Re: [PATCH] powerpc32/modules: Reserve a PLT entry for ftrace_regs_caller

[Madhavan Srinivasan <maddy@linux.ibm.com>]

On 11/11/26 12:58 PM, Bradley Morgan wrote:
> On 11 November 2026 03:48:41 GMT, Ritesh Harjani <ritesh.list@gmail.com>
> wrote:
>> Bradley Morgan <brads@mainlining.org> writes:
>>
>>> Commit 7dfbfb87c243 ("powerpc/ftrace: Activate
>>> HAVE_DYNAMIC_FTRACE_WITH_REGS on PPC32") made count_relocs()
>>> undercount the PLT entries the loader
>>> consumes: module_finalize_ftrace() now creates two trampolines
>>> (mod->arch.tramp for ftrace_caller() and mod->arch.tramp_regs for
>>> ftrace_regs_caller()), while count_relocs() reserves only one entry
>>> for ftrace.
>>>
>>> So the core .plt ends up one ppc_plt_entry (16 bytes) short. The
>>> walk in do_plt_call() scans for a free slot with
>>> "while (entry->jump[0])" and has no bound check, so once the last
>>> reserved slot is used up, the walk steps past the end of the section
>>> and patch_instruction() writes the 4-instruction trampoline into
>>> whatever module memory follows the .plt.
>>>
>>> Count the second entry, mirroring what module_64.c does for the same
>>> pair of stubs.
>>>
>>> Signed-off-by: Bradley Morgan <brads@mainlining.org>
>>> ---
>>>   arch/powerpc/kernel/module_32.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>> Do we also need fixes and stable tag here?
>>
>> Fixes: 7dfbfb87c243 ("powerpc/ftrace: Activate HAVE_DYNAMIC_FTRACE_WITH_REGS on PPC32")
>> Cc: stable@vger.kernel.org
> Hmm.. could the merger add that? If anyone merges.. :(
planned to be part of my fixes PR and will add it.
Thanks for the fix.

Maddy
>>
>> -ritesh
>>
> --- Thanks!