x86/decompressor: Store boot_params pointer in callee save register
authorArd Biesheuvel <ardb@kernel.org>
Mon, 7 Aug 2023 16:27:04 +0000 (18:27 +0200)
committerBorislav Petkov (AMD) <bp@alien8.de>
Mon, 7 Aug 2023 18:41:04 +0000 (20:41 +0200)
commit8b63cba746f86a754d66e302c43209cc9b9b6e39
tree62f16d7fea57b63d048c80b505333bc2621aaa91
parentd7156b986d4cc0657fa6dc05c9fcf51c3d55a0fe
x86/decompressor: Store boot_params pointer in callee save register

Instead of pushing and popping %RSI several times to preserve the struct
boot_params pointer across the execution of the startup code, move it
into a callee save register before the first call into C, and copy it
back when needed.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-8-ardb@kernel.org
arch/x86/boot/compressed/head_64.S