first commit

Based on x86/bios from lkvm

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

14 files changed, 642 insertions, 0 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..0fb6c95
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,27 @@
+obj16-y = e820.o int10.o int15.o
+obj-y = $(obj16-y) entry.o
+all-y = bios.bin
+
+BIOS_CFLAGS += -m32
+BIOS_CFLAGS += -march=i386
+BIOS_CFLAGS += -mregparm=3
+BIOS_CFLAGS += -fno-stack-protector
+BIOS_CFLAGS += -Iinclude
+$(obj16-y): BIOS_CFLAGS += -include code16gcc.h
+
+all: $(all-y)
+
+.PRECIOUS: %.o
+%.o: %.c
+	$(CC) $(CFLAGS) $(BIOS_CFLAGS) -c -s $< -o $@
+%.o: %.S
+	$(CC) $(CFLAGS) $(BIOS_CFLAGS) -c -s $< -o $@
+
+bios.bin.elf: $(obj-y) rom.ld.S
+	$(LD) -T rom.ld.S -o bios.bin.elf $(obj-y)
+
+bios.bin: bios.bin.elf
+	objcopy -O binary bios.bin.elf bios.bin
+
+clean:
+	rm $(obj-y) $(all-y) bios.bin.elf
diff --git a/code16gcc.h b/code16gcc.h
new file mode 100644
index 0000000..a4feb62
--- /dev/null
+++ b/code16gcc.h
@@ -0,0 +1,14 @@
+/*
+ * code16gcc.h
+ *
+ * This file is -include'd when compiling 16-bit C code.
+ * Note: this asm() needs to be emitted before gcc emits any code.
+ * Depending on gcc version, this requires -fno-unit-at-a-time or
+ * -fno-toplevel-reorder.
+ *
+ * Hopefully gcc will eventually have a real -m16 option so we can
+ * drop this hack long term.
+ */
+
+
+asm(".code16gcc");
diff --git a/e820.c b/e820.c
new file mode 100644
index 0000000..4eab157
--- /dev/null
+++ b/e820.c
@@ -0,0 +1,70 @@
+#include "bios.h"
+#include "segment.h"
+
+#include "processor-flags.h"
+#include "e820.h"
+
+static inline void set_fs(uint16_t seg)
+{
+	asm volatile("movw %0,%%fs" : : "rm" (seg));
+}
+
+static inline uint8_t rdfs8(unsigned long addr)
+{
+	uint8_t v;
+
+	asm volatile("addr32 movb %%fs:%1,%0" : "=q" (v) : "m" (*(uint8_t *)addr));
+
+	return v;
+}
+
+static inline uint32_t rdfs32(unsigned long addr)
+{
+	uint32_t v;
+
+	asm volatile("addr32 movl %%fs:%1,%0" : "=q" (v) : "m" (*(uint32_t *)addr));
+
+	return v;
+}
+
+bioscall void e820_query_map(struct biosregs *regs)
+{
+	struct e820map *e820;
+	uint32_t map_size;
+	uint16_t fs_seg;
+	uint32_t ndx;
+
+	e820		= (struct e820map *)E820_MAP_START;
+	fs_seg		= flat_to_seg16(E820_MAP_START);
+	set_fs(fs_seg);
+
+	ndx		= regs->ebx;
+
+	map_size	= rdfs32(flat_to_off16((uint32_t)&e820->nr_map, fs_seg));
+
+	if (ndx < map_size) {
+		uint32_t start;
+		unsigned int i;
+		uint8_t *p;
+
+		fs_seg	= flat_to_seg16(E820_MAP_START);
+		set_fs(fs_seg);
+
+		start	= (uint32_t)&e820->map[ndx];
+
+		p	= (void *) regs->edi;
+
+		for (i = 0; i < sizeof(struct e820entry); i++)
+			*p++	= rdfs8(flat_to_off16(start + i, fs_seg));
+	}
+
+	regs->eax	= SMAP;
+	regs->ecx	= sizeof(struct e820entry);
+	regs->ebx	= ++ndx;
+
+	/* Clear CF to indicate success.  */
+	regs->eflags	&= ~X86_EFLAGS_CF;
+
+	if (ndx >= map_size)
+		regs->ebx	= 0;	/* end of map */
+}
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
+
