[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

@@ -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;
 }

arch/sparc64/mm/fault.c

@@ -457,7 +457,7 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
 	}
 
 	up_read(&mm->mmap_sem);
-	goto fault_done;
+	return;
 
 	/*
 	 * Something tried to access memory that isn't in our memory map..
@@ -469,8 +469,7 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
 
 handle_kernel_fault:
 	do_kernel_fault(regs, si_code, fault_code, insn, address);
-
-	goto fault_done;
+	return;
 
 /*
  * We ran out of memory, or some other thing happened to us that made
@@ -501,9 +500,4 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
 	/* Kernel mode? Handle exceptions or die */
 	if (regs->tstate & TSTATE_PRIV)
 		goto handle_kernel_fault;
-
-fault_done:
-	/* These values are no longer needed, clear them. */
-	set_thread_fault_code(0);
-	current_thread_info()->fault_address = 0;
 }

include/asm-sparc64/uaccess.h

@@ -251,7 +251,7 @@ copy_from_user(void *to, const void __user *from, unsigned long size)
 {
 	unsigned long ret = ___copy_from_user(to, from, size);
 
-	if (ret)
+	if (unlikely(ret))
 		ret = copy_from_user_fixup(to, from, size);
 	return ret;
 }
@@ -267,7 +267,7 @@ copy_to_user(void __user *to, const void *from, unsigned long size)
 {
 	unsigned long ret = ___copy_to_user(to, from, size);
 
-	if (ret)
+	if (unlikely(ret))
 		ret = copy_to_user_fixup(to, from, size);
 	return ret;
 }
@@ -283,7 +283,7 @@ copy_in_user(void __user *to, void __user *from, unsigned long size)
 {
 	unsigned long ret = ___copy_in_user(to, from, size);
 
-	if (ret)
+	if (unlikely(ret))
 		ret = copy_in_user_fixup(to, from, size);
 	return ret;
 }