klibc - Jan 2016 - [PATCH klibc 0/3] Changes to support initramfs-tools 0.117

initramfs-tools version 0.117 requires 'readlink -f' and
'mount -o defaults' to work.

The first two patches were previously submitted but not applied.

Ben.

Ben Hutchings (3):
  Implement realpath()
  readlink: Add -f option
  mount: Implement -o defaults

 usr/include/stdlib.h   |  2 ++
 usr/klibc/Kbuild       |  2 +-
 usr/klibc/realpath.c   | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 usr/utils/mount_opts.c |  9 +++++++--
 usr/utils/readlink.c   | 29 +++++++++++++++++++++++++----
 5 files changed, 84 insertions(+), 7 deletions(-)
 create mode 100644 usr/klibc/realpath.c

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This is needed as the basis for the readlink -f option.

Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
---
 usr/include/stdlib.h |  2 ++
 usr/klibc/Kbuild     |  2 +-
 usr/klibc/realpath.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 usr/klibc/realpath.c

diff --git a/usr/include/stdlib.h b/usr/include/stdlib.h
index 406f446..856c647 100644
--- a/usr/include/stdlib.h
+++ b/usr/include/stdlib.h
@@ -92,4 +92,6 @@ static __inline__ int grantpt(int __fd)
 	return 0;		/* devpts does this all for us! */
 }
 
+__extern char *realpath(const char *, char *);
+
 #endif				/* _STDLIB_H */
diff --git a/usr/klibc/Kbuild b/usr/klibc/Kbuild
index d3e2b9f..7d95e87 100644
--- a/usr/klibc/Kbuild
+++ b/usr/klibc/Kbuild
@@ -61,7 +61,7 @@ klib-y += vsnprintf.o snprintf.o vsprintf.o sprintf.o \
 	  send.o recv.o \
 	  access.o chmod.o chown.o dup2.o mknod.o poll.o rename.o stat.o \
 	  lchown.o link.o rmdir.o unlink.o utimes.o lstat.o mkdir.o \
-	  readlink.o select.o symlink.o pipe.o \
+	  readlink.o realpath.o select.o symlink.o pipe.o \
 	  ctype/isalnum.o ctype/isalpha.o ctype/isascii.o \
 	  ctype/isblank.o ctype/iscntrl.o ctype/isdigit.o \
 	  ctype/isgraph.o ctype/islower.o ctype/isprint.o \
diff --git a/usr/klibc/realpath.c b/usr/klibc/realpath.c
new file mode 100644
index 0000000..1474b1e
--- /dev/null
+++ b/usr/klibc/realpath.c
@@ -0,0 +1,49 @@
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+/*
+ * Note that this requires name to refer to an existing file.  This is
+ * correct according to POSIX.  However, BSD and GNU implementations
+ * also allow name to refer to a non-existing file in an existing
+ * directory.
+ */
+
+char *realpath(const char *name, char *resolved_name)
+{
+	static const char proc_fd_prefix[] = "/proc/self/fd/";
+	char proc_fd_name[sizeof(proc_fd_prefix) + sizeof(int) * 3];
+	int allocated = 0;
+	int fd;
+	ssize_t len;
+
+	/* Open for path lookup only */
+	fd = open(name, O_PATH);
+	if (fd < 0)
+		return NULL;
+
+	if (!resolved_name) {
+		resolved_name = malloc(PATH_MAX);
+		if (!resolved_name)
+			goto out_close;
+		allocated = 1;
+	}
+
+	/* Use procfs to read back the resolved name */
+	sprintf(proc_fd_name, "%s%d", proc_fd_prefix, fd);
+	len = readlink(proc_fd_name, resolved_name, PATH_MAX - 1);
+	if (len < 0) {
+		if (allocated)
+			free(resolved_name);
+		resolved_name = NULL;
+	} else {
+		resolved_name[len] = 0;
+	}
+
+out_close:
+	close(fd);
+	return resolved_name;
+}

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This is needed to support mounting non-root filesystems in
initramfs-tools.

Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
---
 usr/utils/readlink.c | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/usr/utils/readlink.c b/usr/utils/readlink.c
index 4e3cfcb..ffb0b1f 100644
--- a/usr/utils/readlink.c
+++ b/usr/utils/readlink.c
@@ -7,24 +7,45 @@ const char *progname;
 
 static __noreturn usage(void)
 {
-	fprintf(stderr, "Usage: %s link...\n", progname);
+	fprintf(stderr, "Usage: %s [-f] link...\n", progname);
 	exit(1);
 }
 
 int main(int argc, char *argv[])
 {
+	int c, f_flag = 0;
 	const char *name;
 	char link_name[PATH_MAX];
 	int rv;
 	int i;
 
-	progname = *argv++;
+	progname = argv[0];
 
-	if (argc < 2)
+	do {
+		c = getopt(argc, argv, "f");
+		if (c == EOF)
+			break;
+		switch (c) {
+		case 'f':
+			f_flag = 1;
+			break;
+
+		case '?':
+			fprintf(stderr, "%s: invalid option -%c\n",
+				progname, optopt);
+			usage();
+		}
+	} while (1);
+
+	if (optind == argc)
 		usage();
 
+	argv += optind;
 	while ((name = *argv++)) {
-		rv = readlink(name, link_name, sizeof link_name - 1);
+		if (f_flag)
+			rv = realpath(name, link_name) ? strlen(link_name) : -1;
+		else
+			rv = readlink(name, link_name, sizeof link_name - 1);
 		if (rv < 0) {
 			perror(name);
 			exit(1);

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This is needed to support mounting non-root filesystems in
initramfs-tools.

Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
---
 usr/utils/mount_opts.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/usr/utils/mount_opts.c b/usr/utils/mount_opts.c
index 05d1729..bb26c7d 100644
--- a/usr/utils/mount_opts.c
+++ b/usr/utils/mount_opts.c
@@ -89,8 +89,13 @@ parse_mount_options(char *arg, unsigned long rwflag, struct
extra_opts *extra)
 				break;
 		}
 
-		if (res != 0 && s[0])
-			add_extra_option(extra, opt);
+		if (res != 0 && s[0]) {
+			if (!strcmp(opt, "defaults"))
+				rwflag &= ~(MS_RDONLY|MS_NOSUID|MS_NODEV|
+					    MS_NOEXEC|MS_SYNCHRONOUS);
+			else
+				add_extra_option(extra, opt);
+		}
 	}
 
 	return rwflag;
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