futex: Remove duplicated code and fix undefined behaviour

There is code duplicated over all architecture's headers for
futex_atomic_op_inuser. Namely op decoding, access_ok check for uaddr,
and comparison of the result.

Remove this duplication and leave up to the arches only the needed
assembly which is now in arch_futex_atomic_op_inuser.

This effectively distributes the Will Deacon's arm64 fix for undefined
behaviour reported by UBSAN to all architectures. The fix was done in
commit 5f16a046f8e1 (arm64: futex: Fix undefined behaviour with
FUTEX_OP_OPARG_SHIFT usage). Look there for an example dump.

And as suggested by Thomas, check for negative oparg too, because it was
also reported to cause undefined behaviour report.

Note that s390 removed access_ok check in d12a29703 ("s390/uaccess:
remove pointless access_ok() checks") as access_ok there returns true.
We introduce it back to the helper for the sake of simplicity (it gets
optimized away anyway).

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> [s390]
Acked-by: Chris Metcalf <cmetcalf@mellanox.com> [for tile]
Reviewed-by: Darren Hart (VMware) <dvhart@infradead.org>
Reviewed-by: Will Deacon <will.deacon@arm.com> [core/arm64]
Cc: linux-mips@linux-mips.org
Cc: Rich Felker <dalias@libc.org>
Cc: linux-ia64@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: peterz@infradead.org
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: sparclinux@vger.kernel.org
Cc: Jonas Bonn <jonas@southpole.se>
Cc: linux-s390@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: linux-hexagon@vger.kernel.org
Cc: Helge Deller <deller@gmx.de>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: linux-snps-arc@lists.infradead.org
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-xtensa@linux-xtensa.org
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: openrisc@lists.librecores.org
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Stafford Horne <shorne@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Richard Henderson <rth@twiddle.net>
Cc: Chris Zankel <chris@zankel.net>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-parisc@vger.kernel.org
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: linux-alpha@vger.kernel.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: "David S. Miller" <davem@davemloft.net>
Link: http://lkml.kernel.org/r/20170824073105.3901-1-jslaby@suse.cz

19 files changed, 82 insertions, 465 deletions

diff --git a/arch/alpha/include/asm/futex.h b/arch/alpha/include/asm/futex.h
index fb01dfb760c2..05a70edd57b6 100644
--- a/arch/alpha/include/asm/futex.h
+++ b/arch/alpha/include/asm/futex.h
@@ -25,18 +25,10 @@
 	:	"r" (uaddr), "r"(oparg)				\
 	:	"memory")
 
-static inline int futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
+static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+		u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
 
 	pagefault_disable();
 
@@ -62,17 +54,9 @@ static inline int futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/arc/include/asm/futex.h b/arch/arc/include/asm/futex.h
index 11e1b1f3acda..eb887dd13e74 100644
--- a/arch/arc/include/asm/futex.h
+++ b/arch/arc/include/asm/futex.h
@@ -73,20 +73,11 @@
 
 #endif
 
-static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+		u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
-		return -EFAULT;
-
 #ifndef CONFIG_ARC_HAS_LLSC
 	preempt_disable();	/* to guarantee atomic r-m-w of futex op */
 #endif
@@ -118,30 +109,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 	preempt_enable();
 #endif
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ:
-			ret = (oldval == cmparg);
-			break;
-		case FUTEX_OP_CMP_NE:
-			ret = (oldval != cmparg);
-			break;
-		case FUTEX_OP_CMP_LT:
-			ret = (oldval < cmparg);
-			break;
-		case FUTEX_OP_CMP_GE:
-			ret = (oldval >= cmparg);
-			break;
-		case FUTEX_OP_CMP_LE:
-			ret = (oldval <= cmparg);
-			break;
-		case FUTEX_OP_CMP_GT:
-			ret = (oldval > cmparg);
-			break;
-		default:
-			ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
index 6795368ad023..cc414382dab4 100644
--- a/arch/arm/include/asm/futex.h
+++ b/arch/arm/include/asm/futex.h
@@ -128,20 +128,10 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 #endif /* !SMP */
 
 static inline int
-futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret, tmp;
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
-
 #ifndef CONFIG_SMP
 	preempt_disable();
 #endif
@@ -172,17 +162,9 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
 	preempt_enable();
 #endif
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
index f32b42e8725d..5bb2fd4674e7 100644
--- a/arch/arm64/include/asm/futex.h
+++ b/arch/arm64/include/asm/futex.h
@@ -48,20 +48,10 @@ do {									\
 } while (0)
 
 static inline int
-futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr)
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (int)(encoded_op << 8) >> 20;
-	int cmparg = (int)(encoded_op << 20) >> 20;
 	int oldval = 0, ret, tmp;
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1U << (oparg & 0x1f);
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
-
 	pagefault_disable();
 
 	switch (op) {
@@ -91,17 +81,9 @@ futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/frv/include/asm/futex.h b/arch/frv/include/asm/futex.h
index 2e1da71e27a4..ab346f5f8820 100644
--- a/arch/frv/include/asm/futex.h
+++ b/arch/frv/include/asm/futex.h
@@ -7,7 +7,8 @@
 #include <asm/errno.h>
 #include <linux/uaccess.h>
 
