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// 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.googlesource.com/gvisor/pkg/abi/linux"
"gvisor.googlesource.com/gvisor/pkg/cpuid"
"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/futex"
"gvisor.googlesource.com/gvisor/pkg/sentry/loader"
"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
"gvisor.googlesource.com/gvisor/pkg/syserr"
)
var errNoSyscalls = syserr.New("no syscall table found", linux.ENOEXEC)
// Auxmap contains miscellaneous data for the task.
type Auxmap map[string]interface{}
// TaskContext is the subset of a task's data that is provided by the loader.
//
// +stateify savable
type TaskContext 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
}
// release releases all resources held by the TaskContext. release is called by
// the task when it execs into a new TaskContext or exits.
func (tc *TaskContext) 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 tc.MemoryManager != nil {
// TODO(b/38173783)
tc.MemoryManager.DecUsers(context.Background())
tc.MemoryManager = nil
}
tc.fu = nil
}
// Fork returns a duplicate of tc. The copied TaskContext always has an
// independent arch.Context. If shareAddressSpace is true, the copied
// TaskContext shares an address space with the original; otherwise, the copied
// TaskContext has an independent address space that is initially a duplicate
// of the original's.
func (tc *TaskContext) Fork(ctx context.Context, k *Kernel, shareAddressSpace bool) (*TaskContext, error) {
newTC := &TaskContext{
Name: tc.Name,
Arch: tc.Arch.Fork(),
st: tc.st,
}
if shareAddressSpace {
newTC.MemoryManager = tc.MemoryManager
if newTC.MemoryManager != nil {
if !newTC.MemoryManager.IncUsers() {
// Shouldn't be possible since tc.MemoryManager should be a
// counted user.
panic(fmt.Sprintf("TaskContext.Fork called with userless TaskContext.MemoryManager"))
}
}
newTC.fu = tc.fu
} else {
newMM, err := tc.MemoryManager.Fork(ctx)
if err != nil {
return nil, err
}
newTC.MemoryManager = newMM
newTC.fu = k.futexes.Fork()
}
return newTC, 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.tc.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.tc.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.tc.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{t.Arch(), t.MemoryManager(), usermem.Addr(t.Arch().Stack())}
}
// LoadTaskImage loads filename into a new TaskContext.
//
// It takes several arguments:
// * mounts: MountNamespace to lookup filename in
// * root: Root to lookup filename under
// * wd: Working directory to lookup filename under
// * maxTraversals: maximum number of symlinks to follow
// * filename: path to binary to load
// * argv: Binary argv
// * envv: Binary envv
// * fs: Binary FeatureSet
func (k *Kernel) LoadTaskImage(ctx context.Context, mounts *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, filename string, argv, envv []string, fs *cpuid.FeatureSet) (*TaskContext, *syserr.Error) {
// Prepare a new user address space to load into.
m := mm.NewMemoryManager(k, k)
defer m.DecUsers(ctx)
os, ac, name, err := loader.Load(ctx, m, mounts, root, wd, maxTraversals, fs, filename, argv, envv, 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 &TaskContext{
Name: name,
Arch: ac,
MemoryManager: m,
fu: k.futexes.Fork(),
st: st,
}, nil
}
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