[lld] r244050 - Add bare minimum to get a working i386 linux program.

Saleem Abdulrasool compnerd at compnerd.org
Wed Aug 5 11:00:38 PDT 2015


On Wednesday, August 5, 2015, Rafael Espindola <rafael.espindola at gmail.com>
wrote:

> Author: rafael
> Date: Wed Aug  5 10:08:40 2015
> New Revision: 244050
>
> URL: http://llvm.org/viewvc/llvm-project?rev=244050&view=rev
> Log:
> Add bare minimum to get a working i386 linux program.
>
> Added:
>     lld/trunk/test/elf2/basic32.s
> Modified:
>     lld/trunk/ELF/Driver.cpp
>     lld/trunk/ELF/Writer.cpp
>
> Modified: lld/trunk/ELF/Driver.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Driver.cpp?rev=244050&r1=244049&r2=244050&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Driver.cpp (original)
> +++ lld/trunk/ELF/Driver.cpp Wed Aug  5 10:08:40 2015
> @@ -114,6 +114,27 @@ void LinkerDriver::link(ArrayRef<const c
>    Symtab.reportRemainingUndefines();
>
>    // Write the result.
> -  Writer<object::ELF64LE> Out(&Symtab);
> -  Out.write(Config->OutputFile);
> +  ObjectFileBase &FirstObj = *Symtab.ObjectFiles[0];
> +  switch (FirstObj.kind()) {
> +  case InputFile::Object32LEKind: {
> +    Writer<object::ELF32LE> Out(&Symtab);
> +    Out.write(Config->OutputFile);
> +    return;
> +  }
> +  case InputFile::Object32BEKind: {
> +    Writer<object::ELF32BE> Out(&Symtab);
> +    Out.write(Config->OutputFile);
> +    return;
> +  }
> +  case InputFile::Object64LEKind: {
> +    Writer<object::ELF64LE> Out(&Symtab);
> +    Out.write(Config->OutputFile);
> +    return;
> +  }
> +  case InputFile::Object64BEKind: {
> +    Writer<object::ELF64BE> Out(&Symtab);
> +    Out.write(Config->OutputFile);
> +    return;
> +  }
> +  }
>  }
>
> Modified: lld/trunk/ELF/Writer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=244050&r1=244049&r2=244050&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Writer.cpp (original)
> +++ lld/trunk/ELF/Writer.cpp Wed Aug  5 10:08:40 2015
> @@ -119,13 +119,16 @@ template <class ELFT> void Writer<ELFT>:
>    EHdr->e_ident[EI_MAG1] = 0x45;
>    EHdr->e_ident[EI_MAG2] = 0x4C;
>    EHdr->e_ident[EI_MAG3] = 0x46;
> -  EHdr->e_ident[EI_CLASS] = ELFCLASS64;
> -  EHdr->e_ident[EI_DATA] = ELFDATA2LSB;
> +  EHdr->e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
> +  EHdr->e_ident[EI_DATA] = ELFT::TargetEndianness == llvm::support::little
> +                               ? ELFDATA2LSB
> +                               : ELFDATA2MSB;
>    EHdr->e_ident[EI_VERSION] = EV_CURRENT;
>    EHdr->e_ident[EI_OSABI] = ELFOSABI_NONE;
>
>    EHdr->e_type = ET_EXEC;
> -  EHdr->e_machine = EM_X86_64;
> +  auto &FirstObj = cast<ObjectFile<ELFT>>(*Symtab->ObjectFiles[0]);
> +  EHdr->e_machine = FirstObj.getObj()->getHeader()->e_machine;


Is the intent to behave more like link rather than ld?  link bases the
target machine based on the first input file if /machine is not specified.
 ld uses the emulation IIRC.


