Change ring0 & page tables arguments to structs.

This is a refactor of ring0 and ring0/pagetables that changes from
individual arguments to opts structures. This should involve no
functional changes, but sets the stage for subsequent changes.

PiperOrigin-RevId: 198627556
Change-Id: Id4460340f6a73f0c793cd879324398139cd58ae9

6 files changed, 124 insertions, 38 deletions

diff --git a/pkg/sentry/platform/kvm/address_space.go b/pkg/sentry/platform/kvm/address_space.go
index e81cc0caf..a777533c5 100644
--- a/pkg/sentry/platform/kvm/address_space.go
+++ b/pkg/sentry/platform/kvm/address_space.go
@@ -89,7 +89,10 @@ func (as *addressSpace) mapHost(addr usermem.Addr, m hostMapEntry, at usermem.Ac
 		// important; if the pagetable mappings were installed before
 		// ensuring the physical pages were available, then some other
 		// thread could theoretically access them.
-		prev := as.pageTables.Map(addr, length, true /* user */, at, physical)
+		prev := as.pageTables.Map(addr, length, pagetables.MapOpts{
+			AccessType: at,
+			User:       true,
+		}, physical)
 		inv = inv || prev
 		m.addr += length
 		m.length -= length
diff --git a/pkg/sentry/platform/kvm/context.go b/pkg/sentry/platform/kvm/context.go
index dec26a23a..aac84febf 100644
--- a/pkg/sentry/platform/kvm/context.go
+++ b/pkg/sentry/platform/kvm/context.go
@@ -35,10 +35,7 @@ type context struct {
 
 // Switch runs the provided context in the given address space.
 func (c *context) Switch(as platform.AddressSpace, ac arch.Context, _ int32) (*arch.SignalInfo, usermem.AccessType, error) {
-	// Extract data.
 	localAS := as.(*addressSpace)
-	regs := &ac.StateData().Regs
-	fp := (*byte)(ac.FloatingPointData())
 
 	// Grab a vCPU.
 	cpu := c.machine.Get()
@@ -58,17 +55,17 @@ func (c *context) Switch(as platform.AddressSpace, ac arch.Context, _ int32) (*a
 	// that the flush can occur naturally on the next user entry.
 	cpu.active.set(localAS)
 
-	// Mark the address space as dirty.
-	flags := ring0.Flags(0)
-	if localAS.Touch(cpu) {
-		flags |= ring0.FlagFlush
-	}
-	if ac.FullRestore() {
-		flags |= ring0.FlagFull
+	// Prepare switch options.
+	switchOpts := ring0.SwitchOpts{
+		Registers:          &ac.StateData().Regs,
+		FloatingPointState: (*byte)(ac.FloatingPointData()),
+		PageTables:         localAS.pageTables,
+		Flush:              localAS.Touch(cpu),
+		FullRestore:        ac.FullRestore(),
 	}
 
 	// Take the blue pill.
-	si, at, err := cpu.SwitchToUser(regs, fp, localAS.pageTables, flags)
+	si, at, err := cpu.SwitchToUser(switchOpts)
 
 	// Clear the address space.
 	cpu.active.set(nil)
diff --git a/pkg/sentry/platform/kvm/kvm.go b/pkg/sentry/platform/kvm/kvm.go
index 15a241f01..6defb1c46 100644
--- a/pkg/sentry/platform/kvm/kvm.go
+++ b/pkg/sentry/platform/kvm/kvm.go
@@ -25,6 +25,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform/filemem"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform/ring0"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/platform/ring0/pagetables"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 )
 
@@ -123,8 +124,11 @@ func (k *KVM) NewAddressSpace(_ interface{}) (platform.AddressSpace, <-chan stru
 	pageTables := k.machine.kernel.PageTables.New()
 	applyPhysicalRegions(func(pr physicalRegion) bool {
 		// Map the kernel in the upper half.
-		kernelVirtual := usermem.Addr(ring0.KernelStartAddress | pr.virtual)
-		pageTables.Map(kernelVirtual, pr.length, false /* kernel */, usermem.AnyAccess, pr.physical)
+		pageTables.Map(
+			usermem.Addr(ring0.KernelStartAddress|pr.virtual),
+			pr.length,
+			pagetables.MapOpts{AccessType: usermem.AnyAccess},
+			pr.physical)
 		return true // Keep iterating.
 	})
 
