[dev.typeparams] all: merge dev.regabi (23b0c1f) into dev.typeparams

Merge List:

+ 2021-02-02 23b0c1f76e [dev.regabi] all: merge master (fca94ab) into dev.regabi
+ 2021-02-02 fca94ab3ab spec: improve the example in Type assertions section
+ 2021-02-02 98f8454a73 cmd/link: don't decode type symbol in shared library in deadcode
+ 2021-02-02 1426a571b7 cmd/link: fix off-by-1 error in findShlibSection
+ 2021-02-01 32e789f4fb test: fix incorrectly laid out instructions in issue11656.go
+ 2021-02-01 ca6999e27c [dev.regabi] test: add a test for inlining closures
+ 2021-02-01 0b6cfea634 doc/go1.16: document that on OpenBSD syscalls are now made through libc
+ 2021-02-01 26e29aa15a cmd/link: disable TestPIESize if CGO isn't enabled
+ 2021-02-01 6ac91e460c doc/go1.16: minor markup fixes
+ 2021-01-29 44361140c0 embed: update docs for proposal tweaks
+ 2021-01-29 68058edc39 runtime: document pointer write atomicity for memclrNoHeapPointers
+ 2021-01-28 c8bd8010ff syscall: generate readlen/writelen for openbsd libc
+ 2021-01-28 41bb49b878 cmd/go: revert TestScript/build_trimpath to use ioutil.ReadFile
+ 2021-01-28 725a642c2d runtime: correct syscall10/syscall10X on openbsd/amd64
+ 2021-01-28 4b068cafb5 doc/go1.16: document go/build/constraint package
+ 2021-01-28 376518d77f runtime,syscall: convert syscall on openbsd/arm64 to libc
+ 2021-01-27 aca22bddf2 [dev.regabi] cmd/compile: remove nested functions from expands_calls.go
+ 2021-01-27 667e08ba8c [dev.regabi] cmd/go: Use GOMAXPROCS to limit default build, compile parallelism
+ 2021-01-27 00f2ff5c94 api/go1.16: add go/build/constraint APIs
+ 2021-01-27 35334caf18 crypto/x509: remove leftover CertificateRequest field
+ 2021-01-27 a5a5e2c968 runtime: make sure to remove open-coded defer entries in all cases after a recover
+ 2021-01-27 8cfa01943a runtime: block console ctrlhandler when the signal is handled
+ 2021-01-27 ff9e8364c6 cmd/go: skip issue33139 when the 'cc' script command is unavailable
+ 2021-01-27 cd176b3615 runtime: switch runtime to libc for openbsd/arm64
+ 2021-01-27 6c8fbfbdcf runtime: convert openbsd/arm64 locking to libc
+ 2021-01-27 5cdf0da1bf syscall: clean up mkasm related changes
+ 2021-01-27 210f70e298 doc/go1.16: fix closing brace in .Export format
+ 2021-01-27 0f797f168d math: fix typo in sqrt.go code comment
+ 2021-01-26 9b636feafe [dev.regabi] cmd/compile: missing last patch set for cl286013
+ 2021-01-26 f7dad5eae4 [dev.regabi] cmd/compile: remove leftover code form late call lowering work
+ 2021-01-26 8634a234df runtime,syscall: convert syscall on openbsd/amd64 to libc
+ 2021-01-26 1d5e14632e os: further document limitations around naked file descriptors
+ 2021-01-26 cf263e9f77 os: correct names in CreateTemp and MkdirTemp doc comments
+ 2021-01-26 ce8b318624 net/http/fcgi: remove locking added to prevent a test-only race

