On Thu, Oct 18, 2018 at 5:41 AM Guo Ren <ren_...@c-sky.com> wrote: > > 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_...@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) >
I think this will cause warnings for code that passes a pointer. The 64-bit __get_user() is really hard, and most 32-bit architectures don't implement it at all. If you really want to add it, have a look at what x86 and arm do. IIRC they both use __builtin_choose_expr(), Arnd