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In-Reply-To: <8211c633eb5dceeabee2996a4db91cd971cf7c77.1671098103.git.baskov@ispras.ru>
From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Fri, 10 Mar 2023 15:43:34 +0100
Message-ID: <CAMj1kXFPtA4f3kW1U2-LAQFEuOvLsis=Ursj40xRrg-cvtK=gA@mail.gmail.com>
Subject: Re: [PATCH v4 01/26] 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>,
        Peter Jones <pjones@redhat.com>,
        "Limonciello, Mario" <mario.limonciello@amd.com>,
        joeyli <jlee@suse.com>, 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 Thu, 15 Dec 2022 at 13:38, 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.
>
> Tested-by: Mario Limonciello <mario.limonciello@amd.com>
> Tested-by: Peter Jones <pjones@redhat.com>
> 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 = .;
>                 *(.rodata..compressed)

Can you just move this bit into the rodata section below?

> +               _ecompressed = .;
>         }
> +       . = ALIGN(PAGE_SIZE);
>         .text : {

Please use

.text : ALIGN(PAGE_SIZE) {

which marks the section as being page aligned, rather than just being
placed on a 4k boundary.

>                 _text = .;      /* Text */
>                 *(.text)
>                 *(.text.*)
>                 _etext = . ;
>         }
> +       . = ALIGN(PAGE_SIZE);
>         .rodata : {
>                 _rodata = . ;
>                 *(.rodata)       /* read-only data */
>                 *(.rodata.*)
>                 _erodata = . ;
>         }
> +       . = ALIGN(PAGE_SIZE);
>         .data : {
>                 _data = . ;
>                 *(.data)
> --
> 2.37.4
>