Re: [PATCH V3] asm-generic: add a generic uaccess.h

Michal Simek
2009-05-01T14:11:30Z

Arnd Bergmann wrote:
> On Friday 01 May 2009, Michal Simek wrote:
>> Arnd Bergmann wrote:
>>> +
>>> +#include <asm/segment.h>
>>> +
>>> +#ifndef get_fs
>>> +#define MAKE_MM_SEG(s) ((mm_segment_t) { (s) })
>> one line above -> get_fs could be defined in different space
>> and this arch could use MAKE_MM_SEG too -> for example powerpc.
>
> I don't think I understand what you are trying to tell me.
> How do you think this should look?

I meant move MAKE_MM_SEG macro to this position because this macro could be use
with arch which define different get_fs.

#define MAKE_MM_SEG(s) ((mm_segment_t) { (s) })
#ifndef get_fs
...

>
>>> +
>>> +#define VERIFY_READ 0
>>> +#define VERIFY_WRITE 1
>>> +
>>
>> Not sure if any arch do READ/WRITE check but if yes.
>
> I could not find any architecture using it either, but the
> API is defined this way.
>
>> #ifndef access_ok
>>
>>> +#define access_ok(type, addr, size) __access_ok((unsigned long)(addr),(size))
>> #endif
>
> right, will change.
>
>>> +
>>> +/*
>>> + * The architecture should really override this if possible, at least
>>> + * doing a check on the get_fs()
>>> + */
>> If they should really override it but why write it here.
>
> Mostly for documentation purposes, so that an architecture maintainer
> can copy the prototype. I see the asm-generic headers as both fallbacks
> for architectures and as templates of what should be implemented.
>
>>> +#define get_user(x, ptr) \
>>> +({ \
>>> + might_sleep(); \
>>> + __access_ok(ptr, sizeof (*ptr)) ? \
>>> + __get_user(x, ptr) : \
>>> + -EFAULT; \
>>> +})
>> I am getting here (for put_user macro too) any error on noMMU. :-(
>
> What kind of error do you see?

System is getting crazy with -> I am debugging it.

>
>>> +static inline long
>>> +strncpy_from_user(char *dst, const char __user *src, long count)
>>> +{
>>> + if (!__access_ok(src, 1))
>>> + return -EFAULT;
>>> + return __strncpy_from_user(dst, src, count);
>>> +}
>> Is it a good place to add might_sleep() and unlikely(+ some other cases) too?
>> We have almost the same code.
>
> Yes, I think so. The unlikely() can probably go into __access_ok() though,
> so we don't have to write it every time.

ok

Michal

>
> Arnd <><

--
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854