Re: [PATCH v3 4/9] arc: use generic strncpy/strnlen from_user

Vineet Gupta
2021-07-22T15:34:58Z

On 7/22/21 5:48 AM, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> Remove the arc implemenation of strncpy/strnlen and instead use the
> generic versions. The arc 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.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

LGTM. Thx for doing this Arnd !

Acked-by: Vineet Gupta <vgupta@synopsys.com>

-Vineet

> ---
> 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 d8f51eb8963b..64e5f9366401 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