[PATCH 01/18] fs: add readlink support

[Jean-Christophe PLAGNIOL-VILLARD]

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com>
---
 fs/fs.c      |   59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 include/fs.h |    5 +++++
 2 files changed, 64 insertions(+)

diff --git a/fs/fs.c b/fs/fs.c
index 8ab1a3a..64a0d94 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -890,6 +890,65 @@ int close(int fd)
 }
 EXPORT_SYMBOL(close);
 
+ssize_t readlink(const char *pathname, char *buf, size_t bufsiz)
+{
+	struct fs_driver_d *fsdrv;
+	struct fs_device_d *fsdev;
+	char *p = normalise_path(pathname);
+	char *freep = p;
+	int ret;
+	size_t len = 0;
+	char tmp[PATH_MAX];
+
+	tmp[0] = 0;
+	buf[0] = 0;
+
+	ret = path_check_prereq(pathname, S_IFLNK);
+	if (ret)
+		goto out;
+
+	fsdev = get_fs_device_and_root_path(&p);
+	if (!fsdev) {
+		ret = -ENODEV;
+		goto out;
+	}
+	fsdrv = fsdev->driver;
+
+	len = min(bufsiz, (size_t)PATH_MAX);
+	if (fsdrv->readlink) {
+		ret = fsdrv->readlink(&fsdev->dev, p, tmp, len);
+	} else {
+		ret = -EROFS;
+		goto out;
+	}
+
+	if (ret)
+		goto out;
+
+	if (tmp[0] == '/') {
+		int l = strlen(fsdev->path);
+
+		if (fsdev->path[l - 1] == '/')
+			l--;
+
+		if (l) {
+			len -= l;
+			strncat(buf, fsdev->path, l);
+		}
+	}
+
+	strncat(buf, tmp, len);
+
+out:
+	free(freep);
+
+	if (ret)
+		errno = -ret;
+
+	return ret;
+}
+EXPORT_SYMBOL(readlink);
+
 static int fs_match(struct device_d *dev, struct driver_d *drv)
 {
 	return strcmp(dev->name, drv->name) ? -1 : 0;
diff --git a/include/fs.h b/include/fs.h
index 22470e6..4c5a444 100644
--- a/include/fs.h
+++ b/include/fs.h
@@ -51,6 +51,9 @@ struct fs_driver_d {
 	/* Truncate a file to given size */
 	int (*truncate)(struct device_d *dev, FILE *f, ulong size);
 
+	int (*readlink)(struct device_d *dev, const char *pathname, char *name,
+			size_t size);
+
 	int (*open)(struct device_d *dev, FILE *f, const char *pathname);
 	int (*close)(struct device_d *dev, FILE *f);
 	int (*read)(struct device_d *dev, FILE *f, void *buf, size_t size);
@@ -129,6 +132,8 @@ DIR *opendir(const char *pathname);
 struct dirent *readdir(DIR *dir);
 int closedir(DIR *dir);
 
+ssize_t readlink(const char *path, char *buf, size_t bufsiz);
+
 int mount (const char *device, const char *fsname, const char *path);
 int umount(const char *pathname);
 
-- 
1.7.10.4