diff --git a/pkg/sentry/platform/kvm/kvm_test.go b/pkg/sentry/platform/kvm/kvm_test.go
index a3466fbed..00919b214 100644
--- a/pkg/sentry/platform/kvm/kvm_test.go
+++ b/pkg/sentry/platform/kvm/kvm_test.go
@@ -142,7 +142,10 @@ func applicationTest(t testHarness, useHostMappings bool, target func(), fn func
 			// done for regular user code, but is fine for test
 			// purposes.)
 			applyPhysicalRegions(func(pr physicalRegion) bool {
-				pt.Map(usermem.Addr(pr.virtual), pr.length, true /* user */, usermem.AnyAccess, pr.physical)
+				pt.Map(usermem.Addr(pr.virtual), pr.length, pagetables.MapOpts{
+					AccessType: usermem.AnyAccess,
+					User:       true,
+				}, pr.physical)
 				return true // Keep iterating.
 			})
 		}
@@ -154,13 +157,22 @@ func applicationTest(t testHarness, useHostMappings bool, target func(), fn func
 
 func TestApplicationSyscall(t *testing.T) {
 	applicationTest(t, true, testutil.SyscallLoop, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, ring0.FlagFull); err != nil {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+			FullRestore:        true,
+		}); err != nil {
 			t.Errorf("application syscall with full restore failed: %v", err)
 		}
 		return false
 	})
 	applicationTest(t, true, testutil.SyscallLoop, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, 0); err != nil {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+		}); err != nil {
 			t.Errorf("application syscall with partial restore failed: %v", err)
 		}
 		return false
@@ -170,14 +182,23 @@ func TestApplicationSyscall(t *testing.T) {
 func TestApplicationFault(t *testing.T) {
 	applicationTest(t, true, testutil.Touch, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
 		testutil.SetTouchTarget(regs, nil) // Cause fault.
-		if si, _, err := c.SwitchToUser(regs, dummyFPState, pt, ring0.FlagFull); err != platform.ErrContextSignal || (si != nil && si.Signo != int32(syscall.SIGSEGV)) {
+		if si, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+			FullRestore:        true,
+		}); err != platform.ErrContextSignal || (si != nil && si.Signo != int32(syscall.SIGSEGV)) {
 			t.Errorf("application fault with full restore got (%v, %v), expected (%v, SIGSEGV)", err, si, platform.ErrContextSignal)
 		}
 		return false
 	})
 	applicationTest(t, true, testutil.Touch, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
 		testutil.SetTouchTarget(regs, nil) // Cause fault.
-		if si, _, err := c.SwitchToUser(regs, dummyFPState, pt, 0); err != platform.ErrContextSignal || (si != nil && si.Signo != int32(syscall.SIGSEGV)) {
+		if si, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+		}); err != platform.ErrContextSignal || (si != nil && si.Signo != int32(syscall.SIGSEGV)) {
 			t.Errorf("application fault with partial restore got (%v, %v), expected (%v, SIGSEGV)", err, si, platform.ErrContextSignal)
 		}
 		return false
@@ -187,7 +208,11 @@ func TestApplicationFault(t *testing.T) {
 func TestRegistersSyscall(t *testing.T) {
 	applicationTest(t, true, testutil.TwiddleRegsSyscall, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
 		testutil.SetTestRegs(regs) // Fill values for all registers.
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, 0); err != nil {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+		}); err != nil {
 			t.Errorf("application register check with partial restore got unexpected error: %v", err)
 		}
 		if err := testutil.CheckTestRegs(regs, false); err != nil {
@@ -200,7 +225,12 @@ func TestRegistersSyscall(t *testing.T) {
 func TestRegistersFault(t *testing.T) {
 	applicationTest(t, true, testutil.TwiddleRegsFault, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
 		testutil.SetTestRegs(regs) // Fill values for all registers.
-		if si, _, err := c.SwitchToUser(regs, dummyFPState, pt, ring0.FlagFull); err != platform.ErrContextSignal || si.Signo != int32(syscall.SIGSEGV) {
+		if si, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+			FullRestore:        true,
+		}); err != platform.ErrContextSignal || si.Signo != int32(syscall.SIGSEGV) {
 			t.Errorf("application register check with full restore got unexpected error: %v", err)
 		}
 		if err := testutil.CheckTestRegs(regs, true); err != nil {
@@ -213,7 +243,12 @@ func TestRegistersFault(t *testing.T) {
 func TestSegments(t *testing.T) {
 	applicationTest(t, true, testutil.TwiddleSegments, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
 		testutil.SetTestSegments(regs)
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, ring0.FlagFull); err != nil {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+			FullRestore:        true,
+		}); err != nil {
 			t.Errorf("application segment check with full restore got unexpected error: %v", err)
 		}
 		if err := testutil.CheckTestSegments(regs); err != nil {
@@ -229,7 +264,11 @@ func TestBounce(t *testing.T) {
 			time.Sleep(time.Millisecond)
 			c.BounceToKernel()
 		}()
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, 0); err != platform.ErrContextInterrupt {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+		}); err != platform.ErrContextInterrupt {
 			t.Errorf("application partial restore: got %v, wanted %v", err, platform.ErrContextInterrupt)
 		}
 		return false
@@ -239,7 +278,12 @@ func TestBounce(t *testing.T) {
 			time.Sleep(time.Millisecond)
 			c.BounceToKernel()
 		}()
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, ring0.FlagFull); err != platform.ErrContextInterrupt {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+			FullRestore:        true,
+		}); err != platform.ErrContextInterrupt {
 			t.Errorf("application full restore: got %v, wanted %v", err, platform.ErrContextInterrupt)
 		}
 		return false
@@ -265,7 +309,11 @@ func TestBounceStress(t *testing.T) {
 				c.BounceToKernel()
 			}()
 			randomSleep()
-			if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, 0); err != platform.ErrContextInterrupt {
+			if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+				Registers:          regs,
+				FloatingPointState: dummyFPState,
+				PageTables:         pt,
+			}); err != platform.ErrContextInterrupt {
 				t.Errorf("application partial restore: got %v, wanted %v", err, platform.ErrContextInterrupt)
 			}
 			c.unlock()
@@ -280,12 +328,21 @@ func TestInvalidate(t *testing.T) {
 	var data uintptr // Used below.
 	applicationTest(t, true, testutil.Touch, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
 		testutil.SetTouchTarget(regs, &data) // Read legitimate value.
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, 0); err != nil {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+		}); err != nil {
 			t.Errorf("application partial restore: got %v, wanted nil", err)
 		}
 		// Unmap the page containing data & invalidate.
 		pt.Unmap(usermem.Addr(reflect.ValueOf(&data).Pointer() & ^uintptr(usermem.PageSize-1)), usermem.PageSize)
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, ring0.FlagFlush); err != platform.ErrContextSignal {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+			Flush:              true,
+		}); err != platform.ErrContextSignal {
 			t.Errorf("application partial restore: got %v, wanted %v", err, platform.ErrContextSignal)
 		}
 		return false
@@ -299,14 +356,23 @@ func IsFault(err error, si *arch.SignalInfo) bool {
 
