From 14e5093ee56c7e3a807c8924fd2d425cd2b0f376 Mon Sep 17 00:00:00 2001 From: Cherry Mui Date: Thu, 12 Dec 2024 14:31:45 -0500 Subject: [PATCH] cmd/internal/obj: disallow linknamed access to builtin symbols Currently, a symbol reference is counted as a reference to a builtin symbol if the name matches a builtin. Usually builtin references are generated by the compiler. But one could manually write one with linkname. Since the list of builtin functions are subject to change from time to time, we don't want users to depend on their names. So we don't count a linknamed reference as a builtin reference, and instead, count it as a named reference, so it is checked by the linker. Change-Id: Id3543295185c6bbd73a8cff82afb8f9cb4fd6f71 Reviewed-on: https://go-review.googlesource.com/c/go/+/635755 Reviewed-by: Michael Pratt LUCI-TryBot-Result: Go LUCI --- src/cmd/internal/obj/sym.go | 2 +- src/cmd/link/link_test.go | 2 ++ src/cmd/link/testdata/linkname/builtin.go | 17 +++++++++++++++++ 3 files changed, 20 insertions(+), 1 deletion(-) create mode 100644 src/cmd/link/testdata/linkname/builtin.go diff --git a/src/cmd/internal/obj/sym.go b/src/cmd/internal/obj/sym.go index 4feccf54f6..8872579050 100644 --- a/src/cmd/internal/obj/sym.go +++ b/src/cmd/internal/obj/sym.go @@ -320,7 +320,7 @@ func (ctxt *Link) NumberSyms() { // Assign special index for builtin symbols. // Don't do it when linking against shared libraries, as the runtime // may be in a different library. - if i := goobj.BuiltinIdx(rs.Name, int(rs.ABI())); i != -1 { + if i := goobj.BuiltinIdx(rs.Name, int(rs.ABI())); i != -1 && !rs.IsLinkname() { rs.PkgIdx = goobj.PkgIdxBuiltin rs.SymIdx = int32(i) rs.Set(AttrIndexed, true) diff --git a/src/cmd/link/link_test.go b/src/cmd/link/link_test.go index f23951416b..ab56b49e15 100644 --- a/src/cmd/link/link_test.go +++ b/src/cmd/link/link_test.go @@ -1518,6 +1518,8 @@ func TestCheckLinkname(t *testing.T) { {"coro_asm", false}, // pull-only linkname is not ok {"coro2.go", false}, + // pull linkname of a builtin symbol is not ok + {"builtin.go", false}, // legacy bad linkname is ok, for now {"fastrand.go", true}, {"badlinkname.go", true}, diff --git a/src/cmd/link/testdata/linkname/builtin.go b/src/cmd/link/testdata/linkname/builtin.go new file mode 100644 index 0000000000..a238c9b967 --- /dev/null +++ b/src/cmd/link/testdata/linkname/builtin.go @@ -0,0 +1,17 @@ +// Copyright 2024 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. + +// Linkname builtin symbols (that is not already linknamed, +// e.g. mapaccess1) is not allowed. + +package main + +import "unsafe" + +func main() { + mapaccess1(nil, nil, nil) +} + +//go:linkname mapaccess1 runtime.mapaccess1 +func mapaccess1(t, m, k unsafe.Pointer) unsafe.Pointer -- 2.48.1