From 354a15a234c1270bcb9b902503f61835b2ccd2d0 Mon Sep 17 00:00:00 2001
From: Michael Pratt <mpratt@google.com>
Date: Mon, 6 Jan 2020 11:41:13 -0800
Subject: Implement rseq(2)

PiperOrigin-RevId: 288342928
---
 pkg/abi/linux/rseq.go | 130 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 130 insertions(+)
 create mode 100644 pkg/abi/linux/rseq.go

(limited to 'pkg/abi/linux/rseq.go')

diff --git a/pkg/abi/linux/rseq.go b/pkg/abi/linux/rseq.go
new file mode 100644
index 000000000..76253ba30
--- /dev/null
+++ b/pkg/abi/linux/rseq.go
@@ -0,0 +1,130 @@
+// 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.
+
+package linux
+
+// Flags passed to rseq(2).
+//
+// Defined in include/uapi/linux/rseq.h.
+const (
+	// RSEQ_FLAG_UNREGISTER unregisters the current thread.
+	RSEQ_FLAG_UNREGISTER = 1 << 0
+)
+
+// Critical section flags used in RSeqCriticalSection.Flags and RSeq.Flags.
+//
+// Defined in include/uapi/linux/rseq.h.
+const (
+	// RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT inhibits restart on preemption.
+	RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT = 1 << 0
+
+	// RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL inhibits restart on signal
+	// delivery.
+	RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL = 1 << 1
+
+	// RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE inhibits restart on CPU
+	// migration.
+	RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE = 1 << 2
+)
+
+// RSeqCriticalSection describes a restartable sequences critical section. It
+// is equivalent to struct rseq_cs, defined in include/uapi/linux/rseq.h.
+//
+// In userspace, this structure is always aligned to 32 bytes.
+//
+// +marshal
+type RSeqCriticalSection struct {
+	// Version is the version of this structure. Version 0 is defined here.
+	Version uint32
+
+	// Flags are the critical section flags, defined above.
+	Flags uint32
+
+	// Start is the start address of the critical section.
+	Start uint64
+
+	// PostCommitOffset is the offset from Start of the first instruction
+	// outside of the critical section.
+	PostCommitOffset uint64
+
+	// Abort is the abort address. It must be outside the critical section,
+	// and the 4 bytes prior must match the abort signature.
+	Abort uint64
+}
+
+const (
+	// SizeOfRSeqCriticalSection is the size of RSeqCriticalSection.
+	SizeOfRSeqCriticalSection = 32
+
+	// SizeOfRSeqSignature is the size of the signature immediately
+	// preceding RSeqCriticalSection.Abort.
+	SizeOfRSeqSignature = 4
+)
+
+// Special values for RSeq.CPUID, defined in include/uapi/linux/rseq.h.
+const (
+	// RSEQ_CPU_ID_UNINITIALIZED indicates that this thread has not
+	// performed rseq initialization.
+	RSEQ_CPU_ID_UNINITIALIZED = ^uint32(0) // -1
+
+	// RSEQ_CPU_ID_REGISTRATION_FAILED indicates that rseq initialization
+	// failed.
+	RSEQ_CPU_ID_REGISTRATION_FAILED = ^uint32(1) // -2
+)
+
+// RSeq is the thread-local restartable sequences config/status. It
+// is equivalent to struct rseq, defined in include/uapi/linux/rseq.h.
+//
+// In userspace, this structure is always aligned to 32 bytes.
+type RSeq struct {
+	// CPUIDStart contains the current CPU ID if rseq is initialized.
+	//
+	// This field should only be read by the thread which registered this
+	// structure, and must be read atomically.
+	CPUIDStart uint32
+
+	// CPUID contains the current CPU ID or one of the CPU ID special
+	// values defined above.
+	//
+	// This field should only be read by the thread which registered this
+	// structure, and must be read atomically.
+	CPUID uint32
+
+	// RSeqCriticalSection is a pointer to the current RSeqCriticalSection
+	// block, or NULL. It is reset to NULL by the kernel on restart or
+	// non-restarting preempt/signal.
+	//
+	// This field should only be written by the thread which registered
+	// this structure, and must be written atomically.
+	RSeqCriticalSection uint64
+
+	// Flags are the critical section flags that apply to all critical
+	// sections on this thread, defined above.
+	Flags uint32
+}
+
+const (
+	// SizeOfRSeq is the size of RSeq.
+	//
+	// Note that RSeq is naively 24 bytes. However, it has 32-byte
+	// alignment, which in C increases sizeof to 32. That is the size that
+	// the Linux kernel uses.
+	SizeOfRSeq = 32
+
+	// AlignOfRSeq is the standard alignment of RSeq.
+	AlignOfRSeq = 32
+
+	// OffsetOfRSeqCriticalSection is the offset of RSeqCriticalSection in RSeq.
+	OffsetOfRSeqCriticalSection = 8
+)
-- 
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