From 06eb5aad3744336cea6607280edb4491a73b6cc9 Mon Sep 17 00:00:00 2001 From: Rafael Espindola Date: Thu, 22 Jan 2015 14:20:45 +0000 Subject: [PATCH] [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_?@". git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226830 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/MC/ELFObjectWriter.cpp | 45 +++++++++++++++++++++++------ test/MC/ELF/symver-msvc.s | 59 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 95 insertions(+), 9 deletions(-) create mode 100644 test/MC/ELF/symver-msvc.s diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp index 4dcf910e01a..d82dad8093e 100644 --- a/lib/MC/ELFObjectWriter.cpp +++ b/lib/MC/ELFObjectWriter.cpp @@ -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 diff --git a/test/MC/ELF/symver-msvc.s b/test/MC/ELF/symver-msvc.s new file mode 100644 index 00000000000..d6730ca6c6f --- /dev/null +++ b/test/MC/ELF/symver-msvc.s @@ -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: ]