mmap(2) with MAP_ANON honouring offset although it shouldn't
Alan Cox
alc at cs.rice.edu
Thu Nov 5 18:03:45 UTC 2009
Alexander Best wrote:
> Alan Cox schrieb am 2009-11-04:
>
>> Ed Schouten wrote:
>>
>>> * Alan Cox <alc at cs.rice.edu> wrote:
>>>
>
>
>> For what it's worth, I believe that Solaris does the exact opposite.
>>
>>>> They provide MAP_ANONYMOUS for compatibility. It seems like a good
>>>> idea for us to do the same.
>>>>
>
>
>
>>> Something like this?
>>>
>
>
>>> Index: mman.h
>>> ===================================================================
>>> --- mman.h (revision 198919)
>>> +++ mman.h (working copy)
>>> @@ -82,6 +82,9 @@
>>> */
>>> #define MAP_FILE 0x0000 /* map from file (default) */
>>> #define MAP_ANON 0x1000 /* allocated from memory,
>>> swap space */
>>> +#ifndef _KERNEL
>>> +#define MAP_ANONYMOUS MAP_ANON /* For compatibility. */
>>> +#endif /* !_KERNEL */
>>> /*
>>> * Extended flags
>>>
>
>
>
>
>> Yes. If no one objects in the next day or so, then please commit
>> this change.
>>
>
>
>> Alan
>>
>
> should this compatibility addition be documented in the mmap(2) manual?
>
>
I don't have a strong opinion one way or the other, but I would lean
toward "yes". That said, Solaris doesn't.
> any thoughts on the previous change request so mmap fails with MAP_ANON and
> pos=0?
>
>
Unfortunately, no. My FreeBSD time for the last few days has been spent
looking into some anomalies in wiring memory and writing breakpoints.
Alan
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