From: Catalin Marinas Date: Mon, 13 Sep 2010 15:03:21 +0000 (+0100) Subject: ARM: 6384/1: Remove the domain switching on ARMv6k/v7 CPUs X-Git-Tag: v2.6.38-rc1~471^2~2^2~17 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=247055aa21ffef1c49dd64710d5e94c2aee19b58;p=pandora-kernel.git 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 --- Reading git-diff-tree failed