Commit-ID: 9751d7627582fc1cc64625d63bde9528c14f1544 Gitweb: http://git.kernel.org/tip/9751d7627582fc1cc64625d63bde9528c14f1544 Author: H. Peter Anvin <hpa@xxxxxxxxx> AuthorDate: Thu, 21 Jun 2012 10:25:03 -0700 Committer: H. Peter Anvin <hpa@xxxxxxxxx> CommitDate: Thu, 21 Jun 2012 10:25:03 -0700 x86-64, reboot: Be more paranoid in 64-bit reboot=bios Be a bit more paranoid in the transition back to 16-bit mode. In particular, in case the kernel is residing above the 4 GiB mark, switch to the trampoline GDT, and make the jump after turning off paging a far jump. In theory, none of this should matter, but it is exactly the kind of things that broken SMM or virtualization software could trip up on. Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx> Link: http://lkml.kernel.org/r/tip-jopx7y6g6dbcx4tpal8q0jlr@xxxxxxxxxxxxxx --- arch/x86/realmode/rm/reboot.S | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/realmode/rm/reboot.S b/arch/x86/realmode/rm/reboot.S index 6bf8fea..f932ea6 100644 --- a/arch/x86/realmode/rm/reboot.S +++ b/arch/x86/realmode/rm/reboot.S @@ -22,14 +22,18 @@ ENTRY(machine_real_restart_asm) #ifdef CONFIG_X86_64 + /* Switch to trampoline GDT as it is guaranteed < 4 GiB */ + movl $__KERNEL_DS, %eax + movl %eax, %ds + lgdtl pa_tr_gdt /* Disable paging to drop us out of long mode */ movl %cr0, %eax andl $~X86_CR0_PG, %eax movl %eax, %cr0 - jmp 1f /* "A branch" may be needed here, assume near is OK */ + ljmpl $__KERNEL32_CS, $pa_machine_real_restart_paging_off -1: +GLOBAL(machine_real_restart_paging_off) xorl %eax, %eax xorl %edx, %edx movl $MSR_EFER, %ecx -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|