Re: [PATCH v3 25/28] bpf: Use RCU in all users of __module_text_address().
From: Alexei Starovoitov <hidden>
Date: 2025-01-09 18:38:15
Also in:
bpf, linux-modules, lkml
On Wed, Jan 8, 2025 at 1:05 AM Sebastian Andrzej Siewior [off-list ref] wrote:
quoted hunk ↗ jump to hunk
__module_address() can be invoked within a RCU section, there is no requirement to have preemption disabled. Replace the preempt_disable() section around __module_address() with RCU. Cc: Alexei Starovoitov <ast@kernel.org> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Eduard Zingerman <eddyz87@gmail.com> Cc: Hao Luo <redacted> Cc: Jiri Olsa <jolsa@kernel.org> Cc: John Fastabend <john.fastabend@gmail.com> Cc: KP Singh <kpsingh@kernel.org> Cc: Martin KaFai Lau <martin.lau@linux.dev> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Matt Bobrowski <mattbobrowski@google.com> Cc: Song Liu <song@kernel.org> Cc: Stanislav Fomichev <sdf@fomichev.me> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Yonghong Song <yonghong.song@linux.dev> Cc: bpf@vger.kernel.org Cc: linux-trace-kernel@vger.kernel.org Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- kernel/trace/bpf_trace.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-)diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 1b8db5aee9d38..020df7b6ff90c 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c@@ -2336,10 +2336,9 @@ void bpf_put_raw_tracepoint(struct bpf_raw_event_map *btp) { struct module *mod; - preempt_disable(); + guard(rcu)(); mod = __module_address((unsigned long)btp); module_put(mod); - preempt_enable(); } static __always_inline@@ -2907,16 +2906,14 @@ static int get_modules_for_addrs(struct module ***mods, unsigned long *addrs, u3 for (i = 0; i < addrs_cnt; i++) { struct module *mod; - preempt_disable(); - mod = __module_address(addrs[i]); - /* Either no module or we it's already stored */ - if (!mod || has_module(&arr, mod)) { - preempt_enable(); - continue; + scoped_guard(rcu) { + mod = __module_address(addrs[i]); + /* Either no module or we it's already stored */ + if (!mod || has_module(&arr, mod)) + continue; + if (!try_module_get(mod)) + err = -EINVAL;
lgtm. Should we take into bpf-next or the whole set is handled together somewhere?