mmap/munmap with zero length

[Mel Flynn]

On Sun, 19 Jul 2009 22:13:48 -0800, Mel Flynn
<mel.flynn+fbsd.hackers at mailing.thruhere.net> wrote:
> On Mon, 13 Jul 2009 16:39:09 -0400, John Baldwin <jhb at freebsd.org> wrote:
>> On Monday 13 July 2009 3:33:51 pm Tijl Coosemans wrote:
>>> On Monday 13 July 2009 20:28:08 John Baldwin wrote:
>>> > On Sunday 05 July 2009 3:32:25 am Alexander Best wrote:
>>> >> so mmap differs from the POSIX recommendation right. the malloc.conf
>>> >> option seems more like a workaround/hack. imo it's confusing to have
>>> >> mmap und munmap deal differently with len=0. being able to
>>> >> succesfully alocate memory which cannot be removed doesn't seem
>>> >> logical to me.
>>> > 
>>> > This should fix it:
>>> > 
>>> > --- //depot/user/jhb/acpipci/vm/vm_mmap.c
>>> > +++ /home/jhb/work/p4/acpipci/vm/vm_mmap.c
>>> > @@ -229,7 +229,7 @@
>>> > 
>>> >         fp = NULL;
>>> >         /* make sure mapping fits into numeric range etc */
>>> > -       if ((ssize_t) uap->len < 0 ||
>>> > +       if ((ssize_t) uap->len <= 0 ||
>>> >             ((flags & MAP_ANON) && uap->fd != -1))
>>> >                 return (EINVAL);
>>> 
>>> Why not "uap->len == 0"? Sizes of 2GiB and more (32bit) shouldn't cause
>>> an error.
>> 
>> I don't actually disagree and know of locally modified versions of
> FreeBSD 
>> that remove this check for precisely that reason.
> 
> If this has hit the tree recently, I think it broke ccache.
> 
> Since I've also done make delete-old-libs and was about to rebuild all my
> ports on my laptop, I'll investigate, as I'm not looking forward to doing
> this twice for all dependants of libtool :(.
> 
> Failed to mmap
> /var/db/ccache/mel/tmp.cpp_stderr.smoochies.rachie.is-a-geek.net.27934
> 
> kdump:
>  27934 ccache   CALL  open(0x28201280,O_RDONLY,<unused>0x1)
>  27934 ccache   NAMI 
> "/var/db/ccache/mel/tmp.cpp_stderr.smoochies.rachie.is-a-geek.net.27934"
>  27934 ccache   RET   open 4
>  27934 ccache   CALL  fstat(0x4,0xbfbfe7fc)
>  27934 ccache   STRU  struct stat {dev=105, ino=895320, mode=-rw-r--r-- ,
> nlink=1, uid=1003, gid=0, rdev=0, atime=1248069251, stime=1248069251,
> ctime=1248069251, birthtime=1248069251, size=0, blksize=4096, blocks=0,
> flags=0x0 }
>  27934 ccache   RET   fstat 0
>  27934 ccache   CALL  mmap(0,0,PROT_READ,MAP_PRIVATE,0x4,0,0)
>  27934 ccache   RET   mmap -1 errno 22 Invalid argument

Confirmed, attached patch fixes ccache. Probably should be patched in
patch-md4.

-- 
Mel
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