func Loop(
vm *platform.Vm,
vcpu *platform.Vcpu,
model *machine.Model,
tracer *loader.Tracer) error {
// It's not really kosher to switch threads constantly when running a
// KVM VCPU. So we simply lock this goroutine to a single system
// thread. That way we know it won't be bouncing around.
runtime.LockOSThread()
defer runtime.UnlockOSThread()
log.Printf("Vcpu[%d] running.", vcpu.Id)
for {
// Enter the guest.
err := vcpu.Run()
// Trace if requested.
trace_err := tracer.Trace(vcpu, vcpu.IsStepping())
if trace_err != nil {
return trace_err
}
// No reason for exit?
if err == nil {
return ExitWithoutReason
}
// Handle the error.
switch err.(type) {
case *platform.ExitPio:
err = model.HandlePio(vm, err.(*platform.ExitPio))
case *platform.ExitMmio:
err = model.HandleMmio(vm, err.(*platform.ExitMmio))
case *platform.ExitDebug:
err = nil
case *platform.ExitShutdown:
// Vcpu shutdown.
return nil
}
// Error handling the exit.
if err != nil {
return err
}
}
// Unreachable.
return nil
}
func (tracer *Tracer) toPaddr(
vcpu *platform.Vcpu,
reg platform.RegisterValue) string {
phys_addr, valid, _, _, err := vcpu.Translate(platform.Vaddr(reg))
if err != nil {
return "%x->??"
}
if valid {
return fmt.Sprintf("%x->%x", reg, phys_addr)
}
return fmt.Sprintf("%x", reg)
}
func (tracer *Tracer) Trace(vcpu *platform.Vcpu, step bool) error {
// Are we on?
if !tracer.enabled {
return nil
}
// Get the current instruction.
addr, err := vcpu.GetRegister(tracer.convention.instruction)
if err != nil {
return err
}
// Skip duplicates (only if stepping is on).
if step && platform.Vaddr(addr) == tracer.last_addr {
return nil
}
// Lookup the current instruction.
var fname string
var offset uint64
if tracer.sysmap != nil {
fname, offset = tracer.sysmap.Lookup(platform.Vaddr(addr))
}
// Get the stack depth.
stack, err := vcpu.GetRegister(tracer.convention.stack)
if err != nil {
return err
}
// Print the return value if applicable.
if step &&
fname != tracer.last_fname &&
tracer.last_addr != 0 {
rval, err := vcpu.GetRegister(tracer.convention.rvalue)
if err != nil {
return err
}
log.Printf(" trace: [%08x] %s => %s ?",
stack,
tracer.last_fname,
tracer.toPaddr(vcpu, rval))
// Save the current.
tracer.last_fname = fname
}
// Get a physical address string.
rip_phys_str := tracer.toPaddr(vcpu, addr)
if fname != "" {
if offset == 0 {
num_args := len(tracer.convention.arguments)
arg_vals := make([]string, num_args, num_args)
for i, reg := range tracer.convention.arguments {
reg_val, err := vcpu.GetRegister(reg)
if err != nil {
arg_vals[i] = fmt.Sprintf("??")
continue
}
arg_vals[i] = tracer.toPaddr(vcpu, reg_val)
}
log.Printf(" trace: [%08x] %s:%s(%s)",
stack,
fname,
rip_phys_str,
strings.Join(arg_vals, ","))
} else {
log.Printf(" trace: [%08x] %s:%s ... +%x",
stack,
fname,
rip_phys_str,
offset)
}
} else {
log.Printf(" trace: ??:%s", rip_phys_str)
}
// We're okay.
tracer.last_addr = platform.Vaddr(addr)
return nil
}
func SetupLinux(
vcpu *platform.Vcpu,
model *machine.Model,
orig_boot_data []byte,
entry_point uint64,
is_64bit bool,
initrd_addr platform.Paddr,
initrd_len uint64,
cmdline_addr platform.Paddr) error {
// Copy in the GDT table.
