Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH 05/12] unicore32 additional architecture files: low-level lib: uaccess | Date | Sun, 27 Feb 2011 18:21:33 +0100 |
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On Sunday 27 February 2011, Guan Xuetao wrote: > > -----Original Message----- > > From: Arnd Bergmann [mailto:arnd@arndb.de] > > Sent: Friday, February 18, 2011 1:45 AM > > To: Guan Xuetao > > Cc: linux-kernel@vger.kernel.org; linux-arch@vger.kernel.org; '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.
Arnd
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