Re: firefox on aarch64

[maya%NetBSD.org@localhost]

On Tue, Aug 04, 2020 at 04:15:36PM +0200, Tobias Nygren wrote:
> On Sun, 2 Aug 2020 19:00:33 +0000
> maya%NetBSD.org@localhost wrote:
> 
> >    162      1 node     CALL  mmap(0x35140000,0x7f000,PROT_NONE,0x1042<PRIVATE,NORESERVE,ANONYMOUS,ALIGN=NONE>,0xffffffff,0,0)
> >    162      1 node     RET   mmap -1 errno 12 Cannot allocate memory
> >    162      1 node     CALL  mmap(0x35140000,0x7f000,PROT_NONE,0x1042<PRIVATE,NORESERVE,ANONYMOUS,ALIGN=NONE>,0xffffffff,0,0)
> >    162      1 node     RET   mmap -1 errno 12 Cannot allocate memory
> 
> There's no obvious reason why the kernel would ENOMEM for such a small
> allocation. It is interesting that it does two consecutive failing calls
> to mmap with the same hint address. Possibly race condition in the mmap
> syscall?
> 
> -Tobias

mlelstv provided this smaller test case.
Sorry, I ended up making it into a bug report and did not update the
thread.

He says mmapping a mapped address fails on aarch64 but not amd64.

#include <stdio.h>
#include <err.h>
#include <sys/mman.h>

int main()
{
        void *p;

        p = (void *) mmap;

        p = mmap(p,0x7f000,PROT_NONE,MAP_PRIVATE | MAP_NORESERVE | MAP_ANONYMOUS, 0xffffffff, 0);
        if (p == MAP_FAILED)
                err(1,"mmap");

        printf("mmap = %p\n", p);

        return 0;
}