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authorSergey Senozhatsky <senozhatsky@chromium.org>2023-04-15 19:01:10 +0900
committerSteven Rostedt (Google) <rostedt@goodmis.org>2023-04-25 21:03:14 -0400
commit96928d9032a7c34f12a88df879665562bcebf59a (patch)
treeb25e52ee726d90ad73a4591b2eafa67d5cd3ae85
parentc7bdb07902e0b633795372665d0154e7267ecd0e (diff)
seq_buf: Add seq_buf_do_printk() helper
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>
-rw-r--r--include/linux/seq_buf.h2
-rw-r--r--lib/seq_buf.c32
2 files changed, 34 insertions, 0 deletions
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 0a68f7aa85d6..45c450f423fa 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