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

[Bradley Morgan <bradley.morgan@linux.dev>]

On 11 November 2026 11:58:28 GMT, Madhavan Srinivasan <maddy@linux.ibm.com>
wrote:
>
>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.

No worries, mind changing sob to this email?

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

--- Thanks!