s390/cpcmd: fix inline assembly register clobbering

Register variables initialized using arithmetic. That leads to
kasan instrumentaton code corrupting the registers contents.
Follow GCC guidlines and use temporary variables for assigning
init values to register variables.

Fixes: 94c12cc7d196 ("[S390] Inline assembly cleanup.")
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://gcc.gnu.org/onlinedocs/gcc-10.2.0/gcc/Local-Register-Variables.html
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

diff --git a/arch/s390/kernel/cpcmd.c b/arch/s390/kernel/cpcmd.c
index af013b4244d346598a29db32b49af71f20e785fe..2da0273597989b88bf99159e231bcb0d7d66700f 100644 (file)
--- a/arch/s390/kernel/cpcmd.c
+++ b/arch/s390/kernel/cpcmd.c
@@ -37,10 +37,12 @@ static int diag8_noresponse(int cmdlen)
 
 static int diag8_response(int cmdlen, char *response, int *rlen)
 {
+       unsigned long _cmdlen = cmdlen | 0x40000000L;
+       unsigned long _rlen = *rlen;
        register unsigned long reg2 asm ("2") = (addr_t) cpcmd_buf;
        register unsigned long reg3 asm ("3") = (addr_t) response;
-       register unsigned long reg4 asm ("4") = cmdlen | 0x40000000L;
-       register unsigned long reg5 asm ("5") = *rlen;
+       register unsigned long reg4 asm ("4") = _cmdlen;
+       register unsigned long reg5 asm ("5") = _rlen;
 
        asm volatile(
                "       diag    %2,%0,0x8\n"