[op] Move SignalStack to abi/linux package.

Updates #214

PiperOrigin-RevId: 378594929

13 files changed, 62 insertions, 156 deletions

diff --git a/pkg/abi/linux/BUILD b/pkg/abi/linux/BUILD
index 29ead20d0..38288bdb7 100644
--- a/pkg/abi/linux/BUILD
+++ b/pkg/abi/linux/BUILD
@@ -79,6 +79,7 @@ go_library(
         "//pkg/abi",
         "//pkg/bits",
         "//pkg/context",
+        "//pkg/hostarch",
         "//pkg/marshal",
         "//pkg/marshal/primitive",
     ],
diff --git a/pkg/abi/linux/signal.go b/pkg/abi/linux/signal.go
index cedae3014..bbf7f6580 100644
--- a/pkg/abi/linux/signal.go
+++ b/pkg/abi/linux/signal.go
@@ -16,6 +16,7 @@ package linux
 
 import (
 	"gvisor.dev/gvisor/pkg/bits"
+	"gvisor.dev/gvisor/pkg/hostarch"
 )
 
 const (
@@ -165,7 +166,7 @@ const (
 	SIG_IGN = 1
 )
 
-// Signal action flags for rt_sigaction(2), from uapi/asm-generic/signal.h
+// Signal action flags for rt_sigaction(2), from uapi/asm-generic/signal.h.
 const (
 	SA_NOCLDSTOP = 0x00000001
 	SA_NOCLDWAIT = 0x00000002
@@ -179,6 +180,12 @@ const (
 	SA_ONESHOT   = SA_RESETHAND
 )
 
+// Signal stack flags for signalstack(2), from include/uapi/linux/signal.h.
+const (
+	SS_ONSTACK = 1
+	SS_DISABLE = 2
+)
+
 // Signal info types.
 const (
 	SI_MASK  = 0xffff0000
@@ -242,6 +249,33 @@ type SigAction struct {
 
 // LINT.ThenChange(../../safecopy/safecopy_unsafe.go)
 
+// SignalStack represents information about a user stack, and is equivalent to
+// stack_t.
+//
+// +marshal
+// +stateify savable
+type SignalStack struct {
+	Addr  uint64
+	Flags uint32
+	_     uint32
+	Size  uint64
+}
+
+// Contains checks if the stack pointer is within this stack.
+func (s *SignalStack) Contains(sp hostarch.Addr) bool {
+	return hostarch.Addr(s.Addr) < sp && sp <= hostarch.Addr(s.Addr+s.Size)
+}
+
+// Top returns the stack's top address.
+func (s *SignalStack) Top() hostarch.Addr {
+	return hostarch.Addr(s.Addr + s.Size)
+}
+
+// IsEnabled returns true iff this signal stack is marked as enabled.
+func (s *SignalStack) IsEnabled() bool {
+	return s.Flags&SS_DISABLE == 0
+}
+
 // Possible values for Sigevent.Notify, aka struct sigevent::sigev_notify.
 const (
 	SIGEV_SIGNAL    = 0
diff --git a/pkg/sentry/arch/BUILD b/pkg/sentry/arch/BUILD
index d8253ecbe..1f467b7c9 100644
--- a/pkg/sentry/arch/BUILD
+++ b/pkg/sentry/arch/BUILD
@@ -18,7 +18,6 @@ go_library(
         "signal_amd64.go",
         "signal_arm64.go",
         "signal_info.go",
-        "signal_stack.go",
         "stack.go",
         "stack_unsafe.go",
         "syscalls_amd64.go",
diff --git a/pkg/sentry/arch/arch.go b/pkg/sentry/arch/arch.go
index 9db228bab..d765d8374 100644
--- a/pkg/sentry/arch/arch.go
+++ b/pkg/sentry/arch/arch.go
@@ -134,10 +134,6 @@ type Context interface {
 	// RegisterMap returns a map of all registers.
 	RegisterMap() (map[string]uintptr, error)
 