 func TestEmptyAddressSpace(t *testing.T) {
 	applicationTest(t, false, testutil.SyscallLoop, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
-		if si, _, err := c.SwitchToUser(regs, dummyFPState, pt, 0); !IsFault(err, si) {
+		if si, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+		}); !IsFault(err, si) {
 			t.Errorf("first fault with partial restore failed got %v", err)
 			t.Logf("registers: %#v", &regs)
 		}
 		return false
 	})
 	applicationTest(t, false, testutil.SyscallLoop, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
-		if si, _, err := c.SwitchToUser(regs, dummyFPState, pt, ring0.FlagFull); !IsFault(err, si) {
+		if si, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+			FullRestore:        true,
+		}); !IsFault(err, si) {
 			t.Errorf("first fault with full restore failed got %v", err)
 			t.Logf("registers: %#v", &regs)
 		}
@@ -357,7 +423,11 @@ func BenchmarkApplicationSyscall(b *testing.B) {
 		a int // Count for ErrContextInterrupt.
 	)
 	applicationTest(b, true, testutil.SyscallLoop, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, 0); err != nil {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+		}); err != nil {
 			if err == platform.ErrContextInterrupt {
 				a++
 				return true // Ignore.
@@ -390,7 +460,11 @@ func BenchmarkWorldSwitchToUserRoundtrip(b *testing.B) {
 		a int
 	)
 	applicationTest(b, true, testutil.SyscallLoop, func(c *vCPU, regs *syscall.PtraceRegs, pt *pagetables.PageTables) bool {
-		if _, _, err := c.SwitchToUser(regs, dummyFPState, pt, 0); err != nil {
+		if _, _, err := c.SwitchToUser(ring0.SwitchOpts{
+			Registers:          regs,
+			FloatingPointState: dummyFPState,
+			PageTables:         pt,
+		}); err != nil {
 			if err == platform.ErrContextInterrupt {
 				a++
 				return true // Ignore.
diff --git a/pkg/sentry/platform/kvm/machine.go b/pkg/sentry/platform/kvm/machine.go
index 9b7e5130c..5a6109ced 100644
--- a/pkg/sentry/platform/kvm/machine.go
+++ b/pkg/sentry/platform/kvm/machine.go
@@ -186,10 +186,19 @@ func newMachine(vm int, vCPUs int) (*machine, error) {
 	// physical pages are mapped on demand, see kernel_unsafe.go.
 	applyPhysicalRegions(func(pr physicalRegion) bool {
 		// Map everything in the lower half.
-		m.kernel.PageTables.Map(usermem.Addr(pr.virtual), pr.length, false /* kernel */, usermem.AnyAccess, pr.physical)
+		m.kernel.PageTables.Map(
+			usermem.Addr(pr.virtual),
+			pr.length,
+			pagetables.MapOpts{AccessType: usermem.AnyAccess},
+			pr.physical)
+
 		// And keep everything in the upper half.
-		kernelAddr := usermem.Addr(ring0.KernelStartAddress | pr.virtual)
-		m.kernel.PageTables.Map(kernelAddr, pr.length, false /* kernel */, usermem.AnyAccess, pr.physical)
+		m.kernel.PageTables.Map(
+			usermem.Addr(ring0.KernelStartAddress|pr.virtual),
+			pr.length,
+			pagetables.MapOpts{AccessType: usermem.AnyAccess},
+			pr.physical)
+
 		return true // Keep iterating.
 	})
 
