From 2f3e285da53ae6002cabb028438a65b9f9cee534 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Fri, 15 Aug 2014 12:11:50 +0100 Subject: [PATCH] ARM: 8129/1: errata: work around Cortex-A15 erratum 830321 using dummy strex commit 2c32c65e3726c773760038910be30cce1b4d4149 upstream. 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 Signed-off-by: Will Deacon Signed-off-by: Russell King [lizf: Backported to 3.4: - Drop changes to arch/arm/include/asm/cacheflush.h and arch/arm/mach-exynos/mcpm-exynos.c] Signed-off-by: Zefan Li --- arch/arm/kernel/entry-header.S | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S index 9a8531e..9d95a46 100644 --- a/arch/arm/kernel/entry-header.S +++ b/arch/arm/kernel/entry-header.S @@ -76,26 +76,21 @@ #ifndef CONFIG_THUMB2_KERNEL .macro svc_exit, rpsr 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 @@ -123,7 +118,10 @@ .macro svc_exit, rpsr 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 @@ -132,13 +130,16 @@ .endm .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 -- 2.7.4