[release-branch.go1.9] cmd/compile: permit go:cgo_import_dynamic anywhere

It's used on Solaris to import symbols from shared libraries, e.g., in
golang.org/x/sys/unix and golang.org/x/net/internal/socket.
We could use a different directive but that would require build tags
in all the places that use it.

Fixes golang/go#23939

Change-Id: I47fcf72a6d2862e304204705979c2056c2f78ec5
Reviewed-on: https://go-review.googlesource.com/94018
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
(cherry picked from commit 41d3d153eb76f000e9f6e9edf68ed441d15081cb)
Reviewed-on: https://go-review.googlesource.com/110077
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/compile/internal/gc/noder.go b/src/cmd/compile/internal/gc/noder.go
index 7cd941206b21b556e5e74cfec918aa6e098675cc..37fad2d714787bff7492e2a66950047209ce7be1 100644 (file)
--- a/src/cmd/compile/internal/gc/noder.go
+++ b/src/cmd/compile/internal/gc/noder.go
@@ -1190,8 +1190,22 @@ func (p *noder) pragma(pos src.Pos, text string) syntax.Pragma {
                }
                p.linknames = append(p.linknames, linkname{pos, f[1], f[2]})
 
+       case strings.HasPrefix(text, "go:cgo_import_dynamic "):
+               // This is permitted for general use because Solaris
+               // code relies on it in golang.org/x/sys/unix and others.
+               fields := pragmaFields(text)
+               if len(fields) >= 4 {
+                       lib := strings.Trim(fields[3], `"`)
+                       if lib != "" && !safeArg(lib) && !isCgoGeneratedFile(pos) {
+                               p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf("invalid library name %q in cgo_import_dynamic directive", lib)})
+                       }
+                       p.pragcgobuf += p.pragcgo(pos, text)
+                       return pragmaValue("go:cgo_import_dynamic")
+               }
+               fallthrough
        case strings.HasPrefix(text, "go:cgo_"):
-               // For security, we disallow //go:cgo_* directives outside cgo-generated files.
+               // For security, we disallow //go:cgo_* directives other
+               // than cgo_import_dynamic outside cgo-generated files.
                // Exception: they are allowed in the standard library, for runtime and syscall.
                if !isCgoGeneratedFile(pos) && !compiling_std {
                        p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf("//%s only allowed in cgo-generated code", text)})
@@ -1227,6 +1241,18 @@ func isCgoGeneratedFile(pos src.Pos) bool {
        return strings.HasPrefix(filepath.Base(filepath.Clean(pos.AbsFilename())), "_cgo_")
 }
 
+// safeArg reports whether arg is a "safe" command-line argument,
+// meaning that when it appears in a command-line, it probably
+// doesn't have some special meaning other than its own name.
+// This is copied from SafeArg in cmd/go/internal/load/pkg.go.
+func safeArg(name string) bool {
+       if name == "" {
+               return false
+       }
+       c := name[0]
+       return '0' <= c && c <= '9' || 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z' || c == '.' || c == '_' || c == '/' || c >= utf8.RuneSelf
+}
+
 func mkname(sym *types.Sym) *Node {
        n := oldname(sym)
        if n.Name != nil && n.Name.Pack != nil {

diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 65b17012a3df13756fddc4c3446d6c5b9a7a99af..6ca89d946db45d32e76df09ccab47fa5ab10d778 100644 (file)
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -1218,6 +1218,7 @@ func (p *Package) load(stk *ImportStack, bp *build.Package, err error) *Package
 // GNU binutils flagfile specifiers, sometimes called "response files").
 // To be conservative, we reject almost any arg beginning with non-alphanumeric ASCII.
 // We accept leading . _ and / as likely in file system paths.
+// There is a copy of this function in cmd/compile/internal/gc/noder.go.
 func SafeArg(name string) bool {
        if name == "" {
                return false