Re: [PATCH] livepatch-build-tools: allow patch file name sizes up to 128 characters

[Ross Lagerwall <ross.lagerwall@xxxxxxxxx>]

On Wed, Jan 31, 2024 at 4:58 PM Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
>
> XenServer uses quite long Xen version names, and encode such in the livepatch
> filename, and it's currently running out of space in the file name.
>
> Bump max filename size to 128, so it also matches the patch name length in the
> hypervisor interface.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
>  livepatch-build | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/livepatch-build b/livepatch-build
> index cdb852cc7fea..78dd2d801048 100755
> --- a/livepatch-build
> +++ b/livepatch-build
> @@ -72,8 +72,8 @@ function make_patch_name()
>      fi
>
>      # Only allow alphanumerics and '_' and '-' in the patch name.  Everything
> -    # else is replaced with '-'.  Truncate to 48 chars.
> -    echo ${PATCHNAME//[^a-zA-Z0-9_-]/-} |cut -c 1-48
> +    # else is replaced with '-'.  Truncate to 128 chars.
> +    echo ${PATCHNAME//[^a-zA-Z0-9_-]/-} |cut -c -128
>  }

I think it should be XEN_LIVEPATCH_NAME_SIZE - 1 to match the hypervisor
since AFAICT the hypervisor expects the last character to be NUL.

In get_name(), it checks:

    if ( !name->size || name->size > XEN_LIVEPATCH_NAME_SIZE )
        return -EINVAL;

... and:

    if ( n[name->size - 1] )
        return -EINVAL;

Do you agree with that?

Ross