diff --git a/include/assembly.h b/include/assembly.h
new file mode 100644
index 0000000..3601024
--- /dev/null
+++ b/include/assembly.h
@@ -0,0 +1,29 @@
+#ifndef ASSEMBLY_H_
+#define ASSEMBLY_H_
+
+#define __ASSEMBLY__
+
+#define ORG(x)	\
+	.section .fixedaddr._##x
+
+#define __ALIGN	.p2align 4, 0x90
+#define ENTRY(name)	\
+	__ALIGN;	\
+	.globl name;	\
+	name:
+
+#define GLOBAL(name)	\
+	.globl name;	\
+	name:
+
+#define ENTRY_END(name)	GLOBAL(name##_end)
+#define END(name)	GLOBAL(name##_end)
+
+/*
+ * gas produces size override prefix with which
+ * we are unhappy, lets make it hardcoded for
+ * 16 bit mode
+ */
+#define IRET	.byte 0xcf
+
+#endif /* ASSEMBLY_H_ */
diff --git a/include/bios.h b/include/bios.h
new file mode 100644
index 0000000..153c887
--- /dev/null
+++ b/include/bios.h
@@ -0,0 +1,64 @@
+#ifndef BIOS_H_
+#define BIOS_H_
+
+#include <inttypes.h>
+
+/*
+ * X86-32 Memory Map (typical)
+ *					start      end
+ * Real Mode Interrupt Vector Table	0x00000000 0x000003FF
+ * BDA area				0x00000400 0x000004FF
+ * Conventional Low Memory		0x00000500 0x0009FBFF
+ * EBDA area				0x0009FC00 0x0009FFFF
+ * VIDEO RAM				0x000A0000 0x000BFFFF
+ * VIDEO ROM (BIOS)			0x000C0000 0x000C7FFF
+ * ROMs & unus. space (mapped hw & misc)0x000C8000 0x000EFFFF 160 KiB (typically)
+ * Motherboard BIOS			0x000F0000 0x000FFFFF
+ * Extended Memory			0x00100000 0xFEBFFFFF
+ * Reserved (configs, ACPI, PnP, etc)	0xFEC00000 0xFFFFFFFF
+ */
+
+#define REAL_MODE_IVT_BEGIN		0x00000000
+#define REAL_MODE_IVT_END		0x000003ff
+
+#define BDA_START			0x00000400
+#define BDA_END				0x000004ff
+
+#define EBDA_START			0x0009fc00
+#define EBDA_END			0x0009ffff
+
+#define E820_MAP_START			EBDA_START
+
+/*
+ * When interfacing with assembler code we need to be sure how
+ * arguments are passed in real mode.
+ */
+#define bioscall __attribute__((regparm(3)))
+
+#ifndef __ASSEMBLER__
+
+#include <linux/types.h>
+
+struct biosregs {
+	uint32_t			eax;
+	uint32_t			ebx;
+	uint32_t			ecx;
+	uint32_t			edx;
+	uint32_t			esp;
+	uint32_t			ebp;
+	uint32_t			esi;
+	uint32_t			edi;
+	uint32_t			ds;
+	uint32_t			es;
+	uint32_t			fs;
+	uint32_t			eip;
+	uint32_t			eflags;
+};
+
+extern bioscall void int10_handler(struct biosregs *regs);
+extern bioscall void int15_handler(struct biosregs *regs);
+extern bioscall void e820_query_map(struct biosregs *regs);
+
+#endif
+
+#endif /* BIOS_H_ */
diff --git a/include/const.h b/include/const.h
new file mode 100644
index 0000000..3d5213f
--- /dev/null
+++ b/include/const.h
@@ -0,0 +1,27 @@
+/* const.h: Macros for dealing with constants.  */
+
+#ifndef _LINUX_CONST_H
+#define _LINUX_CONST_H
+
+/* Some constant macros are used in both assembler and
+ * C code.  Therefore we cannot annotate them always with
+ * 'UL' and other type specifiers unilaterally.  We
+ * use the following macros to deal with this.
+ *
+ * Similarly, _AT() will cast an expression with a type in C, but
+ * leave it unchanged in asm.
