Commit b5e03080 authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Lu Jialin
Browse files

seq_buf: Add seq_buf_do_printk() helper 

mainline inclusion
from mainline-v6.4-rc1
commit 96928d90
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8C7BS

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=96928d9032a7c34f12a88df879665562bcebf59a

-------------------------------------------------

Sometimes we use seq_buf to format a string buffer, which
we then pass to printk(). However, in certain situations
the seq_buf string buffer can get too big, exceeding the
PRINTKRB_RECORD_MAX bytes limit, and causing printk() to
truncate the string.

Add a new seq_buf helper. This helper prints the seq_buf
string buffer line by line, using \n as a delimiter,
rather than passing the whole string buffer to printk()
at once.

Link: https://lkml.kernel.org/r/20230415100110.1419872-1-senozhatsky@chromium.org



Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarSergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Tested-by: default avatarYosry Ahmed <yosryahmed@google.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarLu Jialin <lujialin4@huawei.com>
parent 87f8b7b4

include/linux/seq_buf.h

+2 −0
Original line number Diff line number Diff line
@@ -159,4 +159,6 @@ extern int 
seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary);

#endif



void seq_buf_do_printk(struct seq_buf *s, const char *lvl);



#endif /* _LINUX_SEQ_BUF_H */

lib/seq_buf.c

+32 −0
Original line number Diff line number Diff line
@@ -93,6 +93,38 @@ int seq_buf_printf(struct seq_buf *s, const char *fmt, ...) 
}

EXPORT_SYMBOL_GPL(seq_buf_printf);



/**

 * seq_buf_do_printk - printk seq_buf line by line

 * @s: seq_buf descriptor

 * @lvl: printk level

 *

 * printk()-s a multi-line sequential buffer line by line. The function

 * makes sure that the buffer in @s is nul terminated and safe to read

 * as a string.

 */

void seq_buf_do_printk(struct seq_buf *s, const char *lvl)

{

	const char *start, *lf;



	if (s->size == 0 || s->len == 0)

		return;



	seq_buf_terminate(s);



	start = s->buffer;

	while ((lf = strchr(start, '\n'))) {

		int len = lf - start + 1;



		printk("%s%.*s", lvl, len, start);

		start = ++lf;

	}



	/* No trailing LF */

	if (start < s->buffer + s->len)

		printk("%s%s\n", lvl, start);

}

EXPORT_SYMBOL_GPL(seq_buf_do_printk);



#ifdef CONFIG_BINARY_PRINTF

/**

 * seq_buf_bprintf - Write the printf string from binary arguments