[RESEND PATCH v4 1/2] Add grub_util_readlink()

[Javier Martinez Canillas]

From: Peter Jones <address@hidden>

Currently grub-editenv and related tools are not able to follow symbolic
links when finding their config file. For example the grub-editenv create
command will wrongly overwrite a symlink in /boot/grub2/grubenv with a new
regular file, instead of creating a file in the path the symlink points to.

A following patch will change that and add support in grub-editenv to
follow symbolic links when finding the grub environment variables file.

Add a grub_util_readlink() helper function that is just a wrapper around
the platform specific function to read the value of a symbolic link. This
helper function will be used by the following patch for grub-editenv.

The helper function is not added for Windows, since this operating system
doesn't have a primitive to read the contents of a symbolic link.

Signed-off-by: Peter Jones <address@hidden>
Reviewed-by: Adam Jackson <address@hidden>
Signed-off-by: Javier Martinez Canillas <address@hidden>
Reviewed-by: Daniel Kiper <address@hidden>

---
Resending the patches rebased on top of the latest master branch so
they apply cleanly. Sorry for the noise.

Changes in v4:
- Don't add this helper for Windows OS since doesn't support it.

Changes in v3: None
Changes in v2:
- Add a better commit message explaining why the change is needed.
- Add Reviewed-by tag from Daniel Kiper.

 include/grub/osdep/hostfile_aros.h | 6 ++++++
 include/grub/osdep/hostfile_unix.h | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/include/grub/osdep/hostfile_aros.h 
b/include/grub/osdep/hostfile_aros.h
index a059c0fa40a..161fbb7bdfd 100644
--- a/include/grub/osdep/hostfile_aros.h
+++ b/include/grub/osdep/hostfile_aros.h
@@ -68,6 +68,12 @@ grub_util_rename (const char *from, const char *to)
   return rename (from, to);
 }
 
+static inline ssize_t
+grub_util_readlink (const char *name, char *buf, size_t bufsize)
+{
+  return readlink(name, buf, bufsize);
+}
+
 #define grub_util_mkdir(a) mkdir ((a), 0755)
 
 struct grub_util_fd
diff --git a/include/grub/osdep/hostfile_unix.h 
b/include/grub/osdep/hostfile_unix.h
index 9ffe46fa3ca..17cd3aa8b30 100644
--- a/include/grub/osdep/hostfile_unix.h
+++ b/include/grub/osdep/hostfile_unix.h
@@ -71,6 +71,12 @@ grub_util_rename (const char *from, const char *to)
   return rename (from, to);
 }
 
+static inline ssize_t
+grub_util_readlink (const char *name, char *buf, size_t bufsize)
+{
+  return readlink(name, buf, bufsize);
+}
+
 #define grub_util_mkdir(a) mkdir ((a), 0755)
 
 #if defined (__NetBSD__)
-- 
2.23.0