diff options
| -rw-r--r-- | src/cmd/compile/internal/objw/objw.go | 7 | ||||
| -rw-r--r-- | src/cmd/compile/internal/reflectdata/reflect.go | 2 | ||||
| -rw-r--r-- | src/cmd/internal/obj/data.go | 7 | ||||
| -rw-r--r-- | src/cmd/internal/objabi/reloctype.go | 1 | ||||
| -rw-r--r-- | src/cmd/link/internal/ld/data.go | 7 | ||||
| -rw-r--r-- | src/cmd/link/internal/ld/deadcode.go | 3 | ||||
| -rw-r--r-- | src/cmd/link/internal/ld/lib.go | 3 | ||||
| -rw-r--r-- | src/cmd/link/internal/ld/testdata/deadcode/ifacemethod4.go | 2 | ||||
| -rw-r--r-- | src/runtime/iface.go | 7 | ||||
| -rw-r--r-- | src/runtime/type.go | 2 |
10 files changed, 39 insertions, 2 deletions
diff --git a/src/cmd/compile/internal/objw/objw.go b/src/cmd/compile/internal/objw/objw.go index 50ce7b747d..ed5ad754d9 100644 --- a/src/cmd/compile/internal/objw/objw.go +++ b/src/cmd/compile/internal/objw/objw.go @@ -46,6 +46,13 @@ func SymPtr(s *obj.LSym, off int, x *obj.LSym, xoff int) int { return off } +func SymPtrWeak(s *obj.LSym, off int, x *obj.LSym, xoff int) int { + off = int(types.Rnd(int64(off), int64(types.PtrSize))) + s.WriteWeakAddr(base.Ctxt, int64(off), types.PtrSize, x, int64(xoff)) + off += types.PtrSize + return off +} + func SymPtrOff(s *obj.LSym, off int, x *obj.LSym) int { s.WriteOff(base.Ctxt, int64(off), x, 0) off += 4 diff --git a/src/cmd/compile/internal/reflectdata/reflect.go b/src/cmd/compile/internal/reflectdata/reflect.go index 0e1de35887..4c974ea324 100644 --- a/src/cmd/compile/internal/reflectdata/reflect.go +++ b/src/cmd/compile/internal/reflectdata/reflect.go @@ -1338,7 +1338,7 @@ func WriteTabs() { o = objw.Uint32(i.lsym, o, types.TypeHash(i.t)) // copy of type hash o += 4 // skip unused field for _, fn := range genfun(i.t, i.itype) { - o = objw.SymPtr(i.lsym, o, fn, 0) // method pointer for each method + o = objw.SymPtrWeak(i.lsym, o, fn, 0) // method pointer for each method } // Nothing writes static itabs, so they are read only. objw.Global(i.lsym, int32(o), int16(obj.DUPOK|obj.RODATA)) diff --git a/src/cmd/internal/obj/data.go b/src/cmd/internal/obj/data.go index f32e07acfe..bcba53c3a4 100644 --- a/src/cmd/internal/obj/data.go +++ b/src/cmd/internal/obj/data.go @@ -135,6 +135,13 @@ func (s *LSym) WriteAddr(ctxt *Link, off int64, siz int, rsym *LSym, roff int64) s.writeAddr(ctxt, off, siz, rsym, roff, objabi.R_ADDR) } +// WriteWeakAddr writes an address of size siz into s at offset off. +// rsym and roff specify the relocation for the address. +// This is a weak reference. +func (s *LSym) WriteWeakAddr(ctxt *Link, off int64, siz int, rsym *LSym, roff int64) { + s.writeAddr(ctxt, off, siz, rsym, roff, objabi.R_WEAKADDR) +} + // WriteCURelativeAddr writes a pointer-sized address into s at offset off. // rsym and roff specify the relocation for the address which will be // resolved by the linker to an offset from the DW_AT_low_pc attribute of diff --git a/src/cmd/internal/objabi/reloctype.go b/src/cmd/internal/objabi/reloctype.go index 217d8565f2..b241127b4e 100644 --- a/src/cmd/internal/objabi/reloctype.go +++ b/src/cmd/internal/objabi/reloctype.go @@ -258,6 +258,7 @@ const ( // reachable. R_WEAK = -1 << 15 + R_WEAKADDR = R_WEAK | R_ADDR R_WEAKADDROFF = R_WEAK | R_ADDROFF ) diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go index 6de2d893ae..b909526de8 100644 --- a/src/cmd/link/internal/ld/data.go +++ b/src/cmd/link/internal/ld/data.go @@ -306,6 +306,10 @@ func (st *relocSymState) relocsym(s loader.Sym, P []byte) { log.Fatalf("cannot handle R_TLS_IE (sym %s) when linking internally", ldr.SymName(s)) } case objabi.R_ADDR: + if weak && !ldr.AttrReachable(rs) { + // Redirect it to runtime.unreachableMethod, which will throw if called. + rs = syms.unreachableMethod + } if target.IsExternal() { nExtReloc++ @@ -586,6 +590,9 @@ func extreloc(ctxt *Link, ldr *loader.Loader, s loader.Sym, r loader.Reloc) (loa case objabi.R_ADDR: // set up addend for eventual relocation via outer symbol. rs := ldr.ResolveABIAlias(r.Sym()) + if r.Weak() && !ldr.AttrReachable(rs) { + rs = ctxt.ArchSyms.unreachableMethod + } rs, off := FoldSubSymbolOffset(ldr, rs) rr.Xadd = r.Add() + off rr.Xsym = rs diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go index 33468b429c..9b04e2cddc 100644 --- a/src/cmd/link/internal/ld/deadcode.go +++ b/src/cmd/link/internal/ld/deadcode.go @@ -64,6 +64,9 @@ func (d *deadcodePass) init() { } } names = append(names, *flagEntrySymbol) + // runtime.unreachableMethod is a function that will throw if called. + // We redirect unreachable methods to it. + names = append(names, "runtime.unreachableMethod") if !d.ctxt.linkShared && d.ctxt.BuildMode != BuildModePlugin { // runtime.buildVersion and runtime.modinfo are referenced in .go.buildinfo section // (see function buildinfo in data.go). They should normally be reachable from the diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go index d136cbad80..c80c29a6a8 100644 --- a/src/cmd/link/internal/ld/lib.go +++ b/src/cmd/link/internal/ld/lib.go @@ -118,6 +118,8 @@ type ArchSyms struct { Dynamic loader.Sym DynSym loader.Sym DynStr loader.Sym + + unreachableMethod loader.Sym } // mkArchSym is a helper for setArchSyms, to set up a special symbol. @@ -142,6 +144,7 @@ func (ctxt *Link) setArchSyms() { ctxt.mkArchSym(".dynamic", 0, &ctxt.Dynamic) ctxt.mkArchSym(".dynsym", 0, &ctxt.DynSym) ctxt.mkArchSym(".dynstr", 0, &ctxt.DynStr) + ctxt.mkArchSym("runtime.unreachableMethod", sym.SymVerABIInternal, &ctxt.unreachableMethod) if ctxt.IsPPC64() { ctxt.mkArchSym("TOC", 0, &ctxt.TOC) diff --git a/src/cmd/link/internal/ld/testdata/deadcode/ifacemethod4.go b/src/cmd/link/internal/ld/testdata/deadcode/ifacemethod4.go index 52ee2e3d86..4af47ad1fa 100644 --- a/src/cmd/link/internal/ld/testdata/deadcode/ifacemethod4.go +++ b/src/cmd/link/internal/ld/testdata/deadcode/ifacemethod4.go @@ -10,6 +10,7 @@ package main type T int +//go:noinline func (T) M() {} type I interface{ M() } @@ -20,4 +21,5 @@ var pp *I func main() { p = new(T) // use type T pp = new(I) // use type I + *pp = *p // convert T to I, build itab } diff --git a/src/runtime/iface.go b/src/runtime/iface.go index 02b18dabff..cd5fead999 100644 --- a/src/runtime/iface.go +++ b/src/runtime/iface.go @@ -553,3 +553,10 @@ var staticuint64s = [...]uint64{ 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff, } + +// The linker redirects a reference of a method that it determined +// unreachable to a reference to this function, so it will throw if +// ever called. +func unreachableMethod() { + throw("unreachable method called. linker bug?") +} diff --git a/src/runtime/type.go b/src/runtime/type.go index 18fc4bbfad..c0911b1dcb 100644 --- a/src/runtime/type.go +++ b/src/runtime/type.go @@ -262,7 +262,7 @@ func (t *_type) textOff(off textOff) unsafe.Pointer { if off == -1 { // -1 is the sentinel value for unreachable code. // See cmd/link/internal/ld/data.go:relocsym. - return unsafe.Pointer(^uintptr(0)) + return unsafe.Pointer(funcPC(unreachableMethod)) } base := uintptr(unsafe.Pointer(t)) var md *moduledata |