Re: question on [uprobes] special vma

[Oleg Nesterov]

Hi Jeff,

On 08/01, Jeff Xu wrote:
>
> __create_xol_area() calls  _install_special_mapping() to create a vma
> named [uprobes].
>
> I'm trying to find out the lifetime of this uprobes vma, e.g. when it
> is created, will it ever be unmapped/remapped/changed during the
> lifetime of the process.
>
> If  the uprobes vma remains the same during the lifetime of the
> process,

Yes,

> I can call mseal on it so user space can't change it, i.e.
> blocking munmap/mremap/mprotect/mmap, etc.

I didn't even know about mm/mseal.c...

at first glance do_mseal() just adds VM_SEALED for can_modify_vma().

So it seems that xol_add_vma() can just pass the additional VM_SEALED
flag to _install_special_mapping(), no?

But why it depends on CONFIG_64_BIT?

Oleg.