From: Sergey Senozhatsky senozhatsky@chromium.org
mainline inclusion from mainline-v6.4-rc1 commit 96928d9032a7c34f12a88df879665562bcebf59a category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8C7BS
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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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: Sergey Senozhatsky senozhatsky@chromium.org Reviewed-by: Petr Mladek pmladek@suse.com Tested-by: Yosry Ahmed yosryahmed@google.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Lu Jialin lujialin4@huawei.com --- include/linux/seq_buf.h | 2 ++ lib/seq_buf.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+)
diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h index 5b31c5147969..515d7fcb9634 100644 --- a/include/linux/seq_buf.h +++ b/include/linux/seq_buf.h @@ -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 */ diff --git a/lib/seq_buf.c b/lib/seq_buf.c index 6dafde851333..5ffae44c1055 100644 --- a/lib/seq_buf.c +++ b/lib/seq_buf.c @@ -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