Dynamically determine the address space size

PiperOrigin-RevId: 501362170

pkg/abi/linux/BUILD

@@ -56,6 +56,8 @@ go_library(
         "linux.go",
         "membarrier.go",
         "mm.go",
+        "mm_amd64.go",
+        "mm_arm64.go",
         "mqueue.go",
         "msgqueue.go",
         "netdevice.go",
@@ -99,6 +101,7 @@ go_library(
         "//pkg/hostarch",
         "//pkg/marshal",
         "//pkg/marshal/primitive",
+        "@org_golang_x_sys//unix:go_default_library",
     ],
 )
 

pkg/abi/linux/mm.go

@@ -14,6 +14,12 @@
 
 package linux
 
+import (
+	"fmt"
+
+	"golang.org/x/sys/unix"
+)
+
 // Protections for mmap(2).
 const (
 	PROT_NONE      = 0
@@ -128,3 +134,26 @@ const (
 
 	MPOL_MF_VALID = MPOL_MF_STRICT | MPOL_MF_MOVE | MPOL_MF_MOVE_ALL
 )
+
+// TaskSize is the address space size.
+var TaskSize = func() uintptr {
+	pageSize := uintptr(unix.Getpagesize())
+	for _, s := range feasibleTaskSizes {
+		// mmap returns ENOMEM if addr is greater than TASK_SIZE,
+		// otherwise it returns EINVAL, because addr isn't aligned to
+		// the page size.
+		_, _, errno := unix.RawSyscall6(
+			unix.SYS_MMAP,
+			s-pageSize-1,
+			512,
+			uintptr(unix.PROT_NONE),
+			uintptr(unix.MAP_ANONYMOUS|unix.MAP_PRIVATE|unix.MAP_FIXED), 0, 0)
+		if errno == unix.EINVAL {
+			return s
+		}
+		if errno != unix.ENOMEM {
+			panic(fmt.Sprintf("mmap returned unexpected error: %d", errno))
+		}
+	}
+	panic("None of the address space sizes could be successfully mmaped")
+}()

pkg/abi/linux/mm_amd64.go

@@ -0,0 +1,24 @@
+// Copyright 2023 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.
+
+//go:build amd64
+// +build amd64
+
+package linux
+
+// TASK_SIZE can be one of two values, corresponding to 4-level and 5-level
+// paging.
+//
+// The array has to be sorted in decreasing order.
+var feasibleTaskSizes = []uintptr{0xffffffffff000, 0x7ffffffff000}

pkg/abi/linux/mm_arm64.go

@@ -0,0 +1,25 @@
+// Copyright 2023 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.
+
+//go:build arm64
+// +build arm64
+
+package linux
+
+// Only 4K page size is supported on arm64. In this case, TASK_SIZE can
+// be one of three values, corresponding to 3-level, 4-level and
+// 5-level paging.
+//
+// The array has to be sorted in decreasing order.
+var feasibleTaskSizes = []uintptr{1 << 52, 1 << 48, 1 << 39}

pkg/sentry/platform/ptrace/subprocess.go

@@ -30,6 +30,14 @@ import (
 	"gvisor.dev/gvisor/pkg/sync"
 )
 
+var (
+	// maximumUserAddress is the largest possible user address.
+	maximumUserAddress = linux.TaskSize
+
+	// stubInitAddress is the initial attempt link address for the stub.
+	stubInitAddress = linux.TaskSize
+)
+
 // Linux kernel errnos which "should never be seen by user programs", but will
 // be revealed to ptrace syscall exit tracing.
 //

pkg/sentry/platform/ptrace/subprocess_amd64.go

@@ -28,12 +28,6 @@ import (
 )
 
 const (
-	// maximumUserAddress is the largest possible user address.
-	maximumUserAddress = 0x7ffffffff000
-
-	// stubInitAddress is the initial attempt link address for the stub.
-	stubInitAddress = 0x7fffffff0000
-
 	// initRegsRipAdjustment is the size of the syscall instruction.
 	initRegsRipAdjustment = 2
 )

pkg/sentry/platform/ptrace/subprocess_arm64.go

@@ -28,13 +28,6 @@ import (
 )
 
 const (
-	// maximumUserAddress is the largest possible user address.
-	maximumUserAddress = 0xfffffffff000
-
-	// stubInitAddress is the initial attempt link address for the stub.
-	// Only support 48bits VA currently.
-	stubInitAddress = 0xffffffff0000
-
 	// initRegsRipAdjustment is the size of the svc instruction.
 	initRegsRipAdjustment = 4
 )