diff options
Diffstat (limited to 'exit.S')
| -rw-r--r-- | exit.S | 31 |
1 files changed, 31 insertions, 0 deletions
@@ -12,6 +12,15 @@ exit: /* Exit status to %eax */ movl 4(%esp), %eax + /* Calculate real-mode exit %ss:esp in %dx:%edi */ + xorw %dx, %dx + xorl %edi, %edi + movl exit_esp, %ebp + cmpl $EXIT_MAGIC, 0(%ebp) + jne 1f + movl 8(%ebp), %edi + movw 6(%ebp), %dx +1: /* Load IDT and GDT and switch to 16-bit code segment */ cli lidt idt_descr @@ -45,6 +54,24 @@ exit: /* Reenable interrupts */ sti + /* If we have a real-mode exit stack, restore registers + * (except exit status) and return + */ + testl %edi, %edi + jz reset + movw %dx, %ss + movl %edi, %esp + movw %sp, %bp + movl %eax, 36(%bp) + popw %ds + popw %es + popw %fs + popw %gs + popal + popfl + lret + +reset: /* Perform a warm reset */ movw $0x1234, %ax movw %ax, 0x472 @@ -79,3 +106,7 @@ gdt_descr: idt_descr: .word 0xffff .long 0 + +.globl exit_esp +exit_esp: + .long 0 |