linux-kernel - [for-linus][PATCH] seq_buf: Make DECLARE_SEQ

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Date: Thu, 18 Jan 2024 09:40:50 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Kees Cook <keescook@...omium.org>, Nathan
 Lynch <nathanl@...ux.ibm.com>
Subject: [for-linus][PATCH] seq_buf: Make DECLARE_SEQ_BUF() usable


Another update for 6.8:

- Fix seq_buf warning and make static work properly.


  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace/urgent

Head SHA1: 7a8e9cdf9405819105ae7405cd91e482bf574b01


Nathan Lynch (1):
      seq_buf: Make DECLARE_SEQ_BUF() usable

----
 include/linux/seq_buf.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
---------------------------
commit 7a8e9cdf9405819105ae7405cd91e482bf574b01
Author: Nathan Lynch <nathanl@...ux.ibm.com>
Date:   Tue Jan 16 08:09:25 2024 -0600

    seq_buf: Make DECLARE_SEQ_BUF() usable
    
    Using the address operator on the array doesn't work:
    
    ./include/linux/seq_buf.h:27:27: error: initialization of ‘char *’
      from incompatible pointer type ‘char (*)[128]’
      [-Werror=incompatible-pointer-types]
       27 |                 .buffer = &__ ## NAME ## _buffer,       \
          |                           ^
    
    Apart from fixing that, we can improve DECLARE_SEQ_BUF() by using a
    compound literal to define the buffer array without attaching a name
    to it. This makes the macro a single statement, allowing constructs
    such as:
    
      static DECLARE_SEQ_BUF(my_seq_buf, MYSB_SIZE);
    
    to work as intended.
    
    Link: https://lkml.kernel.org/r/20240116-declare-seq-buf-fix-v1-1-915db4692f32@linux.ibm.com
    
    Cc: stable@...r.kernel.org
    Acked-by: Kees Cook <keescook@...omium.org>
    Fixes: dcc4e5728eea ("seq_buf: Introduce DECLARE_SEQ_BUF and seq_buf_str()")
    Signed-off-by: Nathan Lynch <nathanl@...ux.ibm.com>
    Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>

diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
index 5fb1f12c33f9..c44f4b47b945 100644
--- a/include/linux/seq_buf.h
+++ b/include/linux/seq_buf.h
@@ -22,9 +22,8 @@ struct seq_buf {
 };
 
 #define DECLARE_SEQ_BUF(NAME, SIZE)			\
-	char __ ## NAME ## _buffer[SIZE] = "";		\
 	struct seq_buf NAME = {				\
-		.buffer = &__ ## NAME ## _buffer,	\
+		.buffer = (char[SIZE]) { 0 },		\
 		.size = SIZE,				\
 	}