ash: [REDIR] Replace copyfd by savefd and use dup2 elsewhere

Upstream commit:

    Date: Sat, 12 May 2007 18:00:57 +1000
    [REDIR] Replace copyfd by savefd and use dup2 elsewhere

    There are two kinds of users to copyfd, those that want to copy an fd to
    an exact value and those that want to move an fd to a value >= 10.  The
    former can simply use dup2 directly while the latter share a lot of common
    code that now constitutes savefd.

This does not change much, just reducing our divergence from dash code.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash.c

@@ -3760,12 +3760,12 @@ setjobctl(int on)
 				if (--fd < 0)
 					goto out;
 		}
+		/* fd is a tty at this point */
 		fd = fcntl(fd, F_DUPFD, 10);
-		if (ofd >= 0)
+		if (ofd >= 0) /* if it is "/dev/tty", close. If 0/1/2, dont */
 			close(ofd);
 		if (fd < 0)
-			goto out;
-		/* fd is a tty at this point */
+			goto out; /* F_DUPFD failed */
 		close_on_exec_on(fd);
 		while (1) { /* while we are in the background */
 			pgrp = tcgetpgrp(fd);
@@ -5181,26 +5181,31 @@ openredirect(union node *redir)
 }
 
 /*
- * Copy a file descriptor to be >= to. Throws exception on error.
+ * Copy a file descriptor to be >= 10. Throws exception on error.
  */
-/* 0x800..00: bit to set in "to" to request dup2 instead of fcntl(F_DUPFD).
- * old code was doing close(to) prior to copyfd() to achieve the same */
-enum {
-	COPYFD_EXACT   = (int)~(INT_MAX),
-	COPYFD_RESTORE = (int)((unsigned)COPYFD_EXACT >> 1),
-};
 static int
-copyfd(int from, int to)
+savefd(int from)
 {
 	int newfd;
+	int err;
 
-	if (to & COPYFD_EXACT) {
-		to &= ~COPYFD_EXACT;
-		/*if (from != to)*/
-			newfd = dup2(from, to);
-	} else {
-		newfd = fcntl(from, F_DUPFD, to);
+	newfd = fcntl(from, F_DUPFD, 10);
+	err = newfd < 0 ? errno : 0;
+	if (err != EBADF) {
+		if (err)
+			ash_msg_and_raise_error("%d: %m", from);
+		close(from);
+		fcntl(newfd, F_SETFD, FD_CLOEXEC);
 	}
+
+	return newfd;
+}
+static int
+dup2_or_raise(int from, int to)
+{
+	int newfd;
+
+	newfd = (from != to) ? dup2(from, to) : to;
 	if (newfd < 0) {
 		/* Happens when source fd is not open: try "echo >&99" */
 		ash_msg_and_raise_error("%d: %m", from);
@@ -5218,6 +5223,9 @@ struct redirtab {
 	struct two_fd_t two_fd[];
 };
 #define redirlist (G_var.redirlist)
+enum {
+	COPYFD_RESTORE = (int)~(INT_MAX),
+};
 
 static int
 need_to_remember(struct redirtab *rp, int fd)
@@ -5391,10 +5399,10 @@ redirect(union node *redir, int flags)
 				if (fd != -1)
 					close(fd);
 			} else {
-				copyfd(redir->ndup.dupfd, fd | COPYFD_EXACT);
+				dup2_or_raise(redir->ndup.dupfd, fd);
 			}
 		} else if (fd != newfd) { /* move newfd to fd */
-			copyfd(newfd, fd | COPYFD_EXACT);
+			dup2_or_raise(newfd, fd);
 #if ENABLE_ASH_BASH_COMPAT
 			if (!(redir->nfile.type == NTO2 && fd == 2))
 #endif
@@ -5440,7 +5448,7 @@ popredir(int drop, int restore)
 			if (!drop || (restore && (copy & COPYFD_RESTORE))) {
 				copy &= ~COPYFD_RESTORE;
 				/*close(fd);*/
-				copyfd(copy, fd | COPYFD_EXACT);
+				dup2_or_raise(copy, fd);
 			}
 			close(copy & ~COPYFD_RESTORE);
 		}
@@ -5894,7 +5902,7 @@ evalbackcmd(union node *n, struct backcmd *result)
 		close(pip[0]);
 		if (pip[1] != 1) {
 			/*close(1);*/
-			copyfd(pip[1], 1 | COPYFD_EXACT);
+			dup2_or_raise(pip[1], 1);
 			close(pip[1]);
 		}
 /* TODO: eflag clearing makes the following not abort:
@@ -10204,7 +10212,6 @@ static int
 setinputfile(const char *fname, int flags)
 {
 	int fd;
-	int fd2;
 
 	INT_OFF;
 	fd = open(fname, O_RDONLY);
@@ -10214,11 +10221,8 @@ setinputfile(const char *fname, int flags)
 		exitstatus = 127;
 		ash_msg_and_raise_error("can't open '%s'", fname);
 	}
-	if (fd < 10) {
-		fd2 = copyfd(fd, 10);
-		close(fd);
-		fd = fd2;
-	}
+	if (fd < 10)
+		fd = savefd(fd);
 	setinputfd(fd, flags & INPUT_PUSH_FILE);
  out:
 	INT_ON;