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Thu, 03 Jul 2025 13:48:33 -0700 (PDT) Received: from localhost ([2a03:2880:30ff:1::]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae3f6bb1418sm36665566b.183.2025.07.03.13.48.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Jul 2025 13:48:33 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Eduard Zingerman , Emil Tsalapatis , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Barret Rhoden , Matt Bobrowski , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf-next v5 07/12] bpf: Report may_goto timeout to BPF stderr Date: Thu, 3 Jul 2025 13:48:13 -0700 Message-ID: <20250703204818.925464-8-memxor@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250703204818.925464-1-memxor@gmail.com> References: <20250703204818.925464-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1521; h=from:subject; bh=E6+Abt1CLjBnfHopnHo3JheIACRIUpzwaEfydiovcAA=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBoZudMthhutS9/HqUajVTGYH0y1qGy3Q5MjLqilB1e +ZaPpSiJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCaGbnTAAKCRBM4MiGSL8RyoGsD/ 916x3IOVJ6RTkxDT9UF3ceFK9iwtlhb/p47G2Ts7Jc7BwWyYawEg1dOCRt1O0p5dOwmJL0Dsvjtsm/ Wk6pGlrl6Qwyo0Eca07uO5AoyTTj53VnVOzhaPTj8BJx94+znCnR98FEpWDABa8r64hZ931kvbwvEd ZhKAXTdhezV/5BU/xuVaiVOkg+B43leqYWmwvaDx9rs5HAfJqQ3NUhIr4v5kyx2XBFurkAN3+RcbCU 1etFbdK4q/3ZNHLWXRMXPQrFG6e1Y0UFfe4+orjpkrN9oKgzSNLTJcvXy5yTzD7ukxLLL0wXkocnN+ Swb3k5wWCWRc3C3OfITSohVXSYbSNxZ5fiB+TFl/x6uCzI9T2ygW5R68mL30D7/lHQ0bkupTSnfI15 UFw91vL0sCfGqtzBvQjZ6WvzajHr0DVoLolRXI0ZpUZiPlNnaSrbldSBo1iVq9DGMW8aSWXYwKDaIk v2xSygLKYOn1qh6DdlTVFRDtDWJkoQt7Zxw2azXiFxbYORYg2NglwWjX/UrOoqiXRqzg+LaSVS8g4Q neJQ4/KNVdAQ/9XNPA8tXAnlv77GvIS1C7ZjZ4v/tCt6UNCA+Ac0DAkga3WbuSOdU+Vkw2cXIYdeRz 1Pb5BhnQj1gNEIdkjsWty7fBMyguhejA499gYzR/xGyuutrDpT1GvWuI6uJQ== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=4BBE2A7E06ECF9D5823C61114CE0C88648BF11CA Content-Transfer-Encoding: 8bit Begin reporting may_goto timeouts to BPF program's stderr stream. Acked-by: Eduard Zingerman Reviewed-by: Emil Tsalapatis Signed-off-by: Kumar Kartikeya Dwivedi --- kernel/bpf/core.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 037d67cf5fb1..fe8a53f3c5bc 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -3168,6 +3168,22 @@ u64 __weak arch_bpf_timed_may_goto(void) return 0; } +static noinline void bpf_prog_report_may_goto_violation(void) +{ +#ifdef CONFIG_BPF_SYSCALL + struct bpf_stream_stage ss; + struct bpf_prog *prog; + + prog = bpf_prog_find_from_stack(); + if (!prog) + return; + bpf_stream_stage(ss, prog, BPF_STDERR, ({ + bpf_stream_printk(ss, "ERROR: Timeout detected for may_goto instruction\n"); + bpf_stream_dump_stack(ss); + })); +#endif +} + u64 bpf_check_timed_may_goto(struct bpf_timed_may_goto *p) { u64 time = ktime_get_mono_fast_ns(); @@ -3178,8 +3194,10 @@ u64 bpf_check_timed_may_goto(struct bpf_timed_may_goto *p) return BPF_MAX_TIMED_LOOPS; } /* Check if we've exhausted our time slice, and zero count. */ - if (time - p->timestamp >= (NSEC_PER_SEC / 4)) + if (unlikely(time - p->timestamp >= (NSEC_PER_SEC / 4))) { + bpf_prog_report_may_goto_violation(); return 0; + } /* Refresh the count for the stack frame. */ return BPF_MAX_TIMED_LOOPS; } -- 2.47.1