// These match the segments below.
gdt_addr, gdt, err := model.Allocate(
machine.MemoryTypeUser,
0, // Start.
model.Max(), // End.
platform.PageSize, // Size.
false) // From bottom.
if err != nil {
return err
}
if is_64bit {
C.build_64bit_gdt(unsafe.Pointer(&gdt[0]))
} else {
C.build_32bit_gdt(unsafe.Pointer(&gdt[0]))
}
BootGdt := platform.DescriptorValue{
Base: uint64(gdt_addr),
Limit: uint16(platform.PageSize),
}
err = vcpu.SetDescriptor(platform.GDT, BootGdt, true)
if err != nil {
return err
}
// Set a null IDT.
BootIdt := platform.DescriptorValue{
Base: 0,
Limit: 0,
}
err = vcpu.SetDescriptor(platform.IDT, BootIdt, true)
if err != nil {
return err
}
// Enable protected-mode.
// This does not set any flags (e.g. paging) beyond the
// protected mode flag. This is according to Linux entry
// protocol for 32-bit protected mode.
cr0, err := vcpu.GetControlRegister(platform.CR0)
if err != nil {
return err
}
cr0 = cr0 | (1 << 0) // Protected mode.
err = vcpu.SetControlRegister(platform.CR0, cr0, true)
if err != nil {
return err
}
// Always have the PAE bit set.
cr4, err := vcpu.GetControlRegister(platform.CR4)
if err != nil {
return err
}
cr4 = cr4 | (1 << 5) // PAE enabled.
err = vcpu.SetControlRegister(platform.CR4, cr4, true)
if err != nil {
return err
}
// For 64-bit kernels, we need to enable long mode,
// and load an identity page table. This will require
// only a page of pages, as we use huge page sizes.
if is_64bit {
// Create our page tables.
pde_addr, pde, err := model.Allocate(
machine.MemoryTypeUser,
0, // Start.
model.Max(), // End.
platform.PageSize, // Size.
false) // From bottom.
if err != nil {
return err
}
pgd_addr, pgd, err := model.Allocate(
machine.MemoryTypeUser,
0, // Start.
model.Max(), // End.
platform.PageSize, // Size.
false) // From bottom.
if err != nil {
return err
}
pml4_addr, pml4, err := model.Allocate(
machine.MemoryTypeUser,
0, // Start.
model.Max(), // End.
platform.PageSize, // Size.
false) // From bottom.
if err != nil {
return err
}
C.build_pde(unsafe.Pointer(&pde[0]), platform.PageSize)
C.build_pgd(unsafe.Pointer(&pgd[0]), C.__u64(pde_addr), platform.PageSize)
C.build_pml4(unsafe.Pointer(&pml4[0]), C.__u64(pgd_addr), platform.PageSize)
log.Printf("loader: Created PDE @ %08x.", pde_addr)
log.Printf("loader: Created PGD @ %08x.", pgd_addr)
log.Printf("loader: Created PML4 @ %08x.", pml4_addr)
// Set our newly build page table.
err = vcpu.SetControlRegister(
platform.CR3,
platform.ControlRegisterValue(pml4_addr),
true)
if err != nil {
return err
}
// Enable long mode.
efer, err := vcpu.GetControlRegister(platform.EFER)
if err != nil {
return err
}
efer = efer | (1 << 8) // Long-mode enable.
err = vcpu.SetControlRegister(platform.EFER, efer, true)
if err != nil {
return err
}
// Enable paging.
cr0, err = vcpu.GetControlRegister(platform.CR0)
if err != nil {
return err
}
cr0 = cr0 | (1 << 31) // Paging enable.
err = vcpu.SetControlRegister(platform.CR0, cr0, true)
if err != nil {
return err
}
}
// NOTE: For 64-bit kernels, we need to enable
// real 64-bit mode. This means that the L bit in
// the segments must be one, the Db bit must be
// zero, and we set the LME bit in EFER (above).
var lVal uint8
var dVal uint8
if is_64bit {
lVal = 1
dVal = 0
} else {
lVal = 0
dVal = 1
}
// Load the VMCS segments.
