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cmd/link: generate .pdata PE section

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This CL adds a .pdata section to the PE file generated by the Go linker.

The .pdata section is a standard section [1] that contains an array of
function table entries that are used for stack unwinding.
The table entries layout is taken from [2].

This CL just generates the table entries without any unwinding
information, which is enough to start doing some E2E tests
between the Go linker and the Win32 APIs.

The goal of the .pdata table is to allow Windows retrieve
unwind information for a function at a given PC. It does so by doing
a binary search on the table, looking for an entry that meets
BeginAddress >= PC < EndAddress.

Each table entry takes 12 bytes and only non-leaf functions with
frame pointer needs an entry on the .pdata table.
The result is that PE binaries will be ~0.7% bigger due to the unwind
information, a reasonable amount considering the benefits in
debuggability.

Updates #57302

[1] https://learn.microsoft.com/en-us/windows/win32/debug/pe-format#the-pdata-section
[2] https://learn.microsoft.com/en-us/cpp/build/exception-handling-x64#struct-runtime_function

Change-Id: If675d10c64452946dbab76709da20569651e3e9f
Reviewed-on: https://go-review.googlesource.com/c/go/+/461738
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
qmuntal 2023-01-17 08:15:33 +01:00 committed by Quim Muntal
parent 53279a6af3
commit 14cf82aa37
16 changed files with 237 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/cmd/link/internal/ld/asmb.go
View File

@ -60,6 +60,10 @@ func asmb(ctxt *Link) {
writeParallel(&wg, dwarfblk, ctxt, Segdwarf.Fileoff, Segdwarf.Vaddr, Segdwarf.Filelen)
if Segpdata.Filelen > 0 {
writeParallel(&wg, pdatablk, ctxt, Segpdata.Fileoff, Segpdata.Vaddr, Segpdata.Filelen)
}
wg.Wait()
}

39
src/cmd/link/internal/ld/data.go
View File

@ -1154,6 +1154,10 @@ func dwarfblk(ctxt *Link, out *OutBuf, addr int64, size int64) {
writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, syms, addr, size, zeros[:])
}
func pdatablk(ctxt *Link, out *OutBuf, addr int64, size int64) {
writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, []loader.Sym{sehp.pdata}, addr, size, zeros[:])
}
var covCounterDataStartOff, covCounterDataLen uint64
var zeros [512]byte
@ -1649,6 +1653,8 @@ func (ctxt *Link) dodata(symGroupType []sym.SymKind) {
// data/rodata (and related) symbols.
state.allocateDataSections(ctxt)
state.allocateSEHSections(ctxt)
// Create *sym.Section objects and assign symbols to sections for
// DWARF symbols.
state.allocateDwarfSections(ctxt)
@ -1676,6 +1682,10 @@ func (ctxt *Link) dodata(symGroupType []sym.SymKind) {
sect.Extnum = n
n++
}
for _, sect := range Segpdata.Sections {
sect.Extnum = n
n++
}
}
// allocateDataSectionForSym creates a new sym.Section into which a
@ -2148,6 +2158,16 @@ func (state *dodataState) allocateDwarfSections(ctxt *Link) {
}
}
// allocateSEHSections allocate a sym.Section object for SEH
// symbols, and assigns symbols to sections.
func (state *dodataState) allocateSEHSections(ctxt *Link) {
if sehp.pdata > 0 {
sect := state.allocateDataSectionForSym(&Segpdata, sehp.pdata, 04)
state.assignDsymsToSection(sect, []loader.Sym{sehp.pdata}, sym.SRODATA, aligndatsize)
state.checkdatsize(sym.SPDATASECT)
}
}
type symNameSize struct {
name string
sz int64
@ -2684,6 +2704,21 @@ func (ctxt *Link) address() []*sym.Segment {
// simply because right now we know where the BSS starts.
Segdata.Filelen = bss.Vaddr - Segdata.Vaddr
if len(Segpdata.Sections) > 0 {
va = uint64(Rnd(int64(va), int64(*FlagRound)))
order = append(order, &Segpdata)
Segpdata.Rwx = 04
Segpdata.Vaddr = va
// Segpdata.Sections is intended to contain just one section.
// Loop through the slice anyway for consistency.
for _, s := range Segpdata.Sections {
va = uint64(Rnd(int64(va), int64(s.Align)))
s.Vaddr = va
va += s.Length
}
Segpdata.Length = va - Segpdata.Vaddr
}
va = uint64(Rnd(int64(va), int64(*FlagRound)))
order = append(order, &Segdwarf)
Segdwarf.Rwx = 06
@ -2735,6 +2770,10 @@ func (ctxt *Link) address() []*sym.Segment {
}
}
if sect := ldr.SymSect(sehp.pdata); sect != nil {
ldr.AddToSymValue(sehp.pdata, int64(sect.Vaddr))
}
if ctxt.BuildMode == BuildModeShared {
s := ldr.LookupOrCreateSym("go:link.abihashbytes", 0)
sect := ldr.SymSect(ldr.LookupOrCreateSym(".note.go.abihash", 0))