-extern int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr);
+extern int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+		u32 __user *uaddr);
 
 static inline int
 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
diff --git a/arch/frv/kernel/futex.c b/arch/frv/kernel/futex.c
index d155ca9e5098..37f7b2bf7f73 100644
--- a/arch/frv/kernel/futex.c
+++ b/arch/frv/kernel/futex.c
@@ -186,20 +186,10 @@ static inline int atomic_futex_op_xchg_xor(int oparg, u32 __user *uaddr, int *_o
 /*
  * do the futex operations
  */
-int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+int arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
-
 	pagefault_disable();
 
 	switch (op) {
@@ -225,18 +215,9 @@ int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS; break;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
 
 	return ret;
 
-} /* end futex_atomic_op_inuser() */
+} /* end arch_futex_atomic_op_inuser() */
diff --git a/arch/hexagon/include/asm/futex.h b/arch/hexagon/include/asm/futex.h
index 7e597f8434da..c607b77c8215 100644
--- a/arch/hexagon/include/asm/futex.h
+++ b/arch/hexagon/include/asm/futex.h
@@ -31,18 +31,9 @@
 
 
 static inline int
-futex_atomic_op_inuser(int encoded_op, int __user *uaddr)
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
-		return -EFAULT;
 
 	pagefault_disable();
 
@@ -72,30 +63,9 @@ futex_atomic_op_inuser(int encoded_op, int __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ:
-			ret = (oldval == cmparg);
-			break;
-		case FUTEX_OP_CMP_NE:
-			ret = (oldval != cmparg);
-			break;
-		case FUTEX_OP_CMP_LT:
-			ret = (oldval < cmparg);
-			break;
-		case FUTEX_OP_CMP_GE:
-			ret = (oldval >= cmparg);
-			break;
-		case FUTEX_OP_CMP_LE:
-			ret = (oldval <= cmparg);
-			break;
-		case FUTEX_OP_CMP_GT:
-			ret = (oldval > cmparg);
-			break;
-		default:
-			ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/ia64/include/asm/futex.h b/arch/ia64/include/asm/futex.h
index 76acbcd5c060..6d67dc1eaf2b 100644
--- a/arch/ia64/include/asm/futex.h
+++ b/arch/ia64/include/asm/futex.h
@@ -45,18 +45,9 @@ do {									\
 } while (0)
 
 static inline int
-futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (! access_ok (VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
 
 	pagefault_disable();
 
@@ -84,17 +75,9 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/microblaze/include/asm/futex.h b/arch/microblaze/include/asm/futex.h
index 01848f056f43..a9dad9e5e132 100644
--- a/arch/microblaze/include/asm/futex.h
+++ b/arch/microblaze/include/asm/futex.h
@@ -29,18 +29,9 @@
 })
 
 static inline int
-futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
 
 	pagefault_disable();
 
@@ -66,30 +57,9 @@ futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ:
-			ret = (oldval == cmparg);
-			break;
-		case FUTEX_OP_CMP_NE:
-			ret = (oldval != cmparg);
-			break;
-		case FUTEX_OP_CMP_LT:
-			ret = (oldval < cmparg);
-			break;
-		case FUTEX_OP_CMP_GE:
-			ret = (oldval >= cmparg);
-			break;
-		case FUTEX_OP_CMP_LE:
-			ret = (oldval <= cmparg);
-			break;
-		case FUTEX_OP_CMP_GT:
-			ret = (oldval > cmparg);
-			break;
-		default:
-			ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/mips/include/asm/futex.h b/arch/mips/include/asm/futex.h
index 1de190bdfb9c..a9e61ea54ca9 100644
--- a/arch/mips/include/asm/futex.h
+++ b/arch/mips/include/asm/futex.h
@@ -83,18 +83,9 @@
 }
 
 static inline int
-futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (! access_ok (VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
 
 	pagefault_disable();
 
