From d13d62c49adca86f2101bc0b7d5a394197ece81b Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@distanz.ch>
Date: Wed, 1 Sep 2021 14:57:18 +0200
Subject: [PATCH] os, syscall: remove fallback to pipe syscall on Linux

The minimum required Linux kernel version for Go 1.18 will be changed to
2.6.32, see #45964. The pipe2 syscall was added in 2.6.27, so the
fallback to use the pipe syscall in os.Pipe and syscall.forkExecPipe on
Linux can be removed.

For #45964

Change-Id: I033a534f2b39e9bafc9980c9ce980e92f1e3a136
Reviewed-on: https://go-review.googlesource.com/c/go/+/346789
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
---
 src/os/pipe_linux.go      | 15 +--------------
 src/syscall/exec_linux.go | 14 +-------------
 2 files changed, 2 insertions(+), 27 deletions(-)

diff --git a/src/os/pipe_linux.go b/src/os/pipe_linux.go
index acd7b88e1d4..52f4e21e7c6 100644
--- a/src/os/pipe_linux.go
+++ b/src/os/pipe_linux.go
@@ -12,20 +12,7 @@ func Pipe() (r *File, w *File, err error) {
 	var p [2]int
 
 	e := syscall.Pipe2(p[0:], syscall.O_CLOEXEC)
-	// pipe2 was added in 2.6.27 and our minimum requirement is 2.6.23, so it
-	// might not be implemented.
-	if e == syscall.ENOSYS {
-		// See ../syscall/exec.go for description of lock.
-		syscall.ForkLock.RLock()
-		e = syscall.Pipe(p[0:])
-		if e != nil {
-			syscall.ForkLock.RUnlock()
-			return nil, nil, NewSyscallError("pipe", e)
-		}
-		syscall.CloseOnExec(p[0])
-		syscall.CloseOnExec(p[1])
-		syscall.ForkLock.RUnlock()
-	} else if e != nil {
+	if e != nil {
 		return nil, nil, NewSyscallError("pipe2", e)
 	}
 
diff --git a/src/syscall/exec_linux.go b/src/syscall/exec_linux.go
index ccc0e39e30b..68bce7559b9 100644
--- a/src/syscall/exec_linux.go
+++ b/src/syscall/exec_linux.go
@@ -553,19 +553,7 @@ childerror:
 
 // Try to open a pipe with O_CLOEXEC set on both file descriptors.
 func forkExecPipe(p []int) (err error) {
-	err = Pipe2(p, O_CLOEXEC)
-	// pipe2 was added in 2.6.27 and our minimum requirement is 2.6.23, so it
-	// might not be implemented.
-	if err == ENOSYS {
-		if err = Pipe(p); err != nil {
-			return
-		}
-		if _, err = fcntl(p[0], F_SETFD, FD_CLOEXEC); err != nil {
-			return
-		}
-		_, err = fcntl(p[1], F_SETFD, FD_CLOEXEC)
-	}
-	return
+	return Pipe2(p, O_CLOEXEC)
 }
 
 func formatIDMappings(idMap []SysProcIDMap) []byte {