From nobody Fri Dec 19 12:31:29 2025 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 9FBE420DDC for ; Tue, 19 Dec 2023 14:32:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0FC71C433CC; Tue, 19 Dec 2023 14:32:01 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rFb9Y-00000003MFP-0VSl; Tue, 19 Dec 2023 09:33:00 -0500 Message-ID: <20231219143259.902317852@goodmis.org> User-Agent: quilt/0.67 Date: Tue, 19 Dec 2023 09:32:37 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton Subject: [for-next][PATCH 04/10] trace_seq: Increase the buffer size to almost two pages References: <20231219143233.204534014@goodmis.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Steven Rostedt (Google)" Now that trace_marker can hold more than 1KB string, and can write as much as the ring buffer can hold, the trace_seq is not big enough to hold writes: ~# a=3D"1234567890" ~# cnt=3D4080 ~# s=3D"" ~# while [ $cnt -gt 10 ]; do ~# s=3D"${s}${a}" ~# cnt=3D$((cnt-10)) ~# done ~# echo $s > trace_marker ~# cat trace # tracer: nop # # entries-in-buffer/entries-written: 2/2 #P:8 # # _-----=3D> irqs-off/BH-disabled # / _----=3D> need-resched # | / _---=3D> hardirq/softirq # || / _--=3D> preempt-depth # ||| / _-=3D> migrate-disable # |||| / delay # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | <...>-860 [002] ..... 105.543465: tracing_mark_write[LINE= TOO BIG] <...>-860 [002] ..... 105.543496: tracing_mark_write: 789= 012345678901234567890 By increasing the trace_seq buffer to almost two pages, it can now print out the first line. This also subtracts the rest of the trace_seq fields from the buffer, so that the entire trace_seq is now PAGE_SIZE aligned. Link: https://lore.kernel.org/linux-trace-kernel/20231209175220.19867af4@ga= ndalf.local.home Cc: Mark Rutland Cc: Mathieu Desnoyers Reviewed-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google) --- include/linux/trace_seq.h | 9 ++++++--- kernel/trace/trace.c | 6 +++--- kernel/trace/trace_seq.c | 3 --- 3 files changed, 9 insertions(+), 9 deletions(-) diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h index 3691e0e76a1a..9ec229dfddaa 100644 --- a/include/linux/trace_seq.h +++ b/include/linux/trace_seq.h @@ -8,11 +8,14 @@ =20 /* * Trace sequences are used to allow a function to call several other func= tions - * to create a string of data to use (up to a max of PAGE_SIZE). + * to create a string of data to use. */ =20 +#define TRACE_SEQ_BUFFER_SIZE (PAGE_SIZE * 2 - \ + (sizeof(struct seq_buf) + sizeof(size_t) + sizeof(int))) + struct trace_seq { - char buffer[PAGE_SIZE]; + char buffer[TRACE_SEQ_BUFFER_SIZE]; struct seq_buf seq; size_t readpos; int full; @@ -21,7 +24,7 @@ struct trace_seq { static inline void trace_seq_init(struct trace_seq *s) { - seq_buf_init(&s->seq, s->buffer, PAGE_SIZE); + seq_buf_init(&s->seq, s->buffer, TRACE_SEQ_BUFFER_SIZE); s->full =3D 0; s->readpos =3D 0; } diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index dba1328e454b..0be30cccabb4 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3753,7 +3753,7 @@ static bool trace_safe_str(struct trace_iterator *ite= r, const char *str, =20 /* OK if part of the temp seq buffer */ if ((addr >=3D (unsigned long)iter->tmp_seq.buffer) && - (addr < (unsigned long)iter->tmp_seq.buffer + PAGE_SIZE)) + (addr < (unsigned long)iter->tmp_seq.buffer + TRACE_SEQ_BUFFER_SIZE)) return true; =20 /* Core rodata can not be freed */ @@ -6932,8 +6932,8 @@ tracing_read_pipe(struct file *filp, char __user *ubu= f, goto out; } =20 - if (cnt >=3D PAGE_SIZE) - cnt =3D PAGE_SIZE - 1; + if (cnt >=3D TRACE_SEQ_BUFFER_SIZE) + cnt =3D TRACE_SEQ_BUFFER_SIZE - 1; =20 /* reset all but tr, trace, and overruns */ trace_iterator_reset(iter); diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c index 7be97229ddf8..c158d65a8a88 100644 --- a/kernel/trace/trace_seq.c +++ b/kernel/trace/trace_seq.c @@ -13,9 +13,6 @@ * trace_seq_init() more than once to reset the trace_seq to start * from scratch. *=20 - * The buffer size is currently PAGE_SIZE, although it may become dynamic - * in the future. - * * A write to the buffer will either succeed or fail. That is, unlike * sprintf() there will not be a partial write (well it may write into * the buffer but it wont update the pointers). This allows users to --=20 2.42.0