Re: [PATCH] init/main: Expose built-in initcalls and blacklist status via debugfs

[Petr Pavlu <petr.pavlu@suse.com>]

On 5/10/26 8:13 AM, Aaron Tomlin wrote:
> At present, identifying the correct function name to supply to the
> "initcall_blacklist=" kernel command-line parameter requires manual
> inspection of the source code or kernel symbol tables. Furthermore,
> administrators lack a reliable runtime mechanism to verify whether a
> specified built-in module has been successfully blacklisted.

My understanding is that initcall_blacklist is primarily a debugging
facility. This is documented in
Documentation/admin-guide/kernel-parameters.txt [1] and also outlined in
the initial commit 7b0b73d76651 ("init/main.c: add initcall_blacklist
kernel parameter") [2]. It is expected that to use it, one must inspect
the kernel source code.

If the goal is to allow specific built-in modules to be blacklisted,
I wonder whether extending module_blacklist to also cover built-in
modules might be a better option. Module names are more appropriate for
administrators to use, while initcall names should remain internal to
the kernel. Additionally, initcalls are typically "static" and therefore
are not guaranteed to have unique names + using module names avoids
a dependency on CONFIG_KALLSYMS=y.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/kernel-parameters.txt?h=v7.1#n2408
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7b0b73d76651e5f88c88b76efa18d719f832bf6f

-- 
Thanks,
Petr