+ */
+
+#ifdef __ASSEMBLY__
+#define _AC(X,Y)	X
+#define _AT(T,X)	X
+#else
+#define __AC(X,Y)	(X##Y)
+#define _AC(X,Y)	__AC(X,Y)
+#define _AT(T,X)	((T)(X))
+#endif
+
+#define BITUL(x)	(_AC(1,UL) << (x))
+#define BITULL(x)	(_AC(1,ULL) << (x))
+
+#endif /* !(_LINUX_CONST_H) */
diff --git a/include/e820.h b/include/e820.h
new file mode 100644
index 0000000..1dfd18f
--- /dev/null
+++ b/include/e820.h
@@ -0,0 +1,66 @@
+#ifndef _UAPI_ASM_X86_E820_H
+#define _UAPI_ASM_X86_E820_H
+
+#define SMAP    0x534d4150	/* ASCII "SMAP" */
+#define E820MAP	0x2d0		/* our map */
+#define E820MAX	128		/* number of entries in E820MAP */
+
+/*
+ * Legacy E820 BIOS limits us to 128 (E820MAX) nodes due to the
+ * constrained space in the zeropage.  If we have more nodes than
+ * that, and if we've booted off EFI firmware, then the EFI tables
+ * passed us from the EFI firmware can list more nodes.  Size our
+ * internal memory map tables to have room for these additional
+ * nodes, based on up to three entries per node for which the
+ * kernel was built: MAX_NUMNODES == (1 << CONFIG_NODES_SHIFT),
+ * plus E820MAX, allowing space for the possible duplicate E820
+ * entries that might need room in the same arrays, prior to the
+ * call to sanitize_e820_map() to remove duplicates.  The allowance
+ * of three memory map entries per node is "enough" entries for
+ * the initial hardware platform motivating this mechanism to make
+ * use of additional EFI map entries.  Future platforms may want
+ * to allow more than three entries per node or otherwise refine
+ * this size.
+ */
+
+#define E820_X_MAX E820MAX
+
+#define E820NR	0x1e8		/* # entries in E820MAP */
+
+#define E820_RAM	1
+#define E820_RESERVED	2
+#define E820_ACPI	3
+#define E820_NVS	4
+#define E820_UNUSABLE	5
+
+
+/*
+ * reserved RAM used by kernel itself
+ * if CONFIG_INTEL_TXT is enabled, memory of this type will be
+ * included in the S3 integrity calculation and so should not include
+ * any memory that BIOS might alter over the S3 transition
+ */
+#define E820_RESERVED_KERN        128
+
+struct e820entry {
+	uint64_t addr;	/* start of memory segment */
+	uint64_t size;	/* size of memory segment */
+	uint32_t type;	/* type of memory segment */
+} __attribute__((packed));
+
+struct e820map {
+	uint32_t nr_map;
+	struct e820entry map[E820_X_MAX];
+};
+
+#define ISA_START_ADDRESS	0xa0000
+#define ISA_END_ADDRESS		0x100000
+
+#define BIOS_BEGIN		0x000a0000
+#define BIOS_END		0x00100000
+
+#define BIOS_ROM_BASE		0xffe00000
+#define BIOS_ROM_END		0xffffffff
+
+
+#endif /* _UAPI_ASM_X86_E820_H */
diff --git a/include/processor-flags.h b/include/processor-flags.h
new file mode 100644
index 0000000..2725d27
--- /dev/null
+++ b/include/processor-flags.h
@@ -0,0 +1,153 @@
+#ifndef _UAPI_ASM_X86_PROCESSOR_FLAGS_H
+#define _UAPI_ASM_X86_PROCESSOR_FLAGS_H
