saner calling conventions for csum_and_copy_..._user()

All callers of these primitives will
	* discard anything we might've copied in case of error
	* ignore the csum value in case of error
	* always pass 0xffffffff as the initial sum, so the
resulting csum value (in case of success, that is) will never be 0.

That suggest the following calling conventions:
	* don't pass err_ptr - just return 0 on error.
	* don't bother with zeroing destination, etc. in case of error
	* don't pass the initial sum - just use 0xffffffff.

This commit does the minimal conversion in the instances of csum_and_copy_...();
the changes of actual asm code behind them are done later in the series.
Note that this asm code is often shared with csum_partial_copy_nocheck();
the difference is that csum_partial_copy_nocheck() passes 0 for initial
sum while csum_and_copy_..._user() pass 0xffffffff.  Fortunately, we are
free to pass 0xffffffff in all cases and subsequent patches will use that
freedom without any special comments.

A part that could be split off: parisc and uml/i386 claimed to have
csum_and_copy_to_user() instances of their own, but those were identical
to the generic one, so we simply drop them.  Not sure if it's worth
a separate commit...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 36 insertions, 43 deletions

diff --git a/arch/sparc/include/asm/checksum_32.h b/arch/sparc/include/asm/checksum_32.h
index d21d114436ba..b5873b7b7bf0 100644
--- a/arch/sparc/include/asm/checksum_32.h
+++ b/arch/sparc/include/asm/checksum_32.h
@@ -60,19 +60,16 @@ csum_partial_copy_nocheck(const void *src, void *dst, int len)
 }
 
 static inline __wsum
-csum_and_copy_from_user(const void __user *src, void *dst, int len,
-			    __wsum sum, int *err)
+csum_and_copy_from_user(const void __user *src, void *dst, int len)
   {
 	register unsigned long ret asm("o0") = (unsigned long)src;
 	register char *d asm("o1") = dst;
 	register int l asm("g1") = len;
-	register __wsum s asm("g7") = sum;
+	register __wsum s asm("g7") = ~0U;
+	int err = 0;
 
-	if (unlikely(!access_ok(src, len))) {
-		if (len)
-			*err = -EFAULT;
-		return sum;
-	}
+	if (unlikely(!access_ok(src, len)))
+		return 0;
 
 	__asm__ __volatile__ (
 	".section __ex_table,#alloc\n\t"
@@ -83,42 +80,40 @@ csum_and_copy_from_user(const void __user *src, void *dst, int len,
 	"call __csum_partial_copy_sparc_generic\n\t"
 	" st %8, [%%sp + 64]\n"
 	: "=&r" (ret), "=&r" (d), "=&r" (l), "=&r" (s)
-	: "0" (ret), "1" (d), "2" (l), "3" (s), "r" (err)
+	: "0" (ret), "1" (d), "2" (l), "3" (s), "r" (&err)
 	: "o2", "o3", "o4", "o5", "o7", "g2", "g3", "g4", "g5",
 	  "cc", "memory");
-	return (__force __wsum)ret;
+	return err ? 0 : (__force __wsum)ret;
 }
 
 #define HAVE_CSUM_COPY_USER
 
 static inline __wsum
-csum_and_copy_to_user(const void *src, void __user *dst, int len,
-			  __wsum sum, int *err)
+csum_and_copy_to_user(const void *src, void __user *dst, int len)
 {
-	if (!access_ok(dst, len)) {
-		*err = -EFAULT;
-		return sum;
-	} else {
-		register unsigned long ret asm("o0") = (unsigned long)src;
-		register char __user *d asm("o1") = dst;
-		register int l asm("g1") = len;
-		register __wsum s asm("g7") = sum;
+	register unsigned long ret asm("o0") = (unsigned long)src;
+	register char __user *d asm("o1") = dst;
+	register int l asm("g1") = len;
+	register __wsum s asm("g7") = ~0U;
+	int err = 0;
 
-		__asm__ __volatile__ (
-		".section __ex_table,#alloc\n\t"
-		".align 4\n\t"
-		".word 1f,1\n\t"
-		".previous\n"
-		"1:\n\t"
-		"call __csum_partial_copy_sparc_generic\n\t"
-		" st %8, [%%sp + 64]\n"
-		: "=&r" (ret), "=&r" (d), "=&r" (l), "=&r" (s)
-		: "0" (ret), "1" (d), "2" (l), "3" (s), "r" (err)
-		: "o2", "o3", "o4", "o5", "o7",
-		  "g2", "g3", "g4", "g5",
-		  "cc", "memory");
-		return (__force __wsum)ret;
-	}
+	if (!access_ok(dst, len))
+		return 0;
+
+	__asm__ __volatile__ (
+	".section __ex_table,#alloc\n\t"
+	".align 4\n\t"
+	".word 1f,1\n\t"
+	".previous\n"
+	"1:\n\t"
+	"call __csum_partial_copy_sparc_generic\n\t"
+	" st %8, [%%sp + 64]\n"
+	: "=&r" (ret), "=&r" (d), "=&r" (l), "=&r" (s)
+	: "0" (ret), "1" (d), "2" (l), "3" (s), "r" (&err)
+	: "o2", "o3", "o4", "o5", "o7",
+	  "g2", "g3", "g4", "g5",
+	  "cc", "memory");
+	return err ? 0 : (__force __wsum)ret;
 }
 
 /* ihl is always 5 or greater, almost always is 5, and iph is word aligned
diff --git a/arch/sparc/include/asm/checksum_64.h b/arch/sparc/include/asm/checksum_64.h
index 7aebdbe3ac96..4d0bbff43e62 100644
--- a/arch/sparc/include/asm/checksum_64.h
+++ b/arch/sparc/include/asm/checksum_64.h
@@ -51,12 +51,11 @@ long __csum_partial_copy_from_user(const void __user *src,
 
 static inline __wsum
 csum_and_copy_from_user(const void __user *src,
-			    void *dst, int len,
-			    __wsum sum, int *err)
+			    void *dst, int len)
 {
-	long ret = __csum_partial_copy_from_user(src, dst, len, sum);
+	long ret = __csum_partial_copy_from_user(src, dst, len, ~0U);
 	if (ret < 0)
-		*err = -EFAULT;
+		return 0;
 	return (__force __wsum) ret;
 }
 
@@ -70,12 +69,11 @@ long __csum_partial_copy_to_user(const void *src,
 
 static inline __wsum
 csum_and_copy_to_user(const void *src,
-		      void __user *dst, int len,
-		      __wsum sum, int *err)
+		      void __user *dst, int len)
 {
-	long ret = __csum_partial_copy_to_user(src, dst, len, sum);
+	long ret = __csum_partial_copy_to_user(src, dst, len, ~0U);
 	if (ret < 0)
-		*err = -EFAULT;
+		return 0;
 	return (__force __wsum) ret;
 }