s390/uaccess: introduce bit field for OAC specifier

Previously, we've used  magic values to specify the OAC
(operand-access control) for mvcos.

Instead we introduce a bit field for it.

When using a bit field, we cannot use an immediate value with K
constraint anymore, since GCC older than 10 doesn't recognize
the bit field union as a compile time constant.
To make things work with older compilers,
load the OAC value through a register.

Bloat-o-meter reports a slight increase in kernel size with this change:
Total: Before=15692135, After=15693015, chg +0.01%

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Co-developed-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Link: https://lore.kernel.org/r/20220111100003.743116-1-scgl@linux.ibm.com
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 77 insertions, 43 deletions

diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index ce550d06abc3..147cb3534ce4 100644
--- a/arch/s390/include/asm/uaccess.h
+++ b/arch/s390/include/asm/uaccess.h
@@ -49,51 +49,85 @@ int __get_user_bad(void) __attribute__((noreturn));
 
 #ifdef CONFIG_HAVE_MARCH_Z10_FEATURES
 
-#define __put_get_user_asm(to, from, size, insn)		\
-({								\
-	int __rc;						\
-								\
-	asm volatile(						\
-		insn "		0,%[spec]\n"			\
-		"0:	mvcos	%[_to],%[_from],%[_size]\n"	\
-		"1:	xr	%[rc],%[rc]\n"			\
-		"2:\n"						\
-		".pushsection .fixup, \"ax\"\n"			\
-		"3:	lhi	%[rc],%[retval]\n"		\
-		"	jg	2b\n"				\
-		".popsection\n"					\
-		EX_TABLE(0b,3b) EX_TABLE(1b,3b)			\
-		: [rc] "=&d" (__rc), [_to] "+Q" (*(to))		\
-		: [_size] "d" (size), [_from] "Q" (*(from)),	\
-		  [retval] "K" (-EFAULT), [spec] "K" (0x81UL)	\
-		: "cc", "0");					\
-	__rc;							\
+union oac {
+	unsigned int val;
+	struct {
+		struct {
+			unsigned short key : 4;
+			unsigned short	   : 4;
+			unsigned short as  : 2;
+			unsigned short	   : 4;
+			unsigned short k   : 1;
+			unsigned short a   : 1;
+		} oac1;
+		struct {
+			unsigned short key : 4;
+			unsigned short	   : 4;
+			unsigned short as  : 2;
+			unsigned short	   : 4;
+			unsigned short k   : 1;
+			unsigned short a   : 1;
+		} oac2;
+	};
+};
+
+#define __put_get_user_asm(to, from, size, oac_spec)			\
+({									\
+	int __rc;							\
+									\
+	asm volatile(							\
+		"	lr	0,%[spec]\n"				\
+		"0:	mvcos	%[_to],%[_from],%[_size]\n"		\
+		"1:	xr	%[rc],%[rc]\n"				\
+		"2:\n"							\
+		".pushsection .fixup, \"ax\"\n"				\
+		"3:	lhi	%[rc],%[retval]\n"			\
+		"	jg	2b\n"					\
+		".popsection\n"						\
+		EX_TABLE(0b,3b) EX_TABLE(1b,3b)				\
+		: [rc] "=&d" (__rc), [_to] "+Q" (*(to))			\
+		: [_size] "d" (size), [_from] "Q" (*(from)),		\
+		  [retval] "K" (-EFAULT), [spec] "d" (oac_spec.val)	\
+		: "cc", "0");						\
+	__rc;								\
 })
 
+#define __put_user_asm(to, from, size)				\
+	__put_get_user_asm(to, from, size, ((union oac) {	\
+		.oac1.as = PSW_BITS_AS_SECONDARY,		\
+		.oac1.a = 1					\
+	}))
+
+#define __get_user_asm(to, from, size)				\
+	__put_get_user_asm(to, from, size, ((union oac) {	\
+		.oac2.as = PSW_BITS_AS_SECONDARY,		\
+		.oac2.a = 1					\
+	}))							\
+
 static __always_inline int __put_user_fn(void *x, void __user *ptr, unsigned long size)
 {
 	int rc;
 
 	switch (size) {
 	case 1:
-		rc = __put_get_user_asm((unsigned char __user *)ptr,
-					(unsigned char *)x,
-					size, "llilh");
+		rc = __put_user_asm((unsigned char __user *)ptr,
+				    (unsigned char *)x,
+				    size);
 		break;
 	case 2:
-		rc = __put_get_user_asm((unsigned short __user *)ptr,
-					(unsigned short *)x,
-					size, "llilh");
+		rc = __put_user_asm((unsigned short __user *)ptr,
+				    (unsigned short *)x,
+				    size);
 		break;
 	case 4:
-		rc = __put_get_user_asm((unsigned int __user *)ptr,
-					(unsigned int *)x,
-					size, "llilh");
+		rc = __put_user_asm((unsigned int __user *)ptr,
+				    (unsigned int *)x,
+				    size);
 		break;
 	case 8:
-		rc = __put_get_user_asm((unsigned long __user *)ptr,
-					(unsigned long *)x,
-					size, "llilh");
+		rc = __put_user_asm((unsigned long __user *)ptr,
+				    (unsigned long *)x,
+				    size);
 		break;
 	default:
 		__put_user_bad();
@@ -108,24 +142,24 @@ static __always_inline int __get_user_fn(void *x, const void __user *ptr, unsign
 
 	switch (size) {
 	case 1:
-		rc = __put_get_user_asm((unsigned char *)x,
-					(unsigned char __user *)ptr,
-					size, "lghi");
+		rc = __get_user_asm((unsigned char *)x,
+				    (unsigned char __user *)ptr,
+				    size);
 		break;
 	case 2:
-		rc = __put_get_user_asm((unsigned short *)x,
-					(unsigned short __user *)ptr,
-					size, "lghi");
+		rc = __get_user_asm((unsigned short *)x,
+				    (unsigned short __user *)ptr,
+				    size);
 		break;
 	case 4:
-		rc = __put_get_user_asm((unsigned int *)x,
-					(unsigned int __user *)ptr,
-					size, "lghi");
+		rc = __get_user_asm((unsigned int *)x,
+				    (unsigned int __user *)ptr,
+				    size);
 		break;
 	case 8:
-		rc = __put_get_user_asm((unsigned long *)x,
-					(unsigned long __user *)ptr,
-					size, "lghi");
+		rc = __get_user_asm((unsigned long *)x,
+				    (unsigned long __user *)ptr,
+				    size);
 		break;
 	default:
 		__get_user_bad();