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hush: massage redirect code to be slightly more like ash

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function                                             old     new   delta
save_fd_on_redirect                                    -     203    +203
xdup_CLOEXEC_and_close                                 -      75     +75
setup_redirects                                      245     250      +5
xdup_and_close                                        72       -     -72
save_fds_on_redirect                                 221       -    -221
------------------------------------------------------------------------------
(add/remove: 2/2 grow/shrink: 1/0 up/down: 283/-293)          Total: -10 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2017-07-30 23:34:04 +02:00
parent d07a15bd1b
commit 657e9005a9
1 changed files with 69 additions and 34 deletions
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103
shell/hush.c
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@ -1454,11 +1454,11 @@ static int fcntl_F_DUPFD(int fd, int avoid_fd)
return newfd; return newfd;
} }
static int xdup_and_close(int fd, int F_DUPFD_maybe_CLOEXEC, int avoid_fd) static int xdup_CLOEXEC_and_close(int fd, int avoid_fd)
{ {
int newfd; int newfd;
repeat: repeat:
newfd = fcntl(fd, F_DUPFD_maybe_CLOEXEC, avoid_fd + 1); newfd = fcntl(fd, F_DUPFD_CLOEXEC, avoid_fd + 1);
if (newfd < 0) { if (newfd < 0) {
if (errno == EBUSY) if (errno == EBUSY)
goto repeat; goto repeat;
@ -1469,6 +1469,8 @@ static int xdup_and_close(int fd, int F_DUPFD_maybe_CLOEXEC, int avoid_fd)
return fd; return fd;
xfunc_die(); xfunc_die();
} }
if (F_DUPFD_CLOEXEC == F_DUPFD) /* if old libc (w/o F_DUPFD_CLOEXEC) */
fcntl(newfd, F_SETFD, FD_CLOEXEC);
close(fd); close(fd);
return newfd; return newfd;
} }
@ -1507,7 +1509,7 @@ static int save_FILEs_on_redirect(int fd, int avoid_fd)
while (fl) { while (fl) {
if (fd == fl->fd) { if (fd == fl->fd) {
/* We use it only on script files, they are all CLOEXEC */ /* We use it only on script files, they are all CLOEXEC */
fl->fd = xdup_and_close(fd, F_DUPFD_CLOEXEC, avoid_fd); fl->fd = xdup_CLOEXEC_and_close(fd, avoid_fd);
debug_printf_redir("redirect_fd %d: matches a script fd, moving it to %d\n", fd, fl->fd); debug_printf_redir("redirect_fd %d: matches a script fd, moving it to %d\n", fd, fl->fd);
return 1; return 1;
} }
@ -6711,18 +6713,42 @@ static struct squirrel *add_squirrel(struct squirrel *sq, int fd, int avoid_fd)
return append_squirrel(sq, i, fd, moved_to); return append_squirrel(sq, i, fd, moved_to);
} }
static struct squirrel *add_squirrel_closed(struct squirrel *sq, int fd)
{
int i;
i = 0;
if (sq) while (sq[i].orig_fd >= 0) {
/* If we collide with an already moved fd... */
if (fd == sq[i].orig_fd) {
/* Examples:
* "echo 3>FILE 3>&- 3>FILE"
* "echo 3>&- 3>FILE"
* No need for last redirect to insert
* another "need to close 3" indicator.
*/
debug_printf_redir("redirect_fd %d: already moved or closed\n", fd);
return sq;
}
i++;
}
debug_printf_redir("redirect_fd %d: previous fd was closed\n", fd);
return append_squirrel(sq, i, fd, -1);
}
/* fd: redirect wants this fd to be used (e.g. 3>file). /* fd: redirect wants this fd to be used (e.g. 3>file).
* Move all conflicting internally used fds, * Move all conflicting internally used fds,
* and remember them so that we can restore them later. * and remember them so that we can restore them later.