+/* Various flags defined: can be included from assembler. */
+
+#include "const.h"
+
+/*
+ * EFLAGS bits
+ */
+#define X86_EFLAGS_CF_BIT	0 /* Carry Flag */
+#define X86_EFLAGS_CF		BITUL(X86_EFLAGS_CF_BIT)
+#define X86_EFLAGS_FIXED_BIT	1 /* Bit 1 - always on */
+#define X86_EFLAGS_FIXED	BITUL(X86_EFLAGS_FIXED_BIT)
+#define X86_EFLAGS_PF_BIT	2 /* Parity Flag */
+#define X86_EFLAGS_PF		BITUL(X86_EFLAGS_PF_BIT)
+#define X86_EFLAGS_AF_BIT	4 /* Auxiliary carry Flag */
+#define X86_EFLAGS_AF		BITUL(X86_EFLAGS_AF_BIT)
+#define X86_EFLAGS_ZF_BIT	6 /* Zero Flag */
+#define X86_EFLAGS_ZF		BITUL(X86_EFLAGS_ZF_BIT)
+#define X86_EFLAGS_SF_BIT	7 /* Sign Flag */
+#define X86_EFLAGS_SF		BITUL(X86_EFLAGS_SF_BIT)
+#define X86_EFLAGS_TF_BIT	8 /* Trap Flag */
+#define X86_EFLAGS_TF		BITUL(X86_EFLAGS_TF_BIT)
+#define X86_EFLAGS_IF_BIT	9 /* Interrupt Flag */
+#define X86_EFLAGS_IF		BITUL(X86_EFLAGS_IF_BIT)
+#define X86_EFLAGS_DF_BIT	10 /* Direction Flag */
+#define X86_EFLAGS_DF		BITUL(X86_EFLAGS_DF_BIT)
+#define X86_EFLAGS_OF_BIT	11 /* Overflow Flag */
+#define X86_EFLAGS_OF		BITUL(X86_EFLAGS_OF_BIT)
+#define X86_EFLAGS_IOPL_BIT	12 /* I/O Privilege Level (2 bits) */
+#define X86_EFLAGS_IOPL		(_AC(3,UL) << X86_EFLAGS_IOPL_BIT)
+#define X86_EFLAGS_NT_BIT	14 /* Nested Task */
+#define X86_EFLAGS_NT		BITUL(X86_EFLAGS_NT_BIT)
+#define X86_EFLAGS_RF_BIT	16 /* Resume Flag */
+#define X86_EFLAGS_RF		BITUL(X86_EFLAGS_RF_BIT)
+#define X86_EFLAGS_VM_BIT	17 /* Virtual Mode */
+#define X86_EFLAGS_VM		BITUL(X86_EFLAGS_VM_BIT)
+#define X86_EFLAGS_AC_BIT	18 /* Alignment Check/Access Control */
+#define X86_EFLAGS_AC		BITUL(X86_EFLAGS_AC_BIT)
+#define X86_EFLAGS_AC_BIT	18 /* Alignment Check/Access Control */
+#define X86_EFLAGS_AC		BITUL(X86_EFLAGS_AC_BIT)
+#define X86_EFLAGS_VIF_BIT	19 /* Virtual Interrupt Flag */
+#define X86_EFLAGS_VIF		BITUL(X86_EFLAGS_VIF_BIT)
+#define X86_EFLAGS_VIP_BIT	20 /* Virtual Interrupt Pending */
+#define X86_EFLAGS_VIP		BITUL(X86_EFLAGS_VIP_BIT)
+#define X86_EFLAGS_ID_BIT	21 /* CPUID detection */
+#define X86_EFLAGS_ID		BITUL(X86_EFLAGS_ID_BIT)
+
+/*
+ * Basic CPU control in CR0
+ */
+#define X86_CR0_PE_BIT		0 /* Protection Enable */
+#define X86_CR0_PE		BITUL(X86_CR0_PE_BIT)
+#define X86_CR0_MP_BIT		1 /* Monitor Coprocessor */
+#define X86_CR0_MP		BITUL(X86_CR0_MP_BIT)
+#define X86_CR0_EM_BIT		2 /* Emulation */
+#define X86_CR0_EM		BITUL(X86_CR0_EM_BIT)
+#define X86_CR0_TS_BIT		3 /* Task Switched */
+#define X86_CR0_TS		BITUL(X86_CR0_TS_BIT)
+#define X86_CR0_ET_BIT		4 /* Extension Type */
+#define X86_CR0_ET		BITUL(X86_CR0_ET_BIT)
+#define X86_CR0_NE_BIT		5 /* Numeric Error */
+#define X86_CR0_NE		BITUL(X86_CR0_NE_BIT)
+#define X86_CR0_WP_BIT		16 /* Write Protect */
+#define X86_CR0_WP		BITUL(X86_CR0_WP_BIT)
+#define X86_CR0_AM_BIT		18 /* Alignment Mask */
+#define X86_CR0_AM		BITUL(X86_CR0_AM_BIT)