diff --git a/pkg/sentry/platform/kvm/machine_amd64.go b/pkg/sentry/platform/kvm/machine_amd64.go
index f583f68f7..ba7bbcb91 100644
--- a/pkg/sentry/platform/kvm/machine_amd64.go
+++ b/pkg/sentry/platform/kvm/machine_amd64.go
@@ -24,7 +24,6 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform/ring0"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/platform/ring0/pagetables"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 )
 
@@ -121,7 +120,7 @@ func (c *vCPU) fault(signal int32) (*arch.SignalInfo, usermem.AccessType, error)
 }
 
 // SwitchToUser unpacks architectural-details.
-func (c *vCPU) SwitchToUser(regs *syscall.PtraceRegs, fpState *byte, pt *pagetables.PageTables, flags ring0.Flags) (*arch.SignalInfo, usermem.AccessType, error) {
+func (c *vCPU) SwitchToUser(switchOpts ring0.SwitchOpts) (*arch.SignalInfo, usermem.AccessType, error) {
 	// See below.
 	var vector ring0.Vector
 
@@ -131,7 +130,7 @@ func (c *vCPU) SwitchToUser(regs *syscall.PtraceRegs, fpState *byte, pt *pagetab
 	// allocations occur.
 	entersyscall()
 	bluepill(c)
-	vector = c.CPU.SwitchToUser(regs, fpState, pt, flags)
+	vector = c.CPU.SwitchToUser(switchOpts)
 	exitsyscall()
 
 	switch vector {
@@ -147,7 +146,7 @@ func (c *vCPU) SwitchToUser(regs *syscall.PtraceRegs, fpState *byte, pt *pagetab
 		return info, usermem.AccessType{}, platform.ErrContextSignal
 
 	case ring0.GeneralProtectionFault:
-		if !ring0.IsCanonical(regs.Rip) {
+		if !ring0.IsCanonical(switchOpts.Registers.Rip) {
 			// If the RIP is non-canonical, it's a SEGV.
 			info := &arch.SignalInfo{Signo: int32(syscall.SIGSEGV)}
 			return info, usermem.AccessType{}, platform.ErrContextSignal