3
src/cmd/link/internal/ld/lib.go
View File

@ -328,8 +328,9 @@ var (
Segrelrodata sym.Segment
Segdata sym.Segment
Segdwarf sym.Segment
Segpdata sym.Segment // windows-only
Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf, &Segpdata}
)
const pkgdef = "__.PKGDEF"

30
src/cmd/link/internal/ld/pe.go
View File

@ -433,6 +433,7 @@ type peFile struct {
dataSect *peSection
bssSect *peSection
ctorsSect *peSection
pdataSect *peSection
nextSectOffset uint32
nextFileOffset uint32
symtabOffset int64 // offset to the start of symbol table
@ -498,6 +499,25 @@ func (f *peFile) addDWARF() {
}
}
// addSEH adds SEH information to the COFF file f.
func (f *peFile) addSEH(ctxt *Link) {
if Segpdata.Length == 0 {
return
}
d := pefile.addSection(".pdata", int(Segpdata.Length), int(Segpdata.Length))
d.characteristics = IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
if ctxt.LinkMode == LinkExternal {
// Some gcc versions don't honor the default alignment for the .pdata section.
d.characteristics |= IMAGE_SCN_ALIGN_4BYTES
}
pefile.pdataSect = d
d.checkSegment(&Segpdata)
// TODO: remove extraSize once the dummy unwind info is removed from the .pdata section.
const extraSize = 12
pefile.dataDirectory[pe.IMAGE_DIRECTORY_ENTRY_EXCEPTION].VirtualAddress = d.virtualAddress + extraSize
pefile.dataDirectory[pe.IMAGE_DIRECTORY_ENTRY_EXCEPTION].Size = d.virtualSize - extraSize
}
// addInitArray adds .ctors COFF section to the file f.
func (f *peFile) addInitArray(ctxt *Link) *peSection {
// The size below was determined by the specification for array relocations,
@ -593,15 +613,19 @@ func (f *peFile) emitRelocations(ctxt *Link) {
return int(sect.Rellen / relocLen)
}
sects := []struct {
type relsect struct {
peSect *peSection
seg *sym.Segment
syms []loader.Sym
}{
}
sects := []relsect{
{f.textSect, &Segtext, ctxt.Textp},
{f.rdataSect, &Segrodata, ctxt.datap},
{f.dataSect, &Segdata, ctxt.datap},
}
if sehp.pdata != 0 {
sects = append(sects, relsect{f.pdataSect, &Segpdata, []loader.Sym{sehp.pdata}})
}
for _, s := range sects {
s.peSect.emitRelocations(ctxt.Out, func() int {
var n int
@ -1595,6 +1619,7 @@ func addPEBaseReloc(ctxt *Link) {
func (ctxt *Link) dope() {
initdynimport(ctxt)
initdynexport(ctxt)
writeSEH(ctxt)
}
func setpersrc(ctxt *Link, syms []loader.Sym) {
@ -1689,6 +1714,7 @@ func asmbPe(ctxt *Link) {
pefile.bssSect = b
}
pefile.addSEH(ctxt)
pefile.addDWARF()
if ctxt.LinkMode == LinkExternal {

54
src/cmd/link/internal/ld/seh.go Normal file
View File

@ -0,0 +1,54 @@
// 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 loader.Sym
}
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.SPDATASECT)
// TODO: the following 12 bytes represent a dummy unwind info,
// remove once unwind infos are encoded in the .xdata section.
pdata.AddUint64(ctxt.Arch, 0)
pdata.AddUint32(ctxt.Arch, 0)
for _, s := range ctxt.Textp {
if fi := ldr.FuncInfo(s); !fi.Valid() || fi.TopFrame() {
continue
}
uw := ldr.SEHUnwindSym(s)
if uw == 0 {
continue
}
// 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))
// TODO: reference the .xdata symbol.
pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, pdata.Sym(), 0)
}
sehp.pdata = pdata.Sym()
}

10
src/cmd/link/internal/loader/loader.go
View File

@ -1646,6 +1646,16 @@ func (l *Loader) WasmImportSym(fnSymIdx Sym) (Sym, bool) {
return 0, false
}
// SEHUnwindSym returns the auxiliary SEH unwind symbol associated with
// a given function symbol.
func (l *Loader) SEHUnwindSym(fnSymIdx Sym) Sym {
if l.SymType(fnSymIdx) != sym.STEXT {
log.Fatalf("error: non-function sym %d/%s t=%s passed to SEHUnwindSym", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
}
return l.aux1(fnSymIdx, goobj.AuxSehUnwindInfo)
}
// GetFuncDwarfAuxSyms collects and returns the auxiliary DWARF
// symbols associated with a given function symbol. Prior to the
// introduction of the loader, this was done purely using name

