Re: [PATCHv3 3/8] mm: Pass down mm_struct to untagged_addr()

[Alexander Potapenko <glider@google.com>]

On Fri, Jun 10, 2022 at 4:35 PM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> Intel Linear Address Masking (LAM) brings per-mm untagging rules. Pass
> down mm_struct to the untagging helper. It will help to apply untagging
> policy correctly.
>
> In most cases, current->mm is the one to use, but there are some
> exceptions, such as get_user_page_remote().

Wouldn't it be easier to keep using current->mm in untagged_addr(addr)
by default, and introduce a separate macro for the exceptions?

>
> +/*
> + * Architectures that support memory tagging (assigning tags to memory regions,
> + * embedding these tags into addresses that point to these memory regions, and
> + * checking that the memory and the pointer tags match on memory accesses)
> + * redefine this macro to strip tags from pointers.
> + * It's defined as noop for architectures that don't support memory tagging.
> + */
> +#ifndef untagged_addr
> +#define untagged_addr(mm, addr) (addr)
> +#endif
The comment above should probably be extended to explain the effect of `mm`.




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Alexander Potapenko
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