From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 2FDA163CB for ; Wed, 4 Oct 2023 07:03:09 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6BA02AD for ; Wed, 4 Oct 2023 00:03:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696402987; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kDu6btx99QXs0kSLMHh2AKh2KZqG8BWNFgkrbgEVHdw=; b=fyWBgOfTQkDbZ1e6NNJtWVmBlXHDvQMx7Dc743WDQKMCy/25uejtDHLKRMF1hw3peo8Y/I jC6+kHlFU6uCOCVW2rUXJhh7/9fRoZ0vCx8Qr7rCRCI39YRh+bNXSf7K7bCd3Tb3PEUjpd p71jvCo7DO3Us/lXXiayysglyQPK08k= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-283-uQEUgsEkNvisFnqZy2eq6Q-1; Wed, 04 Oct 2023 03:03:02 -0400 X-MC-Unique: uQEUgsEkNvisFnqZy2eq6Q-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 68D80382135E; Wed, 4 Oct 2023 07:03:01 +0000 (UTC) Received: from alecto.usersys.redhat.com (unknown [10.43.17.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7E9D2140E950; Wed, 4 Oct 2023 07:02:59 +0000 (UTC) Date: Wed, 4 Oct 2023 09:02:57 +0200 From: Artem Savkov To: Andrii Nakryiko Cc: Steven Rostedt , Masami Hiramatsu , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, netdev@vger.kernel.org, Thomas Gleixner , linux-rt-users@vger.kernel.org, Jiri Olsa Subject: Re: [RFC PATCH] tracing: change syscall number type in struct syscall_trace_* Message-ID: <20231004070257.GA311687@alecto.usersys.redhat.com> References: <20231002135242.247536-1-asavkov@redhat.com> Precedence: bulk X-Mailing-List: linux-rt-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL, SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Tue, Oct 03, 2023 at 03:11:15PM -0700, Andrii Nakryiko wrote: > On Mon, Oct 2, 2023 at 6:53 AM Artem Savkov wrote: > > > > linux-rt-devel tree contains a patch that adds an extra member to struct > > can you please point to the patch itself that makes that change? Of course, some context would be useful. The patch in question is b1773eac3f29c ("sched: Add support for lazy preemption") from rt-devel tree [0]. It came up a couple of times before: [1] [2] [3] [4]. [0] https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=b1773eac3f29cbdcdfd16e0339f1a164066e9f71 [1] https://lore.kernel.org/linux-rt-users/20200221153541.681468-1-jolsa@kernel.org/t/#u [2] https://github.com/iovisor/bpftrace/commit/a2e3d5dbc03ceb49b776cf5602d31896158844a7 [3] https://lore.kernel.org/bpf/xunyjzy64q9b.fsf@redhat.com/t/#u [4] https://lore.kernel.org/bpf/20230727150647.397626-1-ykaliuta@redhat.com/t/#u > > 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 } > > > > This patch changes the type of nr member in syscall_trace_* structs to > > be long so that "args" offset is equal to that in struct > > trace_event_raw_sys_enter. > > > > Signed-off-by: Artem Savkov > > --- > > kernel/trace/trace.h | 4 ++-- > > kernel/trace/trace_syscalls.c | 7 ++++--- > > 2 files changed, 6 insertions(+), 5 deletions(-) > > > > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > > index 77debe53f07cf..cd1d24df85364 100644 > > --- a/kernel/trace/trace.h > > +++ b/kernel/trace/trace.h > > @@ -135,13 +135,13 @@ enum trace_type { > > */ > > struct syscall_trace_enter { > > struct trace_entry ent; > > - int nr; > > + long nr; > > unsigned long args[]; > > }; > > > > struct syscall_trace_exit { > > struct trace_entry ent; > > - int nr; > > + long nr; > > long ret; > > }; > > > > diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c > > index de753403cdafb..c26939119f2e4 100644 > > --- a/kernel/trace/trace_syscalls.c > > +++ b/kernel/trace/trace_syscalls.c > > @@ -101,7 +101,7 @@ find_syscall_meta(unsigned long syscall) > > return NULL; > > } > > > > -static struct syscall_metadata *syscall_nr_to_meta(int nr) > > +static struct syscall_metadata *syscall_nr_to_meta(long nr) > > { > > if (IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) > > return xa_load(&syscalls_metadata_sparse, (unsigned long)nr); > > @@ -132,7 +132,8 @@ print_syscall_enter(struct trace_iterator *iter, int flags, > > struct trace_entry *ent = iter->ent; > > struct syscall_trace_enter *trace; > > struct syscall_metadata *entry; > > - int i, syscall; > > + int i; > > + long syscall; > > > > trace = (typeof(trace))ent; > > syscall = trace->nr; > > @@ -177,7 +178,7 @@ print_syscall_exit(struct trace_iterator *iter, int flags, > > struct trace_seq *s = &iter->seq; > > struct trace_entry *ent = iter->ent; > > struct syscall_trace_exit *trace; > > - int syscall; > > + long syscall; > > struct syscall_metadata *entry; > > > > trace = (typeof(trace))ent; > > -- > > 2.41.0 > > > > > -- Artem