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Thu, 02 Apr 2026 02:26:36 -0700 (PDT) From: Yafang Shao To: jpoimboe@kernel.org, jikos@kernel.org, mbenes@suse.cz, pmladek@suse.com, joe.lawrence@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, kpsingh@kernel.org, mattbobrowski@google.com, song@kernel.org, jolsa@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, memxor@gmail.com, yonghong.song@linux.dev Cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, Yafang Shao Subject: [RFC PATCH 2/4] trace: Allow kprobes to override livepatched functions Date: Thu, 2 Apr 2026 17:26:05 +0800 Message-ID: <20260402092607.96430-3-laoar.shao@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260402092607.96430-1-laoar.shao@gmail.com> References: <20260402092607.96430-1-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Introduce the ability for kprobes to override the return values of functions that have been livepatched. This functionality is guarded by the CONFIG_KPROBE_OVERRIDE_KLP_FUNC configuration option. Signed-off-by: Yafang Shao --- kernel/trace/Kconfig | 14 ++++++++++++++ kernel/trace/bpf_trace.c | 3 ++- kernel/trace/trace_kprobe.c | 17 +++++++++++++++++ kernel/trace/trace_probe.h | 5 +++++ 4 files changed, 38 insertions(+), 1 deletion(-) diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 49de13cae428..db712c8cb745 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -1279,6 +1279,20 @@ config HIST_TRIGGERS_DEBUG If unsure, say N. +config KPROBE_OVERRIDE_KLP_FUNC + bool "Allow kprobes to override livepatched functions" + depends on KPROBES && LIVEPATCH + help + This option allows BPF programs to use kprobes to override functions + that have already been patched by Livepatch (KLP). + + Enabling this provides a mechanism to dynamically control execution + flow without requiring a reboot or a new livepatch module. It + effectively combines the persistence of livepatching with the + programmability of BPF. + + If unsure, say N. + source "kernel/trace/rv/Kconfig" endif # FTRACE diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index c901ace836cb..08ae2b1a912c 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1935,7 +1935,8 @@ int perf_event_attach_bpf_prog(struct perf_event *event, if (!tp) return -EINVAL; if (!trace_kprobe_on_func_entry(tp) || - !trace_kprobe_error_injectable(tp)) + (!trace_kprobe_error_injectable(tp) && + !trace_kprobe_klp_func_overridable(tp))) return -EINVAL; } diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 768702674a5c..6f05451fbc76 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -213,6 +213,23 @@ bool trace_kprobe_error_injectable(struct trace_kprobe *tp) return within_error_injection_list(trace_kprobe_address(tp)); } +bool trace_kprobe_klp_func_overridable(struct trace_kprobe *tp) +{ + bool overridable = false; +#ifdef CONFIG_KPROBE_OVERRIDE_KLP_FUNC + struct module *mod; + unsigned long addr; + + addr = trace_kprobe_address(tp); + rcu_read_lock(); + mod = __module_address(addr); + if (mod && mod->klp) + overridable = true; + rcu_read_unlock(); +#endif + return overridable; +} + static int register_kprobe_event(struct trace_kprobe *tk); static int unregister_kprobe_event(struct trace_kprobe *tk); diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 958eb78a9068..84bd2617db7c 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -271,6 +271,7 @@ struct trace_kprobe { #ifdef CONFIG_KPROBE_EVENTS bool trace_kprobe_on_func_entry(struct trace_kprobe *tp); bool trace_kprobe_error_injectable(struct trace_kprobe *tp); +bool trace_kprobe_klp_func_overridable(struct trace_kprobe *tp); #else static inline bool trace_kprobe_on_func_entry(struct trace_kprobe *tp) { @@ -281,6 +282,10 @@ static inline bool trace_kprobe_error_injectable(struct trace_kprobe *tp) { return false; } +static inline bool trace_kprobe_klp_func_overridable(struct trace_kprobe *tp) +{ + return false; +} #endif /* CONFIG_KPROBE_EVENTS */ static inline unsigned int trace_probe_load_flag(struct trace_probe *tp) -- 2.47.3