Move ring0 package.

This allows the package to serve as a general purpose ring0 support package, as
opposed to being bound to specific sentry platforms.

Updates #5039

PiperOrigin-RevId: 355220044

1 files changed, 85 insertions, 0 deletions

diff --git a/pkg/ring0/kernel_arm64.go b/pkg/ring0/kernel_arm64.go
new file mode 100644
index 000000000..c05284641
--- /dev/null
+++ b/pkg/ring0/kernel_arm64.go
@@ -0,0 +1,85 @@
+// Copyright 2019 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 ring0
+
+// HaltAndResume halts execution and point the pointer to the resume function.
+//go:nosplit
+func HaltAndResume()
+
+// HaltEl1SvcAndResume calls Hooks.KernelSyscall and resume.
+//go:nosplit
+func HaltEl1SvcAndResume()
+
+// HaltEl1ExceptionAndResume calls Hooks.KernelException and resume.
+//go:nosplit
+func HaltEl1ExceptionAndResume()
+
+// init initializes architecture-specific state.
+func (k *Kernel) init(maxCPUs int) {
+}
+
+// init initializes architecture-specific state.
+func (c *CPU) init(cpuID int) {
+	// Set the kernel stack pointer(virtual address).
+	c.registers.Sp = uint64(c.StackTop())
+
+}
+
+// StackTop returns the kernel's stack address.
+//
+//go:nosplit
+func (c *CPU) StackTop() uint64 {
+	return uint64(kernelAddr(&c.stack[0])) + uint64(len(c.stack))
+}
+
+// IsCanonical indicates whether addr is canonical per the arm64 spec.
+//
+//go:nosplit
+func IsCanonical(addr uint64) bool {
+	return addr <= 0x0000ffffffffffff || addr > 0xffff000000000000
+}
+
+// SwitchToUser performs an eret.
+//
+// The return value is the exception vector.
+//
+// +checkescape:all
+//
+//go:nosplit
+func (c *CPU) SwitchToUser(switchOpts SwitchOpts) (vector Vector) {
+	storeAppASID(uintptr(switchOpts.UserASID))
+	if switchOpts.Flush {
+		FlushTlbByASID(uintptr(switchOpts.UserASID))
+	}
+
+	regs := switchOpts.Registers
+
+	regs.Pstate &= ^uint64(PsrFlagsClear)
+	regs.Pstate |= UserFlagsSet
+
+	EnableVFP()
+	LoadFloatingPoint(switchOpts.FloatingPointState)
+
+	kernelExitToEl0()
+
+	SaveFloatingPoint(switchOpts.FloatingPointState)
+	DisableVFP()
+
+	vector = c.vecCode
+
+	return
+}