linux-kernel - Re: [PATCH v8 01/15] x86/boot: Place kernel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <9d01a6d2-4dd9-4331-8fc9-b01c07cfdbb5@apertussolutions.com>
Date: Thu, 21 Mar 2024 09:45:48 -0400
From: "Daniel P. Smith" <dpsmith@...rtussolutions.com>
To: Ard Biesheuvel <ardb@...nel.org>,
 Ross Philipson <ross.philipson@...cle.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
 linux-integrity@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-crypto@...r.kernel.org, kexec@...ts.infradead.org,
 linux-efi@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
 bp@...en8.de, hpa@...or.com, dave.hansen@...ux.intel.com,
 mjg59@...f.ucam.org, James.Bottomley@...senpartnership.com,
 peterhuewe@....de, jarkko@...nel.org, jgg@...pe.ca, luto@...capital.net,
 nivedita@...m.mit.edu, herbert@...dor.apana.org.au, davem@...emloft.net,
 kanth.ghatraju@...cle.com, trenchboot-devel@...glegroups.com
Subject: Re: [PATCH v8 01/15] x86/boot: Place kernel_info at a fixed offset

Hi Ard!

On 2/15/24 02:56, Ard Biesheuvel wrote:
> On Wed, 14 Feb 2024 at 23:31, Ross Philipson <ross.philipson@...cle.com> wrote:
>>
>> From: Arvind Sankar <nivedita@...m.mit.edu>
>>
>> There are use cases for storing the offset of a symbol in kernel_info.
>> For example, the trenchboot series [0] needs to store the offset of the
>> Measured Launch Environment header in kernel_info.
>>
> 
> Why? Is this information consumed by the bootloader?

Yes, the bootloader needs a standardized means to find the offset of the 
MLE header, which communicates a set of meta-data needed by the DCE in 
order to set up for and start the loaded kernel. Arm will also need to 
provide a similar metadata structure and alternative entry point (or a 
complete rewrite of the existing entry point), as the current Arm entry 
point is in direct conflict with Arm DRTM specification.

> I'd like to get away from x86 specific hacks for boot code and boot
> images, so I would like to explore if we can avoid kernel_info, or at
> least expose it in a generic way. We might just add a 32-bit offset
> somewhere in the first 64 bytes of the bootable image: this could
> co-exist with EFI bootable images, and can be implemented on arm64,
> RISC-V and LoongArch as well.

With all due respect, I would not refer to boot params and the kern_info 
extension designed by the x86 maintainers as a hack. It is the 
well-defined boot protocol for x86, just as Arm has its own boot 
protocol around Device Tree.

We would gladly adopt a cross arch/cross image type, zImage and bzImage, 
means to embedded meta-data about the kernel that can be discovered by a 
bootloader. Otherwise, we are relegated to doing a per arch/per image 
type discovery mechanism. If you have any suggestions that are cross 
arch/cross image type that we could explore, we would be grateful and 
willing to investigate how to adopt such a method.

V/r,
Daniel