linux-kernel - [PATCH 4.14 31/95] s390: remove indirect branch from do_softirq_own

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Date:   Mon, 21 May 2018 23:11:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: [PATCH 4.14 31/95] s390: remove indirect branch from do_softirq_own_stack

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Martin Schwidefsky <schwidefsky@...ibm.com>

commit 9f18fff63cfd6f559daa1eaae60640372c65f84b upstream.

The inline assembly to call __do_softirq on the irq stack uses
an indirect branch. This can be replaced with a normal relative
branch.

Cc: stable@...r.kernel.org # 4.16
Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches")
Reviewed-by: Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/s390/kernel/irq.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/arch/s390/kernel/irq.c
+++ b/arch/s390/kernel/irq.c
@@ -176,10 +176,9 @@ void do_softirq_own_stack(void)
 		new -= STACK_FRAME_OVERHEAD;
 		((struct stack_frame *) new)->back_chain = old;
 		asm volatile("   la    15,0(%0)\n"
-			     "   basr  14,%2\n"
+			     "   brasl 14,__do_softirq\n"
 			     "   la    15,0(%1)\n"
-			     : : "a" (new), "a" (old),
-			         "a" (__do_softirq)
+			     : : "a" (new), "a" (old)
 			     : "0", "1", "2", "3", "4", "5", "14",
 			       "cc", "memory" );
 	} else {