x86/boot/compressed/64: Reload CS in startup_32

Exception handling in the startup_32 boot path requires the CS
selector to be correctly set up. Reload it from the current GDT.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210312123824.306-4-joro@8bytes.org

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index e94874f4bbc1d2e563ba76fd74145a8e137b2fc7..c59c80ca546d7371aa15c3182e92148441635c2b 100644 (file)
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -107,9 +107,16 @@ SYM_FUNC_START(startup_32)
        movl    %eax, %gs
        movl    %eax, %ss
 
-/* setup a stack and make sure cpu supports long mode. */
+       /* Setup a stack and load CS from current GDT */
        leal    rva(boot_stack_end)(%ebp), %esp
 
+       pushl   $__KERNEL32_CS
+       leal    rva(1f)(%ebp), %eax
+       pushl   %eax
+       lretl
+1:
+
+       /* Make sure cpu supports long mode. */
        call    verify_cpu
        testl   %eax, %eax
        jnz     .Lno_longmode