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List:       linux-hardening
Subject:    Re: [PATCH v4 22/26] arm64: mm: move ro_after_init section into the data segment
From:       Ard Biesheuvel <ardb () kernel ! org>
Date:       2022-06-16 16:31:55
Message-ID: CAMj1kXG8mWVkrGtb-eSASrOBK4BiMF1b5XUui2cVt33xi23Mwg () mail ! gmail ! com
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On Thu, 16 Jun 2022 at 18:18, Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Jun 16, 2022 at 01:31:23PM +0200, Ard Biesheuvel wrote:
> > We used to have
> >
> > text
> > --
> > rodata
> > (ro_after_init)
> > --
> > inittext
> > --
> > initdata
> > --
> > data
> > bss
> >
> > where -- are the segment boundaries, which are always aligned to 64k on arm64
> >
> > After this patch, we get
> >
> > text
> > --
> > rodata
> > --
> > inittext
> > --
> > initdata
> > --
> > (ro_after_init)
> > data
> > bss
> >
> > so in terms of padding due to alignment, there is not a lot of difference.
>
> But how is ro_after_init read-only and data isn't, if there isn't a
> segment alignment to make that work out?
>

Actually, there is a segment alignment between ro_after_init and data
- my diagram is inaccurate. But we don't actually need that to remap
this slice of memory r/o
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