When kernel starts in 64-bit mode we inherit GDT from a bootloader. It may cause a problem if the GDT doesn't have 32-bit code segment where we expect it to be. Load our own GDT with known segments. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> --- arch/x86/boot/compressed/head_64.S | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index c813cb004056..f0c3a2f7e528 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -313,6 +313,11 @@ ENTRY(startup_64) * first. */ + /* Make sure we have GDT with 32-bit code segment */ + leaq gdt(%rip), %rax + movq %rax, gdt64+2(%rip) + lgdt gdt64(%rip) + /* * paging_prepare() sets up the trampoline and checks if we need to * enable 5-level paging. @@ -547,6 +552,11 @@ no_longmode: #include "../../kernel/verify_cpu.S" .data +gdt64: + .word gdt_end - gdt + .long 0 + .word 0 + .quad 0 gdt: .word gdt_end - gdt .long gdt -- 2.16.1
