first commit

Based on x86/bios from lkvm

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 95 insertions, 0 deletions

diff --git a/entry.S b/entry.S
new file mode 100644
index 0000000..a192c7d
--- /dev/null
+++ b/entry.S
@@ -0,0 +1,95 @@
+/*
+ * Our pretty trivial BIOS emulation
+ */
+
+#include "assembly.h"
+#include "processor-flags.h"
+
+	.org 0
+	.code16gcc
+
+/*
+ * handy BIOS macros
+ */
+
+/* If you change these macros, remember to update 'struct biosregs' */
+.macro SAVE_BIOSREGS
+	pushl	%fs
+	pushl	%es
+	pushl	%ds
+	pushl	%edi
+	pushl	%esi
+	pushl	%ebp
+	pushl	%esp
+	pushl	%edx
+	pushl	%ecx
+	pushl	%ebx
+	pushl	%eax
+.endm
+
+.macro RESTORE_BIOSREGS
+	popl	%eax
+	popl	%ebx
+	popl	%ecx
+	popl	%edx
+	popl	%esp
+	popl	%ebp
+	popl	%esi
+	popl	%edi
+	popl	%ds
+	popl	%es
+	popl	%fs
+.endm
+
+/*
+ * fake interrupt handler, nothing can be faster ever
+ */
+ENTRY(bios_intfake)
+	/*
+	 * Set CF to indicate failure. We don't want callers to think that the
+	 * interrupt handler succeeded and then treat the return values in
+	 * registers as valid data.
+	 */
+	orl	$X86_EFLAGS_CF, 0x4(%esp)
+
+	IRET
+ENTRY_END(bios_intfake)
+
+/*
+ * int 10 - video - service
+ */
+ENTRY(bios_int10)
+	SAVE_BIOSREGS
+
+	movl		%esp, %eax
+	/* this is way easier than doing it in assembly */
+	/* just push all the regs and jump to a C handler */
+	call	int10_handler
+
+	RESTORE_BIOSREGS
+
+	/* Clear CF to indicate success.  */
+	andl	$~X86_EFLAGS_CF, 0x4(%esp)
+
+	IRET
+ENTRY_END(bios_int10)
+
+ENTRY(bios_int15)
+	SAVE_BIOSREGS
+
+	movl	%esp, %eax
+	call	int15_handler
+
+	RESTORE_BIOSREGS
+
+	IRET
+ENTRY_END(bios_int15)
+
+ENTRY(real_entry)
+	cli
+	hlt
+ENTRY_END(real_entry)
+
+	ORG(fff0)
+	jmp	real_entry
+