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H A D | x86-stub.c | 800f84d8 Mon Dec 11 03:00:57 CST 2023 Ard Biesheuvel <ardb@kernel.org> efi/x86: Avoid physical KASLR on older Dell systems
[ Upstream commit 50d7cdf7a9b1ab6f4f74a69c84e974d5dc0c1bf1 ]
River reports boot hangs with v6.6 and v6.7, and the bisect points to commit
a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
which moves the memory allocation and kernel decompression from the legacy decompressor (which executes *after* ExitBootServices()) to the EFI stub, using boot services for allocating the memory. The memory allocation succeeds but the subsequent call to decompress_kernel() never returns, resulting in a failed boot and a hanging system.
As it turns out, this issue only occurs when physical address randomization (KASLR) is enabled, and given that this is a feature we can live without (virtual KASLR is much more important), let's disable the physical part of KASLR when booting on AMI UEFI firmware claiming to implement revision v2.0 of the specification (which was released in 2006), as this is the version these systems advertise.
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot") Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218173 Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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