linux-kernel - [PATCH] openrisc: Fix issue with argument clobbering for clone/fork

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Message-Id: <20200531212500.826332-1-shorne@gmail.com>
Date:   Mon,  1 Jun 2020 06:24:59 +0900
From:   Stafford Horne <shorne@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Stafford Horne <shorne@...il.com>, Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        openrisc@...ts.librecores.org
Subject: [PATCH] openrisc: Fix issue with argument clobbering for clone/fork

Working on the OpenRISC glibc port I found that sometimes clone was
working strange.  That the tls data argument sent in r7 was always
wrong.  Further investigation revealed that the arguments were getting
clobbered in the entry code.  This patch removes the code that writes to
the argument registers.  This was likely due to some old code hanging
around.

This patch fixes this up for clone and fork.  This fork clobber is
harmless but also useless so remove.

Signed-off-by: Stafford Horne <shorne@...il.com>
---
 arch/openrisc/kernel/entry.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/openrisc/kernel/entry.S b/arch/openrisc/kernel/entry.S
index e4a78571f883..c6481cfc5220 100644
--- a/arch/openrisc/kernel/entry.S
+++ b/arch/openrisc/kernel/entry.S
@@ -1166,13 +1166,13 @@ ENTRY(__sys_clone)
 	l.movhi	r29,hi(sys_clone)
 	l.ori	r29,r29,lo(sys_clone)
 	l.j	_fork_save_extra_regs_and_call
-	 l.addi	r7,r1,0
+	 l.nop
 
 ENTRY(__sys_fork)
 	l.movhi	r29,hi(sys_fork)
 	l.ori	r29,r29,lo(sys_fork)
 	l.j	_fork_save_extra_regs_and_call
-	 l.addi	r3,r1,0
+	 l.nop
 
 ENTRY(sys_rt_sigreturn)
 	l.jal	_sys_rt_sigreturn
-- 
2.26.2