Re: [PATCH v2] module: Add stubs.c for CONFIG_MODULES=n module_put_and_kthread_exit()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] bpf: resolve_btfids build failure with CONFIG_MODULES=n and LTO/GC
--

commit caaeb9d0651743944c690c066494bb16509c01e9
Author: Petr Pavlu <petr.pavlu@suse.com>

module: Add stubs.c for CONFIG_MODULES=n module_put_and_kthread_exit()

This commit introduces kernel/module/stubs.c to hold stub functions when
CONFIG_MODULES is disabled. It moves the stub implementation for
__module_put_and_kthread_exit() to this new file and removes the
corresponding #ifdef from the BPF verifier's noreturn list.

> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 72a3f5998dd27..be70f10e49682 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -20417,9 +20417,7 @@ BTF_ID(func, __ia32_sys_exit_group)
>  BTF_ID(func, __kunit_abort)
>  BTF_ID(func, kunit_try_catch_throw)
>  #endif
> -#ifdef CONFIG_MODULES
>  BTF_ID(func, __module_put_and_kthread_exit)

[Severity: Low]
If CONFIG_MODULES=n and dead-code elimination (like CONFIG_LTO_CLANG or
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) is enabled, will this cause 
resolve_btfids to fail?

Because the #ifdef is removed, this unconditionally requires the function to
be present in the BTF. If there are no callers in the kernel, the linker 
might discard the stub function, causing a missing BTF ID and a fatal build 
error under CONFIG_WERROR.

> -#endif
>  #ifdef CONFIG_X86_64
>  BTF_ID(func, __x64_sys_exit)
>  BTF_ID(func, __x64_sys_exit_group)

[ ... ]

> diff --git a/kernel/module/stubs.c b/kernel/module/stubs.c
> new file mode 100644
> index 0000000000000..1385c87e81695
> --- /dev/null
> +++ b/kernel/module/stubs.c
> @@ -0,0 +1,9 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +
> +#include <linux/kthread.h>
> +#include <linux/module.h>
> +
> +void __noreturn __module_put_and_kthread_exit(struct module *mod, long code)
> +{

[Severity: Low]
Does this stub need a __used attribute to prevent the linker from discarding 
it?

If no code references module_put_and_kthread_exit() when CONFIG_MODULES=n, 
this function is silently discarded by the linker during dead code 
elimination, which leads to the resolve_btfids build failure mentioned above.

> +	kthread_exit(code);
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261002-module-stubs-v2-1-a0d8c6ad1738@suse.com?part=1