[S390] Add dynamic size check for usercopy functions.

Use a wrapper for copy_to/from_user to chose the best usercopy method.
The mvcos instruction is better for sizes greater than 256 bytes, if
mvcos is not available a page table walk is better for sizes greater
than 1024 bytes. Also removed the redundant copy_to/from_user_std_small
functions.

Signed-off-by: Gerald Schaefer <geraldsc@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 21 insertions, 6 deletions

diff --git a/arch/s390/lib/uaccess_mvcos.c b/arch/s390/lib/uaccess_mvcos.c
index 121b2935a422..f9a23d57eb79 100644
--- a/arch/s390/lib/uaccess_mvcos.c
+++ b/arch/s390/lib/uaccess_mvcos.c
@@ -27,6 +27,9 @@
 #define SLR     "slgr"
 #endif
 
+extern size_t copy_from_user_std(size_t, const void __user *, void *);
+extern size_t copy_to_user_std(size_t, void __user *, const void *);
+
 size_t copy_from_user_mvcos(size_t size, const void __user *ptr, void *x)
 {
         register unsigned long reg0 asm("0") = 0x81UL;
@@ -66,6 +69,13 @@ size_t copy_from_user_mvcos(size_t size, const void __user *ptr, void *x)
         return size;
 }
 
+size_t copy_from_user_mvcos_check(size_t size, const void __user *ptr, void *x)
+{
+        if (size <= 256)
+                return copy_from_user_std(size, ptr, x);
+        return copy_from_user_mvcos(size, ptr, x);
+}
+
 size_t copy_to_user_mvcos(size_t size, void __user *ptr, const void *x)
 {
         register unsigned long reg0 asm("0") = 0x810000UL;
@@ -95,6 +105,13 @@ size_t copy_to_user_mvcos(size_t size, void __user *ptr, const void *x)
         return size;
 }
 
+size_t copy_to_user_mvcos_check(size_t size, void __user *ptr, const void *x)
+{
+        if (size <= 256)
+                return copy_to_user_std(size, ptr, x);
+        return copy_to_user_mvcos(size, ptr, x);
+}
+
 size_t copy_in_user_mvcos(size_t size, void __user *to, const void __user *from)
 {
         register unsigned long reg0 asm("0") = 0x810081UL;
@@ -145,18 +162,16 @@ size_t clear_user_mvcos(size_t size, void __user *to)
         return size;
 }
 
-extern size_t copy_from_user_std_small(size_t, const void __user *, void *);
-extern size_t copy_to_user_std_small(size_t, void __user *, const void *);
 extern size_t strnlen_user_std(size_t, const char __user *);
 extern size_t strncpy_from_user_std(size_t, const char __user *, char *);
 extern int futex_atomic_op(int, int __user *, int, int *);
 extern int futex_atomic_cmpxchg(int __user *, int, int);
 
 struct uaccess_ops uaccess_mvcos = {
-        .copy_from_user = copy_from_user_mvcos,
-        .copy_from_user_small = copy_from_user_std_small,
-        .copy_to_user = copy_to_user_mvcos,
-        .copy_to_user_small = copy_to_user_std_small,
+        .copy_from_user = copy_from_user_mvcos_check,
+        .copy_from_user_small = copy_from_user_std,
+        .copy_to_user = copy_to_user_mvcos_check,
+        .copy_to_user_small = copy_to_user_std,
         .copy_in_user = copy_in_user_mvcos,
         .clear_user = clear_user_mvcos,
         .strnlen_user = strnlen_user_std,