1
src/cmd/link/internal/sym/symkind.go
View File

@ -126,6 +126,7 @@ const (
// SEH symbol types
SSEHUNWINDINFO
SPDATASECT
)
// AbiSymKindToSymKind maps values read from object files (which are

5
src/cmd/link/internal/sym/symkind_string.go
View File

@ -68,11 +68,12 @@ func _() {
_ = x[SDWARFLOC-57]
_ = x[SDWARFLINES-58]
_ = x[SSEHUNWINDINFO-59]
_ = x[SPDATASECT-60]
}
const _SymKind_name = "SxxxSTEXTSELFRXSECTSMACHOPLTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSLIBFUZZER_8BIT_COUNTERSCOVERAGE_COUNTERSCOVERAGE_AUXVARSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSDYNIMPORTSHOSTOBJSUNDEFEXTSDWARFSECTSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINESSSEHUNWINDINFO"
const _SymKind_name = "SxxxSTEXTSELFRXSECTSMACHOPLTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSLIBFUZZER_8BIT_COUNTERSCOVERAGE_COUNTERSCOVERAGE_AUXVARSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSDYNIMPORTSHOSTOBJSUNDEFEXTSDWARFSECTSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINESSSEHUNWINDINFOSPDATASECT"
var _SymKind_index = [...]uint16{0, 4, 9, 19, 28, 33, 40, 49, 56, 63, 70, 78, 88, 98, 110, 124, 136, 148, 160, 173, 182, 191, 198, 206, 220, 230, 238, 244, 253, 261, 268, 278, 286, 291, 300, 304, 313, 336, 353, 369, 376, 381, 393, 405, 422, 439, 448, 458, 466, 475, 485, 497, 508, 517, 529, 539, 548, 559, 568, 579, 593}
var _SymKind_index = [...]uint16{0, 4, 9, 19, 28, 33, 40, 49, 56, 63, 70, 78, 88, 98, 110, 124, 136, 148, 160, 173, 182, 191, 198, 206, 220, 230, 238, 244, 253, 261, 268, 278, 286, 291, 300, 304, 313, 336, 353, 369, 376, 381, 393, 405, 422, 439, 448, 458, 466, 475, 485, 497, 508, 517, 529, 539, 548, 559, 568, 579, 593, 603}
func (i SymKind) String() string {
if i >= SymKind(len(_SymKind_index)-1) {

2
src/internal/syscall/windows/syscall_windows.go
View File

@ -399,3 +399,5 @@ type FILE_ID_BOTH_DIR_INFO struct {
}
//sys GetVolumeInformationByHandle(file syscall.Handle, volumeNameBuffer *uint16, volumeNameSize uint32, volumeNameSerialNumber *uint32, maximumComponentLength *uint32, fileSystemFlags *uint32, fileSystemNameBuffer *uint16, fileSystemNameSize uint32) (err error) = GetVolumeInformationByHandleW
//sys RtlLookupFunctionEntry(pc uintptr, baseAddress *uintptr, table *byte) (ret uintptr) = kernel32.RtlLookupFunctionEntry

7
src/internal/syscall/windows/zsyscall_windows.go
View File

@ -69,6 +69,7 @@ var (
procModule32NextW = modkernel32.NewProc("Module32NextW")
procMoveFileExW = modkernel32.NewProc("MoveFileExW")
procMultiByteToWideChar = modkernel32.NewProc("MultiByteToWideChar")
procRtlLookupFunctionEntry = modkernel32.NewProc("RtlLookupFunctionEntry")
procSetFileInformationByHandle = modkernel32.NewProc("SetFileInformationByHandle")
procUnlockFileEx = modkernel32.NewProc("UnlockFileEx")
procVirtualQuery = modkernel32.NewProc("VirtualQuery")
@ -289,6 +290,12 @@ func MultiByteToWideChar(codePage uint32, dwFlags uint32, str *byte, nstr int32,
return
}
func RtlLookupFunctionEntry(pc uintptr, baseAddress *uintptr, table *byte) (ret uintptr) {
r0, _, _ := syscall.Syscall(procRtlLookupFunctionEntry.Addr(), 3, uintptr(pc), uintptr(unsafe.Pointer(baseAddress)), uintptr(unsafe.Pointer(table)))
ret = uintptr(r0)
return
}
func SetFileInformationByHandle(handle syscall.Handle, fileInformationClass uint32, buf uintptr, bufsize uint32) (err error) {
r1, _, e1 := syscall.Syscall6(procSetFileInformationByHandle.Addr(), 4, uintptr(handle), uintptr(fileInformationClass), uintptr(buf), uintptr(bufsize), 0, 0)
if r1 == 0 {

