[lld] r197307 - [PECOFF] Export undecorated symbols from DLL.
Rui Ueyama
ruiu at google.com
Sat Dec 14 23:36:52 PST 2013
On Sun, Dec 15, 2013 at 3:27 PM, Saleem Abdulrasool
<compnerd at compnerd.org>wrote:
> On Fri, Dec 13, 2013 at 8:32 PM, Rui Ueyama <ruiu at google.com> wrote:
>
>> Author: ruiu
>> Date: Fri Dec 13 22:32:29 2013
>> New Revision: 197307
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=197307&view=rev
>> Log:
>> [PECOFF] Export undecorated symbols from DLL.
>>
>> Symbol names exported from a DLL should be undecorated, not prefixed by
>> an underscore ones.
>>
>> Modified:
>> lld/trunk/include/lld/ReaderWriter/PECOFFLinkingContext.h
>> lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.cpp
>> lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.h
>> lld/trunk/lib/ReaderWriter/PECOFF/PECOFFLinkingContext.cpp
>> lld/trunk/test/pecoff/export.test
>>
>> Modified: lld/trunk/include/lld/ReaderWriter/PECOFFLinkingContext.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/include/lld/ReaderWriter/PECOFFLinkingContext.h?rev=197307&r1=197306&r2=197307&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/include/lld/ReaderWriter/PECOFFLinkingContext.h (original)
>> +++ lld/trunk/include/lld/ReaderWriter/PECOFFLinkingContext.h Fri Dec 13
>> 22:32:29 2013
>> @@ -99,16 +99,8 @@ public:
>>
>> StringRef searchLibraryFile(StringRef path) const;
>>
>> - /// Returns the decorated name of the given symbol name. On 32-bit
>> x86, it
>> - /// adds "_" at the beginning of the string. On other architectures,
>> the
>> - /// return value is the same as the argument.
>> - StringRef decorateSymbol(StringRef name) const {
>> - if (_machineType != llvm::COFF::IMAGE_FILE_MACHINE_I386)
>> - return name;
>> - std::string str = "_";
>> - str.append(name);
>> - return allocate(str);
>> - }
>> + StringRef decorateSymbol(StringRef name) const;
>> + StringRef undecorateSymbol(StringRef name) const;
>>
>> void setEntrySymbolName(StringRef name) {
>> if (!name.empty())
>>
>> Modified: lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.cpp?rev=197307&r1=197306&r2=197307&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.cpp (original)
>> +++ lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.cpp Fri Dec 13 22:32:29
>> 2013
>> @@ -62,15 +62,16 @@ EdataPass::createAddressTable(const std:
>> }
>>
>> edata::EdataAtom *
>> -EdataPass::createNamePointerTable(const std::vector<const DefinedAtom *>
>> &atoms,
>> +EdataPass::createNamePointerTable(const PECOFFLinkingContext &ctx,
>> + const std::vector<const DefinedAtom *>
>> &atoms,
>> MutableFile *file) {
>> EdataAtom *table =
>> new (_alloc) EdataAtom(_file, sizeof(uint32_t) * atoms.size());
>>
>> size_t offset = 0;
>> for (const DefinedAtom *atom : atoms) {
>> - COFFStringAtom *stringAtom = new (_alloc)
>> - COFFStringAtom(_file, _stringOrdinal++, ".edata", atom->name());
>> + auto *stringAtom = new (_alloc) COFFStringAtom(
>> + _file, _stringOrdinal++, ".edata",
>> ctx.undecorateSymbol(atom->name()));
>> file->addAtom(*stringAtom);
>> addDir32NBReloc(table, stringAtom, offset);
>> offset += sizeof(uint32_t);
>> @@ -121,7 +122,7 @@ void EdataPass::perform(std::unique_ptr<
>> addDir32NBReloc(table, addressTable,
>> offsetof(export_directory_table_entry,
>> ExportAddressTableRVA));
>>
>> - EdataAtom *namePointerTable = createNamePointerTable(atoms,
>> file.get());
>> + EdataAtom *namePointerTable = createNamePointerTable(_ctx, atoms,
>> file.get());
>> file->addAtom(*namePointerTable);
>> addDir32NBReloc(table, namePointerTable,
>> offsetof(export_directory_table_entry,
>> NamePointerRVA));
>>
>> Modified: lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.h?rev=197307&r1=197306&r2=197307&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.h (original)