-	// NewSignalStack returns a new object that is equivalent to stack_t in the
-	// guest architecture.
-	NewSignalStack() NativeSignalStack
-
 	// SignalSetup modifies the context in preparation for handling the
 	// given signal.
 	//
@@ -153,7 +149,7 @@ type Context interface {
 	// stack is not going to be used).
 	//
 	// sigset is the signal mask before entering the signal handler.
-	SignalSetup(st *Stack, act *linux.SigAction, info *SignalInfo, alt *SignalStack, sigset linux.SignalSet) error
+	SignalSetup(st *Stack, act *linux.SigAction, info *SignalInfo, alt *linux.SignalStack, sigset linux.SignalSet) error
 
 	// SignalRestore restores context after returning from a signal
 	// handler.
@@ -163,7 +159,7 @@ type Context interface {
 	// rt is true if SignalRestore is being entered from rt_sigreturn and
 	// false if SignalRestore is being entered from sigreturn.
 	// SignalRestore returns the thread's new signal mask.
-	SignalRestore(st *Stack, rt bool) (linux.SignalSet, SignalStack, error)
+	SignalRestore(st *Stack, rt bool) (linux.SignalSet, linux.SignalStack, error)
 
 	// CPUIDEmulate emulates a CPUID instruction according to current register state.
 	CPUIDEmulate(l log.Logger)
diff --git a/pkg/sentry/arch/signal.go b/pkg/sentry/arch/signal.go
index 3e601b17e..b9fd14d10 100644
--- a/pkg/sentry/arch/signal.go
+++ b/pkg/sentry/arch/signal.go
@@ -19,28 +19,6 @@ import (
 	"gvisor.dev/gvisor/pkg/hostarch"
 )
 
-// SignalStack represents information about a user stack, and is equivalent to
-// stack_t.
-//
-// +marshal
-// +stateify savable
-type SignalStack struct {
-	Addr  uint64
-	Flags uint32
-	_     uint32
-	Size  uint64
-}
-
-// SerializeFrom implements NativeSignalStack.SerializeFrom.
-func (s *SignalStack) SerializeFrom(other *SignalStack) {
-	*s = *other
-}
-
-// DeserializeTo implements NativeSignalStack.DeserializeTo.
-func (s *SignalStack) DeserializeTo(other *SignalStack) {
-	*other = *s
-}
-
 // SignalInfo represents information about a signal being delivered, and is
 // equivalent to struct siginfo in linux kernel(linux/include/uapi/asm-generic/siginfo.h).
 //
diff --git a/pkg/sentry/arch/signal_amd64.go b/pkg/sentry/arch/signal_amd64.go
index 0bf272e16..fa74a2551 100644
--- a/pkg/sentry/arch/signal_amd64.go
+++ b/pkg/sentry/arch/signal_amd64.go
@@ -76,16 +76,11 @@ const (
 type UContext64 struct {
 	Flags    uint64
 	Link     uint64
-	Stack    SignalStack
+	Stack    linux.SignalStack
 	MContext SignalContext64
 	Sigset   linux.SignalSet
 }
 
-// NewSignalStack implements Context.NewSignalStack.
-func (c *context64) NewSignalStack() NativeSignalStack {
-	return &SignalStack{}
-}
-
 // From Linux 'arch/x86/include/uapi/asm/sigcontext.h' the following is the
 // size of the magic cookie at the end of the xsave frame.
 //
@@ -105,7 +100,7 @@ func (c *context64) fpuFrameSize() (size int, useXsave bool) {
 
 // SignalSetup implements Context.SignalSetup. (Compare to Linux's
 // arch/x86/kernel/signal.c:__setup_rt_frame().)
-func (c *context64) SignalSetup(st *Stack, act *linux.SigAction, info *SignalInfo, alt *SignalStack, sigset linux.SignalSet) error {
+func (c *context64) SignalSetup(st *Stack, act *linux.SigAction, info *SignalInfo, alt *linux.SignalStack, sigset linux.SignalSet) error {
 	sp := st.Bottom
 
 	// "The 128-byte area beyond the location pointed to by %rsp is considered
@@ -232,15 +227,15 @@ func (c *context64) SignalSetup(st *Stack, act *linux.SigAction, info *SignalInf
 
