[SPARC64]: Simplify user fault fixup handling.

Instead of doing byte-at-a-time user accesses to figure
out where the fault occurred, read the saved fault_address
from the current thread structure.

For the sake of defensive programming, if the fault_address
does not fall into the user buffer range, simply assume the
whole area faulted.  This will cause the fixup for
copy_from_user() to clear the entire kernel side buffer.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 34 deletions

diff --git a/arch/sparc64/lib/user_fixup.c b/arch/sparc64/lib/user_fixup.c
index 0278e34125db..19d1fdb17d0e 100644
--- a/arch/sparc64/lib/user_fixup.c
+++ b/arch/sparc64/lib/user_fixup.c
@@ -11,61 +11,56 @@
 
 /* Calculating the exact fault address when using
  * block loads and stores can be very complicated.
+ *
  * Instead of trying to be clever and handling all
  * of the cases, just fix things up simply here.
  */
 
-unsigned long copy_from_user_fixup(void *to, const void __user *from, unsigned long size)
+static unsigned long compute_size(unsigned long start, unsigned long size, unsigned long *offset)
 {
-        char *dst = to;
-        const char __user *src = from;
+        unsigned long fault_addr = current_thread_info()->fault_address;
+        unsigned long end = start + size;
 
-        while (size) {
-                if (__get_user(*dst, src))
-                        break;
-                dst++;
-                src++;
-                size--;
+        if (fault_addr < start || fault_addr >= end) {
+                *offset = 0;
+        } else {
+                *offset = start - fault_addr;
+                size = end - fault_addr;
         }
+        return size;
+}
 
-        if (size)
-                memset(dst, 0, size);
+unsigned long copy_from_user_fixup(void *to, const void __user *from, unsigned long size)
+{
+        unsigned long offset;
+
+        size = compute_size((unsigned long) from, size, &offset);
+        if (likely(size))
+                memset(to + offset, 0, size);
 
         return size;
 }
 
 unsigned long copy_to_user_fixup(void __user *to, const void *from, unsigned long size)
 {
-        char __user *dst = to;
-        const char *src = from;
-
-        while (size) {
-                if (__put_user(*src, dst))
-                        break;
-                dst++;
-                src++;
-                size--;
-        }
+        unsigned long offset;
 
-        return size;
+        return compute_size((unsigned long) to, size, &offset);
 }
 
 unsigned long copy_in_user_fixup(void __user *to, void __user *from, unsigned long size)
 {
-        char __user *dst = to;
-        char __user *src = from;
+        unsigned long fault_addr = current_thread_info()->fault_address;
+        unsigned long start = (unsigned long) to;
+        unsigned long end = start + size;
 
-        while (size) {
-                char tmp;
+        if (fault_addr >= start && fault_addr < end)
+                return end - fault_addr;
 
-                if (__get_user(tmp, src))
-                        break;
-                if (__put_user(tmp, dst))
-                        break;
-                dst++;
-                src++;
-                size--;
-        }
+        start = (unsigned long) from;
+        end = start + size;
+        if (fault_addr >= start && fault_addr < end)
+                return end - fault_addr;
 
         return size;
 }