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>

1 files changed, 4 insertions, 3 deletions

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 23ebcf6eab9f..eeeed01ee44a 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 | \