Hi,
I think the subject should be something like
"livepatch: Add "replace" sysfs attribute"
or use a different way to stress "replace" is the name.
On Fri, 7 Jun 2024, Yafang Shao wrote:
> When building a livepatch, a user can set it to be either an atomic-replace
> livepatch or a non-atomic-replace livepatch.
I am not a native speaker but I would drop '-' everywhere in this context.
> However, it is not easy to
> identify whether a livepatch is atomic-replace or not until it actually
> replaces some old livepatches.
Ok.
> This can lead to mistakes in a mixed
> atomic-replace and non-atomic-replace environment, especially when
> transitioning all livepatches from non-atomic-replace to atomic-replace in
> a large fleet of servers.
Out of curiosity, could you describe your setup in more detail here? It is
interesting to mix different type of livepatches so I would like to learn
more.
> To address this issue, a new sysfs interface called 'replace' is introduced
> in this patch. The result after this change is as follows:
>
> $ cat /sys/kernel/livepatch/livepatch-non_replace/replace
> 0
>
> $ cat /sys/kernel/livepatch/livepatch-replace/replace
> 1
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
> Documentation/ABI/testing/sysfs-kernel-livepatch | 8 ++++++++
> kernel/livepatch/core.c | 12 ++++++++++++
> 2 files changed, 20 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-livepatch b/Documentation/ABI/testing/sysfs-kernel-livepatch
> index a5df9b4910dc..3735d868013d 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-livepatch
> +++ b/Documentation/ABI/testing/sysfs-kernel-livepatch
> @@ -47,6 +47,14 @@ Description:
> disabled when the feature is used. See
> Documentation/livepatch/livepatch.rst for more information.
>
> +What: /sys/kernel/livepatch/<patch>/replace
> +Date: Jun 2024
> +KernelVersion: 6.11.0
> +Contact: live-patching@xxxxxxxxxxxxxxx
> +Description:
> + An attribute which indicates whether the patch supports
> + atomic-replace.
> +
> What: /sys/kernel/livepatch/<patch>/<object>
> Date: Nov 2014
> KernelVersion: 3.19.0
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 52426665eecc..0e9832f146f1 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -346,6 +346,7 @@ int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
> * /sys/kernel/livepatch/<patch>/enabled
> * /sys/kernel/livepatch/<patch>/transition
> * /sys/kernel/livepatch/<patch>/force
> + * /sys/kernel/livepatch/<patch>/replace
> * /sys/kernel/livepatch/<patch>/<object>
> * /sys/kernel/livepatch/<patch>/<object>/patched
> * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
> @@ -443,13 +444,24 @@ static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
> return count;
> }
>
> +static ssize_t replace_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + struct klp_patch *patch;
> +
> + patch = container_of(kobj, struct klp_patch, kobj);
> + return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->replace);
It might be better to use sysfs_emit() here. See patched_show() in the
same file. There are still snprintf() occurrences and it might be a
separate cleanup patch if you are interested.
Regards,
Miroslav
