cmd/link,runtime: remove relocations from stkobjs

Use an offset from go.func.* instead. This removes the last relocation from funcdata symbols, which lets us simplify that code. size before after Δ % addr2line 3683218 3680706 -2512 -0.068% api 4951074 4944850 -6224 -0.126% asm 4744258 4757586 +13328 +0.281% buildid 2419986 2418546 -1440 -0.060% cgo 4218306 4197346 -20960 -0.497% compile 22132066 22076882 -55184 -0.249% cover 4432834 4411362 -21472 -0.484% dist 3111202 3091346 -19856 -0.638% doc 3583602 3563234 -20368 -0.568% fix 3023922 3020658 -3264 -0.108% link 6188034 6164642 -23392 -0.378% nm 3665826 3646818 -19008 -0.519% objdump 4015234 4012450 -2784 -0.069% pack 2155010 2153554 -1456 -0.068% pprof 13044178 13011522 -32656 -0.250% test2json 2402146 2383906 -18240 -0.759% trace 9765410 9736514 -28896 -0.296% vet 6681250 6655058 -26192 -0.392% total 104217556 103926980 -290576 -0.279% relocs before after Δ % addr2line 25563 25066 -497 -1.944% api 18409 17176 -1233 -6.698% asm 18903 18271 -632 -3.343% buildid 9513 9233 -280 -2.943% cgo 17103 16222 -881 -5.151% compile 64825 60421 -4404 -6.794% cover 19464 18479 -985 -5.061% dist 10798 10135 -663 -6.140% doc 13503 12735 -768 -5.688% fix 11465 10820 -645 -5.626% link 23214 21849 -1365 -5.880% nm 25480 24987 -493 -1.935% objdump 26610 26057 -553 -2.078% pack 7951 7665 -286 -3.597% pprof 63964 60761 -3203 -5.008% test2json 8735 8389 -346 -3.961% trace 39639 37180 -2459 -6.203% vet 25970 24044 -1926 -7.416% total 431108 409489 -21619 -5.015% Change-Id: I43c26196a008da6d1cb3a782eea2f428778bd569 Reviewed-on: https://go-review.googlesource.com/c/go/+/353138 Trust: Josh Bleecher Snyder <[email protected]> Run-TryBot: Josh Bleecher Snyder <[email protected]> TryBot-Result: Go Bot <[email protected]> Reviewed-by: Cherry Mui <[email protected]>
cloudflare · Oct 5, 2021 · 3100dc1 · 3100dc1
1 parent ae83301
commit 3100dc1
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Showing 8 changed files with 69 additions and 60 deletions.
diff --git a/src/cmd/compile/internal/liveness/plive.go b/src/cmd/compile/internal/liveness/plive.go
@@ -1443,7 +1443,7 @@ func (lv *liveness) emitStackObjects() *obj.LSym {
  }
  off = objw.Uint32(x, off, uint32(sz))
  off = objw.Uint32(x, off, uint32(ptrdata))
- off = objw.SymPtr(x, off, lsym, 0)
+ off = objw.SymPtrOff(x, off, lsym)
  }
 
  if base.Flag.Live != 0 {

diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
@@ -1367,6 +1367,11 @@ func (state *dodataState) makeRelroForSharedLib(target *Link) {
  // the relro data.
  isRelro = true
  }
+ case sym.SGOFUNC:
+ // The only SGOFUNC symbols that contain relocations are .stkobj,
+ // and their relocations are of type objabi.R_ADDROFF,
+ // which always get resolved during linking.
+ isRelro = false
  }
  if isRelro {
  state.setSymType(s, symnrelro)

diff --git a/src/cmd/link/internal/ld/pcln.go b/src/cmd/link/internal/ld/pcln.go
@@ -711,7 +711,7 @@ func writeFuncs(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, inlSym
  ldr := ctxt.loader
  deferReturnSym := ldr.Lookup("runtime.deferreturn", abiInternalVer)
  gofunc := ldr.Lookup("go.func.*", 0)
- gofuncrel := ldr.Lookup("go.funcrel.*", 0)
+ gofuncBase := ldr.SymValue(gofunc)
  textStart := ldr.SymValue(ldr.Lookup("runtime.text", 0))
  funcdata := []loader.Sym{}
  var pcsp, pcfile, pcline, pcinline loader.Sym
@@ -813,24 +813,10 @@ func writeFuncs(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, inlSym
  continue
  }
 
