[PATCH] powerpc/modules: Use WARN_ON() in stub_for_addr()

[Michael Ellerman]

Kamalesh Babulal <kamalesh at linux.vnet.ibm.com> writes:

> On Wednesday 11 October 2017 09:42 AM, Michael Ellerman wrote:
>> Kamalesh Babulal <kamalesh at linux.vnet.ibm.com> writes:
>> 
>>> Use WARN_ON(), while running out of stubs in stub_for_addr()
>>> and abort loading of the module instead of BUG_ON().
>> 
>> Thanks. This looks good in principle. Have you actually tested it to
>> make sure we do in fact gracefully fail the module load?
>> 
>
> Thanks for the review. I tested with little hackish version of this patch:
>
> +       if (!strncmp(me->name, "live", 4))
> +               j = 100;
> +       for (i = 0; stub_func_addr(stubs[i].funcdata); i+=j) {
> +               if (WARN_ON(i >= num_stubs))
> +                       return 0;
>
> and it fails gracefully.
>
> # modprobe livepatch-sample
> modprobe: ERROR: could not insert 'livepatch_sample': Unknown symbol in module, or unknown parameter (see dmesg)
>
> # echo $?
> 1
>
> # dmesg 
> ------------[ cut here ]------------
> WARNING: CPU: 2 PID: 2836 at arch/powerpc/kernel/module_64.c:526 apply_relocate_add+0x71c/0xb00

Thanks.

cheers