>> +++ lld/trunk/lib/ReaderWriter/PECOFF/EdataPass.h Fri Dec 13 22:32:29 2013
>> @@ -66,7 +66,8 @@ private:
>> edata::EdataAtom *
>> createAddressTable(const std::vector<const DefinedAtom *> &atoms);
>> edata::EdataAtom *
>> - createNamePointerTable(const std::vector<const DefinedAtom *> &atoms,
>> + createNamePointerTable(const PECOFFLinkingContext &ctx,
>> + const std::vector<const DefinedAtom *> &atoms,
>> MutableFile *file);
>> edata::EdataAtom *
>> createOrdinalTable(const std::vector<const DefinedAtom *> &atoms);
>>
>> Modified: lld/trunk/lib/ReaderWriter/PECOFF/PECOFFLinkingContext.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/PECOFF/PECOFFLinkingContext.cpp?rev=197307&r1=197306&r2=197307&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/lib/ReaderWriter/PECOFF/PECOFFLinkingContext.cpp (original)
>> +++ lld/trunk/lib/ReaderWriter/PECOFF/PECOFFLinkingContext.cpp Fri Dec 13
>> 22:32:29 2013
>> @@ -183,6 +183,24 @@ StringRef PECOFFLinkingContext::searchLi
>> return filename;
>> }
>>
>> +/// Returns the decorated name of the given symbol name. On 32-bit x86,
>> it
>> +/// adds "_" at the beginning of the string. On other architectures, the
>> +/// return value is the same as the argument.
>> +StringRef PECOFFLinkingContext::decorateSymbol(StringRef name) const {
>> + if (_machineType != llvm::COFF::IMAGE_FILE_MACHINE_I386)
>> + return name;
>> + std::string str = "_";
>> + str.append(name);
>> + return allocate(str);
>> +}
>> +
>> +StringRef PECOFFLinkingContext::undecorateSymbol(StringRef name) const {
>> + if (_machineType != llvm::COFF::IMAGE_FILE_MACHINE_I386)
>> + return name;
>> + assert(name.startswith("_"));
>> + return name.substr(1);
>> +}
>>
>>
> While this is entirely correct, Im left wondering if this can cause a
> subtle bug in the export table. Assume that I have a symbol call _symbol.
> When decorated on x86, it would be __symbol. However, if undecorateSymbol
> is invoked on this symbol, it would happily mangle _symbol to symbol,
> resulting in an invalid export. Do you think a class to wrap a StringRef
> and a flag set would be too expensive to avoid a situation like this?
>
When the control reached that code, it's guaranteed that an underscore has
always been added to a symbol, so it wouldn't happen that *_symbol* would
accidentally be mangled to *symbol*.
>
>> Writer &PECOFFLinkingContext::writer() const { return *_writer; }
>>
>> ErrorOr<Reference::Kind>
>>
>> Modified: lld/trunk/test/pecoff/export.test
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/test/pecoff/export.test?rev=197307&r1=197306&r2=197307&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/test/pecoff/export.test (original)
>> +++ lld/trunk/test/pecoff/export.test Fri Dec 13 22:32:29 2013
>> @@ -8,7 +8,7 @@ CHECK: Contents of section .edata:
>> CHECK-NEXT: 1000 00000000 {{........}} 00000000 3c100000
>> CHECK-NEXT: 1010 01000000 02000000 02000000 28100000
>> CHECK-NEXT: 1020 30100000 38100000 08200000 10200000
>> -CHECK-NEXT: 1030 50100000 5b100000 00000100 6578706f
>> +CHECK-NEXT: 1030 50100000 5a100000 00000100 6578706f
>> CHECK-NEXT: 1040 72742e74 6573742e 746d702e 646c6c00
>> -CHECK-NEXT: 1050 5f657870 6f727466 6e31005f 6578706f
>> -CHECK-NEXT: 1060 7274666e 3200
>> +CHECK-NEXT: 1050 6578706f 7274666e 31006578 706f7274
>> +CHECK-NEXT: 1060 666e3200
>>
>>
>> _______________________________________________
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>> llvm-commits at cs.uiuc.edu
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>>
>
>
>
> --
> Saleem Abdulrasool
> compnerd (at) compnerd (dot) org
>
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