[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 struct tempfile *volatile tempfile_list;

static void remove_tempfiles(int skip_fclose)
{
	pid_t me = getpid();

	while (tempfile_list) {
		if (tempfile_list->owner == me) {
			/* fclose() is not safe to call in a signal handler */
			if (skip_fclose)
				tempfile_list->fp = NULL;
			delete_tempfile(tempfile_list);
		}
		tempfile_list = tempfile_list->next;
	}
}

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 (!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);
		tempfile->next = tempfile_list;
		tempfile_list = tempfile;
		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_reset(&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
	58	static struct tempfile *volatile tempfile_list;
	59
	60	static void remove_tempfiles(int skip_fclose)
	61	{
	62	pid_t me = getpid();
	63
	64	while (tempfile_list) {
	65	if (tempfile_list->owner == me) {
	66	/* fclose() is not safe to call in a signal handler */
	67	if (skip_fclose)
	68	tempfile_list->fp = NULL;
	69	delete_tempfile(tempfile_list);
	70	}
	71	tempfile_list = tempfile_list->next;
	72	}
	73	}
	74
	75	static void remove_tempfiles_on_exit(void)
	76	{
	77	remove_tempfiles(0);
	78	}
	79
	80	static void remove_tempfiles_on_signal(int signo)
	81	{
	82	remove_tempfiles(1);
	83	sigchain_pop(signo);
	84	raise(signo);
	85	}
	86
7eba6ce5 MH	87	/*
	88	* Initialize *tempfile if necessary and add it to tempfile_list.
	89	*/
	90	static void prepare_tempfile_object(struct tempfile *tempfile)
1a9d15db	91	{
1a9d15db MH	92	if (!tempfile_list) {
	93	/* One-time initialization */
	94	sigchain_push_common(remove_tempfiles_on_signal);
	95	atexit(remove_tempfiles_on_exit);
	96	}
	97
e6fc2673	98	if (is_tempfile_active(tempfile))
9b028aa4	99	BUG("prepare_tempfile_object called for active object");
1a9d15db MH	100	if (!tempfile->on_list) {
	101	/* Initialize tempfile and add it to tempfile_list: /
	102	tempfile->fd = -1;
	103	tempfile->fp = NULL;
	104	tempfile->active = 0;
	105	tempfile->owner = 0;
7eba6ce5	106	strbuf_init(&tempfile->filename, 0);
1a9d15db MH	107	tempfile->next = tempfile_list;
	108	tempfile_list = tempfile;
	109	tempfile->on_list = 1;
	110	} else if (tempfile->filename.len) {
	111	/* This shouldn't happen, but better safe than sorry. */
9b028aa4	112	BUG("prepare_tempfile_object called for improperly-reset object");
1a9d15db	113	}
7eba6ce5 MH	114	}
7eba6ce5 MH	115
2933ebba JK	116	static void activate_tempfile(struct tempfile *tempfile)
	117	{
	118	tempfile->owner = getpid();
	119	tempfile->active = 1;
	120	}
	121
b5f4dcb5 JK	122	static void deactivate_tempfile(struct tempfile *tempfile)
	123	{
	124	tempfile->active = 0;
	125	strbuf_reset(&tempfile->filename);
	126	}
	127
7eba6ce5 MH	128	/* Make sure errno contains a meaningful value on error */
	129	int create_tempfile(struct tempfile tempfile, const char path)
	130	{
	131	prepare_tempfile_object(tempfile);
1a9d15db MH	132
1a9d15db MH	133	strbuf_add_absolute_path(&tempfile->filename, path);
05d1ed61 BW	134	tempfile->fd = open(tempfile->filename.buf,
	135	O_RDWR \| O_CREAT \| O_EXCL \| O_CLOEXEC, 0666);
	136	if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
	137	/* Try again w/o O_CLOEXEC: the kernel might not support it */
	138	tempfile->fd = open(tempfile->filename.buf,
	139	O_RDWR \| O_CREAT \| O_EXCL, 0666);
1a9d15db	140	if (tempfile->fd < 0) {
b5f4dcb5	141	deactivate_tempfile(tempfile);
1a9d15db MH	142	return -1;
1a9d15db MH	143	}
2933ebba	144	activate_tempfile(tempfile);
1a9d15db MH	145	if (adjust_shared_perm(tempfile->filename.buf)) {
	146	int save_errno = errno;
	147	error("cannot fix permission bits on %s", tempfile->filename.buf);
	148	delete_tempfile(tempfile);
	149	errno = save_errno;
	150	return -1;
	151	}
	152	return tempfile->fd;
	153	}
	154
99397152 MH	155	void register_tempfile(struct tempfile tempfile, const char path)
	156	{
	157	prepare_tempfile_object(tempfile);
	158	strbuf_add_absolute_path(&tempfile->filename, path);
2933ebba	159	activate_tempfile(tempfile);
99397152 MH	160	}
99397152 MH	161
354ab112 MH	162	int mks_tempfile_sm(struct tempfile *tempfile,
	163	const char *template, int suffixlen, int mode)
	164	{
	165	prepare_tempfile_object(tempfile);
	166
	167	strbuf_add_absolute_path(&tempfile->filename, template);
	168	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	169	if (tempfile->fd < 0) {