 // SignalRestore implements Context.SignalRestore. (Compare to Linux's
 // arch/x86/kernel/signal.c:sys_rt_sigreturn().)
-func (c *context64) SignalRestore(st *Stack, rt bool) (linux.SignalSet, SignalStack, error) {
+func (c *context64) SignalRestore(st *Stack, rt bool) (linux.SignalSet, linux.SignalStack, error) {
 	// Copy out the stack frame.
 	var uc UContext64
 	if _, err := uc.CopyIn(st, StackBottomMagic); err != nil {
-		return 0, SignalStack{}, err
+		return 0, linux.SignalStack{}, err
 	}
 	var info SignalInfo
 	if _, err := info.CopyIn(st, StackBottomMagic); err != nil {
-		return 0, SignalStack{}, err
+		return 0, linux.SignalStack{}, err
 	}
 
 	// Restore registers.
diff --git a/pkg/sentry/arch/signal_arm64.go b/pkg/sentry/arch/signal_arm64.go
index cc3c6ce62..3d632e7fd 100644
--- a/pkg/sentry/arch/signal_arm64.go
+++ b/pkg/sentry/arch/signal_arm64.go
@@ -61,7 +61,7 @@ type FpsimdContext struct {
 type UContext64 struct {
 	Flags  uint64
 	Link   uint64
-	Stack  SignalStack
+	Stack  linux.SignalStack
 	Sigset linux.SignalSet
 	// glibc uses a 1024-bit sigset_t
 	_pad [120]byte // (1024 - 64) / 8 = 120
@@ -71,13 +71,8 @@ type UContext64 struct {
 	MContext SignalContext64
 }
 
-// NewSignalStack implements Context.NewSignalStack.
-func (c *context64) NewSignalStack() NativeSignalStack {
-	return &SignalStack{}
-}
-
 // SignalSetup implements Context.SignalSetup.
-func (c *context64) SignalSetup(st *Stack, act *linux.SigAction, info *SignalInfo, alt *SignalStack, sigset linux.SignalSet) error {
+func (c *context64) SignalSetup(st *Stack, act *linux.SigAction, info *SignalInfo, alt *linux.SignalStack, sigset linux.SignalSet) error {
 	sp := st.Bottom
 
 	// Construct the UContext64 now since we need its size.
@@ -142,15 +137,15 @@ func (c *context64) SignalSetup(st *Stack, act *linux.SigAction, info *SignalInf
 }
 
 // SignalRestore implements Context.SignalRestore.
-func (c *context64) SignalRestore(st *Stack, rt bool) (linux.SignalSet, SignalStack, error) {
+func (c *context64) SignalRestore(st *Stack, rt bool) (linux.SignalSet, linux.SignalStack, error) {
 	// Copy out the stack frame.
 	var uc UContext64
 	if _, err := uc.CopyIn(st, StackBottomMagic); err != nil {
-		return 0, SignalStack{}, err
+		return 0, linux.SignalStack{}, err
 	}
 	var info SignalInfo
 	if _, err := info.CopyIn(st, StackBottomMagic); err != nil {
-		return 0, SignalStack{}, err
+		return 0, linux.SignalStack{}, err
 	}
 
 	// Restore registers.
diff --git a/pkg/sentry/arch/signal_stack.go b/pkg/sentry/arch/signal_stack.go
deleted file mode 100644
index c732c7503..000000000
--- a/pkg/sentry/arch/signal_stack.go
+++ /dev/null
@@ -1,68 +0,0 @@
-// 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.
-
-// +build 386 amd64 arm64
-
-package arch
-
-import (
-	"gvisor.dev/gvisor/pkg/hostarch"
-	"gvisor.dev/gvisor/pkg/marshal"
-)
-
-const (
-	// SignalStackFlagOnStack is possible set on return from getaltstack,
-	// in order to indicate that the thread is currently on the alt stack.
-	SignalStackFlagOnStack = 1
-
-	// SignalStackFlagDisable is a flag to indicate the stack is disabled.
-	SignalStackFlagDisable = 2
-)
-
-// IsEnabled returns true iff this signal stack is marked as enabled.
-func (s SignalStack) IsEnabled() bool {
-	return s.Flags&SignalStackFlagDisable == 0
-}
-
-// Top returns the stack's top address.
-func (s SignalStack) Top() hostarch.Addr {
-	return hostarch.Addr(s.Addr + s.Size)
-}
-
-// SetOnStack marks this signal stack as in use.
-//
-// Note that there is no corresponding ClearOnStack, and that this should only
-// be called on copies that are serialized to userspace.
-func (s *SignalStack) SetOnStack() {
-	s.Flags |= SignalStackFlagOnStack
-}
-
-// Contains checks if the stack pointer is within this stack.
-func (s *SignalStack) Contains(sp hostarch.Addr) bool {
-	return hostarch.Addr(s.Addr) < sp && sp <= hostarch.Addr(s.Addr+s.Size)
-}
-
-// NativeSignalStack is a type that is equivalent to stack_t in the guest
-// architecture.
-type NativeSignalStack interface {
-	marshal.Marshallable
-
-	// SerializeFrom copies the data in the host SignalStack s into this
-	// object.
-	SerializeFrom(s *SignalStack)
-
-	// DeserializeTo copies the data in this object into the host SignalStack
-	// s.
-	DeserializeTo(s *SignalStack)
-}
diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go
index be1371855..9290dc52b 100644
--- a/pkg/sentry/kernel/task.go
+++ b/pkg/sentry/kernel/task.go
@@ -151,7 +151,7 @@ type Task struct {
 	// which the SA_ONSTACK flag is set.
 	//
 	// signalStack is exclusive to the task goroutine.
-	signalStack arch.SignalStack
+	signalStack linux.SignalStack
 