@@ -125,17 +116,9 @@ futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/openrisc/include/asm/futex.h b/arch/openrisc/include/asm/futex.h
index 778087341977..8fed278a24b8 100644
--- a/arch/openrisc/include/asm/futex.h
+++ b/arch/openrisc/include/asm/futex.h
@@ -30,20 +30,10 @@
 })
 
 static inline int
-futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
-
 	pagefault_disable();
 
 	switch (op) {
@@ -68,30 +58,9 @@ futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ:
-			ret = (oldval == cmparg);
-			break;
-		case FUTEX_OP_CMP_NE:
-			ret = (oldval != cmparg);
-			break;
-		case FUTEX_OP_CMP_LT:
-			ret = (oldval < cmparg);
-			break;
-		case FUTEX_OP_CMP_GE:
-			ret = (oldval >= cmparg);
-			break;
-		case FUTEX_OP_CMP_LE:
-			ret = (oldval <= cmparg);
-			break;
-		case FUTEX_OP_CMP_GT:
-			ret = (oldval > cmparg);
-			break;
-		default:
-			ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/parisc/include/asm/futex.h b/arch/parisc/include/asm/futex.h
index 0ba14300cd8e..c601aab2fb36 100644
--- a/arch/parisc/include/asm/futex.h
+++ b/arch/parisc/include/asm/futex.h
@@ -32,22 +32,12 @@ _futex_spin_unlock_irqrestore(u32 __user *uaddr, unsigned long int *flags)
 }
 
 static inline int
-futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 {
 	unsigned long int flags;
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval, ret;
 	u32 tmp;
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(*uaddr)))
-		return -EFAULT;
-
 	_futex_spin_lock_irqsave(uaddr, &flags);
 	pagefault_disable();
 
@@ -85,17 +75,9 @@ out_pagefault_enable:
 	pagefault_enable();
 	_futex_spin_unlock_irqrestore(uaddr, &flags);
 
-	if (ret == 0) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/powerpc/include/asm/futex.h b/arch/powerpc/include/asm/futex.h
index eaada6c92344..719ed9b61ea7 100644
--- a/arch/powerpc/include/asm/futex.h
+++ b/arch/powerpc/include/asm/futex.h
@@ -29,18 +29,10 @@
 	: "b" (uaddr), "i" (-EFAULT), "r" (oparg) \
 	: "cr0", "memory")
 
-static inline int futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
+static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+		u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (! access_ok (VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
 
 	pagefault_disable();
 
@@ -66,17 +58,9 @@ static inline int futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/s390/include/asm/futex.h b/arch/s390/include/asm/futex.h
index a4811aa0304d..8f8eec9e1198 100644
--- a/arch/s390/include/asm/futex.h
+++ b/arch/s390/include/asm/futex.h
@@ -21,17 +21,12 @@
 		: "0" (-EFAULT), "d" (oparg), "a" (uaddr),		\
 		  "m" (*uaddr) : "cc");
 
-static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+		u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, newval, ret;
 
 	load_kernel_asce();
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
 
 	pagefault_disable();
 	switch (op) {
@@ -60,17 +55,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 	}
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/sh/include/asm/futex.h b/arch/sh/include/asm/futex.h
index d0078747d308..8f8cf941a8cd 100644
--- a/arch/sh/include/asm/futex.h
+++ b/arch/sh/include/asm/futex.h
@@ -27,21 +27,12 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 	return atomic_futex_op_cmpxchg_inatomic(uval, uaddr, oldval, newval);
 }
 
-static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+static inline int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval,
+		u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	u32 oparg = (encoded_op << 8) >> 20;
-	u32 cmparg = (encoded_op << 20) >> 20;
 	u32 oldval, newval, prev;
 	int ret;
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
-
 	pagefault_disable();
 
 	do {
@@ -80,17 +71,8 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = ((int)oldval < (int)cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = ((int)oldval >= (int)cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = ((int)oldval <= (int)cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = ((int)oldval > (int)cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
 
 	return ret;
 }
diff --git a/arch/sparc/include/asm/futex_64.h b/arch/sparc/include/asm/futex_64.h
index 4e899b0dabf7..1cfd89d92208 100644
--- a/arch/sparc/include/asm/futex_64.h
+++ b/arch/sparc/include/asm/futex_64.h
@@ -29,22 +29,14 @@
 	: "r" (uaddr), "r" (oparg), "i" (-EFAULT)	\
 	: "memory")
 
-static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+		u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret, tem;
 
