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References: <cover.1662459668.git.baskov@ispras.ru> <27a078f43742063cc30e706b196fb5fff5d5c37e.1662459668.git.baskov@ispras.ru>
In-Reply-To: <27a078f43742063cc30e706b196fb5fff5d5c37e.1662459668.git.baskov@ispras.ru>
From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Wed, 19 Oct 2022 09:01:26 +0200
Message-ID: <CAMj1kXGUvUwy__wD-DtHtpVMoCJsc=G2mvWLe2a7ib2ckqzpow@mail.gmail.com>
Subject: Re: [PATCH 01/16] x86/boot: Align vmlinuz sections on page size
To:     Evgeniy Baskov <baskov@ispras.ru>
Cc:     Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Alexey Khoroshilov <khoroshilov@ispras.ru>,
        lvc-project@linuxtesting.org, x86@kernel.org,
        linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org
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Precedence: bulk

On Tue, 6 Sept 2022 at 12:41, Evgeniy Baskov <baskov@ispras.ru> wrote:
>
> To protect sections on page table level each section
> needs to be aligned on page size (4KB).
>
> Set sections alignment in linker script.
>
> Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
> ---
>  arch/x86/boot/compressed/vmlinux.lds.S | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
> index 112b2375d021..6be90f1a1198 100644
> --- a/arch/x86/boot/compressed/vmlinux.lds.S
> +++ b/arch/x86/boot/compressed/vmlinux.lds.S
> @@ -27,21 +27,27 @@ SECTIONS
>                 HEAD_TEXT
>                 _ehead = . ;
>         }
> +       . = ALIGN(PAGE_SIZE);
>         .rodata..compressed : {
> +               _compressed = .;

Why are you adding these?

>                 *(.rodata..compressed)
> +               _ecompressed = .;
>         }
> +       . = ALIGN(PAGE_SIZE);

On other EFI architectures, we only distinguish between R-X and RW-
regions, and alignment between .rodata and .text is unnecessary. Do we
really need to deviate from that here?


>         .text : {
>                 _text = .;      /* Text */
>                 *(.text)
>                 *(.text.*)
>                 _etext = . ;
>         }
> +       . = ALIGN(PAGE_SIZE);
>         .rodata : {
>                 _rodata = . ;
>                 *(.rodata)       /* read-only data */
>                 *(.rodata.*)
>                 _erodata = . ;
>         }
> +       . = ALIGN(PAGE_SIZE);
>         .data : {
>                 _data = . ;
>                 *(.data)
> --
> 2.35.1
>