syscall: clean up mkasm related changes

The mkasm_darwin.go file was renamed to mkasm.go in CL 270380, with OpenBSD
support being added. The mkasm_openbsd.go file should not have been merged,
so remove it. Fix up references to mkasm_$GOOS.go and provide $GOOS as an
argument on invocation.

Updates #36435

Change-Id: I868d3f2146973d026e6a663d437749dbb6b312ec
Reviewed-on: https://go-review.googlesource.com/c/go/+/286812
Trust: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/syscall/mkall.sh

@@ -125,13 +125,13 @@ darwin_amd64)
 	mkerrors="$mkerrors -m64"
 	mksyscall="./mksyscall.pl -darwin"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
-	mkasm="go run mkasm_darwin.go"
+	mkasm="go run mkasm.go"
 	;;
 darwin_arm64)
 	mkerrors="$mkerrors -m64"
 	mksyscall="./mksyscall.pl -darwin"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
-	mkasm="go run mkasm_darwin.go"
+	mkasm="go run mkasm.go"
 	;;
 dragonfly_amd64)
 	mkerrors="$mkerrors -m64"
@@ -299,7 +299,7 @@ openbsd_amd64)
 	zsysctl="zsysctl_openbsd.go"
 	mksysnum="curl -s 'http://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/kern/syscalls.master' | ./mksysnum_openbsd.pl"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
-	mkasm="go run mkasm_openbsd.go"
+	mkasm="go run mkasm.go"
 	;;
 openbsd_arm)
 	GOOSARCH_in="syscall_openbsd1.go syscall_openbsd_$GOARCH.go"
@@ -372,5 +372,5 @@ esac
 		# Therefore, "go run" tries to recompile syscall package but ztypes is empty and it fails.
 		echo "$mktypes types_$GOOS.go |go run mkpost.go >ztypes_$GOOSARCH.go.NEW && mv ztypes_$GOOSARCH.go.NEW ztypes_$GOOSARCH.go";
 	fi
-	if [ -n "$mkasm" ]; then echo "$mkasm $GOARCH"; fi
+	if [ -n "$mkasm" ]; then echo "$mkasm $GOOS $GOARCH"; fi
 ) | $run

src/syscall/mkasm_openbsd.go

@@ -1,58 +0,0 @@
-// Copyright 2020 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 ignore
-
-// mkasm_openbsd.go generates assembly trampolines to call libc routines from Go.
-// This program must be run after mksyscall.pl.
-package main
-
-import (
-	"bytes"
-	"fmt"
-	"io/ioutil"
-	"log"
-	"os"
-	"strings"
-)
-
-func main() {
-	in1, err := ioutil.ReadFile("syscall_openbsd.go")
-	if err != nil {
-		log.Fatalf("can't open syscall_openbsd.go: %s", err)
-	}
-	arch := os.Args[1]
-	in2, err := ioutil.ReadFile(fmt.Sprintf("syscall_openbsd_%s.go", arch))
-	if err != nil {
-		log.Fatalf("can't open syscall_openbsd_%s.go: %s", arch, err)
-	}
-	in3, err := ioutil.ReadFile(fmt.Sprintf("zsyscall_openbsd_%s.go", arch))
-	if err != nil {
-		log.Fatalf("can't open zsyscall_openbsd_%s.go: %s", arch, err)
-	}
-	in := string(in1) + string(in2) + string(in3)
-
-	trampolines := map[string]bool{}
-
-	var out bytes.Buffer
-
-	fmt.Fprintf(&out, "// go run mkasm_openbsd.go %s\n", strings.Join(os.Args[1:], " "))
-	fmt.Fprintf(&out, "// Code generated by the command above; DO NOT EDIT.\n")
-	fmt.Fprintf(&out, "#include \"textflag.h\"\n")
-	for _, line := range strings.Split(in, "\n") {
-		if !strings.HasPrefix(line, "func ") || !strings.HasSuffix(line, "_trampoline()") {
-			continue
-		}
-		fn := line[5 : len(line)-13]
-		if !trampolines[fn] {
-			trampolines[fn] = true
-			fmt.Fprintf(&out, "TEXT ·%s_trampoline(SB),NOSPLIT,$0-0\n", fn)
-			fmt.Fprintf(&out, "\tJMP\t%s(SB)\n", fn)
-		}
-	}
-	err = ioutil.WriteFile(fmt.Sprintf("zsyscall_openbsd_%s.s", arch), out.Bytes(), 0644)
-	if err != nil {
-		log.Fatalf("can't write zsyscall_openbsd_%s.s: %s", arch, err)
-	}
-}

src/syscall/mksyscall.pl

@@ -352,7 +352,7 @@ while(<>) {
 			# The assembly trampoline that jumps to the libc routine.
 			$text .= "func ${funcname}_trampoline()\n";
 			# Map syscall.funcname to just plain funcname.
-			# (The jump to this function is in the assembly trampoline, generated by mkasm_$GOOS.go.)
+			# (The jump to this function is in the assembly trampoline, generated by mkasm.go.)
 			$text .= "//go:linkname $funcname $funcname\n";
 			# Tell the linker that funcname can be found in libSystem using varname without the libc_ prefix.
 			my $basename = substr $funcname, 5;