b5f4dcb5	170	deactivate_tempfile(tempfile);
354ab112 MH	171	return -1;
354ab112 MH	172	}
2933ebba	173	activate_tempfile(tempfile);
354ab112 MH	174	return tempfile->fd;
	175	}
	176
	177	int mks_tempfile_tsm(struct tempfile *tempfile,
	178	const char *template, int suffixlen, int mode)
	179	{
	180	const char *tmpdir;
	181
	182	prepare_tempfile_object(tempfile);
	183
	184	tmpdir = getenv("TMPDIR");
	185	if (!tmpdir)
	186	tmpdir = "/tmp";
	187
	188	strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
	189	tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
	190	if (tempfile->fd < 0) {
b5f4dcb5	191	deactivate_tempfile(tempfile);
354ab112 MH	192	return -1;
354ab112 MH	193	}
2933ebba	194	activate_tempfile(tempfile);
354ab112 MH	195	return tempfile->fd;
	196	}
	197
	198	int xmks_tempfile_m(struct tempfile tempfile, const char template, int mode)
	199	{
	200	int fd;
	201	struct strbuf full_template = STRBUF_INIT;
	202
	203	strbuf_add_absolute_path(&full_template, template);
	204	fd = mks_tempfile_m(tempfile, full_template.buf, mode);
	205	if (fd < 0)
	206	die_errno("Unable to create temporary file '%s'",
	207	full_template.buf);
	208
	209	strbuf_release(&full_template);
	210	return fd;
	211	}
	212
1a9d15db MH	213	FILE fdopen_tempfile(struct tempfile tempfile, const char *mode)
1a9d15db MH	214	{
e6fc2673	215	if (!is_tempfile_active(tempfile))
9b028aa4	216	BUG("fdopen_tempfile() called for inactive object");
1a9d15db	217	if (tempfile->fp)
9b028aa4	218	BUG("fdopen_tempfile() called for open object");
1a9d15db MH	219
	220	tempfile->fp = fdopen(tempfile->fd, mode);
	221	return tempfile->fp;
	222	}
	223
	224	const char get_tempfile_path(struct tempfile tempfile)
	225	{
e6fc2673	226	if (!is_tempfile_active(tempfile))
9b028aa4	227	BUG("get_tempfile_path() called for inactive object");
1a9d15db MH	228	return tempfile->filename.buf;
	229	}
	230
	231	int get_tempfile_fd(struct tempfile *tempfile)
	232	{
e6fc2673	233	if (!is_tempfile_active(tempfile))
9b028aa4	234	BUG("get_tempfile_fd() called for inactive object");
1a9d15db MH	235	return tempfile->fd;
	236	}
	237
	238	FILE get_tempfile_fp(struct tempfile tempfile)
	239	{
e6fc2673	240	if (!is_tempfile_active(tempfile))
9b028aa4	241	BUG("get_tempfile_fp() called for inactive object");
1a9d15db MH	242	return tempfile->fp;
	243	}
	244
49bd0fc2	245	int close_tempfile_gently(struct tempfile *tempfile)
1a9d15db	246	{
f5b4dc76 JK	247	int fd;
f5b4dc76 JK	248	FILE *fp;
1a9d15db MH	249	int err;
1a9d15db MH	250
f5b4dc76	251	if (!is_tempfile_active(tempfile) \|\| tempfile->fd < 0)
1a9d15db MH	252	return 0;
1a9d15db MH	253
f5b4dc76 JK	254	fd = tempfile->fd;
f5b4dc76 JK	255	fp = tempfile->fp;
1a9d15db MH	256	tempfile->fd = -1;
	257	if (fp) {
	258	tempfile->fp = NULL;
7e8c9355 JK	259	if (ferror(fp)) {
	260	err = -1;
	261	if (!fclose(fp))
	262	errno = EIO;
	263	} else {
	264	err = fclose(fp);
	265	}
1a9d15db MH	266	} else {
	267	err = close(fd);
	268	}
	269
49bd0fc2	270	return err ? -1 : 0;
1a9d15db MH	271	}
	272
	273	int reopen_tempfile(struct tempfile *tempfile)
	274	{
e6fc2673	275	if (!is_tempfile_active(tempfile))
9b028aa4	276	BUG("reopen_tempfile called for an inactive object");
f5b4dc76	277	if (0 <= tempfile->fd)
9b028aa4	278	BUG("reopen_tempfile called for an open object");
1a9d15db MH	279	tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
	280	return tempfile->fd;
	281	}
	282
	283	int rename_tempfile(struct tempfile tempfile, const char path)
	284	{
e6fc2673	285	if (!is_tempfile_active(tempfile))
9b028aa4	286	BUG("rename_tempfile called for inactive object");
1a9d15db	287
49bd0fc2 JK	288	if (close_tempfile_gently(tempfile)) {
49bd0fc2 JK	289	delete_tempfile(tempfile);
1a9d15db	290	return -1;
49bd0fc2	291	}
1a9d15db MH	292
	293	if (rename(tempfile->filename.buf, path)) {
	294	int save_errno = errno;
	295	delete_tempfile(tempfile);
	296	errno = save_errno;
	297	return -1;
	298	}
	299
b5f4dcb5	300	deactivate_tempfile(tempfile);
1a9d15db MH	301	return 0;
	302	}
	303
	304	void delete_tempfile(struct tempfile *tempfile)
	305	{
e6fc2673	306	if (!is_tempfile_active(tempfile))
1a9d15db MH	307	return;
1a9d15db MH	308
49bd0fc2 JK	309	close_tempfile_gently(tempfile);
49bd0fc2 JK	310	unlink_or_warn(tempfile->filename.buf);
b5f4dcb5	311	deactivate_tempfile(tempfile);
1a9d15db	312	}