Re: [PATCH v2 02/12] mm: introduce execmem_text_alloc() and jit_text_alloc()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, Jun 26, 2023 at 5:31 AM Mark Rutland <mark.rutland@xxxxxxx> wrote:
>
[...]
> >
> > So the idea was that jit_text_alloc() will have a cache of large pages
> > mapped ROX, will allocate memory from those caches and there will be
> > jit_update() that uses text poking for writing to that memory.
> >
> > Upon allocation of a large page to increase the cache, that large page will
> > be "invalidated" by filling it with breakpoint instructions (e.g int3 on
> > x86)
>
> Does that work on x86?
>
> That is in no way gauranteed for other architectures; on arm64 you need
> explicit cache maintenance (with I-cache maintenance at the VA to be executed
> from) followed by context-synchronization-events (e.g. via ISB instructions, or
> IPIs).

I guess we need:
1) Invalidate unused part of the huge ROX pages;
2) Do not put two jit users (including module text, bpf, etc.) in the
same cache line;
3) Explicit cache maintenance;
4) context-synchronization-events.

Would these (or a subset of them) be sufficient to protect us from torn read?

Thanks,
Song





[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux