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Tue, 17 Feb 2026 05:39:02 -0800 (PST) X-Received: by 2002:a05:6a00:3919:b0:81f:15b2:21ea with SMTP id d2e1a72fcca58-824d95faaedmr9250179b3a.42.1771335541524; Tue, 17 Feb 2026 05:39:01 -0800 (PST) Received: from hu-kshaikkh-hyd.qualcomm.com ([202.46.23.25]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-824c6b935c6sm14633207b3a.47.2026.02.17.05.38.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Feb 2026 05:39:01 -0800 (PST) From: Khaja Hussain Shaik Khaji To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 0/2] arm64: kprobes: fix XOL preemption window Date: Tue, 17 Feb 2026 19:08:53 +0530 Message-Id: <20260217133855.3142192-1-khaja.khaji@oss.qualcomm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20251106104955.2089268-1-khaja.khaji@oss.qualcomm.com> References: <20251106104955.2089268-1-khaja.khaji@oss.qualcomm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjE3MDExMCBTYWx0ZWRfXwIEmPM5XiI0p XzkUJX0TL+VyUW51DM1pGSPv0SUV4otoi5OvvyiGIuhsDJNNOHtKik/XCtwOdtYuSD1C9KAonWI hTjq/lxMeXytbHcKpyOK1jtGvPtkIrCV8/bh+V5rBX+yh1doqQnDTMuTUHWZ9EsaU/sBN94L/Ji KuR/5Nv69fSqvO4UB2hqkWBi9yynnJWnweVXkfvngD/bFOdi6ZvzfinSU7MsIkint7z5Yt1loVp LG+InAV9uoFRPvfj01lgcO4FzCS9E0NwBGQXUEe9OUKAoD2T0o4DomHihMTtRWM9LdI4O5Zr34j XqGexnn1ZkewpYxY9CM3Tda9UuDZ1oxVG9P+bUHlrp56W9/OXGIYMGTsj2hg5QljSv5oXwSruIU YE/LQqBTDjV5ZnfpWUw7D70HgTf6vuTOghCwngOpBwN+PoBpyGOg+vzBxk3/MddxtweAy8XyY7i 25ceJ3S4Objq5oXdBUQ== X-Proofpoint-GUID: DwAMQaZkqC15NiCobdGrZMdKkjGDqjtZ X-Proofpoint-ORIG-GUID: DwAMQaZkqC15NiCobdGrZMdKkjGDqjtZ X-Authority-Analysis: v=2.4 cv=TPNIilla c=1 sm=1 tr=0 ts=69946f77 cx=c_pps a=WW5sKcV1LcKqjgzy2JUPuA==:117 a=ZePRamnt/+rB5gQjfz0u9A==:17 a=HzLeVaNsDn8A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=_07oBJFWSMtGKjIRfaAA:9 a=OpyuDcXvxspvyRM73sMx:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-17_01,2026-02-16_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 suspectscore=0 clxscore=1015 phishscore=0 lowpriorityscore=0 malwarescore=0 priorityscore=1501 spamscore=0 impostorscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602170110 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260217_053904_767245_67C519F4 X-CRM114-Status: GOOD ( 14.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, catalin.marinas@arm.com, dev.jain@arm.com, linux-kernel@vger.kernel.org, yang@os.amperecomputing.com, linux-arm-msm@vger.kernel.org, will@kernel.org, mhiramat@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Mark, Thanks for the detailed analysis. You're right that this is not BTI-specific. The underlying issue is that XOL execution assumes per-CPU kprobe state remains intact across exception return, which can be violated if execution is preempted or migrated during the XOL window. This v2 series addresses the root cause of kprobe crashes that the previous BTI workaround addressed only indirectly: disable preemption across the XOL instruction and re-enable it in the SS-BRK handler. This ensures the XOL/SS-BRK pair executes on the same CPU and avoids corruption of per-CPU kprobe state. Regarding triggering: this was observed with kretprobes during long stability runs (800+ hours on dwc3 paths), where XOL execution may be preempted or migrated before the SS-BRK is handled, resulting in incorrect per-CPU kprobe state. This series leaves BTI handling unchanged and avoids emulating BTI as NOP. Khaja Hussain Shaik Khaji (2): arm64: kprobes: disable preemption across XOL single-step arm64: insn: drop NOP from steppable hint list arch/arm64/include/asm/insn.h | 1 - arch/arm64/kernel/probes/kprobes.c | 13 +++++++++++++ 2 files changed, 13 insertions(+), 1 deletion(-) -- 2.34.1