Rename kernel.TaskContext to kernel.TaskImage.

This reduces confusion with context.Context (which is also relevant to
kernel.Tasks) and is consistent with existing function kernel.LoadTaskImage().

PiperOrigin-RevId: 342167298

1 files changed, 173 insertions, 0 deletions

diff --git a/pkg/sentry/kernel/task_image.go b/pkg/sentry/kernel/task_image.go
new file mode 100644
index 000000000..ce5fbd299
--- /dev/null
+++ b/pkg/sentry/kernel/task_image.go
@@ -0,0 +1,173 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package kernel
+
+import (
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/futex"
+	"gvisor.dev/gvisor/pkg/sentry/loader"
+	"gvisor.dev/gvisor/pkg/sentry/mm"
+	"gvisor.dev/gvisor/pkg/syserr"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+var errNoSyscalls = syserr.New("no syscall table found", linux.ENOEXEC)
+
+// Auxmap contains miscellaneous data for the task.
+type Auxmap map[string]interface{}
+
+// TaskImage is the subset of a task's data that is provided by the loader.
+//
+// +stateify savable
+type TaskImage struct {
+	// Name is the thread name set by the prctl(PR_SET_NAME) system call.
+	Name string
+
+	// Arch is the architecture-specific context (registers, etc.)
+	Arch arch.Context
+
+	// MemoryManager is the task's address space.
+	MemoryManager *mm.MemoryManager
+
+	// fu implements futexes in the address space.
+	fu *futex.Manager
+
+	// st is the task's syscall table.
+	st *SyscallTable `state:".(syscallTableInfo)"`
+}
+
+// release releases all resources held by the TaskImage. release is called by
+// the task when it execs into a new TaskImage or exits.
+func (image *TaskImage) release() {
+	// Nil out pointers so that if the task is saved after release, it doesn't
+	// follow the pointers to possibly now-invalid objects.
+	if image.MemoryManager != nil {
+		image.MemoryManager.DecUsers(context.Background())
+		image.MemoryManager = nil
+	}
+	image.fu = nil
+}
+
+// Fork returns a duplicate of image. The copied TaskImage always has an
+// independent arch.Context. If shareAddressSpace is true, the copied
+// TaskImage shares an address space with the original; otherwise, the copied
+// TaskImage has an independent address space that is initially a duplicate
+// of the original's.
+func (image *TaskImage) Fork(ctx context.Context, k *Kernel, shareAddressSpace bool) (*TaskImage, error) {
+	newImage := &TaskImage{
+		Name: image.Name,
+		Arch: image.Arch.Fork(),
+		st:   image.st,
+	}
+	if shareAddressSpace {
+		newImage.MemoryManager = image.MemoryManager
+		if newImage.MemoryManager != nil {
+			if !newImage.MemoryManager.IncUsers() {
+				// Shouldn't be possible since image.MemoryManager should be a
+				// counted user.
+				panic(fmt.Sprintf("TaskImage.Fork called with userless TaskImage.MemoryManager"))
+			}
+		}
+		newImage.fu = image.fu
+	} else {
+		newMM, err := image.MemoryManager.Fork(ctx)
+		if err != nil {
+			return nil, err
+		}
+		newImage.MemoryManager = newMM
+		newImage.fu = k.futexes.Fork()
+	}
+	return newImage, nil
+}
+
+// Arch returns t's arch.Context.
+//
+// Preconditions: The caller must be running on the task goroutine, or t.mu
+// must be locked.
+func (t *Task) Arch() arch.Context {
+	return t.image.Arch
+}
+
+// MemoryManager returns t's MemoryManager. MemoryManager does not take an
+// additional reference on the returned MM.
+//
+// Preconditions: The caller must be running on the task goroutine, or t.mu
+// must be locked.
+func (t *Task) MemoryManager() *mm.MemoryManager {
+	return t.image.MemoryManager
+}
+
+// SyscallTable returns t's syscall table.
+//
+// Preconditions: The caller must be running on the task goroutine, or t.mu
+// must be locked.
+func (t *Task) SyscallTable() *SyscallTable {
+	return t.image.st
+}
+
+// Stack returns the userspace stack.
+//
+// Preconditions: The caller must be running on the task goroutine, or t.mu
+// must be locked.
+func (t *Task) Stack() *arch.Stack {
+	return &arch.Stack{
+		Arch:   t.Arch(),
+		IO:     t.MemoryManager(),
+		Bottom: usermem.Addr(t.Arch().Stack()),
+	}
+}
+
+// LoadTaskImage loads a specified file into a new TaskImage.
+//
+// args.MemoryManager does not need to be set by the caller.
+func (k *Kernel) LoadTaskImage(ctx context.Context, args loader.LoadArgs) (*TaskImage, *syserr.Error) {
+	// If File is not nil, we should load that instead of resolving Filename.
+	if args.File != nil {
+		args.Filename = args.File.PathnameWithDeleted(ctx)
+	}
+
+	// Prepare a new user address space to load into.
+	m := mm.NewMemoryManager(k, k, k.SleepForAddressSpaceActivation)
+	defer m.DecUsers(ctx)
+	args.MemoryManager = m
+
+	os, ac, name, err := loader.Load(ctx, args, k.extraAuxv, k.vdso)
+	if err != nil {
+		return nil, err
+	}
+
+	// Lookup our new syscall table.
+	st, ok := LookupSyscallTable(os, ac.Arch())
+	if !ok {
+		// No syscall table found. This means that the ELF binary does not match
+		// the architecture.
+		return nil, errNoSyscalls
+	}
+
+	if !m.IncUsers() {
+		panic("Failed to increment users count on new MM")
+	}
+	return &TaskImage{
+		Name:          name,
+		Arch:          ac,
+		MemoryManager: m,
+		fu:            k.futexes.Fork(),
+		st:            st,
+	}, nil
+}