linux-kernel - [PATCH] x86/boot: Add back some padding for the CRC-32 checksum

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Message-ID: <20250312081204.521411-2-ardb+git@google.com>
Date: Wed, 12 Mar 2025 09:12:05 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org, hpa@...or.com, mingo@...nel.org, 
	Ard Biesheuvel <ardb@...nel.org>
Subject: [PATCH] x86/boot: Add back some padding for the CRC-32 checksum

From: Ard Biesheuvel <ardb@...nel.org>

Even though no uses of the bzImage CRC-32 checksum are known, ensure
that the last 4 bytes of the image are unused zero bytes, so that the
checksum can be generated post-build if needed.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
As requested by hpa, this applies onto today's tip/x86/build

 arch/x86/boot/compressed/vmlinux.lds.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
index 48d0b5184557..083ec6d7722a 100644
--- a/arch/x86/boot/compressed/vmlinux.lds.S
+++ b/arch/x86/boot/compressed/vmlinux.lds.S
@@ -48,7 +48,8 @@ SECTIONS
 		*(.data)
 		*(.data.*)
 
-		. = ALIGN(0x200);
+		/* Add 4 bytes of extra space for a CRC-32 checksum */
+		. = ALIGN(. + 4, 0x200);
 		_edata = . ;
 	}
 	. = ALIGN(L1_CACHE_BYTES);
-- 
2.49.0.rc0.332.g42c0ae87b1-goog