linux-kernel - [PATCH 4.15 038/202] [Variant 3/Meltdown] arm64: mm: Introduce TTBR_ASID

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Date:   Thu, 15 Feb 2018 16:15:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        Laura Abbott <labbott@...hat.com>,
        Shanker Donthineni <shankerd@...eaurora.org>,
        Will Deacon <will.deacon@....com>
Subject: [PATCH 4.15 038/202] [Variant 3/Meltdown] arm64: mm: Introduce TTBR_ASID_MASK for getting at the ASID in the TTBR

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

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

From: Will Deacon <will.deacon@....com>


Commit b519538dfefc upstream.

There are now a handful of open-coded masks to extract the ASID from a
TTBR value, so introduce a TTBR_ASID_MASK and use that instead.

Suggested-by: Mark Rutland <mark.rutland@....com>
Reviewed-by: Mark Rutland <mark.rutland@....com>
Tested-by: Laura Abbott <labbott@...hat.com>
Tested-by: Shanker Donthineni <shankerd@...eaurora.org>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/include/asm/asm-uaccess.h |    3 ++-
 arch/arm64/include/asm/mmu.h         |    1 +
 arch/arm64/include/asm/uaccess.h     |    4 ++--
 arch/arm64/kernel/entry.S            |    2 +-
 4 files changed, 6 insertions(+), 4 deletions(-)

--- a/arch/arm64/include/asm/asm-uaccess.h
+++ b/arch/arm64/include/asm/asm-uaccess.h
@@ -4,6 +4,7 @@
 
 #include <asm/alternative.h>
 #include <asm/kernel-pgtable.h>
+#include <asm/mmu.h>
 #include <asm/sysreg.h>
 #include <asm/assembler.h>
 
@@ -17,7 +18,7 @@
 	msr	ttbr0_el1, \tmp1		// set reserved TTBR0_EL1
 	isb
 	sub	\tmp1, \tmp1, #SWAPPER_DIR_SIZE
-	bic	\tmp1, \tmp1, #(0xffff << 48)
+	bic	\tmp1, \tmp1, #TTBR_ASID_MASK
 	msr	ttbr1_el1, \tmp1		// set reserved ASID
 	isb
 	.endm
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -18,6 +18,7 @@
 
 #define MMCF_AARCH32	0x1	/* mm context flag for AArch32 executables */
 #define USER_ASID_FLAG	(UL(1) << 48)
+#define TTBR_ASID_MASK	(UL(0xffff) << 48)
 
 #ifndef __ASSEMBLY__
 
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -112,7 +112,7 @@ static inline void __uaccess_ttbr0_disab
 	write_sysreg(ttbr + SWAPPER_DIR_SIZE, ttbr0_el1);
 	isb();
 	/* Set reserved ASID */
-	ttbr &= ~(0xffffUL << 48);
+	ttbr &= ~TTBR_ASID_MASK;
 	write_sysreg(ttbr, ttbr1_el1);
 	isb();
 }
@@ -131,7 +131,7 @@ static inline void __uaccess_ttbr0_enabl
 
 	/* Restore active ASID */
 	ttbr1 = read_sysreg(ttbr1_el1);
-	ttbr1 |= ttbr0 & (0xffffUL << 48);
+	ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 	write_sysreg(ttbr1, ttbr1_el1);
 	isb();
 
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -205,7 +205,7 @@ alternative_else_nop_endif
 
 	.if	\el != 0
 	mrs	x21, ttbr1_el1
-	tst	x21, #0xffff << 48		// Check for the reserved ASID
+	tst	x21, #TTBR_ASID_MASK		// Check for the reserved ASID
 	orr	x23, x23, #PSR_PAN_BIT		// Set the emulated PAN in the saved SPSR
 	b.eq	1f				// TTBR0 access already disabled
 	and	x23, x23, #~PSR_PAN_BIT		// Clear the emulated PAN in the saved SPSR