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ARM: 8129/1: errata: work around Cortex-A15 erratum 830321 using dummy strex

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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>
This commit is contained in:
Mark Rutland
2014-08-15 12:11:50 +01:00
committed by Russell King
parent 8586831317
commit 2c32c65e37
3 changed files with 15 additions and 16 deletions
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29
arch/arm/kernel/entry-header.S
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@@ -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