linux-kernel - [PATCH 4.4 82/97] MIPS: uaccess: Add micromips clobbers to bzero invocation

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Date:   Sun, 22 Apr 2018 15:54:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, James Hogan <jhogan@...nel.org>,
        Matt Redfearn <matt.redfearn@...s.com>,
        Ralf Baechle <ralf@...ux-mips.org>, linux-mips@...ux-mips.org
Subject: [PATCH 4.4 82/97] MIPS: uaccess: Add micromips clobbers to bzero invocation

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matt Redfearn <matt.redfearn@...s.com>

commit b3d7e55c3f886493235bfee08e1e5a4a27cbcce8 upstream.

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

Fixes: 26c5e07d1478 ("MIPS: microMIPS: Optimise 'memset' core library function.")
Reported-by: James Hogan <jhogan@...nel.org>
Signed-off-by: Matt Redfearn <matt.redfearn@...s.com>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: linux-mips@...ux-mips.org
Cc: <stable@...r.kernel.org> # 3.10+
Patchwork: https://patchwork.linux-mips.org/patch/19110/
Signed-off-by: James Hogan <jhogan@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -1238,6 +1238,13 @@ __clear_user(void __user *addr, __kernel
 {
 	__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"
@@ -1247,7 +1254,7 @@ __clear_user(void __user *addr, __kernel
 			"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__(
@@ -1258,7 +1265,7 @@ __clear_user(void __user *addr, __kernel
 			"move\t%0, $6"
 			: "=r" (res)
 			: "r" (addr), "r" (size)
-			: "$4", "$5", "$6", __UA_t0, __UA_t1, "$31");
+			: bzero_clobbers);
 	}
 
 	return res;