Change-Id: Ibd38d559c8a5b0aa32dd0d3a8cdf6876368a3aeb

1 files changed, 261 insertions, 0 deletions

diff --git a/src/syscall/exec_libc2.go b/src/syscall/exec_libc2.go
new file mode 100644
index 0000000000..45d3f85baf
--- /dev/null
+++ b/src/syscall/exec_libc2.go
@@ -0,0 +1,261 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin openbsd,amd64 openbsd,arm64
+
+package syscall
+
+import (
+	"unsafe"
+)
+
+type SysProcAttr struct {
+	Chroot     string      // Chroot.
+	Credential *Credential // Credential.
+	Ptrace     bool        // Enable tracing.
+	Setsid     bool        // Create session.
+	// Setpgid sets the process group ID of the child to Pgid,
+	// or, if Pgid == 0, to the new child's process ID.
+	Setpgid bool
+	// Setctty sets the controlling terminal of the child to
+	// file descriptor Ctty. Ctty must be a descriptor number
+	// in the child process: an index into ProcAttr.Files.
+	// This is only meaningful if Setsid is true.
+	Setctty bool
+	Noctty  bool // Detach fd 0 from controlling terminal
+	Ctty    int  // Controlling TTY fd
+	// Foreground places the child process group in the foreground.
+	// This implies Setpgid. The Ctty field must be set to
+	// the descriptor of the controlling TTY.
+	// Unlike Setctty, in this case Ctty must be a descriptor
+	// number in the parent process.
+	Foreground bool
+	Pgid       int // Child's process group ID if Setpgid.
+}
+
+// Implemented in runtime package.
+func runtime_BeforeFork()
+func runtime_AfterFork()
+func runtime_AfterForkInChild()
+
+// Fork, dup fd onto 0..len(fd), and exec(argv0, argvv, envv) in child.
+// If a dup or exec fails, write the errno error to pipe.
+// (Pipe is close-on-exec so if exec succeeds, it will be closed.)
+// In the child, this function must not acquire any locks, because
+// they might have been locked at the time of the fork. This means
+// no rescheduling, no malloc calls, and no new stack segments.
+// For the same reason compiler does not race instrument it.
+// The calls to rawSyscall are okay because they are assembly
+// functions that do not grow the stack.
+//go:norace
+func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr *ProcAttr, sys *SysProcAttr, pipe int) (pid int, err Errno) {
+	// Declare all variables at top in case any
+	// declarations require heap allocation (e.g., err1).
+	var (
+		r1     uintptr
+		err1   Errno
+		nextfd int
+		i      int
+	)
+
+	// guard against side effects of shuffling fds below.
+	// Make sure that nextfd is beyond any currently open files so
+	// that we can't run the risk of overwriting any of them.
+	fd := make([]int, len(attr.Files))
+	nextfd = len(attr.Files)
+	for i, ufd := range attr.Files {
+		if nextfd < int(ufd) {
+			nextfd = int(ufd)
+		}
+		fd[i] = int(ufd)
+	}
+	nextfd++
+
+	// About to call fork.
+	// No more allocation or calls of non-assembly functions.
+	runtime_BeforeFork()
+	r1, _, err1 = rawSyscall(funcPC(libc_fork_trampoline), 0, 0, 0)
+	if err1 != 0 {
+		runtime_AfterFork()
+		return 0, err1
+	}
+
+	if r1 != 0 {
+		// parent; return PID
+		runtime_AfterFork()
+		return int(r1), 0
+	}
+
+	// Fork succeeded, now in child.
+
+	runtime_AfterForkInChild()
+
+	// Enable tracing if requested.
+	if sys.Ptrace {
+		if err := ptrace(PTRACE_TRACEME, 0, 0, 0); err != nil {
+			err1 = err.(Errno)
+			goto childerror
+		}
+	}
+
+	// Session ID
+	if sys.Setsid {
+		_, _, err1 = rawSyscall(funcPC(libc_setsid_trampoline), 0, 0, 0)
+		if err1 != 0 {
+			goto childerror
+		}
+	}
+
+	// Set process group
+	if sys.Setpgid || sys.Foreground {
+		// Place child in process group.
+		_, _, err1 = rawSyscall(funcPC(libc_setpgid_trampoline), 0, uintptr(sys.Pgid), 0)
+		if err1 != 0 {
+			goto childerror
+		}
+	}
+
+	if sys.Foreground {
+		pgrp := sys.Pgid
+		if pgrp == 0 {
+			r1, _, err1 = rawSyscall(funcPC(libc_getpid_trampoline), 0, 0, 0)
