freebsd stable - Oct 2020 - mmap and MAP_STACK

On Wed, Oct 21, 2020 at 04:53:11PM +0300, Nick Kostirya via freebsd-stable
wrote:
> Hello.
> I have question about mmap.
> 
> void *OSMem::AllocateDataArea(size_t &space)
> {
>     // Round up to an integral number of pages.
>     space = (space + pageSize-1) & ~(pageSize-1);
>     int fd = -1; // This value is required by FreeBSD.  Linux doesn't
care
>     int flags = MAP_PRIVATE | MAP_ANON;
> #ifdef MAP_STACK
>     if (memUsage == UsageStack) flags |= MAP_STACK; // OpenBSD seems to
require this
> #endif
>     void *result = mmap(0, space, PROT_READ|PROT_WRITE, flags, fd, 0);
>     // Convert MAP_FAILED (-1) into NULL
>     if (result == MAP_FAILED)
>         return 0;
>     return result;
> }
> 
> 
> When MAP_STACK is used, "insufficient memory" error occurs.
> When MAP_STACK removed, it is all right.
> 
> Please tell me why.
Show ktrace/kdump output of the mmap(2) without and with MAP_STACK.

Or provide a minimal self-contained C source that demonstrates your
issue.

On Wed, 21 Oct 2020 17:16:57 +0300
Konstantin Belousov <kostikbel at gmail.com> wrote:
> On Wed, Oct 21, 2020 at 04:53:11PM +0300, Nick Kostirya via freebsd-stable
wrote:
> > Hello.
> > I have question about mmap.
> > 
> > void *OSMem::AllocateDataArea(size_t &space)
> > {
> >     // Round up to an integral number of pages.
> >     space = (space + pageSize-1) & ~(pageSize-1);
> >     int fd = -1; // This value is required by FreeBSD.  Linux
doesn't care
> >     int flags = MAP_PRIVATE | MAP_ANON;
> > #ifdef MAP_STACK
> >     if (memUsage == UsageStack) flags |= MAP_STACK; // OpenBSD seems
to require this
> > #endif
> >     void *result = mmap(0, space, PROT_READ|PROT_WRITE, flags, fd, 0);
> >     // Convert MAP_FAILED (-1) into NULL
> >     if (result == MAP_FAILED)
> >         return 0;
> >     return result;
> > }
> > 
> > 
> > When MAP_STACK is used, "insufficient memory" error occurs.
> > When MAP_STACK removed, it is all right.
> > 
> > Please tell me why.  
> Show ktrace/kdump output of the mmap(2) without and with MAP_STACK.
> 
> Or provide a minimal self-contained C source that demonstrates your
> issue.
kdump with MAP_STACK.

 87183 polyimport CALL 
mmap(0,0x1000,0x3<PROT_READ|PROT_WRITE>,0x1402<MAP_PRIVATE|MAP_STACK|MAP_ANON>,0xffffffff,0,0)
 87183 polyimport RET   mmap -1 errno 22 Invalid argument


kdump without MAP_STACK.

 93712 polyimport CALL 
mmap(0,0x1000,0x3<PROT_READ|PROT_WRITE>,0x1002<MAP_PRIVATE|MAP_ANON>,0xffffffff,0,0)
 93712 polyimport RET   mmap 547053568/0x209b6000