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Fri, 04 Sep 2026 00:02:20 -0700 (PDT) Received: from ydg-Zenbook-14-UM3406GA ([211.230.25.193]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8615273e3a0sm755511b3a.23.2026.09.04.00.02.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Sep 2026 00:02:19 -0700 (PDT) From: Donggeun Yoo To: Alexei Starovoitov , Andrii Nakryiko , Catalin Marinas , Daniel Borkmann , Eduard Zingerman , Emil Tsalapatis , Ihor Solodrai , Jiri Olsa , Kumar Kartikeya Dwivedi , Mark Rutland , Martin KaFai Lau , Puranjay Mohan , Shuah Khan , Song Liu , Will Deacon , Xu Kuohai , Yonghong Song Cc: bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Xu Kuohai , Donggeun Yoo Subject: [PATCH bpf 0/2] bpf, arm64: fix the exception callback's frame pointer Date: Fri, 4 Sep 2026 16:02:08 +0900 Message-ID: <20260904070210.4163193-1-donggeunyoo.kernel@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The arm64 JIT does not set BPF_REG_FP in the prologue of an exception callback, so the callback runs with whatever x25 held when bpf_throw() was called. A callback that materializes the register, for instance to pass the address of a local variable to a helper, then works on the frame of the subprogram that threw. Patch 1 sets ctx->fp_used on that path, the same fix commit b114fcee766d ("bpf, arm64: Fix fp initialization for exception boundary") made for the exception boundary. Patch 2 adds a selftest that reaches the case. Tested on aarch64 under QEMU with vmtest.sh. Without patch 1 the new test panics the kernel, because the address handed to the helper lands on the helper's own saved return address: pc : 0x1234 lr : 0x1234 Call trace: 0x1234 (P) bpf_test_run+0x188/0x3e0 bpf_prog_test_run_skb+0x47c/0x998 __sys_bpf+0xbdc/0xdd8 Kernel panic - not syncing: Oops: Fatal exception in interrupt With patch 1 applied the whole group passes: #116/11 exceptions/exception_throw_subprog_stack_cb:OK #116 exceptions:OK Summary: 1/118 PASSED, 0 SKIPPED, 0/0 FAILED Not tested on other architectures. Donggeun Yoo (2): bpf, arm64: set up the frame pointer for the exception callback selftests/bpf: cover the exception callback using its own BPF stack arch/arm64/net/bpf_jit_comp.c | 2 ++ .../selftests/bpf/prog_tests/exceptions.c | 1 + .../testing/selftests/bpf/progs/exceptions.c | 29 +++++++++++++++++++ 3 files changed, 32 insertions(+) -- 2.53.0