Re: [PATCH v2] LoongArch: Libvtv add loongarch support.

[Caroline Tice <cmtice@google.com>]

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On Tue, Oct 11, 2022 at 7:52 PM Lulu Cheng <chenglulu@loongson.cn> wrote:

>
> 在 2022/10/12 上午4:57, Caroline Tice 写道:
>
> I think that if VTV_PAGE_SIZE is not set to the actual size being used by
> the system,  it could result in some unexpected failures.  I believe the
> right thing to do in this case, since the size may vary, is to get the
> actual size being used by the system and use that in the definition of
> VTV_PAGE_SIZE.  So in include/vtv-permission.h you would have something
> like:
>
> +#elif defined(__loongarch_lp64)
> +#define VTV_PAGE_SIZE sysconf(_SC_PAGE_SIZE)
>
> Then you would have the accurate, correct size for the current system, and
> there would be no need to update the
> check in vtv_malloc.cc at all.
>
>
>     /* Page-aligned symbol to mark beginning of .vtable_map_vars section.
> */
>     char _vtable_map_vars_start []
>     __attribute__ ((__visibility__ ("protected"), used,
> aligned(VTV_PAGE_SIZE),
>             section(".vtable_map_vars")))
>       = { };
>
> The above code is in the libgcc/vtv_start.c file. Alignment (aligned
> (alignment) ) must be an
> integer constant power of 2. So setting VTV_PAGE_SIZE as a variable is not
> advisable.
>
>
> As xiruoyao notes, the default value for the LoongArch Linux kernel
> configuration is 16KB.
>
> So let's set VTV_PAGE_SIZE to 16KB first and I will indicate in the
> submission information
>
> that only 16KB pages are supported.
>
>
> OK, that would work if you want to go that way.