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x86/boot: Reload GDTR after copying to the end of the buffer

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The GDT may get overwritten during the copy or during extract_kernel,
which will cause problems if any segment register is touched before the
GDTR is reloaded by the decompressed kernel. For safety update the GDTR
to point to the GDT within the copied kernel.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-4-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Arvind Sankar 2020-02-02 12:13:49 -05:00 committed by Ard Biesheuvel
parent 90ff226281
commit 32d009137a
1 changed files with 10 additions and 0 deletions
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10
arch/x86/boot/compressed/head_64.S
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@ -439,6 +439,16 @@ trampoline_return:
cld
popq %rsi
/*
* The GDT may get overwritten either during the copy we just did or
* during extract_kernel below. To avoid any issues, repoint the GDTR
* to the new copy of the GDT.
*/
leaq gdt64(%rbx), %rax
subq %rbp, 2(%rax)
addq %rbx, 2(%rax)
lgdt (%rax)
/*
* Jump to the relocated address.
*/