+			if err1 != 0 {
+				goto childerror
+			}
+
+			pgrp = int(r1)
+		}
+
+		// Place process group in foreground.
+		_, _, err1 = rawSyscall(funcPC(libc_ioctl_trampoline), uintptr(sys.Ctty), uintptr(TIOCSPGRP), uintptr(unsafe.Pointer(&pgrp)))
+		if err1 != 0 {
+			goto childerror
+		}
+	}
+
+	// Chroot
+	if chroot != nil {
+		_, _, err1 = rawSyscall(funcPC(libc_chroot_trampoline), uintptr(unsafe.Pointer(chroot)), 0, 0)
+		if err1 != 0 {
+			goto childerror
+		}
+	}
+
+	// User and groups
+	if cred := sys.Credential; cred != nil {
+		ngroups := uintptr(len(cred.Groups))
+		groups := uintptr(0)
+		if ngroups > 0 {
+			groups = uintptr(unsafe.Pointer(&cred.Groups[0]))
+		}
+		if !cred.NoSetGroups {
+			_, _, err1 = rawSyscall(funcPC(libc_setgroups_trampoline), ngroups, groups, 0)
+			if err1 != 0 {
+				goto childerror
+			}
+		}
+		_, _, err1 = rawSyscall(funcPC(libc_setgid_trampoline), uintptr(cred.Gid), 0, 0)
+		if err1 != 0 {
+			goto childerror
+		}
+		_, _, err1 = rawSyscall(funcPC(libc_setuid_trampoline), uintptr(cred.Uid), 0, 0)
+		if err1 != 0 {
+			goto childerror
+		}
+	}
+
+	// Chdir
+	if dir != nil {
+		_, _, err1 = rawSyscall(funcPC(libc_chdir_trampoline), uintptr(unsafe.Pointer(dir)), 0, 0)
+		if err1 != 0 {
+			goto childerror
+		}
+	}
+
+	// Pass 1: look for fd[i] < i and move those up above len(fd)
+	// so that pass 2 won't stomp on an fd it needs later.
+	if pipe < nextfd {
+		_, _, err1 = rawSyscall(funcPC(libc_dup2_trampoline), uintptr(pipe), uintptr(nextfd), 0)
+		if err1 != 0 {
+			goto childerror
+		}
+		rawSyscall(funcPC(libc_fcntl_trampoline), uintptr(nextfd), F_SETFD, FD_CLOEXEC)
+		pipe = nextfd
+		nextfd++
+	}
+	for i = 0; i < len(fd); i++ {
+		if fd[i] >= 0 && fd[i] < int(i) {
+			if nextfd == pipe { // don't stomp on pipe
+				nextfd++
+			}
+			_, _, err1 = rawSyscall(funcPC(libc_dup2_trampoline), uintptr(fd[i]), uintptr(nextfd), 0)
+			if err1 != 0 {
+				goto childerror
+			}
+			rawSyscall(funcPC(libc_fcntl_trampoline), uintptr(nextfd), F_SETFD, FD_CLOEXEC)
+			fd[i] = nextfd
+			nextfd++
+		}
+	}
+
+	// Pass 2: dup fd[i] down onto i.
+	for i = 0; i < len(fd); i++ {
+		if fd[i] == -1 {
+			rawSyscall(funcPC(libc_close_trampoline), uintptr(i), 0, 0)
+			continue
+		}
+		if fd[i] == int(i) {
+			// dup2(i, i) won't clear close-on-exec flag on Linux,
+			// probably not elsewhere either.
+			_, _, err1 = rawSyscall(funcPC(libc_fcntl_trampoline), uintptr(fd[i]), F_SETFD, 0)
+			if err1 != 0 {
+				goto childerror
+			}
+			continue
+		}
+		// The new fd is created NOT close-on-exec,
+		// which is exactly what we want.
+		_, _, err1 = rawSyscall(funcPC(libc_dup2_trampoline), uintptr(fd[i]), uintptr(i), 0)
+		if err1 != 0 {
+			goto childerror
+		}
+	}
+
+	// By convention, we don't close-on-exec the fds we are
+	// started with, so if len(fd) < 3, close 0, 1, 2 as needed.
+	// Programs that know they inherit fds >= 3 will need
+	// to set them close-on-exec.
+	for i = len(fd); i < 3; i++ {
+		rawSyscall(funcPC(libc_close_trampoline), uintptr(i), 0, 0)
+	}
+
+	// Detach fd 0 from tty
+	if sys.Noctty {
+		_, _, err1 = rawSyscall(funcPC(libc_ioctl_trampoline), 0, uintptr(TIOCNOTTY), 0)
+		if err1 != 0 {
+			goto childerror
+		}
+	}
+
+	// Set the controlling TTY to Ctty
+	if sys.Setctty {
+		_, _, err1 = rawSyscall(funcPC(libc_ioctl_trampoline), uintptr(sys.Ctty), uintptr(TIOCSCTTY), 0)
+		if err1 != 0 {
+			goto childerror
+		}
+	}
+
+	// Time to exec.
+	_, _, err1 = rawSyscall(funcPC(libc_execve_trampoline),
+		uintptr(unsafe.Pointer(argv0)),
+		uintptr(unsafe.Pointer(&argv[0])),
+		uintptr(unsafe.Pointer(&envv[0])))
+
+childerror:
+	// send error code on pipe
+	rawSyscall(funcPC(libc_write_trampoline), uintptr(pipe), uintptr(unsafe.Pointer(&err1)), unsafe.Sizeof(err1))
+	for {
+		rawSyscall(funcPC(libc_exit_trampoline), 253, 0, 0)
+	}
+}