linux-kernel - [PATCH v2 2/4] MIPS: uaccess: Add micromips clobbers to bzero invocation

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Date:   Tue, 17 Apr 2018 16:40:01 +0100
From:   Matt Redfearn <matt.redfearn@...s.com>
To:     James Hogan <jhogan@...nel.org>, Ralf Baechle <ralf@...ux-mips.org>
CC:     <linux-mips@...ux-mips.org>,
        Matt Redfearn <matt.redfearn@...s.com>,
        <stable@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH v2 2/4] MIPS: uaccess: Add micromips clobbers to bzero invocation

The micromips implementation of bzero additionally clobbers registers t7
& t8. Specify this in the clobbers list when invoking bzero.

Reported-by: James Hogan <jhogan@...nel.org>
Fixes: 26c5e07d1478 ("MIPS: microMIPS: Optimise 'memset' core library function.")
Cc: stable@...r.kernel.org
Signed-off-by: Matt Redfearn <matt.redfearn@...s.com>
---

Changes in v2: None

 arch/mips/include/asm/uaccess.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index b71306947290..06629011a434 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -654,6 +654,13 @@ __clear_user(void __user *addr, __kernel_size_t size)
 {
 	__kernel_size_t res;
 
+#ifdef CONFIG_CPU_MICROMIPS
+/* micromips memset / bzero also clobbers t7 & t8 */
+#define bzero_clobbers "$4", "$5", "$6", __UA_t0, __UA_t1, "$15", "$24", "$31"
+#else
+#define bzero_clobbers "$4", "$5", "$6", __UA_t0, __UA_t1, "$31"
+#endif /* CONFIG_CPU_MICROMIPS */
+
 	if (eva_kernel_access()) {
 		__asm__ __volatile__(
 			"move\t$4, %1\n\t"
@@ -663,7 +670,7 @@ __clear_user(void __user *addr, __kernel_size_t size)
 			"move\t%0, $6"
 			: "=r" (res)
 			: "r" (addr), "r" (size)
-			: "$4", "$5", "$6", __UA_t0, __UA_t1, "$31");
+			: bzero_clobbers);
 	} else {
 		might_fault();
 		__asm__ __volatile__(
@@ -674,7 +681,7 @@ __clear_user(void __user *addr, __kernel_size_t size)
 			"move\t%0, $6"
 			: "=r" (res)
 			: "r" (addr), "r" (size)
-			: "$4", "$5", "$6", __UA_t0, __UA_t1, "$31");
+			: bzero_clobbers);
 	}
 
 	return res;
-- 
2.7.4