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[pr21886] Change MCJIT/ELF to support MSVC C++ mangled symbol. 

The ELF format is used on Windows by the MCJIT engine. Thus, on Windows, the
ELFObjectWriter can encounter symbols mangled using the MS Visual Studio C++
name mangling. Symbols mangled using the MSVC C++ name mangling can legally
have "@@@" as a substring. The EFLObjectWriter should not interpret the "@@@"
substring as specifying GNU-style symbol versioning. The ELFObjectWriter
therefore check for the MSVC C++ name mangling prefix which is either "?", "@?",
"imp_?" or "imp_?@".

llvm-svn: 226830
This commit is contained in:
Rafael Espindola 2015-01-22 14:20:45 +00:00
parent 48846ba570
commit 5a67ed1038
2 changed files with 95 additions and 9 deletions
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45
llvm/lib/MC/ELFObjectWriter.cpp
View File

@ -1033,16 +1033,43 @@ ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
assert(MSD.SectionIndex && "Invalid section index!");
}
// The @@@ in symbol version is replaced with @ in undefined symbols and
// @@ in defined ones.
// The @@@ in symbol version is replaced with @ in undefined symbols and @@
// in defined ones.
//
// FIXME: All name handling should be done before we get to the writer,
// including dealing with GNU-style version suffixes. Fixing this isn’t
// trivial.
//
// We thus have to be careful to not perform the symbol version replacement
// blindly:
//
// The ELF format is used on Windows by the MCJIT engine. Thus, on
// Windows, the ELFObjectWriter can encounter symbols mangled using the MS
// Visual Studio C++ name mangling scheme. Symbols mangled using the MSVC
// C++ name mangling can legally have "@@@" as a sub-string. In that case,
// the EFLObjectWriter should not interpret the "@@@" sub-string as
// specifying GNU-style symbol versioning. The ELFObjectWriter therefore
// checks for the MSVC C++ name mangling prefix which is either "?", "@?",
// "__imp_?" or "__imp_@?".
//
// It would have been interesting to perform the MS mangling prefix check
// only when the target triple is of the form *-pc-windows-elf. But, it
// seems that this information is not easily accessible from the
// ELFObjectWriter.
StringRef Name = Symbol.getName();
SmallString<32> Buf;
size_t Pos = Name.find("@@@");
if (Pos != StringRef::npos) {
Buf += Name.substr(0, Pos);
unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
Buf += Name.substr(Pos + Skip);
Name = Buf;
if (!Name.startswith("?") && !Name.startswith("@?") &&
!Name.startswith("__imp_?") && !Name.startswith("__imp_@?")) {
// This symbol isn't following the MSVC C++ name mangling convention. We
// can thus safely interpret the @@@ in symbol names as specifying symbol
// versioning.
SmallString<32> Buf;
size_t Pos = Name.find("@@@");
if (Pos != StringRef::npos) {
Buf += Name.substr(0, Pos);
unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
Buf += Name.substr(Pos + Skip);
Name = Buf;
}
}
// Sections have their own string table

59
llvm/test/MC/ELF/symver-msvc.s Normal file
View File

@ -0,0 +1,59 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-windows-elf %s -o - | llvm-readobj -r -t | FileCheck %s
// Verify that MSVC C++ mangled symbols are not affected by the ELF
// GNU-style symbol versioning. The ELF format is used on Windows by
// the MCJIT execution engine.
.long "??_R0?AVexception@std@@@8"
.long "@??_R0?AVinvalid_argument@std@@@8"
.long "__imp_??_R0?AVlogic_error@std@@@8"
.long "__imp_@??_R0PAVexception@std@@@8"
// CHECK: Relocations [
// CHECK-NEXT: Section (2) .rela.text {
// CHECK-NEXT: 0x0 R_X86_64_32 ??_R0?AVexception@std@@@8 0x0
// CHECK-NEXT: 0x4 R_X86_64_32 @??_R0?AVinvalid_argument@std@@@8 0x0
// CHECK-NEXT: 0x8 R_X86_64_32 __imp_??_R0?AVlogic_error@std@@@8 0x0
// CHECK-NEXT: 0xC R_X86_64_32 __imp_@??_R0PAVexception@std@@@8 0x0
// CHECK-NEXT: }
// CHECK-NEXT: ]
// CHECK: Symbols [
// CHECK: Symbol {
// CHECK: Name: ??_R0?AVexception@std@@@8 (102)
// CHECK-NEXT: Value: 0x0
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Global (0x1)
// CHECK-NEXT: Type: None (0x0)
// CHECK-NEXT: Other: 0
// CHECK-NEXT: Section: Undefined (0x0)
// CHECK-NEXT: }
// CHECK-NEXT: Symbol {
// CHECK-NEXT: Name: @??_R0?AVinvalid_argument@std@@@8 (1)
// CHECK-NEXT: Value: 0x0
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Global (0x1)
// CHECK-NEXT: Type: None (0x0)
// CHECK-NEXT: Other: 0
// CHECK-NEXT: Section: Undefined (0x0)
// CHECK-NEXT: }
// CHECK-NEXT: Symbol {
// CHECK-NEXT: Name: __imp_??_R0?AVlogic_error@std@@@8 (35)
// CHECK-NEXT: Value: 0x0
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Global (0x1)
// CHECK-NEXT: Type: None (0x0)
// CHECK-NEXT: Other: 0
// CHECK-NEXT: Section: Undefined (0x0)
// CHECK-NEXT: }
// CHECK-NEXT: Symbol {
// CHECK-NEXT: Name: __imp_@??_R0PAVexception@std@@@8 (69)
// CHECK-NEXT: Value: 0x0
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Global (0x1)
// CHECK-NEXT: Type: None (0x0)
// CHECK-NEXT: Other: 0
// CHECK-NEXT: Section: Undefined (0x0)
// CHECK-NEXT: }
// CHECK-NEXT: ]