cmd/compile: make jump table symbol local

When using plugins, if the plugin and the main executable both
have the same function, and if it uses jump table, currently the
jump table symbol have the same name so it will be deduplicated by
the dynamic linker. This causes a function in the plugin may (in
the middle of the function) jump to the function with the same name
in the main executable (or vice versa). But the function may be
compiled slightly differently, because the plugin needs to be PIC.
Jumping from the middle of one function to the other will not work.
Avoid this problem by marking the jump table symbol local to a DSO.

Fixes #53989.

Change-Id: I2b573b9dfc22401c8a09ffe9b9ea8bb83d3700ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/418960
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

misc/cgo/testplugin/plugin_test.go

@@ -307,6 +307,12 @@ func TestIssue52937(t *testing.T) {
 	goCmd(t, "build", "-buildmode=plugin", "-o", "issue52937.so", "./issue52937/main.go")
 }
 
+func TestIssue53989(t *testing.T) {
+	goCmd(t, "build", "-buildmode=plugin", "-o", "issue53989.so", "./issue53989/plugin.go")
+	goCmd(t, "build", "-o", "issue53989.exe", "./issue53989/main.go")
+	run(t, "./issue53989.exe")
+}
+
 func TestForkExec(t *testing.T) {
 	// Issue 38824: importing the plugin package causes it hang in forkExec on darwin.
 

misc/cgo/testplugin/testdata/issue53989/main.go

@@ -0,0 +1,32 @@
+// Copyright 2022 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.
+
+// Issue 53989: the use of jump table caused a function
+// from the plugin jumps in the middle of the function
+// to the function with the same name in the main
+// executable. As these two functions may be compiled
+// differently as plugin needs to be PIC, this causes
+// crash.
+
+package main
+
+import (
+	"plugin"
+
+	"testplugin/issue53989/p"
+)
+
+func main() {
+	p.Square(7) // call the function in main executable
+
+	p, err := plugin.Open("issue53989.so")
+	if err != nil {
+		panic(err)
+	}
+	f, err := p.Lookup("Square")
+	if err != nil {
+		panic(err)
+	}
+	f.(func(int))(7) // call the plugin one
+}

misc/cgo/testplugin/testdata/issue53989/p/p.go

@@ -0,0 +1,52 @@
+// Copyright 2022 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.
+
+package p
+
+import (
+	"fmt"
+	"runtime"
+)
+
+var y int
+
+//go:noinline
+func Square(x int) {
+	var pc0, pc1 [1]uintptr
+	runtime.Callers(1, pc0[:]) // get PC at entry
+
+	// a switch using jump table
+	switch x {
+	case 1:
+		y = 1
+	case 2:
+		y = 4
+	case 3:
+		y = 9
+	case 4:
+		y = 16
+	case 5:
+		y = 25
+	case 6:
+		y = 36
+	case 7:
+		y = 49
+	case 8:
+		y = 64
+	default:
+		panic("too large")
+	}
+
+	// check PC is in the same function
+	runtime.Callers(1, pc1[:])
+	if pc1[0] < pc0[0] || pc1[0] > pc0[0]+1000000 {
+		fmt.Printf("jump across DSO boundary. pc0=%x, pc1=%x\n", pc0[0], pc1[0])
+		panic("FAIL")
+	}
+
+	if y != x*x {
+		fmt.Printf("x=%d y=%d!=%d\n", x, y, x*x)
+		panic("FAIL")
+	}
+}

misc/cgo/testplugin/testdata/issue53989/plugin.go

@@ -0,0 +1,13 @@
+// Copyright 2022 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.
+
+package main
+
+import "testplugin/issue53989/p"
+
+func Square(x int) { // export Square for plugin
+	p.Square(x)
+}
+
+func main() {}

src/cmd/compile/internal/ssa/rewrite.go

@@ -1959,5 +1959,6 @@ func logicFlags32(x int32) flagConstant {
 func makeJumpTableSym(b *Block) *obj.LSym {
 	s := base.Ctxt.Lookup(fmt.Sprintf("%s.jump%d", b.Func.fe.LSym(), b.ID))
 	s.Set(obj.AttrDuplicateOK, true)
+	s.Set(obj.AttrLocal, true)
 	return s
 }