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>

diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index ce550d0..147cb35 100644 (file)
--- 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();

diff --git a/arch/s390/lib/uaccess.c b/arch/s390/lib/uaccess.c
index a596e69..8a5d214 100644 (file)
--- a/arch/s390/lib/uaccess.c
+++ b/arch/s390/lib/uaccess.c
@@ -62,10 +62,14 @@ static inline unsigned long copy_from_user_mvcos(void *x, const void __user *ptr
                                                 unsigned long size)
 {
        unsigned long tmp1, tmp2;
+       union oac spec = {
+               .oac2.as = PSW_BITS_AS_SECONDARY,
+               .oac2.a = 1,
+       };
 
        tmp1 = -4096UL;
        asm volatile(
-               "   lghi  0,%[spec]\n"
+               "   lr    0,%[spec]\n"
                "0: .insn ss,0xc80000000000,0(%0,%2),0(%1),0\n"
                "6: jz    4f\n"
                "1: algr  %0,%3\n"
@@ -84,7 +88,7 @@ static inline unsigned long copy_from_user_mvcos(void *x, const void __user *ptr
                "5:\n"
                EX_TABLE(0b,2b) EX_TABLE(3b,5b) EX_TABLE(6b,2b) EX_TABLE(7b,5b)
                : "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
-               : [spec] "K" (0x81UL)
+               : [spec] "d" (spec.val)
                : "cc", "memory", "0");
        return size;
 }
@@ -135,10 +139,14 @@ static inline unsigned long copy_to_user_mvcos(void __user *ptr, const void *x,
                                               unsigned long size)
 {
        unsigned long tmp1, tmp2;
+       union oac spec = {
+               .oac1.as = PSW_BITS_AS_SECONDARY,
+               .oac1.a = 1,
+       };
 
        tmp1 = -4096UL;
        asm volatile(
-               "   llilh 0,%[spec]\n"
+               "   lr    0,%[spec]\n"
                "0: .insn ss,0xc80000000000,0(%0,%1),0(%2),0\n"
                "6: jz    4f\n"
                "1: algr  %0,%3\n"
@@ -157,7 +165,7 @@ static inline unsigned long copy_to_user_mvcos(void __user *ptr, const void *x,
                "5:\n"
                EX_TABLE(0b,2b) EX_TABLE(3b,5b) EX_TABLE(6b,2b) EX_TABLE(7b,5b)
                : "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
-               : [spec] "K" (0x81UL)
+               : [spec] "d" (spec.val)
                : "cc", "memory", "0");
        return size;
 }
@@ -207,10 +215,14 @@ EXPORT_SYMBOL(raw_copy_to_user);
 static inline unsigned long clear_user_mvcos(void __user *to, unsigned long size)
 {
        unsigned long tmp1, tmp2;
+       union oac spec = {
+               .oac1.as = PSW_BITS_AS_SECONDARY,
+               .oac1.a = 1,
+       };
 
        tmp1 = -4096UL;
        asm volatile(
-               "   llilh 0,%[spec]\n"
+               "   lr    0,%[spec]\n"
                "0: .insn ss,0xc80000000000,0(%0,%1),0(%4),0\n"
                "   jz    4f\n"
                "1: algr  %0,%2\n"
@@ -228,7 +240,7 @@ static inline unsigned long clear_user_mvcos(void __user *to, unsigned long size
                "5:\n"
                EX_TABLE(0b,2b) EX_TABLE(3b,5b)
                : "+a" (size), "+a" (to), "+a" (tmp1), "=a" (tmp2)
-               : "a" (empty_zero_page), [spec] "K" (0x81UL)
+               : "a" (empty_zero_page), [spec] "d" (spec.val)
                : "cc", "memory", "0");
        return size;
 }