1 files changed, 81 insertions, 0 deletions
diff --git a/pkg/sentry/arch/syscalls_arm64.go b/pkg/sentry/arch/syscalls_arm64.go
new file mode 100644
index 000000000..92d062513
--- /dev/null
+++ b/pkg/sentry/arch/syscalls_arm64.go
@@ -0,0 +1,81 @@
+// 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 arch
+
+const restartSyscallNr = uintptr(128)
+
+// SyscallSaveOrig save the value of the register R0 which is clobbered in
+// syscall handler(doSyscall()).
+//
+// In linux, at the entry of the syscall handler(el0_svc_common()), value of R0
+// is saved to the pt_regs.orig_x0 in kernel code. But currently, the orig_x0
+// was not accessible to the user space application, so we have to do the same
+// operation in the sentry code to save the R0 value into the App context.
+func (c *context64) SyscallSaveOrig() {
+	c.OrigR0 = c.Regs.Regs[0]
+}
+
+// SyscallNo returns the syscall number according to the 64-bit convention.
+func (c *context64) SyscallNo() uintptr {
+	return uintptr(c.Regs.Regs[8])
+}
+
+// SyscallArgs provides syscall arguments according to the 64-bit convention.
+//
+// Due to the way addresses are mapped for the sentry this binary *must* be
+// built in 64-bit mode. So we can just assume the syscall numbers that come
+// back match the expected host system call numbers.
+// General purpose registers usage on Arm64:
+// R0...R7: parameter/result registers.
+// R8: indirect result location register.
+// R9...R15: temporary registers.
+// R16: the first intra-procedure-call scratch register.
+// R17: the second intra-procedure-call scratch register.
+// R18: the platform register.
+// R19...R28: callee-saved registers.
+// R29: the frame pointer.
+// R30: the link register.
+func (c *context64) SyscallArgs() SyscallArguments {
+	return SyscallArguments{
+		SyscallArgument{Value: uintptr(c.OrigR0)},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[1])},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[2])},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[3])},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[4])},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[5])},
+	}
+}
+
+// RestartSyscall implements Context.RestartSyscall.
+// Prepare for system call restart, OrigR0 will be restored to R0.
+// Please see the linux code as reference:
+// arch/arm64/kernel/signal.c:do_signal()
+func (c *context64) RestartSyscall() {
+	c.Regs.Pc -= SyscallWidth
+	// R0 will be backed up into OrigR0 when entering doSyscall().
+	// Please see the linux code as reference:
+	// arch/arm64/kernel/syscall.c:el0_svc_common().
+	// Here we restore it back.
+	c.Regs.Regs[0] = uint64(c.OrigR0)
+}
+
+// RestartSyscallWithRestartBlock implements Context.RestartSyscallWithRestartBlock.
+func (c *context64) RestartSyscallWithRestartBlock() {
+	c.Regs.Pc -= SyscallWidth
+	c.Regs.Regs[0] = uint64(c.OrigR0)
+	c.Regs.Regs[8] = uint64(restartSyscallNr)
+}