From 98989f2a74aa53e9ea64c41c94e66f02beceecc9 Mon Sep 17 00:00:00 2001 From: Cherry Mui Date: Tue, 21 Sep 2021 14:35:37 -0400 Subject: [PATCH] cmd/compile, cmd/link: avoid ABI aliases In the past we introduced ABI aliases, in preparation for ABI wrappers. Now that we have ABI wrappers implemented, we don't need ABI aliases. If ABI wrappers are not enabled, ABI0 and ABIInternal are actually identical, so we can resolve symbol references without distinguish them. This CL does so by normalizing ABIInternal to ABI0 at link time. This way, we no longer need to generate ABI aliases. This CL doesn't clean up everything related to ABI aliases, which will be done in followup CLs. Change-Id: I5b5db43370d29b8ad153078c70a853e3263ae6f7 Reviewed-on: https://go-review.googlesource.com/c/go/+/351271 Trust: Cherry Mui Run-TryBot: Cherry Mui TryBot-Result: Go Bot Reviewed-by: Than McIntosh --- src/cmd/compile/internal/ssagen/abi.go | 20 ------------------- src/cmd/internal/goobj/builtin.go | 4 +++- src/cmd/link/internal/ld/deadcode.go | 10 ++++++---- src/cmd/link/internal/ld/lib.go | 27 +++++++------------------- src/cmd/link/internal/ld/macho.go | 3 +-- src/cmd/link/internal/ld/main.go | 4 ++++ src/cmd/link/internal/ld/pcln.go | 2 +- src/cmd/link/internal/loader/loader.go | 2 +- src/cmd/link/internal/sym/symbol.go | 6 ++++++ 9 files changed, 29 insertions(+), 49 deletions(-) diff --git a/src/cmd/compile/internal/ssagen/abi.go b/src/cmd/compile/internal/ssagen/abi.go index c54a734c75..eabd232791 100644 --- a/src/cmd/compile/internal/ssagen/abi.go +++ b/src/cmd/compile/internal/ssagen/abi.go @@ -257,10 +257,6 @@ func InitLSym(f *ir.Func, hasBody bool) { // when we see that. staticdata.NeedFuncSym(f) } - if !buildcfg.Experiment.RegabiWrappers { - // Create ABI aliases instead of wrappers. - forEachWrapperABI(f, makeABIAlias) - } } if hasBody { setupTextLSym(f, 0) @@ -281,22 +277,6 @@ func forEachWrapperABI(fn *ir.Func, cb func(fn *ir.Func, wrapperABI obj.ABI)) { } } -// makeABIAlias creates a new ABI alias so calls to f via wrapperABI -// will be resolved directly to f's ABI by the linker. -func makeABIAlias(f *ir.Func, wrapperABI obj.ABI) { - // These LSyms have the same name as the native function, so - // we create them directly rather than looking them up. - // The uniqueness of f.lsym ensures uniqueness of asym. - asym := &obj.LSym{ - Name: f.LSym.Name, - Type: objabi.SABIALIAS, - R: []obj.Reloc{{Sym: f.LSym}}, // 0 size, so "informational" - } - asym.SetABI(wrapperABI) - asym.Set(obj.AttrDuplicateOK, true) - base.Ctxt.ABIAliases = append(base.Ctxt.ABIAliases, asym) -} - // makeABIWrapper creates a new function that will be called with // wrapperABI and calls "f" using f.ABI. func makeABIWrapper(f *ir.Func, wrapperABI obj.ABI) { diff --git a/src/cmd/internal/goobj/builtin.go b/src/cmd/internal/goobj/builtin.go index e7d612aeb7..aa665fde99 100644 --- a/src/cmd/internal/goobj/builtin.go +++ b/src/cmd/internal/goobj/builtin.go @@ -4,6 +4,8 @@ package goobj +import "internal/buildcfg" + // Builtin (compiler-generated) function references appear // frequently. We assign special indices for them, so they // don't need to be referenced by name. @@ -27,7 +29,7 @@ func BuiltinIdx(name string, abi int) int { if !ok { return -1 } - if builtins[i].abi != abi { + if buildcfg.Experiment.RegabiWrappers && builtins[i].abi != abi { return -1 } return i diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go index dd5dafc21b..0221024d56 100644 --- a/src/cmd/link/internal/ld/deadcode.go +++ b/src/cmd/link/internal/ld/deadcode.go @@ -96,8 +96,10 @@ func (d *deadcodePass) init() { for _, name := range names { // Mark symbol as a data/ABI0 symbol. d.mark(d.ldr.Lookup(name, 0), 0) - // Also mark any Go functions (internal ABI). - d.mark(d.ldr.Lookup(name, sym.SymVerABIInternal), 0) + if abiInternalVer != 0 { + // Also mark any Go functions (internal ABI). + d.mark(d.ldr.Lookup(name, abiInternalVer), 0) + } } // All dynamic exports are roots. @@ -327,8 +329,8 @@ func deadcode(ctxt *Link) { d.init() d.flood() - methSym := ldr.Lookup("reflect.Value.Method", sym.SymVerABIInternal) - methByNameSym := ldr.Lookup("reflect.Value.MethodByName", sym.SymVerABIInternal) + methSym := ldr.Lookup("reflect.Value.Method", abiInternalVer) + methByNameSym := ldr.Lookup("reflect.Value.MethodByName", abiInternalVer) if ctxt.DynlinkingGo() { // Exported methods may satisfy interfaces we don't know diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go index cf70374b16..f46d1f0221 100644 --- a/src/cmd/link/internal/ld/lib.go +++ b/src/cmd/link/internal/ld/lib.go @@ -144,7 +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) + ctxt.mkArchSym("runtime.unreachableMethod", abiInternalVer, &ctxt.unreachableMethod) if ctxt.IsPPC64() { ctxt.mkArchSym("TOC", 0, &ctxt.TOC) @@ -281,6 +281,10 @@ const ( MINFUNC = 16 // minimum size for a function ) +// Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers +// are used, 0 otherwise. +var abiInternalVer = sym.SymVerABIInternal + // DynlinkingGo reports whether we are producing Go code that can live // in separate shared libraries linked together at runtime. func (ctxt *Link) DynlinkingGo() bool { @@ -500,10 +504,6 @@ func (ctxt *Link) loadlib() { default: log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups) } - if !buildcfg.Experiment.RegabiWrappers { - // Use ABI aliases if ABI wrappers are not used. - flags |= loader.FlagUseABIAlias - } elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) } ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter) ctxt.ErrorReporter.SymName = func(s loader.Sym) string { @@ -769,7 +769,7 @@ func (ctxt *Link) linksetup() { // Set runtime.disableMemoryProfiling bool if // runtime.MemProfile is not retained in the binary after // deadcode (and we're not dynamically linking). - memProfile := ctxt.loader.Lookup("runtime.MemProfile", sym.SymVerABIInternal) + memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer) if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() { memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0) sb := ctxt.loader.MakeSymbolUpdater(memProfSym) @@ -2115,7 +2115,7 @@ func ldshlibsyms(ctxt *Link, shlib string) { ver := 0 symname := elfsym.Name // (unmangled) symbol name if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type.") { - ver = sym.SymVerABIInternal + ver = abiInternalVer } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC { // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName. if strings.HasSuffix(elfsym.Name, ".abiinternal") { @@ -2156,19 +2156,6 @@ func ldshlibsyms(ctxt *Link, shlib string) { if symname != elfsym.Name { l.SetSymExtname(s, elfsym.Name) } - - // For function symbols, if ABI wrappers are not used, we don't - // know what ABI is available, so alias it under both ABIs. - if !buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && ver == 0 { - alias := ctxt.loader.LookupOrCreateSym(symname, sym.SymVerABIInternal) - if l.SymType(alias) != 0 { - continue - } - su := l.MakeSymbolUpdater(alias) - su.SetType(sym.SABIALIAS) - r, _ := su.AddRel(0) // type doesn't matter - r.SetSym(s) - } } ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f}) } diff --git a/src/cmd/link/internal/ld/macho.go b/src/cmd/link/internal/ld/macho.go index 45a3971c33..a577a5308d 100644 --- a/src/cmd/link/internal/ld/macho.go +++ b/src/cmd/link/internal/ld/macho.go @@ -7,7 +7,6 @@ package ld import ( "bytes" "cmd/internal/codesign" - "cmd/internal/obj" "cmd/internal/objabi" "cmd/internal/sys" "cmd/link/internal/loader" @@ -561,7 +560,7 @@ func (ctxt *Link) domacho() { ver := 0 // _cgo_panic is a Go function, so it uses ABIInternal. if name == "_cgo_panic" { - ver = sym.ABIToVersion(obj.ABIInternal) + ver = abiInternalVer } s := ctxt.loader.Lookup(name, ver) if s != 0 { diff --git a/src/cmd/link/internal/ld/main.go b/src/cmd/link/internal/ld/main.go index 33b03b5024..4d3b8b904c 100644 --- a/src/cmd/link/internal/ld/main.go +++ b/src/cmd/link/internal/ld/main.go @@ -173,6 +173,10 @@ func Main(arch *sys.Arch, theArch Arch) { checkStrictDups = *FlagStrictDups + if !buildcfg.Experiment.RegabiWrappers { + abiInternalVer = 0 + } + startProfile() if ctxt.BuildMode == BuildModeUnset { ctxt.BuildMode.Set("exe") diff --git a/src/cmd/link/internal/ld/pcln.go b/src/cmd/link/internal/ld/pcln.go index 5294da5724..3abbf05c54 100644 --- a/src/cmd/link/internal/ld/pcln.go +++ b/src/cmd/link/internal/ld/pcln.go @@ -739,7 +739,7 @@ func (state *pclntab) writeFuncData(ctxt *Link, sb *loader.SymbolBuilder, funcs // writeFuncs writes the func structures and pcdata to runtime.functab. func writeFuncs(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, inlSyms map[loader.Sym]loader.Sym, startLocations, cuOffsets []uint32, nameOffsets map[loader.Sym]uint32) { ldr := ctxt.loader - deferReturnSym := ldr.Lookup("runtime.deferreturn", sym.SymVerABIInternal) + deferReturnSym := ldr.Lookup("runtime.deferreturn", abiInternalVer) funcdata, funcdataoff := []loader.Sym{}, []int64{} // Write the individual func objects. diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go index b9a1da6f45..487559829f 100644 --- a/src/cmd/link/internal/loader/loader.go +++ b/src/cmd/link/internal/loader/loader.go @@ -2192,7 +2192,7 @@ func (st *loadState) preloadSyms(r *oReader, kind int) { } if strings.HasPrefix(name, "runtime.") || (loadingRuntimePkg && strings.HasPrefix(name, "type.")) { - if bi := goobj.BuiltinIdx(name, v); bi != -1 { + if bi := goobj.BuiltinIdx(name, int(osym.ABI())); bi != -1 { // This is a definition of a builtin symbol. Record where it is. l.builtinSyms[bi] = gi } diff --git a/src/cmd/link/internal/sym/symbol.go b/src/cmd/link/internal/sym/symbol.go index 4687aa53bb..2f2c839006 100644 --- a/src/cmd/link/internal/sym/symbol.go +++ b/src/cmd/link/internal/sym/symbol.go @@ -6,6 +6,7 @@ package sym import ( "cmd/internal/obj" + "internal/buildcfg" ) const ( @@ -20,6 +21,11 @@ func ABIToVersion(abi obj.ABI) int { case obj.ABI0: return SymVerABI0 case obj.ABIInternal: + if !buildcfg.Experiment.RegabiWrappers { + // If wrappers are not enabled, ABI0 and ABIInternal are actually same + // so we normalize everything to ABI0. + return SymVerABI0 + } return SymVerABIInternal } return -1 -- 2.51.0