 	// signalQueue is a set of registered waiters for signal-related events.
 	//
diff --git a/pkg/sentry/kernel/task_exec.go b/pkg/sentry/kernel/task_exec.go
index d9897e802..cf8571262 100644
--- a/pkg/sentry/kernel/task_exec.go
+++ b/pkg/sentry/kernel/task_exec.go
@@ -66,7 +66,6 @@ package kernel
 
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
@@ -181,7 +180,7 @@ func (r *runSyscallAfterExecStop) execute(t *Task) taskRunState {
 	t.tg.signalHandlers = t.tg.signalHandlers.CopyForExec()
 	t.endStopCond.L = &t.tg.signalHandlers.mu
 	// "Any alternate signal stack is not preserved (sigaltstack(2))." - execve(2)
-	t.signalStack = arch.SignalStack{Flags: arch.SignalStackFlagDisable}
+	t.signalStack = linux.SignalStack{Flags: linux.SS_DISABLE}
 	// "The termination signal is reset to SIGCHLD (see clone(2))."
 	t.tg.terminationSignal = linux.SIGCHLD
 	// execed indicates that the process can no longer join a process group
diff --git a/pkg/sentry/kernel/task_signals.go b/pkg/sentry/kernel/task_signals.go
index 466256fe4..b0ed0e023 100644
--- a/pkg/sentry/kernel/task_signals.go
+++ b/pkg/sentry/kernel/task_signals.go
@@ -249,7 +249,7 @@ func (t *Task) deliverSignalToHandler(info *arch.SignalInfo, act linux.SigAction
 	// handler expects to see in its ucontext (even if it's not in use).
 	alt := t.signalStack
 	if act.Flags&linux.SA_ONSTACK != 0 && alt.IsEnabled() {
-		alt.SetOnStack()
+		alt.Flags |= linux.SS_ONSTACK
 		if !alt.Contains(sp) {
 			sp = hostarch.Addr(alt.Top())
 		}
@@ -641,17 +641,17 @@ func (t *Task) SetSavedSignalMask(mask linux.SignalSet) {
 }
 
 // SignalStack returns the task-private signal stack.
-func (t *Task) SignalStack() arch.SignalStack {
+func (t *Task) SignalStack() linux.SignalStack {
 	t.p.PullFullState(t.MemoryManager().AddressSpace(), t.Arch())
 	alt := t.signalStack
 	if t.onSignalStack(alt) {
-		alt.Flags |= arch.SignalStackFlagOnStack
+		alt.Flags |= linux.SS_ONSTACK
 	}
 	return alt
 }
 
