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>

1 files changed, 8 insertions, 8 deletions

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 33e4a48fe103..b293616a1a1a 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -227,7 +227,7 @@ do {									\
 
 #define __get_user_asm_byte(x,addr,err)                         \
         __asm__ __volatile__(                                   \
-        "1:     ldrbt   %1,[%2]\n"                              \
+        "1:     " T(ldrb) "     %1,[%2],#0\n"                   \
         "2:\n"                                                  \
         "       .pushsection .fixup,\"ax\"\n"                   \
         "       .align  2\n"                                    \
@@ -263,7 +263,7 @@ do {									\
 
 #define __get_user_asm_word(x,addr,err)                         \
         __asm__ __volatile__(                                   \
-        "1:     ldrt    %1,[%2]\n"                              \
+        "1:     " T(ldr) "      %1,[%2],#0\n"                   \
         "2:\n"                                                  \
         "       .pushsection .fixup,\"ax\"\n"                   \
         "       .align  2\n"                                    \
@@ -308,7 +308,7 @@ do {									\
 
 #define __put_user_asm_byte(x,__pu_addr,err)                    \
         __asm__ __volatile__(                                   \
-        "1:     strbt   %1,[%2]\n"                              \
+        "1:     " T(strb) "     %1,[%2],#0\n"                   \
         "2:\n"                                                  \
         "       .pushsection .fixup,\"ax\"\n"                   \
         "       .align  2\n"                                    \
@@ -341,7 +341,7 @@ do {									\
 
 #define __put_user_asm_word(x,__pu_addr,err)                    \
         __asm__ __volatile__(                                   \
-        "1:     strt    %1,[%2]\n"                              \
+        "1:     " T(str) "      %1,[%2],#0\n"                   \
         "2:\n"                                                  \
         "       .pushsection .fixup,\"ax\"\n"                   \
         "       .align  2\n"                                    \
@@ -366,10 +366,10 @@ do {									\
 
 #define __put_user_asm_dword(x,__pu_addr,err)                   \
         __asm__ __volatile__(                                   \
- ARM(   "1:     strt    " __reg_oper1 ", [%1], #4\n"    )       \
- ARM(   "2:     strt    " __reg_oper0 ", [%1]\n"        )       \
- THUMB( "1:     strt    " __reg_oper1 ", [%1]\n"        )       \
- THUMB( "2:     strt    " __reg_oper0 ", [%1, #4]\n"    )       \
+ ARM(   "1:     " T(str) "      " __reg_oper1 ", [%1], #4\n"    )       \
+ ARM(   "2:     " T(str) "      " __reg_oper0 ", [%1]\n"        )       \
+ THUMB( "1:     " T(str) "      " __reg_oper1 ", [%1]\n"        )       \
+ THUMB( "2:     " T(str) "      " __reg_oper0 ", [%1, #4]\n"    )       \
         "3:\n"                                                  \
         "       .pushsection .fixup,\"ax\"\n"                   \
         "       .align  2\n"                                    \