On Sat, 28 Oct 2006, Andrew Morton wrote:
> On Sat, 28 Oct 2006 11:56:24 -0400 (EDT)
> "Robert P. J. Day" <[email protected]> wrote:
>
> >
> > it seems odd that the purpose of the "probe_kernel_address()" macro
> > is, in fact, to probe a *user* address (from linux/uaccess.h):
> >
> > #define probe_kernel_address(addr, retval) \
> > ({ \
> > long ret; \
> > \
> > inc_preempt_count(); \
> > ret = __get_user(retval, addr); \
> > dec_preempt_count(); \
> > ret; \
> > })
> >
> > given that that routine is referenced only 5 places in the
> > entire source tree, wouldn't it be more meaningful to use a more
> > appropriate name?
>
> You'll notice that all callers are indeed probing kernel addresses.
> The function _could_ be used for user addresses and could perhaps be
> called probe_address().
>
> One of the reasons this wrapper exists is to communicate that the
> __get_user() it is in fact not being used to access user memory.
um ... ok. i think. i agree that "probe_address()" would be a more
appropriate name, but i'm still a bit confused as to why
"__get_user()" would be used to access something *not* in user memory,
given this seemingly unambiguous explanation in
include/asm-i386/uaccess.h:
=====
* get_user: - Get a simple variable from user space.
* @x: Variable to store result.
* @ptr: Source address, in user space.
*
* Context: User context only. This function may sleep.
*
* This macro copies a single simple variable from user space to kernel
* space. It supports simple types like char and int, but not larger
* data types like structures or arrays.
...
=====
so having probe_kernel_address() invoke __get_user() does seem to be
just a wee bit confusing for us newbies. in any event, i'll leave the
clarification for someone much higher up the food chain.
rday
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