| From | Joerg Roedel <> | Subject | [PATCH v3 12/75] x86/boot/compressed/64: Switch to __KERNEL_CS after GDT is loaded | Date | Tue, 28 Apr 2020 17:16:22 +0200 |
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From: Joerg Roedel <jroedel@suse.de>
When the pre-decompression code loads its first GDT in startup_64, it is still running on the CS value of the previous GDT. In the case of SEV-ES this is the EFI GDT.
To make exception handling work (especially IRET) the CPU needs to switch to a CS value in the current GDT, so jump to __KERNEL_CS after the first GDT is loaded.
Signed-off-by: Joerg Roedel <jroedel@suse.de> --- arch/x86/boot/compressed/head_64.S | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 4f7e6b84be07..6b11060c3a0f 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -393,6 +393,14 @@ SYM_CODE_START(startup_64) addq %rax, 2(%rax) lgdt (%rax) + /* Reload CS so IRET returns to a CS actually in the GDT */ + pushq $__KERNEL_CS + leaq .Lon_kernel_cs(%rip), %rax + pushq %rax + lretq + +.Lon_kernel_cs: + /* * paging_prepare() sets up the trampoline and checks if we need to * enable 5-level paging. -- 2.17.1
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