internal/runtime/syscall: rename to internal/runtime/syscall/linux

All code in internal/runtime/syscall is Linux-specific, so better
move it to a new linux sub-directory. This way it will be easier
to factor out runtime syscall code from other platforms, e.g.
Windows.

Updates #51087.

Change-Id: Idd2a52444b33bf3ad576b47fd232e990cdc8ae75
Reviewed-on: https://go-review.googlesource.com/c/go/+/689155
Reviewed-by: Michael Knyszek <[email protected]>
Reviewed-by: Michael Pratt <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: qmuntal

src/cmd/internal/objabi/pkgspecial.go

@@ -56,7 +56,7 @@ var runtimePkgs = []string{
 	"internal/runtime/math",
 	"internal/runtime/strconv",
 	"internal/runtime/sys",
-	"internal/runtime/syscall",
+	"internal/runtime/syscall/linux",
 
 	"internal/abi",
 	"internal/bytealg",
@@ -94,7 +94,7 @@ var allowAsmABIPkgs = []string{
 	"syscall",
 	"internal/bytealg",
 	"internal/chacha8rand",
-	"internal/runtime/syscall",
+	"internal/runtime/syscall/linux",
 	"internal/runtime/startlinetest",
 }
 

src/go/build/deps_test.go

@@ -91,7 +91,7 @@ var depsRules = `
 	< internal/msan
 	< internal/asan
 	< internal/runtime/sys
-	< internal/runtime/syscall
+	< internal/runtime/syscall/linux
 	< internal/runtime/atomic
 	< internal/runtime/exithook
 	< internal/runtime/gc

src/internal/coverage/pkid.go

@@ -31,7 +31,7 @@ package coverage
 //    slot: 6 path='internal/runtime/math'  hard-coded id: 6
 //    slot: 7 path='internal/bytealg'  hard-coded id: 7
 //    slot: 8 path='internal/goexperiment'
-//    slot: 9 path='internal/runtime/syscall'  hard-coded id: 8
+//    slot: 9 path='internal/runtime/syscall/linux'  hard-coded id: 8
 //    slot: 10 path='runtime'  hard-coded id: 9
 //    fatal error: runtime.addCovMeta
 //
@@ -66,7 +66,7 @@ var rtPkgs = [...]string{
 	"internal/runtime/strconv",
 	"internal/runtime/sys",
 	"internal/runtime/maps",
-	"internal/runtime/syscall",
+	"internal/runtime/syscall/linux",
 	"internal/runtime/cgroup",
 	"internal/stringslite",
 	"runtime",

src/internal/runtime/cgroup/cgroup_linux.go

@@ -7,7 +7,7 @@ package cgroup
 import (
 	"internal/bytealg"
 	"internal/runtime/strconv"
-	"internal/runtime/syscall"
+	"internal/runtime/syscall/linux"
 )
 
 var (
@@ -77,10 +77,10 @@ type CPU struct {
 func (c CPU) Close() {
 	switch c.version {
 	case V1:
-		syscall.Close(c.quotaFD)
-		syscall.Close(c.periodFD)
+		linux.Close(c.quotaFD)
+		linux.Close(c.periodFD)
 	case V2:
-		syscall.Close(c.quotaFD)
+		linux.Close(c.quotaFD)
 	default:
 		throw("impossible cgroup version")
 	}
@@ -112,7 +112,7 @@ func OpenCPU(scratch []byte) (CPU, error) {
 	case 1:
 		n2 := copy(base[n:], v1QuotaFile)
 		path := base[:n+n2]
-		quotaFD, errno := syscall.Open(&path[0], syscall.O_RDONLY|syscall.O_CLOEXEC, 0)
+		quotaFD, errno := linux.Open(&path[0], linux.O_RDONLY|linux.O_CLOEXEC, 0)
 		if errno != 0 {
 			// This may fail if this process was migrated out of
 			// the cgroup found by FindCPU and that cgroup has been
@@ -122,7 +122,7 @@ func OpenCPU(scratch []byte) (CPU, error) {
 
