Re: [PATCH v5 21/38] uprobes: remove VM_IO, set VM_MIXEDMAP for mapped kernel pages

[David Hildenbrand (Arm)]

On 10/9/26 20:04, Lorenzo Stoakes (ARM) wrote:
> These are not MMIO pages so VMA_IO_BIT is an inappropriate flag to set.
> 
> Instead, set them VMA_MIXEDMAP_BIT as they are kernel mappings and this is
> the appropriate flag to set for those.
> 
> This provides the semantics required - no VMA merging is permitted, but
> does not prevent GUP.
> 
> However this has no meaningful impact as these are refcounted and thus can
> be GUPed.
> 
> A previous commit already prevented __mm_populate() from being invoked on
> XOL areas, which VMA_IO_BIT was previously relied upon to do, so that is no
> longer required.
> 
> Both VMAs set a VMA name, so always_dump_vma() returns true before
> vma_dump_size() reaches its VMA_IO_BIT check, and thus there is no change
> in core dump behaviour.
> 
> Change this for both the core xol_add_vma() function and the x86-specific
> get_uprobe_trampoline() function.
> 
> Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> ---
>  arch/x86/kernel/uprobes.c | 2 +-
>  kernel/events/uprobes.c   | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index 65a2de82ecd2..0f60c0d076b6 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -715,7 +715,7 @@ static struct vm_area_struct *get_uprobe_trampoline(struct mm_struct *mm, unsign
>  
>  	*new_mapping = true;
>  	return _install_special_mapping(mm, vaddr, PAGE_SIZE,
> -				VM_READ|VM_EXEC|VM_MAYEXEC|VM_MAYREAD|VM_IO,
> +				VM_READ|VM_EXEC|VM_MAYEXEC|VM_MAYREAD|VM_MIXEDMAP,
>  				&tramp_mapping);

So these can now be GUP'ed. Let's hope that's fine ;)

Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David