[PATCH] ARM: 2656/1: Access permission bits are wrong for kernel XIP …

…sections on ARMv6

Patch from George G. Davis

This patch is required for kernel XIP support on ARMv6 machines.  It ensures that the access permission bits for kernel XIP section descriptors are APX=1 and AP[1:0]=01, which is Kernel read-only/User no access permissions.  Prior to this change, kernel XIP section descriptor access permissions were set to Kernel no access/User no access on ARMv6 machines and the kernel would therefore hang upon entry to userspace when set_fs(USER_DS) was executed.

Signed-off-by: Steve Longerbeam
Signed-off-by: George G. Davis
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/mm-armv.c

@@ -411,9 +411,10 @@ static void __init build_mem_type_table(void)
 		mem_types[MT_MEMORY].prot_sect &= ~PMD_BIT4;
 		mem_types[MT_ROM].prot_sect &= ~PMD_BIT4;
 		/*
-		 * Mark cache clean areas read only from SVC mode
-		 * and no access from userspace.
+		 * Mark cache clean areas and XIP ROM read only
+		 * from SVC mode and no access from userspace.
 		 */
+		mem_types[MT_ROM].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
 		mem_types[MT_MINICLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
 		mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
 	}