Re: [PATCH 2/2] Make editenv chase symlinks including those across devices.

[Vladimir 'φ-coder/phcoder' Serbinenko]

On 04.09.2014 17:36, Peter Jones wrote:
> This lets us make /boot/grub2/grubenv a symlink to
> /boot/efi/EFI/fedora/grubenv even though they're different mount points,
> which allows /usr/bin/grub2-editenv to be the same across platforms
> (i.e. UEFI vs BIOS).
> 
> Signed-off-by: Peter Jones <address@hidden>
> Reviewed-by: Adam Jackson <address@hidden>
> ---
>  Makefile.util.def |  9 +++++++++
>  util/editenv.c    | 46 ++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 53 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile.util.def b/Makefile.util.def
> index 8f40e78..87029a1 100644
> --- a/Makefile.util.def
> +++ b/Makefile.util.def
> @@ -228,8 +228,17 @@ program = {
>  
>    common = util/grub-editenv.c;
>    common = util/editenv.c;
> +  common = util/grub-install-common.c;
>    common = grub-core/osdep/init.c;
> +  common = grub-core/osdep/compress.c;
> +  extra_dist = grub-core/osdep/unix/compress.c;
> +  extra_dist = grub-core/osdep/basic/compress.c;
> +  common = util/mkimage.c;
> +  common = grub-core/osdep/config.c;
> +  common = util/config.c;
> +  common = util/resolve.c;
>  
> +  ldadd = '$(LIBLZMA)';
>    ldadd = libgrubmods.a;
>    ldadd = libgrubgcry.a;
>    ldadd = libgrubkern.a;
> diff --git a/util/editenv.c b/util/editenv.c
> index c6f8d22..d8d1dad 100644
> --- a/util/editenv.c
> +++ b/util/editenv.c
> @@ -37,6 +37,7 @@ grub_util_create_envblk_file (const char *name)
>    FILE *fp;
>    char *buf;
>    char *namenew;
> +  char *rename_target = xstrdup(name);
>  
>    buf = xmalloc (DEFAULT_ENVBLK_SIZE);
>  
> @@ -59,7 +60,48 @@ grub_util_create_envblk_file (const char *name)
>    free (buf);
>    fclose (fp);
>  
> -  if (grub_util_rename (namenew, name) < 0)
> -    grub_util_error (_("cannot rename the file %s to %s"), namenew, name);
> +  ssize_t size = 1;
> +  while (1)
> +    {
> +      char *linkbuf;
> +      ssize_t retsize;
> +
> +      linkbuf = xmalloc(size+1);
> +      retsize = grub_util_readlink (rename_target, linkbuf, size);

If I get this code correctly you essentially canonicalize the link
manually. Why not use already available canonicalization functions?
> +      if (retsize < 0 && (errno == ENOENT || errno == EINVAL))
> +     {
> +       free (linkbuf);
> +       break;
> +     }
> +      else if (retsize < 0)
> +     {
> +       grub_util_error (_("cannot rename the file %s to %s: %m"), namenew, 
> name);
> +       free (linkbuf);
> +       free (namenew);
> +       return;
> +     }
> +      else if (retsize == size)
> +     {
> +       free(linkbuf);
> +       size += 128;
> +       continue;
> +     }
> +
> +      free (rename_target);
> +      linkbuf[retsize] = '\0';
> +      rename_target = linkbuf;
> +    }
> +
> +  int rc = grub_util_rename (namenew, rename_target);
> +  if (rc < 0 && errno == EXDEV)
> +    {
> +      rc = grub_install_copy_file (namenew, rename_target, 1);
> +      grub_util_unlink (namenew);
> +    }
> +
> +  if (rc < 0)
> +    grub_util_error (_("cannot rename the file %s to %s: %m"), namenew, 
> name);
> +
>    free (namenew);
> +  free (rename_target);
>  }
>

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