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Thu, 11 Sep 2025 10:07:55 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: Atl5U7xjKeAs Date: Thu, 11 Sep 2025 16:07:33 +0200 From: "Hugo Osvaldo Barrera" To: "Ard Biesheuvel" Cc: "Bagas Sanjaya" , "Linux Kernel Mailing List" , "Linux Documentation" , "Linux EFI" , "Jonathan Corbet" , "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Dave Hansen" , x86@kernel.org, "H. Peter Anvin" Message-Id: <4f36eee9-7e25-4e2f-ab9d-82f9732d0bf1@app.fastmail.com> In-Reply-To: References: <20250910015738.14848-2-bagasdotme@gmail.com> Subject: Re: [PATCH] x86/Documentation: explain LINUX_EFI_INITRD_MEDIA_GUID Content-Type: text/plain Content-Transfer-Encoding: 7bit On Thu, 11 Sep 2025, at 14:49, Ard Biesheuvel wrote: > On Thu, 11 Sept 2025 at 13:23, Hugo Osvaldo Barrera wrote: >> >> >> >> On Thu, 11 Sep 2025, at 08:46, Ard Biesheuvel wrote: >> > On Wed, 10 Sept 2025 at 03:58, Bagas Sanjaya wrote: >> >> >> >> From: Hugo Osvaldo Barrera >> >> > ... >> >> +For sample implementations, refer to `the original u-boot implementation`_ or >> >> +`the implementation in candyboot`_. >> >> + >> >> +.. _the original u-boot implementation: https://github.com/u-boot/u-boot/commit/ec80b4735a593961fe701cc3a5d717d4739b0fd0 >> >> +.. _the implementation in candyboot: https://git.sr.ht/~whynothugo/candyboot/tree/4097b2538d7f1cf85f03922bf42409490b666202/item/src/main.rs#L225 >> >> >> > >> > What is candyboot, and why are we adding this plug for it into the >> > Linux documentation? >> >> It's a UEFI stub loader which can load the Linux kernel and provide it with an >> initramfs using the above described protocol. >> >> The original version of this patch was based on my notes researching _how_ >> to implement this stub loader. The implementation is quite minimal, so I think >> it serves as a useful reference example. >> > > I think one example reference is sufficient, and I think piggybacking > a plug of your own project onto a documentation refactoring patch is > slightly dodgy, to be completely honest. I don't know what kind of reaction you're expecting. The documentation improvements were a side-effect of developing candyboot. You're free to exclude the mention if you feel it is inadequate, but I don't appreciate the personal attack. > Where is candyboot used, and what does it add to the existing u-boot > reference, which is the most widely used EFI implementation after EDK2 > for non-x86 systems? candyboot can be used to produce a single bootable UEFI binary bundling the kernel, cmdline and initrd. This binary can be signed to boot using SecureBoot on regular consumer hardware. It is typically useful is situations where u-boot isn't supported, and useless in most situations where u-boot is usable. The use-case is somewhat tangential here; the reference is merely as a minimal (single file) reference implementation of the feature being described here. > If anything, we should be referring to the OVMF implementation here. Agreed (I didn't know of its existence), here's a link to it: https://github.com/tianocore/edk2/blob/502f0dfda4f2c4d1cc091f68b6467b6ef12cab45/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c#L908 -- Hugo