netdev - [PATCH net-next 4/5] net/iucv: get rid of register asm usage

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210809083050.2328336-5-kgraul@linux.ibm.com>
Date:   Mon,  9 Aug 2021 10:30:49 +0200
From:   Karsten Graul <kgraul@...ux.ibm.com>
To:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        Heiko Carstens <hca@...ux.ibm.com>,
        Julian Wiedmann <jwi@...ux.ibm.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH net-next 4/5] net/iucv: get rid of register asm usage

From: Heiko Carstens <hca@...ux.ibm.com>

Using register asm statements has been proven to be very error prone,
especially when using code instrumentation where gcc may add function
calls, which clobbers register contents in an unexpected way.

Therefore get rid of register asm statements in iucv code, even though
there is currently nothing wrong with it. This way we know for sure
that the above mentioned bug class won't be introduced here.

Acked-by: Karsten Graul <kgraul@...ux.ibm.com>
Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@...ux.ibm.com>
---
 net/iucv/iucv.c | 42 ++++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/net/iucv/iucv.c b/net/iucv/iucv.c
index e6795d5a546a..bebc7d09815d 100644
--- a/net/iucv/iucv.c
+++ b/net/iucv/iucv.c
@@ -286,19 +286,19 @@ static union iucv_param *iucv_param_irq[NR_CPUS];
  */
 static inline int __iucv_call_b2f0(int command, union iucv_param *parm)
 {
-	register unsigned long reg0 asm ("0");
-	register unsigned long reg1 asm ("1");
-	int ccode;
+	int cc;
 
-	reg0 = command;
-	reg1 = (unsigned long)parm;
 	asm volatile(
-		"	.long 0xb2f01000\n"
-		"	ipm	%0\n"
-		"	srl	%0,28\n"
-		: "=d" (ccode), "=m" (*parm), "+d" (reg0), "+a" (reg1)
-		:  "m" (*parm) : "cc");
-	return ccode;
+		"	lgr	0,%[reg0]\n"
+		"	lgr	1,%[reg1]\n"
+		"	.long	0xb2f01000\n"
+		"	ipm	%[cc]\n"
+		"	srl	%[cc],28\n"
+		: [cc] "=&d" (cc), "+m" (*parm)
+		: [reg0] "d" ((unsigned long)command),
+		  [reg1] "d" ((unsigned long)parm)
+		: "cc", "0", "1");
+	return cc;
 }
 
 static inline int iucv_call_b2f0(int command, union iucv_param *parm)
@@ -319,19 +319,21 @@ static inline int iucv_call_b2f0(int command, union iucv_param *parm)
  */
 static int __iucv_query_maxconn(void *param, unsigned long *max_pathid)
 {
-	register unsigned long reg0 asm ("0");
-	register unsigned long reg1 asm ("1");
-	int ccode;
+	unsigned long reg1 = (unsigned long)param;
+	int cc;
 
-	reg0 = IUCV_QUERY;
-	reg1 = (unsigned long) param;
 	asm volatile (
+		"	lghi	0,%[cmd]\n"
+		"	lgr	1,%[reg1]\n"
 		"	.long	0xb2f01000\n"
-		"	ipm	%0\n"
-		"	srl	%0,28\n"
-		: "=d" (ccode), "+d" (reg0), "+d" (reg1) : : "cc");
+		"	ipm	%[cc]\n"
+		"	srl	%[cc],28\n"
+		"	lgr	%[reg1],1\n"
+		: [cc] "=&d" (cc), [reg1] "+&d" (reg1)
+		: [cmd] "K" (IUCV_QUERY)
+		: "cc", "0", "1");
 	*max_pathid = reg1;
-	return ccode;
+	return cc;
 }
 
 static int iucv_query_maxconn(void)
-- 
2.25.1