From: marc.zyngier@arm•com (Marc Zyngier)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] Make the 32-bit ARM get_user() and put_user() work for 16-bit quantities
Date: Tue, 29 Oct 2013 17:49:37 +0000 [thread overview]
Message-ID: <526FF531.9080705@arm.com> (raw)
In-Reply-To: <1383065529-20001-1-git-send-email-wcohen@redhat.com>
Hi William,
On 29/10/13 16:52, William Cohen wrote:
> The 32-bit ARM does not have instructions to perform 16-bit loads or
> stores. The __get_user_asm_half and __put_user_asm_half macros
> sythesize those operations. However, in most cases the pointers
> passed into these macros are pointers to 16-bit types and the pointer
> arithmetic will end up pointing at the next 16-bit quantity rather
> than the second half (byte) of the 16-bit quantity. The macros need
> to explicitly typecast the pointers as pointers to 8-bit quantities to
> make the pointer arithmetic work out properly.
So I'm a bit perplex here. Looks like nobody but __{ge,pu}t_user_err
calls these macros directly, and the sole users cast the pointer to an
unsigned long, for which the arithmetic ought to work properly.
What am I missing?
M.
> Signed-off-by: William Cohen <wcohen@redhat•com>
> ---
> arch/arm/include/asm/uaccess.h | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
> index 7e1f760..c2d9439 100644
> --- a/arch/arm/include/asm/uaccess.h
> +++ b/arch/arm/include/asm/uaccess.h
> @@ -277,16 +277,16 @@ do { \
> #define __get_user_asm_half(x,__gu_addr,err) \
> ({ \
> unsigned long __b1, __b2; \
> - __get_user_asm_byte(__b1, __gu_addr, err); \
> - __get_user_asm_byte(__b2, __gu_addr + 1, err); \
> + __get_user_asm_byte(__b1, (u8 *)(__gu_addr), err); \
> + __get_user_asm_byte(__b2, ((u8 *)(__gu_addr)) + 1, err);\
> (x) = __b1 | (__b2 << 8); \
> })
> #else
> #define __get_user_asm_half(x,__gu_addr,err) \
> ({ \
> unsigned long __b1, __b2; \
> - __get_user_asm_byte(__b1, __gu_addr, err); \
> - __get_user_asm_byte(__b2, __gu_addr + 1, err); \
> + __get_user_asm_byte(__b1, (u8 *)(__gu_addr), err); \
> + __get_user_asm_byte(__b2, ((u8 *)(__gu_addr)) + 1, err);\
> (x) = (__b1 << 8) | __b2; \
> })
> #endif
> @@ -358,15 +358,15 @@ do { \
> #define __put_user_asm_half(x,__pu_addr,err) \
> ({ \
> unsigned long __temp = (unsigned long)(x); \
> - __put_user_asm_byte(__temp, __pu_addr, err); \
> - __put_user_asm_byte(__temp >> 8, __pu_addr + 1, err); \
> + __put_user_asm_byte(__temp, (u8 *)(__pu_addr), err); \
> + __put_user_asm_byte(__temp >> 8, ((u8 *)(__pu_addr)) + 1, err);\
> })
> #else
> #define __put_user_asm_half(x,__pu_addr,err) \
> ({ \
> unsigned long __temp = (unsigned long)(x); \
> - __put_user_asm_byte(__temp >> 8, __pu_addr, err); \
> - __put_user_asm_byte(__temp, __pu_addr + 1, err); \
> + __put_user_asm_byte(__temp >> 8, (u8 *)(__pu_addr), err);\
> + __put_user_asm_byte(__temp, ((u8 *)(__pu_addr)) + 1, err);\
> })
> #endif
>
>
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2013-10-29 17:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-29 16:52 [PATCH] Make the 32-bit ARM get_user() and put_user() work for 16-bit quantities William Cohen
2013-10-29 17:49 ` Marc Zyngier [this message]
2013-10-29 18:04 ` Russell King - ARM Linux
2013-10-29 18:38 ` William Cohen
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