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Wed, 11 Nov 2026 11:58:30 +0000 (GMT) Received: from [9.43.120.194] (unknown [9.43.120.194]) by smtpav01.wdc07v.mail.ibm.com (Postfix) with ESMTP; Wed, 11 Nov 2026 11:58:30 +0000 (GMT) Message-ID: <371108c3-0314-4015-9ca4-d96a11f1e597@linux.ibm.com> Date: Wed, 11 Nov 2026 17:28:28 +0530 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] powerpc32/modules: Reserve a PLT entry for ftrace_regs_caller To: Bradley Morgan , ritesh.list@gmail.com Cc: brads@mainlining.org, chleroy@kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au, npiggin@gmail.com, sshegde@linux.ibm.com References: <80D9FEB3-9FB3-4878-BC66-74C13761CC9A@linux.dev> Content-Language: en-US From: Madhavan Srinivasan In-Reply-To: <80D9FEB3-9FB3-4878-BC66-74C13761CC9A@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYxMTExMDA0NiBTYWx0ZWRfX3qV1DL2OHVag Zqlb9DqDPD0lGP/BWR/tRUCm1seYIO+NPpoII8OF5335q/E6h3wUlm80jRDw68/v5R6cde18T67 ZsJtEI4R8nyRAXnVIySWxAoBNSgt0Yw= X-Authority-Analysis: v=2.4 cv=HbCB3SE8 c=1 sm=1 tr=0 ts=6af4586b cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=zJRp6_cAMcgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=pGLkceISAAAA:8 a=OuZLqq7tAAAA:8 a=VwQbUJbxAAAA:8 a=FkolyUzucbp6SESKabkA:9 a=QEXdDO2ut3YA:10 a=AKGiAy9iJ-JzxKVHQNES:22 X-Proofpoint-ORIG-GUID: 6jB0qBBVKKLf_LWT1BYIJF81JuJJB3kG X-Proofpoint-GUID: ecDCVwa_RUsimFmT9_CUwxKBP-_SYvyv X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTExMDA0NiBTYWx0ZWRfXxt2F+2/kQ+tU 1VJJg2l/Orp7U/RosHTb45Y5vmws0yiv/AdkCvVvMQua0exK+OUI/Yf7RbL+PbPmEuLKuvzduuU ujZ1NqxQZjsx4JDnWTUvHPkU2dMvYTxDc23MY8Xqyto1E9m13dnyAvGDIMzTLqQ8q6vYqGGh1Kd r7qEnWJ5sODIa00PzVaKBuqKEv3YS+bQX7/dj1IvydYqcMop+6gI7ZWXIcXt5XHUqJ5kBQEhpvE btNhvzhkHLgCTrXqK8MjNL5LAaAzPISRDr+tfys6Jhu3nsGKZ0QtKdJaZmsDy6Ft5Ye8myX7qFV FcwCWvgcccqescpi+fSW7dsU6r33FJKXznmWeOr6sFK2tZI283aRyySvu89z9H3wyBO4UnfcCJc sXIPLRzMsVl0zWzBg1M0AgvaKKWZZGaHcRrHyee+hLFcFzVI4xfoyNEzS71ce0/QeMvr72qnn14 /fL7jkKV2fw2aAXhsmQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-11_02,2026-11-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 adultscore=0 spamscore=0 bulkscore=0 phishscore=0 impostorscore=0 priorityscore=1501 clxscore=1011 lowpriorityscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611110046 On 11/11/26 12:58 PM, Bradley Morgan wrote: > On 11 November 2026 03:48:41 GMT, Ritesh Harjani > wrote: >> 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 > 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!