The following commit has been merged in the linux branch: commit 4b46d6416548fb6a0940dfd9911fd895eb6247b3 Author: Russell King rmk+kernel@arm.linux.org.uk Date: Sun Nov 1 17:44:24 2009 +0000

ARM: ensure initial page tables are setup for SMP systems

Mapping the same memory using two different attributes (memory type, shareability, cacheability) is unpredictable. During boot, we encounter a situation when we're updating the kernel's page tables which can lead to dirty cache lines existing in the cache which are subsequently missed. This causes stack corruption, and therefore a crash.

Therefore, ensure that the shared and cacheability settings matches the configuration that will be used later; this together with the restriction in early_cachepolicy() ensures that we won't create a mismatch during boot.

Acked-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Russell King rmk+kernel@arm.linux.org.uk

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index 02243ee..ea67be0 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -117,6 +117,13 @@ static void __init early_cachepolicy(char **p) } if (i == ARRAY_SIZE(cache_policies)) printk(KERN_ERR "ERROR: unknown or unsupported cache policy\n"); + /* + * This restriction is partly to do with the way we boot; it is + * unpredictable to have memory mapped using two different sets of + * memory attributes (shared, type, and cache attribs). We can not + * change these attributes once the initial assembly has setup the + * page tables. + */ if (cpu_architecture() >= CPU_ARCH_ARMv6) { printk(KERN_WARNING "Only cachepolicy=writeback supported on ARMv6 and later\n"); cachepolicy = CPOLICY_WRITEBACK; diff --git a/arch/arm/mm/proc-v6.S b/arch/arm/mm/proc-v6.S index 194737d..70f75d2 100644 --- a/arch/arm/mm/proc-v6.S +++ b/arch/arm/mm/proc-v6.S @@ -32,8 +32,10 @@

#ifndef CONFIG_SMP #define TTB_FLAGS TTB_RGN_WBWA +#define PMD_FLAGS PMD_SECT_WB #else #define TTB_FLAGS TTB_RGN_WBWA|TTB_S +#define PMD_FLAGS PMD_SECT_WBWA|PMD_SECT_S #endif

ENTRY(cpu_v6_proc_init) @@ -222,10 +224,9 @@ __v6_proc_info: .long 0x0007b000 .long 0x0007f000 .long PMD_TYPE_SECT | \ - PMD_SECT_BUFFERABLE | \ - PMD_SECT_CACHEABLE | \ PMD_SECT_AP_WRITE | \ - PMD_SECT_AP_READ + PMD_SECT_AP_READ | \ + PMD_FLAGS .long PMD_TYPE_SECT | \ PMD_SECT_XN | \ PMD_SECT_AP_WRITE | \ diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S index 23ebcf6..eeeed01 100644 --- a/arch/arm/mm/proc-v7.S +++ b/arch/arm/mm/proc-v7.S @@ -33,9 +33,11 @@ #ifndef CONFIG_SMP /* PTWs cacheable, inner WB not shareable, outer WB not shareable */ #define TTB_FLAGS TTB_IRGN_WB|TTB_RGN_OC_WB +#define PMD_FLAGS PMD_SECT_WB #else /* PTWs cacheable, inner WBWA shareable, outer WBWA not shareable */ #define TTB_FLAGS TTB_IRGN_WBWA|TTB_S|TTB_NOS|TTB_RGN_OC_WBWA +#define PMD_FLAGS PMD_SECT_WBWA|PMD_SECT_S #endif

ENTRY(cpu_v7_proc_init) @@ -326,10 +328,9 @@ __v7_proc_info: .long 0x000f0000 @ Required ID value .long 0x000f0000 @ Mask for ID .long PMD_TYPE_SECT | \ - PMD_SECT_BUFFERABLE | \ - PMD_SECT_CACHEABLE | \ PMD_SECT_AP_WRITE | \ - PMD_SECT_AP_READ + PMD_SECT_AP_READ | \ + PMD_FLAGS .long PMD_TYPE_SECT | \ PMD_SECT_XN | \ PMD_SECT_AP_WRITE | \