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/*
* 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 removed from `tempfile_list` (but could be used again)
*
* 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);
}
static struct tempfile *new_tempfile(void)
{
struct tempfile *tempfile = xmalloc(sizeof(*tempfile));
tempfile->fd = -1;
tempfile->fp = NULL;
tempfile->active = 0;
tempfile->owner = 0;
INIT_LIST_HEAD(&tempfile->list);
strbuf_init(&tempfile->filename, 0);
return tempfile;
}
static void activate_tempfile(struct tempfile *tempfile)
{
static int initialized;
if (is_tempfile_active(tempfile))
BUG("activate_tempfile called for active object");
if (!initialized) {
sigchain_push_common(remove_tempfiles_on_signal);
atexit(remove_tempfiles_on_exit);
initialized = 1;
}
volatile_list_add(&tempfile->list, &tempfile_list);
tempfile->owner = getpid();
tempfile->active = 1;
}
static void deactivate_tempfile(struct tempfile *tempfile)
{
tempfile->active = 0;
strbuf_release(&tempfile->filename);
volatile_list_del(&tempfile->list);
free(tempfile);
}
/* Make sure errno contains a meaningful value on error */
struct tempfile *create_tempfile(const char *path)
{
struct tempfile *tempfile = new_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 NULL;
}
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 NULL;
}
return tempfile;
}
struct tempfile *register_tempfile(const char *path)
{
struct tempfile *tempfile = new_tempfile();
strbuf_add_absolute_path(&tempfile->filename, path);
activate_tempfile(tempfile);
return tempfile;
}
struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)
{
struct tempfile *tempfile = new_tempfile();
strbuf_add_absolute_path(&tempfile->filename, filename_template);
tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
if (tempfile->fd < 0) {
deactivate_tempfile(tempfile);
return NULL;
}
activate_tempfile(tempfile);
return tempfile;
}
struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)
{
struct tempfile *tempfile = new_tempfile();
const char *tmpdir;
tmpdir = getenv("TMPDIR");
if (!tmpdir)
tmpdir = "/tmp";
strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, filename_template);
tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
if (tempfile->fd < 0) {
deactivate_tempfile(tempfile);
return NULL;
}
activate_tempfile(tempfile);
return tempfile;
}
struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)
{
struct tempfile *tempfile;
struct strbuf full_template = STRBUF_INIT;
strbuf_add_absolute_path(&full_template, filename_template);
tempfile = mks_tempfile_m(full_template.buf, mode);
if (!tempfile)
die_errno("Unable to create temporary file '%s'",
full_template.buf);
strbuf_release(&full_template);
return tempfile;
}
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|O_TRUNC);
return tempfile->fd;
}
int rename_tempfile(struct tempfile **tempfile_p, const char *path)
{
struct tempfile *tempfile = *tempfile_p;
if (!is_tempfile_active(tempfile))
BUG("rename_tempfile called for inactive object");
if (close_tempfile_gently(tempfile)) {
delete_tempfile(tempfile_p);
return -1;
}
if (rename(tempfile->filename.buf, path)) {
int save_errno = errno;
delete_tempfile(tempfile_p);
errno = save_errno;
return -1;
}
deactivate_tempfile(tempfile);
*tempfile_p = NULL;
return 0;
}
void delete_tempfile(struct tempfile **tempfile_p)
{
struct tempfile *tempfile = *tempfile_p;
if (!is_tempfile_active(tempfile))
return;
close_tempfile_gently(tempfile);
unlink_or_warn(tempfile->filename.buf);
deactivate_tempfile(tempfile);
*tempfile_p = NULL;
}
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