[PATCH 1/1] fat: fix listing the root directory

[PATCH 1/1] fat: fix listing the root directory

[Heinrich Schuchardt]

ls / for a FAT partition leads to

   error: invalid modification timestamp for /.

Not all entries of the directory are displayed.

Linux never updates the modification timestamp of the /. directory entry.
The FAT specification allows the access and creation date fields to be
zero.

We should follow Linux and render initial FAT timestamps as start of
the epoch.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
---
 grub-core/fs/fat.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/grub-core/fs/fat.c b/grub-core/fs/fat.c
index dd82e4ee3..35ff0b27c 100644
--- a/grub-core/fs/fat.c
+++ b/grub-core/fs/fat.c
@@ -901,6 +901,18 @@ grub_fat_timestamp (grub_uint16_t time, grub_uint16_t date, grub_int64_t *nix) {
     .second = (time & 0x001F) * 2,
   };
 
+  /*
+   * The modification time of the root directory is never set by Linux.
+   * Creation and access time are optional and can be zero.
+   * Follow Linux and render FAT initial timestamps as the start of the epoch.
+   */
+  if (date == 0 && time == 0)
+    {
+      datetime.year = 1970;
+      datetime.month = 1;
+      datetime.day = 1;
+    }
+
   /* The conversion below allows seconds=60, so don't trust its validation. */
   if ((time & 0x1F) > 29)
     return 0;
-- 
2.33.1

Re: [PATCH 1/1] fat: fix listing the root directory

[Vladimir 'phcoder' Serbinenko]

Inserting dummy date of 1970-1-1 is a bad idea. Can we rather allow
timestamp to be missing instead of throwing error?

On Fri, Jan 21, 2022 at 8:33 PM Heinrich Schuchardt
<heinrich.schuchardt@canonical.com> wrote:
>
> ls / for a FAT partition leads to
>
>    error: invalid modification timestamp for /.
>
> Not all entries of the directory are displayed.
>
> Linux never updates the modification timestamp of the /. directory entry.
> The FAT specification allows the access and creation date fields to be
> zero.
>
> We should follow Linux and render initial FAT timestamps as start of
> the epoch.
>
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
> ---
>  grub-core/fs/fat.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/grub-core/fs/fat.c b/grub-core/fs/fat.c
> index dd82e4ee3..35ff0b27c 100644
> --- a/grub-core/fs/fat.c
> +++ b/grub-core/fs/fat.c
> @@ -901,6 +901,18 @@ grub_fat_timestamp (grub_uint16_t time, grub_uint16_t date, grub_int64_t *nix) {
>      .second = (time & 0x001F) * 2,
>    };
>
> +  /*
> +   * The modification time of the root directory is never set by Linux.
> +   * Creation and access time are optional and can be zero.
> +   * Follow Linux and render FAT initial timestamps as the start of the epoch.
> +   */
> +  if (date == 0 && time == 0)
> +    {
> +      datetime.year = 1970;
> +      datetime.month = 1;
> +      datetime.day = 1;
> +    }
> +
>    /* The conversion below allows seconds=60, so don't trust its validation. */
>    if ((time & 0x1F) > 29)
>      return 0;
> --
> 2.33.1
>
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> https://lists.gnu.org/mailman/listinfo/grub-devel



-- 
Regards
Vladimir 'phcoder' Serbinenko

Re: [PATCH 1/1] fat: fix listing the root directory

[Heinrich Schuchardt]

On 1/22/22 10:07, Vladimir 'phcoder' Serbinenko wrote:
> Inserting dummy date of 1970-1-1 is a bad idea. Can we rather allow
> timestamp to be missing instead of throwing error?

This function seems only to be used for validation of the timestamp.
I never have seen the ls command in GRUB actually display a timestamp.

If you use ls -la in Linux it will display 1970-01-01. Wouldn't this be 
what a user would expect to see in GRUB too?

Anyway the filtering would have to be done in a different function than 
the one corrected here.

Best regards

Heinrich

> 
> On Fri, Jan 21, 2022 at 8:33 PM Heinrich Schuchardt
> <heinrich.schuchardt@canonical.com> wrote:
>>
>> ls / for a FAT partition leads to
>>
>>     error: invalid modification timestamp for /.
>>
>> Not all entries of the directory are displayed.
>>
>> Linux never updates the modification timestamp of the /. directory entry.
>> The FAT specification allows the access and creation date fields to be
>> zero.
>>
>> We should follow Linux and render initial FAT timestamps as start of
>> the epoch.
>>
>> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
>> ---
>>   grub-core/fs/fat.c | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/grub-core/fs/fat.c b/grub-core/fs/fat.c
>> index dd82e4ee3..35ff0b27c 100644
>> --- a/grub-core/fs/fat.c
>> +++ b/grub-core/fs/fat.c
>> @@ -901,6 +901,18 @@ grub_fat_timestamp (grub_uint16_t time, grub_uint16_t date, grub_int64_t *nix) {
>>       .second = (time & 0x001F) * 2,
>>     };
>>
>> +  /*
>> +   * The modification time of the root directory is never set by Linux.
>> +   * Creation and access time are optional and can be zero.
>> +   * Follow Linux and render FAT initial timestamps as the start of the epoch.
>> +   */
>> +  if (date == 0 && time == 0)
>> +    {
>> +      datetime.year = 1970;
>> +      datetime.month = 1;
>> +      datetime.day = 1;
>> +    }
>> +
>>     /* The conversion below allows seconds=60, so don't trust its validation. */
>>     if ((time & 0x1F) > 29)
>>       return 0;
>> --
>> 2.33.1
>>
>>
>> _______________________________________________
>> Grub-devel mailing list
>> Grub-devel@gnu.org
>> https://lists.gnu.org/mailman/listinfo/grub-devel
> 
> 
>