297	return -1;
49bd0fc2	298	}
1a9d15db MH	299
	300	if (rename(tempfile->filename.buf, path)) {
	301	int save_errno = errno;
	302	delete_tempfile(tempfile);
	303	errno = save_errno;
	304	return -1;
	305	}
	306
b5f4dcb5	307	deactivate_tempfile(tempfile);
1a9d15db MH	308	return 0;
	309	}
	310
	311	void delete_tempfile(struct tempfile *tempfile)
	312	{
e6fc2673	313	if (!is_tempfile_active(tempfile))
1a9d15db MH	314	return;
1a9d15db MH	315
49bd0fc2 JK	316	close_tempfile_gently(tempfile);
49bd0fc2 JK	317	unlink_or_warn(tempfile->filename.buf);
b5f4dcb5	318	deactivate_tempfile(tempfile);
1a9d15db	319	}