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 <cbouatmailru@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
index 540a044..b33fe70 100644
--- a/arch/arm/include/asm/futex.h
+++ b/arch/arm/include/asm/futex.h
@@ -13,12 +13,13 @@
#include <linux/preempt.h>
#include <linux/uaccess.h>
#include <asm/errno.h>
+#include <asm/domain.h>
#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
__asm__ __volatile__( \
- "1: ldrt %1, [%2]\n" \
+ "1: " T(ldr) " %1, [%2]\n" \
" " insn "\n" \
- "2: strt %0, [%2]\n" \
+ "2: " T(str) " %0, [%2]\n" \
" mov %0, #0\n" \
"3:\n" \
" .pushsection __ex_table,\"a\"\n" \
@@ -97,10 +98,10 @@
pagefault_disable(); /* implies preempt_disable() */
__asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
- "1: ldrt %0, [%3]\n"
+ "1: " T(ldr) " %0, [%3]\n"
" teq %0, %1\n"
" it eq @ explicit IT needed for the 2b label\n"
- "2: streqt %2, [%3]\n"
+ "2: " T(streq) " %2, [%3]\n"
"3:\n"
" .pushsection __ex_table,\"a\"\n"
" .align 3\n"