[ARM] Set bit 4 on section mappings correctly depending on CPU

On some CPUs, bit 4 of section mappings means "update the
cache when written to".  On others, this bit is required to
be one, and others it's required to be zero.  Finally, on
ARMv6 and above, setting it turns on "no execute" and prevents
speculative prefetches.

With all these combinations, no one value fits all CPUs, so we
have to pick a value depending on the CPU type, and the area
we're mapping.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 22 insertions, 15 deletions

diff --git a/arch/arm/mm/mm-armv.c b/arch/arm/mm/mm-armv.c
index 95273de4f772..d06440cc4e8f 100644
--- a/arch/arm/mm/mm-armv.c
+++ b/arch/arm/mm/mm-armv.c
@@ -303,16 +303,16 @@ static struct mem_types mem_types[] __initdata = {
 		.prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
 				L_PTE_WRITE,
 		.prot_l1   = PMD_TYPE_TABLE,
-		.prot_sect = PMD_TYPE_SECT | PMD_SECT_UNCACHED |
+		.prot_sect = PMD_TYPE_SECT | PMD_BIT4 | PMD_SECT_UNCACHED |
 				PMD_SECT_AP_WRITE,
 		.domain    = DOMAIN_IO,
 	},
 	[MT_CACHECLEAN] = {
-		.prot_sect = PMD_TYPE_SECT,
+		.prot_sect = PMD_TYPE_SECT | PMD_BIT4,
 		.domain    = DOMAIN_KERNEL,
 	},
 	[MT_MINICLEAN] = {
-		.prot_sect = PMD_TYPE_SECT | PMD_SECT_MINICACHE,
+		.prot_sect = PMD_TYPE_SECT | PMD_BIT4 | PMD_SECT_MINICACHE,
 		.domain    = DOMAIN_KERNEL,
 	},
 	[MT_LOW_VECTORS] = {
@@ -328,25 +328,25 @@ static struct mem_types mem_types[] __initdata = {
 		.domain    = DOMAIN_USER,
 	},
 	[MT_MEMORY] = {
-		.prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE,
+		.prot_sect = PMD_TYPE_SECT | PMD_BIT4 | PMD_SECT_AP_WRITE,
 		.domain    = DOMAIN_KERNEL,
 	},
 	[MT_ROM] = {
-		.prot_sect = PMD_TYPE_SECT,
+		.prot_sect = PMD_TYPE_SECT | PMD_BIT4,
 		.domain    = DOMAIN_KERNEL,
 	},
 	[MT_IXP2000_DEVICE] = { /* IXP2400 requires XCB=101 for on-chip I/O */
 		.prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
 				L_PTE_WRITE,
 		.prot_l1   = PMD_TYPE_TABLE,
-		.prot_sect = PMD_TYPE_SECT | PMD_SECT_UNCACHED |
+		.prot_sect = PMD_TYPE_SECT | PMD_BIT4 | PMD_SECT_UNCACHED |
 				PMD_SECT_AP_WRITE | PMD_SECT_BUFFERABLE |
 				PMD_SECT_TEX(1),
 		.domain    = DOMAIN_IO,
 	},
 	[MT_NONSHARED_DEVICE] = {
 		.prot_l1   = PMD_TYPE_TABLE,
-		.prot_sect = PMD_TYPE_SECT | PMD_SECT_NONSHARED_DEV |
+		.prot_sect = PMD_TYPE_SECT | PMD_BIT4 | PMD_SECT_NONSHARED_DEV |
 				PMD_SECT_AP_WRITE,
 		.domain    = DOMAIN_IO,
 	}
@@ -376,14 +376,21 @@ void __init build_mem_type_table(void)
 		ecc_mask = 0;
 	}
 
-	if (cpu_arch <= CPU_ARCH_ARMv5TEJ && !cpu_is_xscale()) {
-		for (i = 0; i < ARRAY_SIZE(mem_types); i++) {
+	/*
+	 * Xscale must not have PMD bit 4 set for section mappings.
+	 */
+	if (cpu_is_xscale())
+		for (i = 0; i < ARRAY_SIZE(mem_types); i++)
+			mem_types[i].prot_sect &= ~PMD_BIT4;
+
+	/*
+	 * ARMv5 and lower, excluding Xscale, bit 4 must be set for
+	 * page tables.
+	 */
+	if (cpu_arch < CPU_ARCH_ARMv6 && !cpu_is_xscale())
+		for (i = 0; i < ARRAY_SIZE(mem_types); i++)
 			if (mem_types[i].prot_l1)
 				mem_types[i].prot_l1 |= PMD_BIT4;
-			if (mem_types[i].prot_sect)
-				mem_types[i].prot_sect |= PMD_BIT4;
-		}
-	}
 
 	cp = &cache_policies[cachepolicy];
 	kern_pgprot = user_pgprot = cp->pte;
@@ -407,8 +414,8 @@ void __init build_mem_type_table(void)
 		 * bit 4 becomes XN which we must clear for the
 		 * kernel memory mapping.
 		 */
-		mem_types[MT_MEMORY].prot_sect &= ~PMD_BIT4;
-		mem_types[MT_ROM].prot_sect &= ~PMD_BIT4;
+		mem_types[MT_MEMORY].prot_sect &= ~PMD_SECT_XN;
+		mem_types[MT_ROM].prot_sect &= ~PMD_SECT_XN;
 
 		/*
 		 * Mark cache clean areas and XIP ROM read only