From 247055aa21ffef1c49dd64710d5e94c2aee19b58 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 13 Sep 2010 16:03:21 +0100 Subject: ARM: 6384/1: Remove the domain switching on ARMv6k/v7 CPUs This patch removes the domain switching functionality via the set_fs and __switch_to functions on cores that have a TLS register. Currently, the ioremap and vmalloc areas share the same level 1 page tables and therefore have the same domain (DOMAIN_KERNEL). When the kernel domain is modified from Client to Manager (via the __set_fs or in the __switch_to function), the XN (eXecute Never) bit is overridden and newer CPUs can speculatively prefetch the ioremap'ed memory. Linux performs the kernel domain switching to allow user-specific functions (copy_to/from_user, get/put_user etc.) to access kernel memory. In order for these functions to work with the kernel domain set to Client, the patch modifies the LDRT/STRT and related instructions to the LDR/STR ones. The user pages access rights are also modified for kernel read-only access rather than read/write so that the copy-on-write mechanism still works. CPU_USE_DOMAINS gets disabled only if the hardware has a TLS register (CPU_32v6K is defined) since writing the TLS value to the high vectors page isn't possible. The user addresses passed to the kernel are checked by the access_ok() function so that they do not point to the kernel space. Tested-by: Anton Vorontsov Cc: Tony Lindgren Signed-off-by: Catalin Marinas Signed-off-by: Russell King --- arch/arm/mm/proc-macros.S | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'arch/arm/mm/proc-macros.S') diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S index 7d63bea..337f102 100644 --- a/arch/arm/mm/proc-macros.S +++ b/arch/arm/mm/proc-macros.S @@ -99,6 +99,10 @@ * 110x 0 1 0 r/w r/o * 11x0 0 1 0 r/w r/o * 1111 0 1 1 r/w r/w + * + * If !CONFIG_CPU_USE_DOMAINS, the following permissions are changed: + * 110x 1 1 1 r/o r/o + * 11x0 1 1 1 r/o r/o */ .macro armv6_mt_table pfx \pfx\()_mt_table: @@ -138,8 +142,11 @@ tst r1, #L_PTE_USER orrne r3, r3, #PTE_EXT_AP1 +#ifdef CONFIG_CPU_USE_DOMAINS + @ allow kernel read/write access to read-only user pages tstne r3, #PTE_EXT_APX bicne r3, r3, #PTE_EXT_APX | PTE_EXT_AP0 +#endif tst r1, #L_PTE_EXEC orreq r3, r3, #PTE_EXT_XN -- cgit v1.1