Re: [PATCH] ARM: add get_user() support for 8 byte types

Nicolas Pitre
2012-11-15T22:23:06Z

On Thu, 15 Nov 2012, Rob Clark wrote:

> From: Rob Clark <rob@ti.com>
>
> A new atomic modeset/pageflip ioctl being developed in DRM requires
> get_user() to work for 64bit types (in addition to just put_user()).
>
> v1: original
> v2: pass correct size to check_uaccess, and better handling of narrowing
> double word read with __get_user_xb() (Russell King's suggestion)
> v3: explain in comment about why this works for narrowing fetch to 1,
> 2, or 4 byte type on ARM.
>
> Signed-off-by: Rob Clark <rob@ti.com>

Acked-by: Nicolas Pitre <nico@linaro.org>

> ---
> arch/arm/include/asm/uaccess.h | 22 +++++++++++++++++++++-
> arch/arm/lib/getuser.S | 17 ++++++++++++++++-
> 2 files changed, 37 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
> index 7e1f760..4cfa793 100644
> --- a/arch/arm/include/asm/uaccess.h
> +++ b/arch/arm/include/asm/uaccess.h
> @@ -100,6 +100,7 @@ static inline void set_fs(mm_segment_t fs)
> extern int __get_user_1(void *);
> extern int __get_user_2(void *);
> extern int __get_user_4(void *);
> +extern int __get_user_8(void *);
>
> #define __GUP_CLOBBER_1 "lr", "cc"
> #ifdef CONFIG_CPU_USE_DOMAINS
> @@ -108,6 +109,7 @@ extern int __get_user_4(void *);
> #define __GUP_CLOBBER_2 "lr", "cc"
> #endif
> #define __GUP_CLOBBER_4 "lr", "cc"
> +#define __GUP_CLOBBER_8 "lr", "cc"
>
> #define __get_user_x(__r2,__p,__e,__l,__s) \
> __asm__ __volatile__ ( \
> @@ -118,11 +120,23 @@ extern int __get_user_4(void *);
> : "0" (__p), "r" (__l) \
> : __GUP_CLOBBER_##__s)
>
> +/*
> + * Narrowing a double-word get into a single 32bit word register, which works
> + * for 1, 2, or 4 byte types on ARM because there are no integer registers
> + * smaller than 32bit
> + */
> +#ifdef BIG_ENDIAN
> +#define __get_user_xb(__r2,__p,__e,__l,__s) \
> + __get_user_x(__r2,(uintptr_t)__p + 4,__e,__l,__s)
> +#else
> +#define __get_user_xb __get_user_x
> +#endif
> +
> #define __get_user_check(x,p) \
> ({ \
> unsigned long __limit = current_thread_info()->addr_limit - 1; \
> register const typeof(*(p)) __user *__p asm("r0") = (p);\
> - register unsigned long __r2 asm("r2"); \
> + register typeof(x) __r2 asm("r2"); \
> register unsigned long __l asm("r1") = __limit; \
> register int __e asm("r0"); \
> switch (sizeof(*(__p))) { \
> @@ -135,6 +149,12 @@ extern int __get_user_4(void *);
> case 4: \
> __get_user_x(__r2, __p, __e, __l, 4); \
> break; \
> + case 8: \
> + if (sizeof((x)) < 8) \
> + __get_user_xb(__r2, __p, __e, __l, 4); \
> + else \
> + __get_user_x(__r2, __p, __e, __l, 8); \
> + break; \
> default: __e = __get_user_bad(); break; \
> } \
> x = (typeof(*(p))) __r2; \
> diff --git a/arch/arm/lib/getuser.S b/arch/arm/lib/getuser.S
> index 9b06bb4..ed98707 100644
> --- a/arch/arm/lib/getuser.S
> +++ b/arch/arm/lib/getuser.S
> @@ -18,7 +18,7 @@
> * Inputs: r0 contains the address
> * r1 contains the address limit, which must be preserved
> * Outputs: r0 is the error code
> - * r2 contains the zero-extended value
> + * r2, r3 contains the zero-extended value
> * lr corrupted
> *
> * No other registers must be altered. (see <asm/uaccess.h>
> @@ -66,6 +66,19 @@ ENTRY(__get_user_4)
> mov pc, lr
> ENDPROC(__get_user_4)
>
> +ENTRY(__get_user_8)
> + check_uaccess r0, 8, r1, r2, __get_user_bad
> +#ifdef CONFIG_THUMB2_KERNEL
> +5: TUSER(ldr) r2, [r0]
> +6: TUSER(ldr) r3, [r0, #4]
> +#else
> +5: TUSER(ldr) r2, [r0], #4
> +6: TUSER(ldr) r3, [r0]
> +#endif
> + mov r0, #0
> + mov pc, lr
> +ENDPROC(__get_user_8)
> +
> __get_user_bad:
> mov r2, #0
> mov r0, #-EFAULT
> @@ -77,4 +90,6 @@ ENDPROC(__get_user_bad)
> .long 2b, __get_user_bad
> .long 3b, __get_user_bad
> .long 4b, __get_user_bad
> + .long 5b, __get_user_bad
> + .long 6b, __get_user_bad
> .popsection
> --
> 1.8.0
>
> --
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