- outer := ldr.OuterSym(fdsym)
- if outer == 0 {
- panic(fmt.Sprintf("no carrier sym for symbol %s (funcdata %s#%d)", ldr.SymName(fdsym), ldr.SymName(s), j))
+ if outer := ldr.OuterSym(fdsym); outer != gofunc {
+ panic(fmt.Sprintf("bad carrier sym for symbol %s (funcdata %s#%d), want go.func.* got %s", ldr.SymName(fdsym), ldr.SymName(s), j, ldr.SymName(outer)))
  }
- rel := uint32(ldr.SymValue(fdsym) - ldr.SymValue(outer))
- // Record gofunc vs gofuncrel in bottom bit. See runtime/symtab.go:funcdata.
- // TODO: The only symbols that in gofuncrel are .stkobj symbols.
- // Remove those relocations, and simplify this.
- rel <<= 1
- switch outer {
- case gofunc:
- case gofuncrel:
- rel |= 1
- default:
- panic(fmt.Sprintf("expected symbol %s (funcdata %s#%d) to be placed in go.func.* or go.funcrel.*, got %s (%d)",
- ldr.SymName(fdsym), ldr.SymName(s), j, ldr.SymName(outer), outer))
- }
- sb.SetUint32(ctxt.Arch, int64(dataoff), rel)
+ sb.SetUint32(ctxt.Arch, int64(dataoff), uint32(ldr.SymValue(fdsym)-gofuncBase))
  }
  }
 }

diff --git a/src/cmd/link/internal/ld/symtab.go b/src/cmd/link/internal/ld/symtab.go
@@ -569,13 +569,8 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
  strings.HasSuffix(name, ".args_stackmap"),
  strings.HasSuffix(name, ".stkobj"):
  ldr.SetAttrNotInSymbolTable(s, true)
- if ctxt.UseRelro() && strings.HasSuffix(name, ".stkobj") {
- symGroupType[s] = sym.SGOFUNCRELRO
- ldr.SetCarrierSym(s, symgofuncrel)
- } else {
- symGroupType[s] = sym.SGOFUNC
- ldr.SetCarrierSym(s, symgofunc)
- }
+ symGroupType[s] = sym.SGOFUNC
+ ldr.SetCarrierSym(s, symgofunc)
  if ctxt.Debugvlog != 0 {
  align := ldr.SymAlign(s)
  liveness += (ldr.SymSize(s) + int64(align) - 1) &^ (int64(align) - 1)
@@ -676,12 +671,8 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
  moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.gcbss", 0))
  moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.types", 0))
  moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.etypes", 0))
+ moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.rodata", 0))
  moduledata.AddAddr(ctxt.Arch, ldr.Lookup("go.func.*", 0))
- if gofuncrel := ldr.Lookup("go.funcrel.*", 0); gofuncrel != 0 {
- moduledata.AddAddr(ctxt.Arch, gofuncrel)
- } else {
- moduledata.AddUint(ctxt.Arch, 0)
- }
 
  if ctxt.IsAIX() && ctxt.IsExternal() {
  // Add R_XCOFFREF relocation to prevent ld's garbage collection of

diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
@@ -803,7 +803,7 @@ func scanstack(gp *g, gcw *gcWork) {
  println()
  printunlock()
  }
- gcdata := r.gcdata
+ gcdata := r.gcdata()
  var s *mspan
  if r.useGCProg() {
  // This path is pretty unlikely, an object large enough
@@ -923,7 +923,8 @@ func scanframeworker(frame *stkframe, state *stackScanState, gcw *gcWork) {
  // varp is 0 for defers, where there are no locals.
  // In that case, there can't be a pointer to its args, either.
  // (And all args would be scanned above anyway.)
- for i, obj := range objs {
+ for i := range objs {
+ obj := &objs[i]
  off := obj.off
  base := frame.varp // locals base pointer
  if off >= 0 {
@@ -937,7 +938,7 @@ func scanframeworker(frame *stkframe, state *stackScanState, gcw *gcWork) {
  if stackTraceDebug {
  println("stkobj at", hex(ptr), "of size", obj.size)
  }
- state.addObject(ptr, &objs[i])
+ state.addObject(ptr, obj)
  }
  }
 }

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
@@ -687,6 +687,7 @@ func schedinit() {
  modulesinit() // provides activeModules
  typelinksinit() // uses maps, activeModules
  itabsinit() // uses activeModules
+ stkobjinit() // must run before GC starts
 
  sigsave(&_g_.m.sigmask)
  initSigmask = _g_.m.sigmask

diff --git a/src/runtime/stack.go b/src/runtime/stack.go
@@ -691,7 +691,8 @@ func adjustframe(frame *stkframe, arg unsafe.Pointer) bool {
  // Adjust pointers in all stack objects (whether they are live or not).
  // See comments in mgcmark.go:scanframeworker.
  if frame.varp != 0 {
- for _, obj := range objs {
+ for i := range objs {
+ obj := &objs[i]
  off := obj.off
  base := frame.varp // locals base pointer
  if off >= 0 {
@@ -705,7 +706,7 @@ func adjustframe(frame *stkframe, arg unsafe.Pointer) bool {
  continue
  }
  ptrdata := obj.ptrdata()
- gcdata := obj.gcdata
+ gcdata := obj.gcdata()
  var s *mspan
  if obj.useGCProg() {
  // See comments in mgcmark.go:scanstack
@@ -1321,7 +1322,7 @@ func getStackMap(frame *stkframe, cache *pcvalueCache, debug bool) (locals, args
  // We don't actually use argmap in this case, but we need to fake the stack object
  // record for these frames which contain an internal/abi.RegArgs at a hard-coded offset.
  // This offset matches the assembly code on amd64 and arm64.
- objs = methodValueCallFrameObjs
+ objs = methodValueCallFrameObjs[:]
  } else {
  p := funcdata(f, _FUNCDATA_StackObjects)
  if p != nil {
@@ -1340,23 +1341,33 @@ func getStackMap(frame *stkframe, cache *pcvalueCache, debug bool) (locals, args
  return
 }
 
