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cmd/link/internal/loadpe: generalize handling of "__imp_*" syms

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The existing PE file loader has a special case for the symbol
"__acrt_iob_func", whose hosting object file contains both an actual
definition and also a DLL import symbol "__imp___acrt_iob_func". The
normal way of handling __imp_XXX symbols is for the host object loader
to rename them to their intended target (e.g. "XXX") however if the
target is also defined locally, you get a duplicate definition.

This patch generalizes the def/import symbol detection to apply to all
symbols in the object file being loaded (not just a hard-coded set),
since it will be needed when reading things like crt2.o.

Updates #35006.

Change-Id: I0d0607c27bb7d5f3cb415bc95db816aa13746ba2
Reviewed-on: https://go-review.googlesource.com/c/go/+/382837
Reviewed-by: Cherry Mui <cherryyz@google.com>
Trust: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Than McIntosh 2022-02-03 08:11:53 -05:00
parent 0a5bbba366
commit 821420d6bb
1 changed files with 51 additions and 17 deletions
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68
src/cmd/link/internal/loadpe/ldpe.go
View File

@ -180,6 +180,7 @@ type peLoaderState struct {
arch *sys.Arch
f *pe.File
sectsyms map[*pe.Section]loader.Sym
defWithImp map[string]struct{}
sectdata map[*pe.Section][]byte
localSymVersion int
}
@ -261,6 +262,13 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
}
}
// Make a prepass over the symbols to detect situations where
// we have both a defined symbol X and an import symbol __imp_X
// (needed by readpesym()).
if err := state.preprocessSymbols(); err != nil {
return nil, nil, err
}
// load relocations
for _, rsect := range f.Sections {
if _, found := state.sectsyms[rsect]; !found {
@ -516,26 +524,20 @@ func (state *peLoaderState) readpesym(pesym *pe.COFFSymbol) (*loader.SymbolBuild
name = state.l.SymName(state.sectsyms[state.f.Sections[pesym.SectionNumber-1]])
} else {
name = symname
switch state.arch.Family {
case sys.AMD64:
if name == "__imp___acrt_iob_func" {
// Do not rename __imp___acrt_iob_func into __acrt_iob_func,
// because __imp___acrt_iob_func symbol is real
// (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for details).
if strings.HasPrefix(symname, "__imp_") {
orig := symname[len("__imp_"):]
if _, ok := state.defWithImp[orig]; ok {
// Don't rename __imp_XXX to XXX, since if we do this
// we'll wind up with a duplicate definition. One
// example is "__acrt_iob_func"; see commit b295099
// from git://git.code.sf.net/p/mingw-w64/mingw-w64
// for details.
} else {
name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
}
case sys.I386:
if name == "__imp____acrt_iob_func" {
// Do not rename __imp____acrt_iob_func into ___acrt_iob_func,
// because __imp____acrt_iob_func symbol is real
// (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for details).
} else {
name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
}
if name[0] == '_' {
name = name[1:] // _Name => Name
}
}
if state.arch.Family == sys.I386 && name[0] == '_' {
name = name[1:] // _Name => Name
}
}
@ -576,3 +578,35 @@ func (state *peLoaderState) readpesym(pesym *pe.COFFSymbol) (*loader.SymbolBuild
return bld, s, nil
}
// preprocessSymbols walks the COFF symbols for the PE file we're
// reading and looks for cases where we have both a symbol definition
// for "XXX" and an "__imp_XXX" symbol, recording these cases in a map
// in the state struct. This information will be used in readpesym()
// above to give such symbols special treatment.
func (state *peLoaderState) preprocessSymbols() error {
imp := make(map[string]struct{})
def := make(map[string]struct{})
for i, numaux := 0, 0; i < len(state.f.COFFSymbols); i += numaux + 1 {
pesym := &state.f.COFFSymbols[i]
numaux = int(pesym.NumberOfAuxSymbols)
if pesym.SectionNumber == 0 { // extern
continue
}
symname, err := pesym.FullName(state.f.StringTable)
if err != nil {
return err
}
def[symname] = struct{}{}
if strings.HasPrefix(symname, "__imp_") {
imp[strings.TrimPrefix(symname, "__imp_")] = struct{}{}
}
}
state.defWithImp = make(map[string]struct{})
for n := range imp {
if _, ok := def[n]; ok {
state.defWithImp[n] = struct{}{}
}
}
return nil
}