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Tue, 10 Nov 2026 19:51:11 -0800 (PST) From: Ritesh Harjani (IBM) To: Bradley Morgan , Madhavan Srinivasan , Christophe Leroy Cc: Michael Ellerman , Nicholas Piggin , Shrikanth Hegde , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, brads@mainlining.org Subject: Re: [PATCH] powerpc32/modules: Reserve a PLT entry for ftrace_regs_caller In-Reply-To: <20260923175631.235276-1-brads@mainlining.org> Date: Wed, 11 Nov 2026 09:18:41 +0530 Message-ID: References: <20260923175631.235276-1-brads@mainlining.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Bradley Morgan 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 > --- > 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 -ritesh