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SubjectRe: [PATCH V9 21/21] csky: support dword access for get_user_size()
On Wed, Oct 17, 2018 at 05:44:17PM +0200, Arnd Bergmann wrote:
> On Tue, Oct 16, 2018 at 5:33 AM Guo Ren <ren_guo@c-sky.com> wrote:
> >
> > Support dword access for get_user_size and redesign put_user_size with
> > the same style of get_user_size. It's Ok to use xxx_user_asm_common for
> > all size of variable with ldb, ldh, ldw, ld.d
> >
> > ld.d rx, (addr, 0) could "rx <= addr" "and r(x+1) <= addr+4" and this also
> > follow abiv2 gcc ABI for dword access.
>
> Are you sure this is correct for this?
>
> static inline u32 get_64_to_32(__u64 __user *p)
> {
> u32 ret;
> get_user(ret, p);
> return ret;
> }
>
> If I read __get_user_asm_common() right, the ld.d would overwrite
> two registers, but the caller only expects one, so it clobbers one
> that might be in use.
Ah... BUG! I only consider the get_user(u64, u64 *) :P

Change to:
case 8: \
__get_user_asm_dword((x), ptr, "ld.d", retval); \
break;

#define __get_user_asm_dword(x, ptr, err) \
do { \
u64 tmp; \
__get_user_asm_common(tmp, ptr, "ld.d", err); \
x = typeof(x) tmp; \
} while(0)

#define __put_user_asm_dword(x, ptr, err) \
do { \
u64 tmp = (u64) x; \
__put_user_asm_common(tmp, ptr, "st.d", err); \
} while(0)

Hmm?

Best Regards
Guo Ren

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