linux-kernel - Re: [PATCH v5 04/13] module: Move livepatch support to a separate file

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Date:   Thu, 10 Feb 2022 17:20:16 +0000
From:   Aaron Tomlin <atomlin@...hat.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     "mcgrof@...nel.org" <mcgrof@...nel.org>,
        "cl@...ux.com" <cl@...ux.com>,
        "pmladek@...e.com" <pmladek@...e.com>,
        "mbenes@...e.cz" <mbenes@...e.cz>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "jeyu@...nel.org" <jeyu@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
        "live-patching@...r.kernel.org" <live-patching@...r.kernel.org>,
        "atomlin@...mlin.com" <atomlin@...mlin.com>,
        "ghalat@...hat.com" <ghalat@...hat.com>,
        "allen.lkml@...il.com" <allen.lkml@...il.com>,
        "void@...ifault.com" <void@...ifault.com>,
        "joe@...ches.com" <joe@...ches.com>,
        "msuchanek@...e.de" <msuchanek@...e.de>,
        "oleksandr@...alenko.name" <oleksandr@...alenko.name>
Subject: Re: [PATCH v5 04/13] module: Move livepatch support to a separate file

On Thu 2022-02-10 11:44 +0000, Christophe Leroy wrote:
> This change is wrong, build fails with it because is_livepatch_module()
> is nowhere defined.

Yes, sorry about that. This was an omission/or oversight during the rebase
attempt.

> You could move is_livepatch_module() to include/linux/livepatch.h but as
> a separate patch.

Fair enough. Albeit, I'd prefer to revert and keep is_livepatch_module()
in include/linux/module.h - this is likely the best solution.
Note: set_livepatch_module() will remain for internal use only.

> >   #else /* !CONFIG_LIVEPATCH */
> >   static inline bool is_livepatch_module(struct module *mod)
> >   {
> > diff --git a/kernel/module/Makefile b/kernel/module/Makefile
> > index 2902fc7d0ef1..ee20d864ad19 100644
> > --- a/kernel/module/Makefile
> > +++ b/kernel/module/Makefile
> > @@ -7,3 +7,6 @@ obj-$(CONFIG_MODULES) += main.o
> >   obj-$(CONFIG_MODULE_DECOMPRESS) += decompress.o
> >   obj-$(CONFIG_MODULE_SIG) += signing.o
> >   obj-$(CONFIG_MODULE_SIG_FORMAT) += signature.o
> > +ifdef CONFIG_MODULES
>
> CONFIG_LIVEPATCH depends on CONFIG_MODULES so this ifdef is not needed

Agreed.

> Checkpatch reports the following:
>
> WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
> #80:
> new file mode 100644
>
> CHECK: Comparison to NULL could be written "!mod->klp_info"
> #109: FILE: kernel/module/livepatch.c:25:
> +    if (mod->klp_info == NULL)
>
> CHECK: Comparison to NULL could be written "!mod->klp_info->sechdrs"
> #119: FILE: kernel/module/livepatch.c:35:
> +    if (mod->klp_info->sechdrs == NULL) {
>
> CHECK: Comparison to NULL could be written "!mod->klp_info->secstrings"
> #127: FILE: kernel/module/livepatch.c:43:
> +    if (mod->klp_info->secstrings == NULL) {
>
> CHECK: No space is necessary after a cast
> #142: FILE: kernel/module/livepatch.c:58:
> +    mod->klp_info->sechdrs[symndx].sh_addr = (unsigned long)
> mod->core_kallsyms.symtab;

Ok.

> Given how simple this function is, it should be a 'static inline' in
> internal.c

Agreed.

> CHECK: Alignment should match open parenthesis
> #285: FILE: kernel/module/main.c:3033:
> +    pr_err("%s: module is marked as livepatch module, but livepatch
> support is disabled",
> +        mod->name);

Fair enough.


Kind regards,

-- 
Aaron Tomlin