[PATCH 4/6] [v2] arc: use generic strncpy/strnlen from_user

Arnd Bergmann
2021-05-15T10:19:53Z

Most per-architecture versions of these functions are broken
in some form, and they are almost certainly slower than the
generic code as well.

This version is fairly slow because it always does byte accesses
even for aligned data, and its checks for user_addr_max() differ
from the generic code.

Remove the ones for arc and instead use the generic version.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/arc/Kconfig | 2 +
arch/arc/include/asm/uaccess.h | 83 ++--------------------------------
arch/arc/mm/extable.c | 12 -----
3 files changed, 7 insertions(+), 90 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 2d98501c0897..a38f403a8811 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -27,6 +27,8 @@ config ARC
select GENERIC_PENDING_IRQ if SMP
select GENERIC_SCHED_CLOCK
select GENERIC_SMP_IDLE_THREAD
+ select GENERIC_STRNCPY_FROM_USER
+ select GENERIC_STRNLEN_USER
select HAVE_ARCH_KGDB
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE if ARC_MMU_V4
diff --git a/arch/arc/include/asm/uaccess.h b/arch/arc/include/asm/uaccess.h
index 3476348f361e..754a23f26736 100644
--- a/arch/arc/include/asm/uaccess.h
+++ b/arch/arc/include/asm/uaccess.h
@@ -655,96 +655,23 @@ static inline unsigned long __arc_clear_user(void __user *to, unsigned long n)
return res;
}

-static inline long
-__arc_strncpy_from_user(char *dst, const char __user *src, long count)
-{
- long res = 0;
- char val;
-
- if (!access_ok(src, 1))
- return -EFAULT;
-
- if (count == 0)
- return 0;
-
- __asm__ __volatile__(
- " mov lp_count, %5 \n"
- " lp 3f \n"
- "1: ldb.ab %3, [%2, 1] \n"
- " breq.d %3, 0, 3f \n"
- " stb.ab %3, [%1, 1] \n"
- " add %0, %0, 1 # Num of NON NULL bytes copied \n"
- "3: \n"
- " .section .fixup, \"ax\" \n"
- " .align 4 \n"
- "4: mov %0, %4 # sets @res as -EFAULT \n"
- " j 3b \n"
- " .previous \n"
- " .section __ex_table, \"a\" \n"
- " .align 4 \n"
- " .word 1b, 4b \n"
- " .previous \n"
- : "+r"(res), "+r"(dst), "+r"(src), "=r"(val)
- : "g"(-EFAULT), "r"(count)
- : "lp_count", "memory");
-
- return res;
-}
-
-static inline long __arc_strnlen_user(const char __user *s, long n)
-{
- long res, tmp1, cnt;
- char val;
-
- if (!access_ok(s, 1))
- return 0;
-
- __asm__ __volatile__(
- " mov %2, %1 \n"
- "1: ldb.ab %3, [%0, 1] \n"
- " breq.d %3, 0, 2f \n"
- " sub.f %2, %2, 1 \n"
- " bnz 1b \n"
- " sub %2, %2, 1 \n"
- "2: sub %0, %1, %2 \n"
- "3: ;nop \n"
- " .section .fixup, \"ax\" \n"
- " .align 4 \n"
- "4: mov %0, 0 \n"
- " j 3b \n"
- " .previous \n"
- " .section __ex_table, \"a\" \n"
- " .align 4 \n"
- " .word 1b, 4b \n"
- " .previous \n"
- : "=r"(res), "=r"(tmp1), "=r"(cnt), "=r"(val)
- : "0"(s), "1"(n)
- : "memory");
-
- return res;
-}
-
#ifndef CONFIG_CC_OPTIMIZE_FOR_SIZE

#define INLINE_COPY_TO_USER
#define INLINE_COPY_FROM_USER

#define __clear_user(d, n) __arc_clear_user(d, n)
-#define strncpy_from_user(d, s, n) __arc_strncpy_from_user(d, s, n)
-#define strnlen_user(s, n) __arc_strnlen_user(s, n)
#else
extern unsigned long arc_clear_user_noinline(void __user *to,
unsigned long n);
-extern long arc_strncpy_from_user_noinline (char *dst, const char __user *src,
- long count);
-extern long arc_strnlen_user_noinline(const char __user *src, long n);
-
#define __clear_user(d, n) arc_clear_user_noinline(d, n)
-#define strncpy_from_user(d, s, n) arc_strncpy_from_user_noinline(d, s, n)
-#define strnlen_user(s, n) arc_strnlen_user_noinline(s, n)
-
#endif

+extern long strncpy_from_user(char *dst, const char __user *src, long count);
+#define strncpy_from_user(d, s, n) strncpy_from_user(d, s, n)
+extern long strnlen_user(const char __user *src, long n);
+#define strnlen_user(s, n) strnlen_user(s, n)
+
#include <asm/segment.h>
#include <asm-generic/uaccess.h>

diff --git a/arch/arc/mm/extable.c b/arch/arc/mm/extable.c
index b06b09ddf924..4e14c4244ea2 100644
--- a/arch/arc/mm/extable.c
+++ b/arch/arc/mm/extable.c
@@ -32,16 +32,4 @@ unsigned long arc_clear_user_noinline(void __user *to,
}
EXPORT_SYMBOL(arc_clear_user_noinline);

-long arc_strncpy_from_user_noinline(char *dst, const char __user *src,
- long count)
-{
- return __arc_strncpy_from_user(dst, src, count);
-}
-EXPORT_SYMBOL(arc_strncpy_from_user_noinline);
-
-long arc_strnlen_user_noinline(const char __user *src, long n)
-{
- return __arc_strnlen_user(src, n);
-}
-EXPORT_SYMBOL(arc_strnlen_user_noinline);
#endif
--
2.29.2