 		n2 = copy(base[n:], v1PeriodFile)
 		path = base[:n+n2]
-		periodFD, errno := syscall.Open(&path[0], syscall.O_RDONLY|syscall.O_CLOEXEC, 0)
+		periodFD, errno := linux.Open(&path[0], linux.O_RDONLY|linux.O_CLOEXEC, 0)
 		if errno != 0 {
 			// This may fail if this process was migrated out of
 			// the cgroup found by FindCPU and that cgroup has been
@@ -139,7 +139,7 @@ func OpenCPU(scratch []byte) (CPU, error) {
 	case 2:
 		n2 := copy(base[n:], v2MaxFile)
 		path := base[:n+n2]
-		maxFD, errno := syscall.Open(&path[0], syscall.O_RDONLY|syscall.O_CLOEXEC, 0)
+		maxFD, errno := linux.Open(&path[0], linux.O_RDONLY|linux.O_CLOEXEC, 0)
 		if errno != 0 {
 			// This may fail if this process was migrated out of
 			// the cgroup found by FindCPU and that cgroup has been
@@ -200,7 +200,7 @@ func readV1Number(fd int) (int64, error) {
 	//
 	// Always read from the beginning of the file to get a fresh value.
 	var b [64]byte
-	n, errno := syscall.Pread(fd, b[:], 0)
+	n, errno := linux.Pread(fd, b[:], 0)
 	if errno != 0 {
 		return 0, errSyscallFailed
 	}
@@ -248,7 +248,7 @@ func readV2Limit(fd int) (float64, bool, error) {
 	//
 	// Always read from the beginning of the file to get a fresh value.
 	var b [64]byte
-	n, errno := syscall.Pread(fd, b[:], 0)
+	n, errno := linux.Pread(fd, b[:], 0)
 	if errno != 0 {
 		return 0, false, errSyscallFailed
 	}
@@ -345,22 +345,22 @@ func FindCPU(out []byte, scratch []byte) (int, Version, error) {
 // Returns ErrNoCgroup if the process is not in a CPU cgroup.
 func FindCPURelativePath(out []byte, scratch []byte) (int, Version, error) {
 	path := []byte("/proc/self/cgroup\x00")
-	fd, errno := syscall.Open(&path[0], syscall.O_RDONLY|syscall.O_CLOEXEC, 0)
-	if errno == syscall.ENOENT {
+	fd, errno := linux.Open(&path[0], linux.O_RDONLY|linux.O_CLOEXEC, 0)
+	if errno == linux.ENOENT {
 		return 0, 0, ErrNoCgroup
 	} else if errno != 0 {
 		return 0, 0, errSyscallFailed
 	}
 
 	// The relative path always starts with /, so we can directly append it
 	// to the mount point.
-	n, version, err := parseCPURelativePath(fd, syscall.Read, out[:], scratch)
+	n, version, err := parseCPURelativePath(fd, linux.Read, out[:], scratch)
 	if err != nil {
-		syscall.Close(fd)
+		linux.Close(fd)
 		return 0, 0, err
 	}
 
-	syscall.Close(fd)
+	linux.Close(fd)
 	return n, version, nil
 }
 
@@ -489,19 +489,19 @@ func FindCPUMountPoint(out []byte, scratch []byte) (int, error) {
 	checkBufferSize(scratch, ParseSize)
 
 	path := []byte("/proc/self/mountinfo\x00")
-	fd, errno := syscall.Open(&path[0], syscall.O_RDONLY|syscall.O_CLOEXEC, 0)
-	if errno == syscall.ENOENT {
+	fd, errno := linux.Open(&path[0], linux.O_RDONLY|linux.O_CLOEXEC, 0)
+	if errno == linux.ENOENT {
 		return 0, ErrNoCgroup
 	} else if errno != 0 {
 		return 0, errSyscallFailed
 	}
 
-	n, err := parseCPUMount(fd, syscall.Read, out, scratch)
+	n, err := parseCPUMount(fd, linux.Read, out, scratch)
 	if err != nil {
-		syscall.Close(fd)
+		linux.Close(fd)
 		return 0, err
 	}
-	syscall.Close(fd)
+	linux.Close(fd)
 
 	return n, nil
 }

src/internal/runtime/cgroup/line_reader.go

@@ -55,7 +55,7 @@ type lineReader struct {
 // remainder of the line skipped. See next for more details.
 //
 // read is the function used to read more bytes from fd. This is usually
-// internal/runtime/syscall.Read. Note that this follows syscall semantics (not
+// internal/runtime/syscall/linux.Read. Note that this follows syscall semantics (not
 // io.Reader), so EOF is indicated with n=0, errno=0.
 func newLineReader(fd int, scratch []byte, read func(fd int, b []byte) (n int, errno uintptr)) *lineReader {
 	return &lineReader{