> -----Original Message----- > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > Sent: Monday, February 28, 2011 1:22 AM > To: Guan Xuetao > Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-arch@xxxxxxxxxxxxxxx; 'Greg KH' > Subject: Re: [PATCH 05/12] unicore32 additional architecture files: low-level lib: uaccess > > On Sunday 27 February 2011, Guan Xuetao wrote: > > > -----Original Message----- > > > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > > > Sent: Friday, February 18, 2011 1:45 AM > > > To: Guan Xuetao > > > Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-arch@xxxxxxxxxxxxxxx; 'Greg KH' > > > Subject: Re: [PATCH 05/12] unicore32 additional architecture files: low-level lib: uaccess > > > > > > On Wednesday 16 February 2011, Guan Xuetao wrote: > > > > + > > > > +#define __kernel_ok (segment_eq(get_fs(), KERNEL_DS)) > > > > +#define __user_ok(addr, size) (((size) <= TASK_SIZE) \ > > > > + && ((addr) <= TASK_SIZE - (size))) > > > > +#define __access_ok(addr, size) (__kernel_ok || __user_ok((addr), (size))) > > > > > > A nice trick to simplify this is to introduce a per-process variable for comparing > > > the pointer, set_fs() then sets this variable to either TASK_SIZE or > > > UINT_MAX. > > > > Perhaps like this: > > 1. add a member named kaddr in thread_info > > 2. add following assignment codes in set_fs: > > current_thread_info()->kaddr = segment_eq(fs, KERNEL_DS) ? UINT_MAX : TASK_SIZE; > > 3. then __access_ok will be: > > #define addr > > #define __access_ok(addr, size) (((size) <= TASK_SIZE) \ > > && ((addr) <= current_thread_info()->kaddr) - (size))) > > That would also work. What I meant was to have > > #define set_fs(fs) \ > do { current_thread_info()->kaddr = (fs); } while (0) > > #define KERNEL_DS UINT_MAX > #define USER_DS TASK_SIZE > > Either way is fine with me, just choose whichever works best for you in terms of code size. I can't find the difference between this way and the way in asm-generic/uaccess.h. Perhaps, under this idea, __kernel_ok could be ignored. > > Arnd Thanks & Regards. Guan Xuetao -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
