Hi Khalid,
On Fri, Oct 23, 2020 at 11:56:11AM -0600, Khalid Aziz wrote:
> diff --git a/arch/sparc/include/asm/mman.h b/arch/sparc/include/asm/mman.h
> index f94532f25db1..274217e7ed70 100644
> --- a/arch/sparc/include/asm/mman.h
> +++ b/arch/sparc/include/asm/mman.h
> @@ -57,35 +57,39 @@ static inline int sparc_validate_prot(unsigned long prot, unsigned long addr)
> {
> if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | PROT_ADI))
> return 0;
> - if (prot & PROT_ADI) {
> - if (!adi_capable())
> - return 0;
> + return 1;
> +}
We kept the equivalent of !adi_capable() check in the arm64
arch_validate_prot() and left arch_validate_flags() more relaxed. I.e.
you can pass PROT_MTE to mmap() even if the hardware doesn't support
MTE. This is in line with the pre-MTE ABI where unknown mmap() flags
would be ignored while mprotect() would reject them. This discrepancy
isn't nice but we decided to preserve the pre-MTE mmap ABI behaviour.
Anyway, it's up to you if you want to change the sparc behaviour, I
don't think it matters in practice.
I think with this patch, arch_validate_prot() no longer needs the 'addr'
argument. Maybe you can submit an additional patch to remove them (not
urgent, the compiler should get rid of them).
>
> - if (addr) {
> - struct vm_area_struct *vma;
> +#define arch_validate_flags(vm_flags) arch_validate_flags(vm_flags)
> +/* arch_validate_flags() - Ensure combination of flags is valid for a
> + * VMA.
> + */
> +static inline bool arch_validate_flags(unsigned long vm_flags)
> +{
> + /* If ADI is being enabled on this VMA, check for ADI
> + * capability on the platform and ensure VMA is suitable
> + * for ADI
> + */
> + if (vm_flags & VM_SPARC_ADI) {
> + if (!adi_capable())
> + return false;
>
> - vma = find_vma(current->mm, addr);
> - if (vma) {
> - /* ADI can not be enabled on PFN
> - * mapped pages
> - */
> - if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
> - return 0;
> + /* ADI can not be enabled on PFN mapped pages */
> + if (vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
> + return false;
>
> - /* Mergeable pages can become unmergeable
> - * if ADI is enabled on them even if they
> - * have identical data on them. This can be
> - * because ADI enabled pages with identical
> - * data may still not have identical ADI
> - * tags on them. Disallow ADI on mergeable
> - * pages.
> - */
> - if (vma->vm_flags & VM_MERGEABLE)
> - return 0;
> - }
> - }
> + /* Mergeable pages can become unmergeable
> + * if ADI is enabled on them even if they
> + * have identical data on them. This can be
> + * because ADI enabled pages with identical
> + * data may still not have identical ADI
> + * tags on them. Disallow ADI on mergeable
> + * pages.
> + */
> + if (vm_flags & VM_MERGEABLE)
> + return false;
Ah, you added a check to the madvise(MADV_MERGEABLE) path to ignore the
flag if VM_SPARC_ADI. On arm64 we intercept memcmp_pages() but we have a
PG_arch_2 flag to mark a page as containing tags. Either way should
work.
FWIW, if you are happy with the mmap() rejecting PROT_ADI on
!adi_capable() hardware:
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