>    EHdr->e_version = EV_CURRENT;
>    EHdr->e_entry = 0x401000;
>    EHdr->e_phoff = sizeof(Elf_Ehdr_Impl<ELFT>);
>
> Added: lld/trunk/test/elf2/basic32.s
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/basic32.s?rev=244050&view=auto
>
> ==============================================================================
> --- lld/trunk/test/elf2/basic32.s (added)
> +++ lld/trunk/test/elf2/basic32.s Wed Aug  5 10:08:40 2015
> @@ -0,0 +1,116 @@
> +# RUN: llvm-mc -filetype=obj -triple=i686-unknown-linux %s -o %t
> +# RUN: lld -flavor gnu2 %t -o %t2
> +# RUN: llvm-readobj -file-headers -sections -program-headers %t2 |
> FileCheck %s
> +# REQUIRES: x86
> +
> +# exits with return code 42 on linux
> +.globl _start;
> +_start:
> +  mov $1, %eax
> +  mov $42, %ebx
> +  int $0x80
> +
> +# CHECK:      ElfHeader {
> +# CHECK-NEXT:   Ident {
> +# CHECK-NEXT:     Magic: (7F 45 4C 46)
> +# CHECK-NEXT:     Class: 32-bit (0x1)
> +# CHECK-NEXT:     DataEncoding: LittleEndian (0x1)
> +# CHECK-NEXT:     FileVersion: 1
> +# CHECK-NEXT:     OS/ABI: SystemV (0x0)
> +# CHECK-NEXT:     ABIVersion: 0
> +# CHECK-NEXT:     Unused: (00 00 00 00 00 00 00)
> +# CHECK-NEXT:   }
> +# CHECK-NEXT:   Type: Executable (0x2)
> +# CHECK-NEXT:   Machine: EM_386 (0x3)
> +# CHECK-NEXT:   Version: 1
> +# CHECK-NEXT:   Entry: 0x401000
> +# CHECK-NEXT:   ProgramHeaderOffset: 0x34
> +# CHECK-NEXT:   SectionHeaderOffset: 0x1010
> +# CHECK-NEXT:   Flags [ (0x0)
> +# CHECK-NEXT:   ]
> +# CHECK-NEXT:   HeaderSize: 52
> +# CHECK-NEXT:   ProgramHeaderEntrySize: 32
> +# CHECK-NEXT:   ProgramHeaderCount: 1
> +# CHECK-NEXT:   SectionHeaderEntrySize: 40
> +# CHECK-NEXT:   SectionHeaderCount: 4
> +# CHECK-NEXT:    StringTableSectionIndex: 0
> +# CHECK-NEXT: }
> +# CHECK-NEXT: Sections [
> +# CHECK-NEXT:   Section {
> +# CHECK-NEXT:     Index: 0
> +# CHECK-NEXT:     Name:  (0)
> +# CHECK-NEXT:     Type: SHT_NULL (0x0)
> +# CHECK-NEXT:     Flags [ (0x0)
> +# CHECK-NEXT:     ]
> +# CHECK-NEXT:     Address: 0x0
> +# CHECK-NEXT:     Offset: 0x0
> +# CHECK-NEXT:     Size: 0
> +# CHECK-NEXT:     Link: 0
> +# CHECK-NEXT:     Info: 0
> +# CHECK-NEXT:     AddressAlignment: 0
> +# CHECK-NEXT:     EntrySize: 0
> +# CHECK-NEXT:   }
> +# CHECK-NEXT:   Section {
> +# CHECK-NEXT:     Index: 1
> +# CHECK-NEXT:     Name:  (0)
> +# CHECK-NEXT:     Type: SHT_PROGBITS (0x1)
> +# CHECK-NEXT:     Flags [ (0x6)
> +# CHECK-NEXT:       SHF_ALLOC (0x2)
> +# CHECK-NEXT:       SHF_EXECINSTR (0x4)
> +# CHECK-NEXT:     ]
> +# CHECK-NEXT:     Address: 0x1000
> +# CHECK-NEXT:     Offset: 0x1000
> +# CHECK-NEXT:     Size: 12
> +# CHECK-NEXT:     Link: 0
> +# CHECK-NEXT:     Info: 0
> +# CHECK-NEXT:     AddressAlignment: 0
> +# CHECK-NEXT:     EntrySize: 0
> +# CHECK-NEXT:   }
> +# CHECK-NEXT:   Section {
> +# CHECK-NEXT:     Index: 2
> +# CHECK-NEXT:     Name:  (0)
> +# CHECK-NEXT:     Type: SHT_PROGBITS (0x1)
> +# CHECK-NEXT:     Flags [ (0x3)
> +# CHECK-NEXT:       SHF_ALLOC (0x2)
> +# CHECK-NEXT:       SHF_WRITE (0x1)
> +# CHECK-NEXT:     ]
> +# CHECK-NEXT:     Address: 0x2000
> +# CHECK-NEXT:     Offset: 0x0
> +# CHECK-NEXT:     Size: 0
> +# CHECK-NEXT:     Link: 0
> +# CHECK-NEXT:     Info: 0
> +# CHECK-NEXT:     AddressAlignment: 0
> +# CHECK-NEXT:     EntrySize: 0
> +# CHECK-NEXT:   }
> +# CHECK-NEXT:   Section {
> +# CHECK-NEXT:     Index: 3
> +# CHECK-NEXT:     Name:  (0)
> +# CHECK-NEXT:     Type: SHT_NOBITS (0x8)
> +# CHECK-NEXT:     Flags [ (0x3)
> +# CHECK-NEXT:       SHF_ALLOC (0x2)
> +# CHECK-NEXT:       SHF_WRITE (0x1)
> +# CHECK-NEXT:     ]
> +# CHECK-NEXT:     Address: 0x2000
> +# CHECK-NEXT:     Offset: 0x0
> +# CHECK-NEXT:     Size: 0
> +# CHECK-NEXT:     Link: 0
> +# CHECK-NEXT:     Info: 0
> +# CHECK-NEXT:     AddressAlignment: 0
> +# CHECK-NEXT:     EntrySize: 0
> +# CHECK-NEXT:   }
> +# CHECK-NEXT: ]
> +# CHECK-NEXT: ProgramHeaders [
> +# CHECK-NEXT:   ProgramHeader {
> +# CHECK-NEXT:     Type: PT_LOAD (0x1)
> +# CHECK-NEXT:     Offset: 0x0
> +# CHECK-NEXT:     VirtualAddress: 0x400000
> +# CHECK-NEXT:     PhysicalAddress: 0x400000
> +# CHECK-NEXT:     FileSize: 4272
> +# CHECK-NEXT:     MemSize: 4272
> +# CHECK-NEXT:     Flags [ (0x5)
> +# CHECK-NEXT:       PF_R (0x4)
> +# CHECK-NEXT:       PF_X (0x1)
> +# CHECK-NEXT:     ]
> +# CHECK-NEXT:     Alignment: 16384
> +# CHECK-NEXT:   }
> +# CHECK-NEXT: ]
>
>
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-- 
Saleem Abdulrasool
compnerd (at) compnerd (dot) org
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