Re: [Xenomai-core] [2.4.x PATCH] POSIX: Remove mutex/cond_init locking, fix NULL attribute

[Philippe Gerum <rpm@xenomai.org>]

Gilles Chanteperdrix wrote:
> On Fri, Apr 25, 2008 at 3:44 PM, Jan Kiszka <jan.kiszka@domain.hid> wrote:
>> Gilles Chanteperdrix wrote:
>>  > On Fri, Apr 25, 2008 at 2:59 PM, Jan Kiszka <jan.kiszka@domain.hid> wrote:
>>  >> Hi,
>>  >>
>>  >>  trunk check-in #3369 did not just remove some "questionable critical
>>  >>  sections", it also happen to fix two ugly bugs in the POSIX skin: The
>>  >>  user was not able to pass NULL attributes down to mutex_init and
>>  >>  cond_init. Find a backport of that patch for 2.4.x attached.
>>  >
>>  > I am using pthread_mutex_init and pthread_cond_init from user-space
>>  > with NULL attributes with pre 2.4 versions all the time, and never had
>>  > any problem.
>>
>>  Maybe a x86-64 issue: __xn_access_ok() triggers here when you stuff in a
>>  NULL pointer.
> 
> Ok. I had a look at the code now, and understood your patch. We simply
> have been lucky until now that xn_access_ok did not fail with NULL
> pointers.
> 

Unlike other ports, x86_64 specifically tests for page zero pointers...

#define __xn_access_ok(task,type,addr,size)    ((unsigned long)(addr) >=
PAGE_SIZE && \
						__xn_range_ok(task, addr, size))
-- 
Philippe.