MIPS: uaccess: Take EVA into account in [__]clear_user

__clear_user() (and clear_user() which uses it), always access the user
mode address space, which results in EVA store instructions when EVA is
enabled even if the current user address limit is KERNEL_DS.

Fix this by adding a new symbol __bzero_kernel for the normal kernel
address space bzero in EVA mode, and call that from __clear_user() if
eva_kernel_access().

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10844/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 26 insertions, 10 deletions

diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index 5014e187df23..2e3b3991cf0b 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -1235,16 +1235,28 @@ __clear_user(void __user *addr, __kernel_size_t size)
 {
         __kernel_size_t res;
 
-        might_fault();
-        __asm__ __volatile__(
-                "move\t$4, %1\n\t"
-                "move\t$5, $0\n\t"
-                "move\t$6, %2\n\t"
-                __MODULE_JAL(__bzero)
-                "move\t%0, $6"
-                : "=r" (res)
-                : "r" (addr), "r" (size)
-                : "$4", "$5", "$6", __UA_t0, __UA_t1, "$31");
+        if (eva_kernel_access()) {
+                __asm__ __volatile__(
+                        "move\t$4, %1\n\t"
+                        "move\t$5, $0\n\t"
+                        "move\t$6, %2\n\t"
+                        __MODULE_JAL(__bzero_kernel)
+                        "move\t%0, $6"
+                        : "=r" (res)
+                        : "r" (addr), "r" (size)
+                        : "$4", "$5", "$6", __UA_t0, __UA_t1, "$31");
+        } else {
+                might_fault();
+                __asm__ __volatile__(
+                        "move\t$4, %1\n\t"
+                        "move\t$5, $0\n\t"
+                        "move\t$6, %2\n\t"
+                        __MODULE_JAL(__bzero)
+                        "move\t%0, $6"
+                        : "=r" (res)
+                        : "r" (addr), "r" (size)
+                        : "$4", "$5", "$6", __UA_t0, __UA_t1, "$31");
+        }
 
         return res;
 }
diff --git a/arch/mips/kernel/mips_ksyms.c b/arch/mips/kernel/mips_ksyms.c
index 291af0b5c482..e2b6ab74643d 100644
--- a/arch/mips/kernel/mips_ksyms.c
+++ b/arch/mips/kernel/mips_ksyms.c
@@ -17,6 +17,7 @@
 #include <asm/fpu.h>
 #include <asm/msa.h>
 
+extern void *__bzero_kernel(void *__s, size_t __count);
 extern void *__bzero(void *__s, size_t __count);
 extern long __strncpy_from_kernel_nocheck_asm(char *__to,
                                               const char *__from, long __len);
@@ -64,6 +65,7 @@ EXPORT_SYMBOL(__copy_from_user_eva);
 EXPORT_SYMBOL(__copy_in_user_eva);
 EXPORT_SYMBOL(__copy_to_user_eva);
 EXPORT_SYMBOL(__copy_user_inatomic_eva);
+EXPORT_SYMBOL(__bzero_kernel);
 #endif
 EXPORT_SYMBOL(__bzero);
 EXPORT_SYMBOL(__strncpy_from_kernel_nocheck_asm);
diff --git a/arch/mips/lib/memset.S b/arch/mips/lib/memset.S
index b8e63fd00375..8f0019a2e5c8 100644
--- a/arch/mips/lib/memset.S
+++ b/arch/mips/lib/memset.S
@@ -283,6 +283,8 @@ LEAF(memset)
 1:
 #ifndef CONFIG_EVA
 FEXPORT(__bzero)
+#else
+FEXPORT(__bzero_kernel)
 #endif
         __BUILD_BZERO LEGACY_MODE