From: Will Deacon <will@kernel.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: mark.rutland@arm.com, catalin.marinas@arm.com,
james.morse@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/4] arm64: omit [_text, _stext) from permanent kernel mapping
Date: Wed, 28 Oct 2020 14:10:48 +0000 [thread overview]
Message-ID: <20201028141048.GC28554@willie-the-truck> (raw)
In-Reply-To: <20201027073209.2897-3-ardb@kernel.org>
On Tue, Oct 27, 2020 at 08:32:07AM +0100, Ard Biesheuvel wrote:
> In a previous patch, we increased the size of the EFI PE/COFF header
> to 64 KB, which resulted in the _stext symbol to appear at a fixed
> offset of 64 KB into the image.
>
> Since 64 KB is also the largest page size we support, this completely
> removes the need to map the first 64 KB of the kernel image, given that
> it only contains the arm64 Image header and the EFI header, none of which
> we ever access again after booting the kernel. More importantly, we should
> avoid an executable mapping of non-executable and not entirely predictable
> data, in the unlikely event that we emitted something that looks like an
> opcode that could be used as a gadget for speculative execution.
>
> So let's limit the kernel mapping of .text to the [_stext, _etext) region,
> which matches the view of generic code (such as kallsyms) when it reasons
> about the boundaries of the kernel's .text section.
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> arch/arm64/kernel/efi-header.S | 7 -------
> arch/arm64/kernel/setup.c | 4 ++--
> arch/arm64/kernel/vmlinux.lds.S | 2 +-
> arch/arm64/mm/init.c | 2 +-
> arch/arm64/mm/mmu.c | 10 +++++-----
> 5 files changed, 9 insertions(+), 16 deletions(-)
Acked-by: Will Deacon <will@kernel.org>
Will
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next prev parent reply other threads:[~2020-10-28 14:11 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-27 7:32 [PATCH 0/4] arm64: head: pad Image header to 64 KB and unmap it Ard Biesheuvel
2020-10-27 7:32 ` [PATCH 1/4] arm64: efi: increase EFI PE/COFF header padding to 64 KB Ard Biesheuvel
2020-10-27 7:32 ` [PATCH 2/4] arm64: omit [_text, _stext) from permanent kernel mapping Ard Biesheuvel
2020-10-28 14:10 ` Will Deacon [this message]
2020-10-27 7:32 ` [PATCH 3/4] arm64/head: avoid symbol names pointing into first 64 KB of kernel image Ard Biesheuvel
2020-10-28 14:12 ` Will Deacon
2020-10-27 7:32 ` [PATCH 4/4] arm64: head: tidy up the Image header definition Ard Biesheuvel
2020-10-28 14:17 ` Will Deacon
2020-10-28 17:56 ` Robin Murphy
2020-10-29 7:30 ` Ard Biesheuvel
2020-10-29 13:06 ` Robin Murphy
2020-11-03 7:13 ` Ard Biesheuvel
2020-11-04 11:29 ` Robin Murphy
2020-10-28 15:12 ` [PATCH 0/4] arm64: head: pad Image header to 64 KB and unmap it Will Deacon
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