+#define X86_CR0_NW_BIT		29 /* Not Write-through */
+#define X86_CR0_NW		BITUL(X86_CR0_NW_BIT)
+#define X86_CR0_CD_BIT		30 /* Cache Disable */
+#define X86_CR0_CD		BITUL(X86_CR0_CD_BIT)
+#define X86_CR0_PG_BIT		31 /* Paging */
+#define X86_CR0_PG		BITUL(X86_CR0_PG_BIT)
+
+/*
+ * Paging options in CR3
+ */
+#define X86_CR3_PWT_BIT		3 /* Page Write Through */
+#define X86_CR3_PWT		BITUL(X86_CR3_PWT_BIT)
+#define X86_CR3_PCD_BIT		4 /* Page Cache Disable */
+#define X86_CR3_PCD		BITUL(X86_CR3_PCD_BIT)
+#define X86_CR3_PCID_MASK	_AC(0x00000fff,UL) /* PCID Mask */
+
+/*
+ * Intel CPU features in CR4
+ */
+#define X86_CR4_VME_BIT		0 /* enable vm86 extensions */
+#define X86_CR4_VME		BITUL(X86_CR4_VME_BIT)
+#define X86_CR4_PVI_BIT		1 /* virtual interrupts flag enable */
+#define X86_CR4_PVI		BITUL(X86_CR4_PVI_BIT)
+#define X86_CR4_TSD_BIT		2 /* disable time stamp at ipl 3 */
+#define X86_CR4_TSD		BITUL(X86_CR4_TSD_BIT)
+#define X86_CR4_DE_BIT		3 /* enable debugging extensions */
+#define X86_CR4_DE		BITUL(X86_CR4_DE_BIT)
+#define X86_CR4_PSE_BIT		4 /* enable page size extensions */
+#define X86_CR4_PSE		BITUL(X86_CR4_PSE_BIT)
+#define X86_CR4_PAE_BIT		5 /* enable physical address extensions */
+#define X86_CR4_PAE		BITUL(X86_CR4_PAE_BIT)
+#define X86_CR4_MCE_BIT		6 /* Machine check enable */
+#define X86_CR4_MCE		BITUL(X86_CR4_MCE_BIT)
+#define X86_CR4_PGE_BIT		7 /* enable global pages */
+#define X86_CR4_PGE		BITUL(X86_CR4_PGE_BIT)
+#define X86_CR4_PCE_BIT		8 /* enable performance counters at ipl 3 */
+#define X86_CR4_PCE		BITUL(X86_CR4_PCE_BIT)
+#define X86_CR4_OSFXSR_BIT	9 /* enable fast FPU save and restore */
+#define X86_CR4_OSFXSR		BITUL(X86_CR4_OSFXSR_BIT)
+#define X86_CR4_OSXMMEXCPT_BIT	10 /* enable unmasked SSE exceptions */
+#define X86_CR4_OSXMMEXCPT	BITUL(X86_CR4_OSXMMEXCPT_BIT)
+#define X86_CR4_VMXE_BIT	13 /* enable VMX virtualization */
+#define X86_CR4_VMXE		BITUL(X86_CR4_VMXE_BIT)
+#define X86_CR4_SMXE_BIT	14 /* enable safer mode (TXT) */
+#define X86_CR4_SMXE		BITUL(X86_CR4_SMXE_BIT)
+#define X86_CR4_FSGSBASE_BIT	16 /* enable RDWRFSGS support */
+#define X86_CR4_FSGSBASE	BITUL(X86_CR4_FSGSBASE_BIT)
+#define X86_CR4_PCIDE_BIT	17 /* enable PCID support */
+#define X86_CR4_PCIDE		BITUL(X86_CR4_PCIDE_BIT)
+#define X86_CR4_OSXSAVE_BIT	18 /* enable xsave and xrestore */
+#define X86_CR4_OSXSAVE		BITUL(X86_CR4_OSXSAVE_BIT)
+#define X86_CR4_SMEP_BIT	20 /* enable SMEP support */
+#define X86_CR4_SMEP		BITUL(X86_CR4_SMEP_BIT)
+#define X86_CR4_SMAP_BIT	21 /* enable SMAP support */
+#define X86_CR4_SMAP		BITUL(X86_CR4_SMAP_BIT)
+
+/*
+ * x86-64 Task Priority Register, CR8
+ */
+#define X86_CR8_TPR		_AC(0x0000000f,UL) /* task priority register */
+
+/*
+ * AMD and Transmeta use MSRs for configuration; see <asm/msr-index.h>
+ */
+
+/*