3
src/runtime/defs_windows_386.go
View File

@ -56,6 +56,9 @@ func (c *context) set_lr(x uintptr) {}
func (c *context) set_ip(x uintptr) { c.eip = uint32(x) }
func (c *context) set_sp(x uintptr) { c.esp = uint32(x) }
// 386 does not have frame pointer register.
func (c *context) set_fp(x uintptr) {}
func prepareContextForSigResume(c *context) {
c.edx = c.esp
c.ecx = c.eip

1
src/runtime/defs_windows_amd64.go
View File

@ -69,6 +69,7 @@ func (c *context) set_lr(x uintptr) {}
func (c *context) set_ip(x uintptr) { c.rip = uint64(x) }
func (c *context) set_sp(x uintptr) { c.rsp = uint64(x) }
func (c *context) set_fp(x uintptr) { c.rbp = uint64(x) }
func prepareContextForSigResume(c *context) {
c.r8 = c.rsp

3
src/runtime/defs_windows_arm.go
View File

@ -58,6 +58,9 @@ func (c *context) set_ip(x uintptr) { c.pc = uint32(x) }
func (c *context) set_sp(x uintptr) { c.spr = uint32(x) }
func (c *context) set_lr(x uintptr) { c.lrr = uint32(x) }
// arm does not have frame pointer register.
func (c *context) set_fp(x uintptr) {}
func prepareContextForSigResume(c *context) {
c.r0 = c.spr
c.r1 = c.pc

1
src/runtime/defs_windows_arm64.go
View File

@ -40,6 +40,7 @@ func (c *context) lr() uintptr { return uintptr(c.x[30]) }
func (c *context) set_ip(x uintptr) { c.pc = uint64(x) }
func (c *context) set_sp(x uintptr) { c.xsp = uint64(x) }
func (c *context) set_lr(x uintptr) { c.x[30] = uint64(x) }
func (c *context) set_fp(x uintptr) { c.x[29] = uint64(x) }
func prepareContextForSigResume(c *context) {
c.x[0] = c.xsp

16
src/runtime/export_windows_test.go
View File

@ -20,3 +20,19 @@ func NumberOfProcessors() int32 {
stdcall1(_GetSystemInfo, uintptr(unsafe.Pointer(&info)))
return int32(info.dwnumberofprocessors)
}
type ContextStub struct {
context
}
func (c ContextStub) GetPC() uintptr {
return c.ip()
}
func NewContextStub() ContextStub {
var ctx context
ctx.set_ip(getcallerpc())
ctx.set_sp(getcallersp())
ctx.set_fp(getcallerfp())
return ContextStub{ctx}
}

63
src/runtime/runtime-seh_windows_test.go Normal file
View File

@ -0,0 +1,63 @@
// 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 runtime_test
import (
"internal/abi"
"internal/syscall/windows"
"runtime"
"testing"
)
func sehf1() int {
return sehf1()
}
func sehf2() {}
func TestSehLookupFunctionEntry(t *testing.T) {
if runtime.GOARCH != "amd64" {
t.Skip("skipping amd64-only test")
}
// This test checks that Win32 is able to retrieve
// function metadata stored in the .pdata section
// by the Go linker.
// Win32 unwinding will fail if this test fails,
// as RtlUnwindEx uses RtlLookupFunctionEntry internally.
// If that's the case, don't bother investigating further,
// first fix the .pdata generation.
sehf1pc := abi.FuncPCABIInternal(sehf1)
var fnwithframe func()
fnwithframe = func() {
fnwithframe()
}
fnwithoutframe := func() {}
tests := []struct {
name string
pc uintptr
hasframe bool
}{
{"no frame func", abi.FuncPCABIInternal(sehf2), false},
{"no func", sehf1pc - 1, false},
{"func at entry", sehf1pc, true},
{"func in prologue", sehf1pc + 1, true},
{"anonymous func with frame", abi.FuncPCABIInternal(fnwithframe), true},
{"anonymous func without frame", abi.FuncPCABIInternal(fnwithoutframe), false},
{"pc at func body", runtime.NewContextStub().GetPC(), true},
}
for _, tt := range tests {
var base uintptr
fn := windows.RtlLookupFunctionEntry(tt.pc, &base, nil)
if !tt.hasframe {
if fn != 0 {
t.Errorf("%s: unexpected frame", tt.name)
}
continue
}
if fn == 0 {
t.Errorf("%s: missing frame", tt.name)
}
}
}