linux-kernel - [PATCH 3/3] livepatch: Use static buffer for debugging messages under rq lock

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Date:   Fri, 31 May 2019 09:41:47 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>
Cc:     Joe Lawrence <joe.lawrence@...hat.com>,
        Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Petr Mladek <pmladek@...e.com>
Subject: [PATCH 3/3] livepatch: Use static buffer for debugging messages under rq lock

The err_buf array uses 128 bytes of stack space.  Move it off the stack
by making it static.  It's safe to use a shared buffer because
klp_try_switch_task() is called under klp_mutex.

Signed-off-by: Petr Mladek <pmladek@...e.com>
Acked-by: Miroslav Benes <mbenes@...e.cz>
Reviewed-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
---
 kernel/livepatch/transition.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 1bf362df76e1..5c4f0c1f826e 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -280,11 +280,11 @@ static int klp_check_stack(struct task_struct *task, char *err_buf)
  */
 static bool klp_try_switch_task(struct task_struct *task)
 {
+	static char err_buf[STACK_ERR_BUF_SIZE];
 	struct rq *rq;
 	struct rq_flags flags;
 	int ret;
 	bool success = false;
-	char err_buf[STACK_ERR_BUF_SIZE];
 
 	err_buf[0] = '\0';
 
@@ -327,7 +327,6 @@ static bool klp_try_switch_task(struct task_struct *task)
 		pr_debug("%s", err_buf);
 
 	return success;
-
 }
 
 /*
-- 
2.16.4