 // onSignalStack returns true if the task is executing on the given signal stack.
-func (t *Task) onSignalStack(alt arch.SignalStack) bool {
+func (t *Task) onSignalStack(alt linux.SignalStack) bool {
 	sp := hostarch.Addr(t.Arch().Stack())
 	return alt.Contains(sp)
 }
@@ -661,20 +661,20 @@ func (t *Task) onSignalStack(alt arch.SignalStack) bool {
 // This value may not be changed if the task is currently executing on the
 // signal stack, i.e. if t.onSignalStack returns true. In this case, this
 // function will return false. Otherwise, true is returned.
-func (t *Task) SetSignalStack(alt arch.SignalStack) bool {
+func (t *Task) SetSignalStack(alt linux.SignalStack) bool {
 	// Check that we're not executing on the stack.
 	if t.onSignalStack(t.signalStack) {
 		return false
 	}
 
-	if alt.Flags&arch.SignalStackFlagDisable != 0 {
+	if alt.Flags&linux.SS_DISABLE != 0 {
 		// Don't record anything beyond the flags.
-		t.signalStack = arch.SignalStack{
-			Flags: arch.SignalStackFlagDisable,
+		t.signalStack = linux.SignalStack{
+			Flags: linux.SS_DISABLE,
 		}
 	} else {
 		// Mask out irrelevant parts: only disable matters.
-		alt.Flags &= arch.SignalStackFlagDisable
+		alt.Flags &= linux.SS_DISABLE
 		t.signalStack = alt
 	}
 	return true
@@ -718,27 +718,6 @@ func (tg *ThreadGroup) SetSigAction(sig linux.Signal, actptr *linux.SigAction) (
 	return oldact, nil
 }
 
-// CopyOutSignalStack converts the given SignalStack into an
-// architecture-specific type and then copies it out to task memory.
-func (t *Task) CopyOutSignalStack(addr hostarch.Addr, s *arch.SignalStack) error {
-	n := t.Arch().NewSignalStack()
-	n.SerializeFrom(s)
-	_, err := n.CopyOut(t, addr)
-	return err
-}
-
-// CopyInSignalStack copies an architecture-specific stack_t from task memory
-// and then converts it into a SignalStack.
-func (t *Task) CopyInSignalStack(addr hostarch.Addr) (arch.SignalStack, error) {
-	n := t.Arch().NewSignalStack()
-	var s arch.SignalStack
-	if _, err := n.CopyIn(t, addr); err != nil {
-		return s, err
-	}
-	n.DeserializeTo(&s)
-	return s, nil
-}
-
 // groupStop is a TaskStop placed on tasks that have received a stop signal
 // (SIGSTOP, SIGTSTP, SIGTTIN, SIGTTOU). (The term "group-stop" originates from
 // the ptrace man page.)
diff --git a/pkg/sentry/kernel/task_start.go b/pkg/sentry/kernel/task_start.go
index 32031cd70..41fd2d471 100644
--- a/pkg/sentry/kernel/task_start.go
+++ b/pkg/sentry/kernel/task_start.go
@@ -18,7 +18,6 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/hostarch"
-	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/futex"
@@ -131,7 +130,7 @@ func (ts *TaskSet) newTask(cfg *TaskConfig) (*Task, error) {
 		runState:           (*runApp)(nil),
 		interruptChan:      make(chan struct{}, 1),
 		signalMask:         cfg.SignalMask,
-		signalStack:        arch.SignalStack{Flags: arch.SignalStackFlagDisable},
+		signalStack:        linux.SignalStack{Flags: linux.SS_DISABLE},
 		image:              *image,
 		fsContext:          cfg.FSContext,
 		fdTable:            cfg.FDTable,
diff --git a/pkg/sentry/syscalls/linux/sys_signal.go b/pkg/sentry/syscalls/linux/sys_signal.go
index 1249c31a2..39a333215 100644
--- a/pkg/sentry/syscalls/linux/sys_signal.go
+++ b/pkg/sentry/syscalls/linux/sys_signal.go
@@ -325,13 +325,12 @@ func Sigaltstack(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 
 	alt := t.SignalStack()
 	if oldaddr != 0 {
-		if err := t.CopyOutSignalStack(oldaddr, &alt); err != nil {
+		if _, err := alt.CopyOut(t, oldaddr); err != nil {
 			return 0, nil, err
 		}
 	}
 	if setaddr != 0 {
-		alt, err := t.CopyInSignalStack(setaddr)
-		if err != nil {
+		if _, err := alt.CopyIn(t, setaddr); err != nil {
 			return 0, nil, err
 		}
 		// The signal stack cannot be changed if the task is currently