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| author | Mark Rutland <mark.rutland@arm.com> | 2014-08-15 13:11:50 +0200 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-08-27 16:40:13 +0200 |
| commit | 2c32c65e3726c773760038910be30cce1b4d4149 (patch) | |
| tree | 5882204a965a7b819f20bc8cc7ae33088d3bde88 /arch/arm/kernel/entry-header.S | |
| parent | ARM: 8128/1: abort: don't clear the exclusive monitors (diff) | |
| download | linux-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>
Diffstat (limited to 'arch/arm/kernel/entry-header.S')
| -rw-r--r-- | arch/arm/kernel/entry-header.S | 29 |
1 files changed, 15 insertions, 14 deletions
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 |