From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1C34126E2D; Thu, 12 Oct 2023 13:43:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A10AC433C7; Thu, 12 Oct 2023 13:43:21 +0000 (UTC) Date: Thu, 12 Oct 2023 09:44:44 -0400 From: Steven Rostedt To: Artem Savkov Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, netdev@vger.kernel.org, Masami Hiramatsu , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Thomas Gleixner , linux-rt-users@vger.kernel.org, Jiri Olsa Subject: Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t Message-ID: <20231012094444.0967fa79@gandalf.local.home> In-Reply-To: <20231012114550.152846-1-asavkov@redhat.com> References: <20231005123413.GA488417@alecto.usersys.redhat.com> <20231012114550.152846-1-asavkov@redhat.com> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 12 Oct 2023 13:45:50 +0200 Artem Savkov wrote: > linux-rt-devel tree contains a patch (b1773eac3f29c ("sched: Add support > for lazy preemption")) that adds an extra member to struct trace_entry. > This causes the offset of args field in struct trace_event_raw_sys_enter > be different from the one in struct syscall_trace_enter: > > struct trace_event_raw_sys_enter { > struct trace_entry ent; /* 0 12 */ > > /* XXX last struct has 3 bytes of padding */ > /* XXX 4 bytes hole, try to pack */ > > long int id; /* 16 8 */ > long unsigned int args[6]; /* 24 48 */ > /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */ > char __data[]; /* 72 0 */ > > /* size: 72, cachelines: 2, members: 4 */ > /* sum members: 68, holes: 1, sum holes: 4 */ > /* paddings: 1, sum paddings: 3 */ > /* last cacheline: 8 bytes */ > }; > > struct syscall_trace_enter { > struct trace_entry ent; /* 0 12 */ > > /* XXX last struct has 3 bytes of padding */ > > int nr; /* 12 4 */ > long unsigned int args[]; /* 16 0 */ > > /* size: 16, cachelines: 1, members: 3 */ > /* paddings: 1, sum paddings: 3 */ > /* last cacheline: 16 bytes */ > }; > > This, in turn, causes perf_event_set_bpf_prog() fail while running bpf > test_profiler testcase because max_ctx_offset is calculated based on the > former struct, while off on the latter: > > 10488 if (is_tracepoint || is_syscall_tp) { > 10489 int off = trace_event_get_offsets(event->tp_event); > 10490 > 10491 if (prog->aux->max_ctx_offset > off) > 10492 return -EACCES; > 10493 } > > What bpf program is actually getting is a pointer to struct > syscall_tp_t, defined in kernel/trace/trace_syscalls.c. This patch fixes > the problem by aligning struct syscall_tp_t with with struct > syscall_trace_(enter|exit) and changing the tests to use these structs > to dereference context. > > Signed-off-by: Artem Savkov Thanks for doing a proper fix. Acked-by: Steven Rostedt (Google) -- Steve