From efdc1e2083e04cc70721d55803889b346c1a3de2 Mon Sep 17 00:00:00 2001
From: "David S. Miller" <davem@sunset.davemloft.net>
Date: Wed, 28 Sep 2005 21:06:47 -0700
Subject: [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>
---
 arch/sparc64/lib/user_fixup.c | 63 ++++++++++++++++++++-----------------------
 1 file changed, 29 insertions(+), 34 deletions(-)

(limited to 'arch/sparc64/lib')

diff --git a/arch/sparc64/lib/user_fixup.c b/arch/sparc64/lib/user_fixup.c
index 0278e34125d..19d1fdb17d0 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;
 }
-- 
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