linux-kernel - [PATCH 4.14 035/315] seq_buf: Make trace_seq_putmem

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Message-Id: <20210719144944.031752351@linuxfoundation.org>
Date:   Mon, 19 Jul 2021 16:48:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yun Zhou <yun.zhou@...driver.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 4.14 035/315] seq_buf: Make trace_seq_putmem_hex() support data longer than 8

From: Yun Zhou <yun.zhou@...driver.com>

commit 6a2cbc58d6c9d90cd74288cc497c2b45815bc064 upstream.

Since the raw memory 'data' does not go forward, it will dump repeated
data if the data length is more than 8. If we want to dump longer data
blocks, we need to repeatedly call macro SEQ_PUT_HEX_FIELD. I think it
is a bit redundant, and multiple function calls also affect the performance.

Link: https://lore.kernel.org/lkml/20210625122453.5e2fe304@oasis.local.home/
Link: https://lkml.kernel.org/r/20210626032156.47889-2-yun.zhou@windriver.com

Cc: stable@...r.kernel.org
Fixes: 6d2289f3faa7 ("tracing: Make trace_seq_putmem_hex() more robust")
Signed-off-by: Yun Zhou <yun.zhou@...driver.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 lib/seq_buf.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/lib/seq_buf.c
+++ b/lib/seq_buf.c
@@ -242,12 +242,14 @@ int seq_buf_putmem_hex(struct seq_buf *s
 			break;
 
 		/* j increments twice per loop */
-		len -= j / 2;
 		hex[j++] = ' ';
 
 		seq_buf_putmem(s, hex, j);
 		if (seq_buf_has_overflowed(s))
 			return -1;
+
+		len -= start_len;
+		data += start_len;
 	}
 	return 0;
 }