-	if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
-		return -EFAULT;
 	if (unlikely((((unsigned long) uaddr) & 0x3UL)))
 		return -EINVAL;
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
 	pagefault_disable();
 
 	switch (op) {
@@ -69,17 +61,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
-		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
-		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
-		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
-		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
-		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
-		default: ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/tile/include/asm/futex.h b/arch/tile/include/asm/futex.h
index e64a1b75fc38..83c1e639b411 100644
--- a/arch/tile/include/asm/futex.h
+++ b/arch/tile/include/asm/futex.h
@@ -106,12 +106,9 @@
 	lock = __atomic_hashed_lock((int __force *)uaddr)
 #endif
 
-static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+static inline int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval,
+		u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int uninitialized_var(val), ret;
 
 	__futex_prolog();
@@ -119,12 +116,6 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 	/* The 32-bit futex code makes this assumption, so validate it here. */
 	BUILD_BUG_ON(sizeof(atomic_t) != sizeof(int));
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
-
 	pagefault_disable();
 	switch (op) {
 	case FUTEX_OP_SET:
@@ -148,30 +139,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 	}
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ:
-			ret = (val == cmparg);
-			break;
-		case FUTEX_OP_CMP_NE:
-			ret = (val != cmparg);
-			break;
-		case FUTEX_OP_CMP_LT:
-			ret = (val < cmparg);
-			break;
-		case FUTEX_OP_CMP_GE:
-			ret = (val >= cmparg);
-			break;
-		case FUTEX_OP_CMP_LE:
-			ret = (val <= cmparg);
-			break;
-		case FUTEX_OP_CMP_GT:
-			ret = (val > cmparg);
-			break;
-		default:
-			ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = val;
+
 	return ret;
 }
 
diff --git a/arch/x86/include/asm/futex.h b/arch/x86/include/asm/futex.h
index b4c1f5453436..f4dc9b63bdda 100644
--- a/arch/x86/include/asm/futex.h
+++ b/arch/x86/include/asm/futex.h
@@ -41,20 +41,11 @@
 		       "+m" (*uaddr), "=&r" (tem)		\
 		     : "r" (oparg), "i" (-EFAULT), "1" (0))
 
-static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+		u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret, tem;
 
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
-
 	pagefault_disable();
 
 	switch (op) {
@@ -80,30 +71,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (!ret) {
-		switch (cmp) {
-		case FUTEX_OP_CMP_EQ:
-			ret = (oldval == cmparg);
-			break;
-		case FUTEX_OP_CMP_NE:
-			ret = (oldval != cmparg);
-			break;
-		case FUTEX_OP_CMP_LT:
-			ret = (oldval < cmparg);
-			break;
-		case FUTEX_OP_CMP_GE:
-			ret = (oldval >= cmparg);
-			break;
-		case FUTEX_OP_CMP_LE:
-			ret = (oldval <= cmparg);
-			break;
-		case FUTEX_OP_CMP_GT:
-			ret = (oldval > cmparg);
-			break;
-		default:
-			ret = -ENOSYS;
-		}
-	}
+	if (!ret)
+		*oval = oldval;
+
 	return ret;
 }
 
diff --git a/arch/xtensa/include/asm/futex.h b/arch/xtensa/include/asm/futex.h
index b39531babec0..eaaf1ebcc7a4 100644
--- a/arch/xtensa/include/asm/futex.h
+++ b/arch/xtensa/include/asm/futex.h
@@ -44,18 +44,10 @@
 	: "r" (uaddr), "I" (-EFAULT), "r" (oparg)	\
 	: "memory")
 
-static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+		u32 __user *uaddr)
 {
-	int op = (encoded_op >> 28) & 7;
-	int cmp = (encoded_op >> 24) & 15;
-	int oparg = (encoded_op << 8) >> 20;
-	int cmparg = (encoded_op << 20) >> 20;
 	int oldval = 0, ret;
-	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
-		oparg = 1 << oparg;
-
-	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
-		return -EFAULT;
 
 #if !XCHAL_HAVE_S32C1I
 	return -ENOSYS;
@@ -89,19 +81,10 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 
 	pagefault_enable();
 
-	if (ret)
-		return ret;
+	if (!ret)
+		*oval = oldval;
 
-	switch (cmp) {
-	case FUTEX_OP_CMP_EQ: return (oldval == cmparg);
-	case FUTEX_OP_CMP_NE: return (oldval != cmparg);
-	case FUTEX_OP_CMP_LT: return (oldval < cmparg);
-	case FUTEX_OP_CMP_GE: return (oldval >= cmparg);
-	case FUTEX_OP_CMP_LE: return (oldval <= cmparg);
-	case FUTEX_OP_CMP_GT: return (oldval > cmparg);
-	}
-
-	return -ENOSYS;
+	return ret;
 }
 
 static inline int