Solve two ergonomic issues with struct seq_buf:
1) Too much boilerplate is required to initialize:
struct seq_buf s;
char buf[32];
seq_buf_init(s, buf, sizeof(buf));
Instead, we can build this directly on the stack. Provide
DECLARE_SEQ_BUF() macro to do this:
DECLARE_SEQ_BUF(s, 32);
2) %NUL termination is fragile and requires 2 steps to get a valid
C String (and is a layering violation exposing the "internals" of
seq_buf):
seq_buf_terminate(s);
do_something(s->buffer);
Instead, we can just return s->buffer direction after terminating it
in refactored seq_buf_terminate(), now known as seq_buf_cstr():
do_soemthing(seq_buf_cstr(s));
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: "Matthew Wilcox (Oracle)" <wi...@infradead.org>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Justin Stitt <justinst...@google.com>
Cc: Kent Overstreet <kent.overstr...@linux.dev>
Cc: Petr Mladek <pmla...@suse.com>
Cc: Andy Shevchenko <andriy.shevche...@linux.intel.com>
Cc: Rasmus Villemoes <li...@rasmusvillemoes.dk>
Cc: Sergey Senozhatsky <senozhat...@chromium.org>
Cc: Masami Hiramatsu <mhira...@kernel.org>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: Arnd Bergmann <a...@arndb.de>
Cc: Jonathan Corbet <cor...@lwn.net>
Cc: Yun Zhou <yun.z...@windriver.com>
Cc: Jacob Keller <jacob.e.kel...@intel.com>
Cc: Zhen Lei <thunder.leiz...@huawei.com>
Cc: linux-trace-ker...@vger.kernel.org
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
include/linux/seq_buf.h | 19 +++++++++++++++----
kernel/trace/trace.c | 11 +----------
lib/seq_buf.c | 4 +---
3 files changed, 17 insertions(+), 17 deletions(-)
diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
index 8483e4b2d0d2..8896b830eb3d 100644
--- a/include/linux/seq_buf.h
+++ b/include/linux/seq_buf.h
@@ -21,9 +21,16 @@ struct seq_buf {
size_t len;
};
+#define DECLARE_SEQ_BUF(NAME, SIZE) \
+ char __ ## NAME ## _buffer[SIZE] = ""; \
+ struct seq_buf NAME = { .buffer = &__ ## NAME ## _buffer, \
+ .size = SIZE }
+
static inline void seq_buf_clear(struct seq_buf *s)
{
s->len = 0;
+ if (s->size)
+ s->buffer[0] = '\0';
}
static inline void
@@ -69,8 +76,8 @@ static inline unsigned int seq_buf_used(struct seq_buf *s)
}
/**
- * seq_buf_terminate - Make sure buffer is nul terminated
- * @s: the seq_buf descriptor to terminate.
+ * seq_buf_cstr - get %NUL-terminated C string from seq_buf
+ * @s: the seq_buf handle
*
* This makes sure that the buffer in @s is nul terminated and
* safe to read as a string.
@@ -81,16 +88,20 @@ static inline unsigned int seq_buf_used(struct seq_buf *s)
*
* After this function is called, s->buffer is safe to use
* in string operations.
+ *
+ * Returns @s->buf after making sure it is terminated.
*/
-static inline void seq_buf_terminate(struct seq_buf *s)
+static inline char *seq_buf_cstr(struct seq_buf *s)
{
if (WARN_ON(s->size == 0))
- return;
+ return "";
if (seq_buf_buffer_left(s))
s->buffer[s->len] = 0;
else
s->buffer[s->size - 1] = 0;
+
+ return s->buffer;
}
/**
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d629065c2383..d83f36dc4bf8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3828,15 +3828,6 @@ static bool trace_safe_str(struct trace_iterator *iter,
const char *str,
return false;
}
-static const char *show_buffer(struct trace_seq *s)
-{
- struct seq_buf *seq = &s->seq;
-
- seq_buf_terminate(seq);
-
- return seq->buffer;
-}
-
static DEFINE_STATIC_KEY_FALSE(trace_no_verify);
static int test_can_verify_check(const char *fmt, ...)
@@ -3976,7 +3967,7 @@ void trace_check_vprintf(struct trace_iterator *iter,
const char *fmt,
*/
if (WARN_ONCE(!trace_safe_str(iter, str, star, len),
"fmt: '%s' current_buffer: '%s'",
- fmt, show_buffer(&iter->seq))) {
+ fmt, seq_buf_cstr(&iter->seq.seq))) {
int ret;
/* Try to safely read the string */
diff --git a/lib/seq_buf.c b/lib/seq_buf.c
index b7477aefff53..165caed5a74e 100644
--- a/lib/seq_buf.c
+++ b/lib/seq_buf.c
@@ -109,9 +109,7 @@ void seq_buf_do_printk(struct seq_buf *s, const char *lvl)
if (s->size == 0 || s->len == 0)
return;
- seq_buf_terminate(s);
-
- start = s->buffer;
+ start = seq_buf_cstr(s);
while ((lf = strchr(start, '\n'))) {
int len = lf - start + 1;
--
2.34.1