*/ */
static int save_fds_on_redirect(int fd, int avoid_fd, struct squirrel **sqp) static int save_fd_on_redirect(int fd, int avoid_fd, struct squirrel **sqp)
{ {
if (avoid_fd < 9) /* the important case here is that it can be -1 */ if (avoid_fd < 9) /* the important case here is that it can be -1 */
avoid_fd = 9; avoid_fd = 9;
#if ENABLE_HUSH_INTERACTIVE #if ENABLE_HUSH_INTERACTIVE
if (fd != 0 && fd == G.interactive_fd) { if (fd != 0 && fd == G.interactive_fd) {
G.interactive_fd = xdup_and_close(G.interactive_fd, F_DUPFD_CLOEXEC, avoid_fd); G.interactive_fd = xdup_CLOEXEC_and_close(G.interactive_fd, avoid_fd);
debug_printf_redir("redirect_fd %d: matches interactive_fd, moving it to %d\n", fd, G.interactive_fd); debug_printf_redir("redirect_fd %d: matches interactive_fd, moving it to %d\n", fd, G.interactive_fd);
return 1; /* "we closed fd" */ return 1; /* "we closed fd" */
} }
@ -6748,7 +6774,6 @@ static int save_fds_on_redirect(int fd, int avoid_fd, struct squirrel **sqp)
static void restore_redirects(struct squirrel *sq) static void restore_redirects(struct squirrel *sq)
{ {
if (sq) { if (sq) {
int i = 0; int i = 0;
while (sq[i].orig_fd >= 0) { while (sq[i].orig_fd >= 0) {
@ -6775,13 +6800,15 @@ static void restore_redirects(struct squirrel *sq)
* and stderr if they are redirected. */ * and stderr if they are redirected. */
static int setup_redirects(struct command *prog, struct squirrel **sqp) static int setup_redirects(struct command *prog, struct squirrel **sqp)
{ {
int openfd, mode;
struct redir_struct *redir; struct redir_struct *redir;
for (redir = prog->redirects; redir; redir = redir->next) { for (redir = prog->redirects; redir; redir = redir->next) {
int newfd;
int closed;
if (redir->rd_type == REDIRECT_HEREDOC2) { if (redir->rd_type == REDIRECT_HEREDOC2) {
/* "rd_fd<<HERE" case */ /* "rd_fd<<HERE" case */
save_fds_on_redirect(redir->rd_fd, /*avoid:*/ 0, sqp); save_fd_on_redirect(redir->rd_fd, /*avoid:*/ 0, sqp);
/* for REDIRECT_HEREDOC2, rd_filename holds _contents_ /* for REDIRECT_HEREDOC2, rd_filename holds _contents_
* of the heredoc */ * of the heredoc */
debug_printf_parse("set heredoc '%s'\n", debug_printf_parse("set heredoc '%s'\n",
@ -6793,6 +6820,8 @@ static int setup_redirects(struct command *prog, struct squirrel **sqp)
if (redir->rd_dup == REDIRFD_TO_FILE) { if (redir->rd_dup == REDIRFD_TO_FILE) {
/* "rd_fd<*>file" case (<*> is <,>,>>,<>) */ /* "rd_fd<*>file" case (<*> is <,>,>>,<>) */
char *p; char *p;
int mode;
if (redir->rd_filename == NULL) { if (redir->rd_filename == NULL) {
/* /*
* Examples: * Examples:
@ -6804,9 +6833,9 @@ static int setup_redirects(struct command *prog, struct squirrel **sqp)
} }
mode = redir_table[redir->rd_type].mode; mode = redir_table[redir->rd_type].mode;
p = expand_string_to_string(redir->rd_filename, /*unbackslash:*/ 1); p = expand_string_to_string(redir->rd_filename, /*unbackslash:*/ 1);
openfd = open_or_warn(p, mode); newfd = open_or_warn(p, mode);
free(p); free(p);
if (openfd < 0) { if (newfd < 0) {
/* Error message from open_or_warn can be lost /* Error message from open_or_warn can be lost
* if stderr has been redirected, but bash * if stderr has been redirected, but bash
* and ash both lose it as well * and ash both lose it as well
@ -6814,40 +6843,46 @@ static int setup_redirects(struct command *prog, struct squirrel **sqp)
*/ */
return 1; return 1;
} }
if (openfd == redir->rd_fd && sqp) { if (newfd == redir->rd_fd && sqp) {
/* open() gave us precisely the fd we wanted. /* open() gave us precisely the fd we wanted.
* This means that this fd was not busy * This means that this fd was not busy
* (not opened to anywhere). * (not opened to anywhere).
* Remember to close it on restore: * Remember to close it on restore:
*/ */
struct squirrel *sq = *sqp; *sqp = add_squirrel_closed(*sqp, newfd);
int i = 0; debug_printf_redir("redir to previously closed fd %d\n", newfd);
if (sq) while (sq[i].orig_fd >= 0)
i++;
*sqp = append_squirrel(sq, i, openfd, -1); /* -1 = "it was closed" */
debug_printf_redir("redir to previously closed fd %d\n", openfd);
} }
} else { } else {
/* "rd_fd<*>rd_dup" or "rd_fd<*>-" cases */ /* "rd_fd>&rd_dup" or "rd_fd>&-" case */
openfd = redir->rd_dup; newfd = redir->rd_dup;
} }
if (openfd != redir->rd_fd) { if (newfd == redir->rd_fd)
int closed = save_fds_on_redirect(redir->rd_fd, /*avoid:*/ openfd, sqp); continue;
if (openfd == REDIRFD_CLOSE) {
/* "rd_fd >&-" means "close me" */ /* if "N>FILE": move newfd to redir->rd_fd */
if (!closed) { /* if "N>&M": dup newfd to redir->rd_fd */
/* ^^^ optimization: saving may already /* if "N>&-": close redir->rd_fd (newfd is REDIRFD_CLOSE) */
* have closed it. If not... */
close(redir->rd_fd); closed = save_fd_on_redirect(redir->rd_fd, /*avoid:*/ newfd, sqp);
} if (newfd == REDIRFD_CLOSE) {
} else { /* "N>&-" means "close me" */
xdup2(openfd, redir->rd_fd); if (!closed) {
if (redir->rd_dup == REDIRFD_TO_FILE) /* ^^^ optimization: saving may already
/* "rd_fd > FILE" */ * have closed it. If not... */
close(openfd); close(redir->rd_fd);
/* else: "rd_fd > rd_dup" */
} }
/* Sometimes we do another close on restore, getting EBADF.
* Consider "echo 3>FILE 3>&-"
* first redirect remembers "need to close 3",
* and second redirect closes 3! Restore code then closes 3 again.
*/
} else {
xdup2(newfd, redir->rd_fd);
if (redir->rd_dup == REDIRFD_TO_FILE)
/* "rd_fd > FILE" */
close(newfd);
/* else: "rd_fd > rd_dup" */
} }
} }
return 0; return 0;