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authorMark Rutland <mark.rutland@arm.com>2014-08-15 13:11:50 +0200
committerRussell King <rmk+kernel@arm.linux.org.uk>2014-08-27 16:40:13 +0200
commit2c32c65e3726c773760038910be30cce1b4d4149 (patch)
tree5882204a965a7b819f20bc8cc7ae33088d3bde88
parentARM: 8128/1: abort: don't clear the exclusive monitors (diff)
downloadlinux-2c32c65e3726c773760038910be30cce1b4d4149.tar.xz
linux-2c32c65e3726c773760038910be30cce1b4d4149.zip
ARM: 8129/1: errata: work around Cortex-A15 erratum 830321 using dummy strex
On revisions of Cortex-A15 prior to r3p3, a CLREX instruction at PL1 may falsely trigger a watchpoint exception, leading to potential data aborts during exception return and/or livelock. This patch resolves the issue in the following ways: - Replacing our uses of CLREX with a dummy STREX sequence instead (as we did for v6 CPUs). - Removing the clrex code from v7_exit_coherency_flush and derivatives, since this only exists as a minor performance improvement when non-cached exclusives are in use (Linux doesn't use these). Benchmarking on a variety of ARM cores revealed no measurable performance difference with this change applied, so the change is performed unconditionally and no new Kconfig entry is added. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Cc: stable@vger.kernel.org Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
-rw-r--r--arch/arm/include/asm/cacheflush.h1
-rw-r--r--arch/arm/kernel/entry-header.S29
-rw-r--r--arch/arm/mach-exynos/mcpm-exynos.c1
3 files changed, 15 insertions, 16 deletions
diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index fd43f7f55b70..79ecb4f34ffb 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -472,7 +472,6 @@ static inline void __sync_cache_range_r(volatile void *p, size_t size)
"mcr p15, 0, r0, c1, c0, 0 @ set SCTLR \n\t" \
"isb \n\t" \
"bl v7_flush_dcache_"__stringify(level)" \n\t" \
- "clrex \n\t" \
"mrc p15, 0, r0, c1, c0, 1 @ get ACTLR \n\t" \
"bic r0, r0, #(1 << 6) @ disable local coherency \n\t" \
"mcr p15, 0, r0, c1, c0, 1 @ set ACTLR \n\t" \
diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index 8db307d0954b..2fdf8679b46e 100644
--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -208,26 +208,21 @@
#endif
.endif
msr spsr_cxsf, \rpsr
-#if defined(CONFIG_CPU_V6)
- ldr r0, [sp]
- strex r1, r2, [sp] @ clear the exclusive monitor
- ldmib sp, {r1 - pc}^ @ load r1 - pc, cpsr
-#elif defined(CONFIG_CPU_32v6K)
- clrex @ clear the exclusive monitor
- ldmia sp, {r0 - pc}^ @ load r0 - pc, cpsr
-#else
- ldmia sp, {r0 - pc}^ @ load r0 - pc, cpsr
+#if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K)
+ @ We must avoid clrex due to Cortex-A15 erratum #830321
+ sub r0, sp, #4 @ uninhabited address
+ strex r1, r2, [r0] @ clear the exclusive monitor
#endif
+ ldmia sp, {r0 - pc}^ @ load r0 - pc, cpsr
.endm
.macro restore_user_regs, fast = 0, offset = 0
ldr r1, [sp, #\offset + S_PSR] @ get calling cpsr
ldr lr, [sp, #\offset + S_PC]! @ get pc
msr spsr_cxsf, r1 @ save in spsr_svc
-#if defined(CONFIG_CPU_V6)
+#if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K)
+ @ We must avoid clrex due to Cortex-A15 erratum #830321
strex r1, r2, [sp] @ clear the exclusive monitor
-#elif defined(CONFIG_CPU_32v6K)
- clrex @ clear the exclusive monitor
#endif
.if \fast
ldmdb sp, {r1 - lr}^ @ get calling r1 - lr
@@ -261,7 +256,10 @@
.endif
ldr lr, [sp, #S_SP] @ top of the stack
ldrd r0, r1, [sp, #S_LR] @ calling lr and pc
- clrex @ clear the exclusive monitor
+
+ @ We must avoid clrex due to Cortex-A15 erratum #830321
+ strex r2, r1, [sp, #S_LR] @ clear the exclusive monitor
+
stmdb lr!, {r0, r1, \rpsr} @ calling lr and rfe context
ldmia sp, {r0 - r12}
mov sp, lr
@@ -282,13 +280,16 @@
.endm
#else /* ifdef CONFIG_CPU_V7M */
.macro restore_user_regs, fast = 0, offset = 0
- clrex @ clear the exclusive monitor
mov r2, sp
load_user_sp_lr r2, r3, \offset + S_SP @ calling sp, lr
ldr r1, [sp, #\offset + S_PSR] @ get calling cpsr
ldr lr, [sp, #\offset + S_PC] @ get pc
add sp, sp, #\offset + S_SP
msr spsr_cxsf, r1 @ save in spsr_svc
+
+ @ We must avoid clrex due to Cortex-A15 erratum #830321
+ strex r1, r2, [sp] @ clear the exclusive monitor
+
.if \fast
ldmdb sp, {r1 - r12} @ get calling r1 - r12
.else
diff --git a/arch/arm/mach-exynos/mcpm-exynos.c b/arch/arm/mach-exynos/mcpm-exynos.c
index b2f8b60cf0e9..dc9a764a7c37 100644
--- a/arch/arm/mach-exynos/mcpm-exynos.c
+++ b/arch/arm/mach-exynos/mcpm-exynos.c
@@ -43,7 +43,6 @@
"mcr p15, 0, r0, c1, c0, 0 @ set SCTLR\n\t" \
"isb\n\t"\
"bl v7_flush_dcache_"__stringify(level)"\n\t" \
- "clrex\n\t"\
"mrc p15, 0, r0, c1, c0, 1 @ get ACTLR\n\t" \
"bic r0, r0, #(1 << 6) @ disable local coherency\n\t" \
/* Dummy Load of a device register to avoid Erratum 799270 */ \