Linux-EFI Archive on
 help / color / Atom feed
From: Jarkko Sakkinen <>
To: Kairui Song <>
	Ard Biesheuvel <>,
	Thomas Gleixner <>,
	Ingo Molnar <>, Borislav Petkov <>,
	Matthew Garrett <>,
	Baoquan He <>, Dave Young <>,,
Subject: Re: [PATCH v2] x86, efi: never relocate kernel below lowest acceptable address
Date: Wed, 25 Sep 2019 12:51:14 +0300
Message-ID: <> (raw)
In-Reply-To: <>

On Fri, Sep 20, 2019 at 12:05:21AM +0800, Kairui Song wrote:
> Currently, kernel fails to boot on some HyperV VMs when using EFI.
> And it's a potential issue on all platforms.
> It's caused a broken kernel relocation on EFI systems, when below three
> conditions are met:
> 1. Kernel image is not loaded to the default address (LOAD_PHYSICAL_ADDR)
>    by the loader.
> 2. There isn't enough room to contain the kernel, starting from the
>    default load address (eg. something else occupied part the region).
> 3. In the memmap provided by EFI firmware, there is a memory region
>    starts below LOAD_PHYSICAL_ADDR, and suitable for containing the
>    kernel.
> Efi stub will perform a kernel relocation when condition 1 is met. But
> due to condition 2, efi stub can't relocate kernel to the preferred
> address, so it fallback to query and alloc from EFI firmware for lowest
> usable memory region.
> It's incorrect to use the lowest memory address. In later stage, kernel
> will assume LOAD_PHYSICAL_ADDR as the minimal acceptable relocate address,
> but efi stub will end up relocating kernel below it.
> Then before the kernel decompressing. Kernel will do another relocation
> to address not lower than LOAD_PHYSICAL_ADDR, this time the relocate will
> over write the blockage at the default load address, which efi stub tried
> to avoid, and lead to unexpected behavior. Beside, the memory region it
> writes to is not allocated from EFI firmware, which is also wrong.
> To fix it, just don't let efi stub relocate the kernel to any address
> lower than lowest acceptable address.
> Signed-off-by: Kairui Song <>

Acked-by:  <>


  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-19 16:05 Kairui Song
2019-09-25  9:51 ` Jarkko Sakkinen [this message]
2019-09-25 15:25 ` Ard Biesheuvel
2019-09-25 17:36   ` Kairui Song
2019-10-11 10:18     ` Kairui Song
2019-10-11 13:23 ` Borislav Petkov
2019-10-12  3:46   ` Kairui Song

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-EFI Archive on

Archives are clonable:
	git clone --mirror linux-efi/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-efi linux-efi/ \
	public-inbox-index linux-efi

Example config snippet for mirrors

Newsgroup available over NNTP:

AGPL code for this site: git clone