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seq_buf: Introduce DECLARE_SEQ_BUF and seq_buf_str()
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 directly after terminating it in the refactored seq_buf_terminate(), now known as seq_buf_str(): do_something(seq_buf_str(s)); Link: https://lore.kernel.org/linux-trace-kernel/20231027155634.make.260-kees@kernel.org Link: https://lore.kernel.org/linux-trace-kernel/20231026194033.it.702-kees@kernel.org/ Cc: Yosry Ahmed <yosryahmed@google.com> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Justin Stitt <justinstitt@google.com> Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: Petr Mladek <pmladek@suse.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Yun Zhou <yun.zhou@windriver.com> Cc: Jacob Keller <jacob.e.keller@intel.com> Cc: Zhen Lei <thunder.leizhen@huawei.com> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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@ -21,9 +21,18 @@ struct seq_buf {
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size_t len;
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};
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#define DECLARE_SEQ_BUF(NAME, SIZE) \
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char __ ## NAME ## _buffer[SIZE] = ""; \
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struct seq_buf NAME = { \
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.buffer = &__ ## NAME ## _buffer, \
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.size = SIZE, \
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}
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static inline void seq_buf_clear(struct seq_buf *s)
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{
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s->len = 0;
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if (s->size)
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s->buffer[0] = '\0';
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}
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static inline void
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@ -69,8 +78,8 @@ static inline unsigned int seq_buf_used(struct seq_buf *s)
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}
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/**
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* seq_buf_terminate - Make sure buffer is nul terminated
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* @s: the seq_buf descriptor to terminate.
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* seq_buf_str - get %NUL-terminated C string from seq_buf
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* @s: the seq_buf handle
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*
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* This makes sure that the buffer in @s is nul terminated and
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* safe to read as a string.
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@ -81,16 +90,20 @@ static inline unsigned int seq_buf_used(struct seq_buf *s)
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*
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* After this function is called, s->buffer is safe to use
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* in string operations.
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*
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* Returns @s->buf after making sure it is terminated.
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*/
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static inline void seq_buf_terminate(struct seq_buf *s)
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static inline const char *seq_buf_str(struct seq_buf *s)
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{
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if (WARN_ON(s->size == 0))
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return;
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return "";
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if (seq_buf_buffer_left(s))
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s->buffer[s->len] = 0;
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else
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s->buffer[s->size - 1] = 0;
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return s->buffer;
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}
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/**
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@ -3828,15 +3828,6 @@ static bool trace_safe_str(struct trace_iterator *iter, const char *str,
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return false;
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}
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static const char *show_buffer(struct trace_seq *s)
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{
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struct seq_buf *seq = &s->seq;
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seq_buf_terminate(seq);
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return seq->buffer;
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}
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static DEFINE_STATIC_KEY_FALSE(trace_no_verify);
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static int test_can_verify_check(const char *fmt, ...)
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@ -3976,7 +3967,7 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt,
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*/
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if (WARN_ONCE(!trace_safe_str(iter, str, star, len),
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"fmt: '%s' current_buffer: '%s'",
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fmt, show_buffer(&iter->seq))) {
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fmt, seq_buf_str(&iter->seq.seq))) {
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int ret;
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/* Try to safely read the string */
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@ -109,9 +109,7 @@ void seq_buf_do_printk(struct seq_buf *s, const char *lvl)
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if (s->size == 0 || s->len == 0)
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return;
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seq_buf_terminate(s);
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start = s->buffer;
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start = seq_buf_str(s);
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while ((lf = strchr(start, '\n'))) {
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int len = lf - start + 1;
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