+ *      NSC/Cyrix CPU configuration register indexes
+ */
+#define CX86_PCR0	0x20
+#define CX86_GCR	0xb8
+#define CX86_CCR0	0xc0
+#define CX86_CCR1	0xc1
+#define CX86_CCR2	0xc2
+#define CX86_CCR3	0xc3
+#define CX86_CCR4	0xe8
+#define CX86_CCR5	0xe9
+#define CX86_CCR6	0xea
+#define CX86_CCR7	0xeb
+#define CX86_PCR1	0xf0
+#define CX86_DIR0	0xfe
+#define CX86_DIR1	0xff
+#define CX86_ARR_BASE	0xc4
+#define CX86_RCR_BASE	0xdc
+
+
+#endif /* _UAPI_ASM_X86_PROCESSOR_FLAGS_H */
diff --git a/include/segment.h b/include/segment.h
new file mode 100644
index 0000000..694eb4b
--- /dev/null
+++ b/include/segment.h
@@ -0,0 +1,19 @@
+#ifndef KVM_SEGMENT_H
+#define KVM_SEGMENT_H
+
+static inline uint32_t segment_to_flat(uint16_t selector, uint16_t offset)
+{
+	return ((uint32_t)selector << 4) + (uint32_t) offset;
+}
+
+static inline uint16_t flat_to_seg16(uint32_t address)
+{
+	return address >> 4;
+}
+
+static inline uint16_t flat_to_off16(uint32_t address, uint32_t segment)
+{
+	return address - (segment << 4);
+}
+
+#endif /* KVM_SEGMENT_H */
diff --git a/int10.c b/int10.c
new file mode 100644
index 0000000..9d9604c
--- /dev/null
+++ b/int10.c
@@ -0,0 +1,43 @@
+#include "bios.h"
+#include "segment.h"
+
+static inline void outb(unsigned short port, unsigned char val)
+{
+	asm volatile("outb %0, %1" : : "a"(val), "Nd"(port));
+}
+
+/*
+ * It's probably much more useful to make this print to the serial
+ * line rather than print to a non-displayed VGA memory
+ */
+static inline void int10_putchar(struct biosregs *args)
+{
+	uint8_t al = args->eax & 0xFF;
+
+	outb(0x3f8, al);
+}
+
+#define VBE_STATUS_OK		0x004F
+#define VBE_STATUS_FAIL		0x014F
+
+static void int10_vesa(struct biosregs *args)
+{
+	args->eax = VBE_STATUS_FAIL;
+}
+
+bioscall void int10_handler(struct biosregs *args)
+{
+	uint8_t ah;
+
+	ah = (args->eax & 0xff00) >> 8;
+
+	switch (ah) {
+	case 0x0e:
+		int10_putchar(args);
+		break;
+	case 0x4f:
+		int10_vesa(args);
+		break;
+	}
+
+}
diff --git a/int15.c b/int15.c
new file mode 100644
index 0000000..d8ff820
--- /dev/null
+++ b/int15.c
@@ -0,0 +1,16 @@
+#include "bios.h"
+
+#include "processor-flags.h"
+
+bioscall void int15_handler(struct biosregs *regs)
+{
+	switch (regs->eax) {
+	case 0xe820:
+		e820_query_map(regs);
+		break;
+	default:
+		/* Set CF to indicate failure.  */
+		regs->eflags	|= X86_EFLAGS_CF;
+		break;
+	}
+}
diff --git a/memcpy.o b/memcpy.o
new file mode 100644
index 0000000..d24e386
--- /dev/null
+++ b/memcpy.o
diff --git a/rom.ld.S b/rom.ld.S
new file mode 100644
index 0000000..04f2ff9
--- /dev/null
+++ b/rom.ld.S
@@ -0,0 +1,19 @@
+OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
+OUTPUT_ARCH(i386)
+
+SECTIONS {
+	.text 0	: {
+		*(.text)
+		. = 0xfff0 ;
+		*(.fixedaddr._fff0)
+		. = 0x10000 ;
+	}
+
+	/DISCARD/ : {
+		*(.debug*)
+		*(.data)
+		*(.bss)
+		*(.eh_frame*)
+	}
+}
+