| // Copyright 2023 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. |
| |
| package ld |
| |
| import ( |
| "cmd/internal/sys" |
| "cmd/link/internal/loader" |
| "cmd/link/internal/sym" |
| ) |
| |
| var sehp struct { |
| pdata []sym.LoaderSym |
| xdata []sym.LoaderSym |
| } |
| |
| func writeSEH(ctxt *Link) { |
| switch ctxt.Arch.Family { |
| case sys.AMD64: |
| writeSEHAMD64(ctxt) |
| } |
| } |
| |
| func writeSEHAMD64(ctxt *Link) { |
| ldr := ctxt.loader |
| mkSecSym := func(name string, kind sym.SymKind) *loader.SymbolBuilder { |
| s := ldr.CreateSymForUpdate(name, 0) |
| s.SetType(kind) |
| s.SetAlign(4) |
| return s |
| } |
| pdata := mkSecSym(".pdata", sym.SSEHSECT) |
| xdata := mkSecSym(".xdata", sym.SSEHSECT) |
| // The .xdata entries have very low cardinality |
| // as it only contains frame pointer operations, |
| // which are very similar across functions. |
| // These are referenced by .pdata entries using |
| // an RVA, so it is possible, and binary-size wise, |
| // to deduplicate .xdata entries. |
| uwcache := make(map[string]int64) // aux symbol name --> .xdata offset |
| for _, s := range ctxt.Textp { |
| if fi := ldr.FuncInfo(s); !fi.Valid() { |
| continue |
| } |
| uw := ldr.SEHUnwindSym(s) |
| if uw == 0 { |
| continue |
| } |
| name := ctxt.SymName(uw) |
| off, cached := uwcache[name] |
| if !cached { |
| off = xdata.Size() |
| uwcache[name] = off |
| xdata.AddBytes(ldr.Data(uw)) |
| // The SEH unwind data can contain relocations, |
| // make sure those are copied over. |
| rels := ldr.Relocs(uw) |
| for i := 0; i < rels.Count(); i++ { |
| r := rels.At(i) |
| rel, _ := xdata.AddRel(r.Type()) |
| rel.SetOff(int32(off) + r.Off()) |
| rel.SetSiz(r.Siz()) |
| rel.SetSym(r.Sym()) |
| rel.SetAdd(r.Add()) |
| } |
| } |
| |
| // Reference: |
| // https://learn.microsoft.com/en-us/cpp/build/exception-handling-x64#struct-runtime_function |
| pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, s, 0) |
| pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, s, ldr.SymSize(s)) |
| pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, xdata.Sym(), off) |
| } |
| sehp.pdata = append(sehp.pdata, pdata.Sym()) |
| sehp.xdata = append(sehp.xdata, xdata.Sym()) |
| } |