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>

5 files changed, 51 insertions, 20 deletions

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 062b58c029ab..4e84d09c9c1b 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -18,6 +18,7 @@
 #endif
 
 #include <asm/ptrace.h>
+#include <asm/domain.h>
 
 /*
  * Endian independent macros for shifting bytes within registers.
@@ -206,12 +207,12 @@
  */
 #ifdef CONFIG_THUMB2_KERNEL
 
-        .macro  usraccoff, instr, reg, ptr, inc, off, cond, abort
+        .macro  usraccoff, instr, reg, ptr, inc, off, cond, abort, t=T()
 9999:
         .if     \inc == 1
-        \instr\cond\()bt \reg, [\ptr, #\off]
+        \instr\cond\()b\()\t\().w \reg, [\ptr, #\off]
         .elseif \inc == 4
-        \instr\cond\()t \reg, [\ptr, #\off]
+        \instr\cond\()\t\().w \reg, [\ptr, #\off]
         .else
         .error  "Unsupported inc macro argument"
         .endif
@@ -246,13 +247,13 @@
 
 #else   /* !CONFIG_THUMB2_KERNEL */
 
-        .macro  usracc, instr, reg, ptr, inc, cond, rept, abort
+        .macro  usracc, instr, reg, ptr, inc, cond, rept, abort, t=T()
         .rept   \rept
 9999:
         .if     \inc == 1
-        \instr\cond\()bt \reg, [\ptr], #\inc
+        \instr\cond\()b\()\t \reg, [\ptr], #\inc
         .elseif \inc == 4
-        \instr\cond\()t \reg, [\ptr], #\inc
+        \instr\cond\()\t \reg, [\ptr], #\inc
         .else
         .error  "Unsupported inc macro argument"
         .endif
diff --git a/arch/arm/include/asm/domain.h b/arch/arm/include/asm/domain.h
index cc7ef4080711..af18ceaacf5d 100644
--- a/arch/arm/include/asm/domain.h
+++ b/arch/arm/include/asm/domain.h
@@ -45,13 +45,17 @@
  */
 #define DOMAIN_NOACCESS 0
 #define DOMAIN_CLIENT   1
+#ifdef CONFIG_CPU_USE_DOMAINS
 #define DOMAIN_MANAGER  3
+#else
+#define DOMAIN_MANAGER  1
+#endif
 
 #define domain_val(dom,type)    ((type) << (2*(dom)))
 
 #ifndef __ASSEMBLY__
 
-#ifdef CONFIG_MMU
+#ifdef CONFIG_CPU_USE_DOMAINS
 #define set_domain(x)                                   \
         do {                                            \
         __asm__ __volatile__(                           \
@@ -74,5 +78,28 @@
 #define modify_domain(dom,type) do { } while (0)
 #endif
 
+/*
+ * Generate the T (user) versions of the LDR/STR and related
+ * instructions (inline assembly)
+ */
+#ifdef CONFIG_CPU_USE_DOMAINS
+#define T(instr)        #instr "t"
+#else
+#define T(instr)        #instr
 #endif
-#endif /* !__ASSEMBLY__ */
+
+#else /* __ASSEMBLY__ */
+
+/*
+ * Generate the T (user) versions of the LDR/STR and related
+ * instructions
+ */
+#ifdef CONFIG_CPU_USE_DOMAINS
+#define T(instr)        instr ## t
+#else
+#define T(instr)        instr
+#endif
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* !__ASM_PROC_DOMAIN_H */
diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
index 540a044153a5..b33fe7065b38 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 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
         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"
diff --git a/arch/arm/include/asm/traps.h b/arch/arm/include/asm/traps.h
index 491960bf4260..af5d5d1388c6 100644
--- a/arch/arm/include/asm/traps.h
+++ b/arch/arm/include/asm/traps.h
@@ -27,4 +27,6 @@ static inline int in_exception_text(unsigned long ptr)
 extern void __init early_trap_init(void);
 extern void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long frame);
 
+extern void *vectors_page;
+
 #endif
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"                                    \