Re: [PATCHv4 02/13] uprobes/x86: Remove struct uprobe_trampoline object

[Oleg Nesterov <oleg@redhat.com>]

On 06/25, Jiri Olsa wrote:
>
> On Wed, Jun 24, 2026 at 04:36:23PM +0200, Oleg Nesterov wrote:
> >
> > Perhaps we can later optimize this code a bit? I mean something like
> >
> > 	start_reachable = ...;
> > 	end_reachable = ...;
> >
> > 	VMA_ITERATOR(vmi, mm, start_reachable);
> >
> > 	for_each_vma(vmi, vma) {
> > 		if (!vma_is_special_mapping(...))
> > 			continue;
> > 		if (vma->vm_start > end_reachable)
> > 			break;
> > 		return vma;
> > 	}
>
> looks good, will try to use that

See my next email, we can use for_each_vma_range().

But let me repeat, we can add this mimor optimization later, I don't want
to delay this series.

> > >  static int __arch_uprobe_optimize(struct arch_uprobe *auprobe, struct mm_struct *mm,
> > >  				  unsigned long vaddr)
> > >  {
> > > -	struct uprobe_trampoline *tramp;
> > > -	struct vm_area_struct *vma;
> > > -	bool new = false;
> > > -	int err = 0;
> > > +	struct pt_regs *regs = task_pt_regs(current);
> > > +	struct vm_area_struct *vma, *tramp;
> > >
> > > +	if (!user_64bit_mode(regs))
> > > +		return -EINVAL;
> > >  	vma = find_vma(mm, vaddr);
> > >  	if (!vma)
> > >  		return -EINVAL;
> >
> > I guess find_vma() can't fail, the caller arch_uprobe_optimize() has called
> > copy_from_vaddr() under mmap_write_lock()... Nevermind.
>
> hum, how's that.. I'll check, but where's the magic? :)

arch_uprobe_optimize() -> copy_from_vaddr() reads this mm at the same vaddr,
this means that vma at this vaddr must exist. Unless I am totally confused ;)
But even if I am right please ignore. I just tried to understand if find_vma()
can fail or not here.

Oleg.