-var (
- abiRegArgsEface interface{} = abi.RegArgs{}
- abiRegArgsType *_type = efaceOf(&abiRegArgsEface)._type
- methodValueCallFrameObjs = []stackObjectRecord{
- {
- off: -int32(alignUp(abiRegArgsType.size, 8)), // It's always the highest address local.
- size: int32(abiRegArgsType.size),
- _ptrdata: int32(abiRegArgsType.ptrdata),
- gcdata: abiRegArgsType.gcdata,
- },
- }
-)
+var methodValueCallFrameObjs [1]stackObjectRecord // initialized in stackobjectinit
 
-func init() {
+func stkobjinit() {
+ var abiRegArgsEface interface{} = abi.RegArgs{}
+ abiRegArgsType := efaceOf(&abiRegArgsEface)._type
  if abiRegArgsType.kind&kindGCProg != 0 {
  throw("abiRegArgsType needs GC Prog, update methodValueCallFrameObjs")
  }
+ // Set methodValueCallFrameObjs[0].gcdataoff so that
+ // stackObjectRecord.gcdata() will work correctly with it.
+ ptr := uintptr(unsafe.Pointer(&methodValueCallFrameObjs[0]))
+ var mod *moduledata
+ for datap := &firstmoduledata; datap != nil; datap = datap.next {
+ if datap.gofunc <= ptr && ptr < datap.end {
+ mod = datap
+ break
+ }
+ }
+ if mod == nil {
+ throw("methodValueCallFrameObjs is not in a module")
+ }
+ methodValueCallFrameObjs[0] = stackObjectRecord{
+ off: -int32(alignUp(abiRegArgsType.size, 8)), // It's always the highest address local.
+ size: int32(abiRegArgsType.size),
+ _ptrdata: int32(abiRegArgsType.ptrdata),
+ gcdataoff: uint32(uintptr(unsafe.Pointer(abiRegArgsType.gcdata)) - mod.rodata),
+ }
 }
 
 // A stackObjectRecord is generated by the compiler for each stack object in a stack frame.
@@ -1365,10 +1376,10 @@ type stackObjectRecord struct {
  // offset in frame
  // if negative, offset from varp
  // if non-negative, offset from argp
- off int32
- size int32
- _ptrdata int32 // ptrdata, or -ptrdata is GC prog is used
- gcdata *byte // pointer map or GC prog of the type
+ off  int32
+ size  int32
+ _ptrdata  int32  // ptrdata, or -ptrdata is GC prog is used
+ gcdataoff uint32 // offset to gcdata from moduledata.rodata
 }
 
 func (r *stackObjectRecord) useGCProg() bool {
@@ -1383,6 +1394,23 @@ func (r *stackObjectRecord) ptrdata() uintptr {
  return uintptr(x)
 }
 
+// gcdata returns pointer map or GC prog of the type.
+func (r *stackObjectRecord) gcdata() *byte {
+ ptr := uintptr(unsafe.Pointer(r))
+ var mod *moduledata
+ for datap := &firstmoduledata; datap != nil; datap = datap.next {
+ if datap.gofunc <= ptr && ptr < datap.end {
+ mod = datap
+ break
+ }
+ }
+ // If you get a panic here due to a nil mod,
+ // you may have made a copy of a stackObjectRecord.
+ // You must use the original pointer.
+ res := mod.rodata + uintptr(r.gcdataoff)
+ return (*byte)(unsafe.Pointer(res))
+}
+
 // This is exported as ABI0 via linkname so obj can call it.
 //
 //go:nosplit

diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
@@ -427,7 +427,8 @@ type moduledata struct {
  noptrbss, enoptrbss uintptr
  end, gcdata, gcbss uintptr
  types, etypes uintptr
- gofunc, gofuncrel uintptr // go.func.*, go.funcrel.*
+ rodata uintptr
+ gofunc uintptr // go.func.*
 
  textsectmap []textsect
  typelinks []int32 // offsets from types
@@ -1092,11 +1093,7 @@ func funcdata(f funcInfo, i uint8) unsafe.Pointer {
  if off == ^uint32(0) {
  return nil
  }
- base := f.datap.gofunc
- if off&1 != 0 {
- base = f.datap.gofuncrel
- }
- return unsafe.Pointer(base + uintptr(off>>1))
+ return unsafe.Pointer(f.datap.gofunc + uintptr(off))
 }
 
 // step advances to the next pc, value pair in the encoded table.