src/cmd/link/internal/ld/seh.go

   1 // Copyright 2023 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package ld
   6
   7 import (
   8         "cmd/internal/sys"
   9         "cmd/link/internal/loader"
  10         "cmd/link/internal/sym"
  11 )
  12
  13 var sehp struct {
  14         pdata loader.Sym
  15 }
  16
  17 func writeSEH(ctxt *Link) {
  18         switch ctxt.Arch.Family {
  19         case sys.AMD64:
  20                 writeSEHAMD64(ctxt)
  21         }
  22 }
  23
  24 func writeSEHAMD64(ctxt *Link) {
  25         ldr := ctxt.loader
  26         mkSecSym := func(name string, kind sym.SymKind) *loader.SymbolBuilder {
  27                 s := ldr.CreateSymForUpdate(name, 0)
  28                 s.SetType(kind)
  29                 s.SetAlign(4)
  30                 return s
  31         }
  32         pdata := mkSecSym(".pdata", sym.SPDATASECT)
  33         // TODO: the following 12 bytes represent a dummy unwind info,
  34         // remove once unwind infos are encoded in the .xdata section.
  35         pdata.AddUint64(ctxt.Arch, 0)
  36         pdata.AddUint32(ctxt.Arch, 0)
  37         for _, s := range ctxt.Textp {
  38                 if fi := ldr.FuncInfo(s); !fi.Valid() || fi.TopFrame() {
  39                         continue
  40                 }
  41                 uw := ldr.SEHUnwindSym(s)
  42                 if uw == 0 {
  43                         continue
  44                 }
  45
  46                 // Reference:
  47                 // https://learn.microsoft.com/en-us/cpp/build/exception-handling-x64#struct-runtime_function
  48                 pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, s, 0)
  49                 pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, s, ldr.SymSize(s))
  50                 // TODO: reference the .xdata symbol.
  51                 pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, pdata.Sym(), 0)
  52         }
  53         sehp.pdata = pdata.Sym()
  54 }