Enable stat syscall support on arm64.

x86 and arm64 use a different stat struct in Linux
kernel, so the stat() syscall implementation has
to handle the file stat data separately.

Signed-off-by: Haibo Xu <haibo.xu@arm.com>
Change-Id: If3986e915a667362257a54e7fbbcc1fe18951015
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/gvisor/pull/1493 from xiaobo55x:stat f15a216d9297eb9a96d2c483d396a9919145d7fa
PiperOrigin-RevId: 290274287

1 files changed, 77 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/sys_stat_arm64.go b/pkg/sentry/syscalls/linux/sys_stat_arm64.go
new file mode 100644
index 000000000..3e1251e0b
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_stat_arm64.go
@@ -0,0 +1,77 @@
+// Copyright 2020 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 arm64
+
+package linux
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/binary"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+)
+
+// copyOutStat copies the attributes (sattr, uattr) to the struct stat at
+// address dst in t's address space. It encodes the stat struct to bytes
+// manually, as stat() is a very common syscall for many applications, and
+// t.CopyObjectOut has noticeable performance impact due to its many slice
+// allocations and use of reflection.
+func copyOutStat(t *kernel.Task, dst usermem.Addr, sattr fs.StableAttr, uattr fs.UnstableAttr) error {
+	b := t.CopyScratchBuffer(int(linux.SizeOfStat))[:0]
+
+	// Dev (uint64)
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(sattr.DeviceID))
+	// Ino (uint64)
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(sattr.InodeID))
+	// Mode (uint32)
+	b = binary.AppendUint32(b, usermem.ByteOrder, sattr.Type.LinuxType()|uint32(uattr.Perms.LinuxMode()))
+	// Nlink (uint32)
+	b = binary.AppendUint32(b, usermem.ByteOrder, uint32(uattr.Links))
+	// UID (uint32)
+	b = binary.AppendUint32(b, usermem.ByteOrder, uint32(uattr.Owner.UID.In(t.UserNamespace()).OrOverflow()))
+	// GID (uint32)
+	b = binary.AppendUint32(b, usermem.ByteOrder, uint32(uattr.Owner.GID.In(t.UserNamespace()).OrOverflow()))
+	// Rdev (uint64)
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(linux.MakeDeviceID(sattr.DeviceFileMajor, sattr.DeviceFileMinor)))
+	// Padding (uint64)
+	b = binary.AppendUint64(b, usermem.ByteOrder, 0)
+	// Size (uint64)
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(uattr.Size))
+	// Blksize (uint32)
+	b = binary.AppendUint32(b, usermem.ByteOrder, uint32(sattr.BlockSize))
+	// Padding (uint32)
+	b = binary.AppendUint32(b, usermem.ByteOrder, 0)
+	// Blocks (uint64)
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(uattr.Usage/512))
+
+	// ATime
+	atime := uattr.AccessTime.Timespec()
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(atime.Sec))
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(atime.Nsec))
+
+	// MTime
+	mtime := uattr.ModificationTime.Timespec()
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(mtime.Sec))
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(mtime.Nsec))
+
+	// CTime
+	ctime := uattr.StatusChangeTime.Timespec()
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(ctime.Sec))
+	b = binary.AppendUint64(b, usermem.ByteOrder, uint64(ctime.Nsec))
+
+	_, err := t.CopyOutBytes(dst, b)
+	return err
+}