//
// NOTE: These values are loaded into the VMCS
// registers and are expected to match the descriptors
// we've used above. Unfortunately the API format doesn't
// match, so we need to duplicate some work here. Ah, well
// at least the below serves as an explanation for what
// the magic numbers in GDT_ENTRY() above mean.
BootCs := platform.SegmentValue{
Base: 0,
Limit: 0xffffffff,
Selector: uint16(C.BootCsSelector), // @ 0x10
Dpl: 0, // Privilege level (kernel).
Db: dVal, // 32-bit segment?
G: 1, // Granularity (page).
S: 1, // As per BOOT_CS (code/data).
L: lVal, // 64-bit extension.
Type: 0xb, // As per BOOT_CS (access must be set).
Present: 1,
}
BootDs := platform.SegmentValue{
Base: 0,
Limit: 0xffffffff,
Selector: uint16(C.BootDsSelector), // @ 0x18
Dpl: 0, // Privilege level (kernel).
Db: 1, // 32-bit segment?
G: 1, // Granularity (page).
S: 1, // As per BOOT_DS (code/data).
L: 0, // 64-bit extension.
Type: 0x3, // As per BOOT_DS (access must be set).
Present: 1,
}
BootTr := platform.SegmentValue{
Base: 0,
Limit: 0xffffffff,
Selector: uint16(C.BootTrSelector), // @ 0x20
Dpl: 0, // Privilege level (kernel).
Db: 1, // 32-bit segment?
G: 1, // Granularity (page).
S: 0, // As per BOOT_TR (system).
L: 0, // 64-bit extension.
Type: 0xb, // As per BOOT_TR.
Present: 1,
}
err = vcpu.SetSegment(platform.CS, BootCs, true)
if err != nil {
return err
}
err = vcpu.SetSegment(platform.DS, BootDs, true)
if err != nil {
return err
}
err = vcpu.SetSegment(platform.ES, BootDs, true)
if err != nil {
return err
}
err = vcpu.SetSegment(platform.FS, BootDs, true)
if err != nil {
return err
}
err = vcpu.SetSegment(platform.GS, BootDs, true)
if err != nil {
return err
}
err = vcpu.SetSegment(platform.SS, BootDs, true)
if err != nil {
return err
}
err = vcpu.SetSegment(platform.TR, BootTr, true)
if err != nil {
return err
}
// Create our boot parameters.
boot_addr, boot_data, err := model.Allocate(
machine.MemoryTypeUser,
0, // Start.
model.Max(), // End.
platform.PageSize, // Size.
false) // From bottom.
if err != nil {
return err
}
err = SetupLinuxBootParams(
model,
boot_data,
orig_boot_data,
cmdline_addr,
initrd_addr,
initrd_len)
if err != nil {
return err
}
// Set our registers.
// This is according to the Linux 32-bit boot protocol.
log.Printf("loader: boot_params @ %08x.", boot_addr)
err = vcpu.SetRegister(platform.RSI, platform.RegisterValue(boot_addr))
if err != nil {
return err
}
err = vcpu.SetRegister(platform.RBP, 0)
if err != nil {
return err
}
err = vcpu.SetRegister(platform.RDI, 0)
if err != nil {
return err
}
err = vcpu.SetRegister(platform.RBX, 0)
if err != nil {
return err
}
// Jump to our entry point.
err = vcpu.SetRegister(platform.RIP, platform.RegisterValue(entry_point))
if err != nil {
return err
}
// Make sure interrupts are disabled.
// This will actually clear out all other flags.
rflags, err := vcpu.GetRegister(platform.RFLAGS)
if err != nil {
return err
}
rflags = rflags &^ (1 << 9) // Interrupts off.
rflags = rflags | (1 << 1) // Reserved 1.
err = vcpu.SetRegister(
platform.RFLAGS,
platform.RegisterValue(rflags))
if err != nil {
return err
}
// We're done.
return nil
}