[lld] r292512 - Create _end symbol even if a .so defines it.

[Rafael Avila de Espindola via llvm-commits]

I would like to port this to 4.0. OK?

Cheers,
Rafael

Rafael Espindola via llvm-commits <llvm-commits at lists.llvm.org> writes:

> Author: rafael
> Date: Thu Jan 19 13:43:34 2017
> New Revision: 292512
>
> URL: http://llvm.org/viewvc/llvm-project?rev=292512&view=rev
> Log:
> Create _end symbol even if a .so defines it.
>
> The freebsd sbrk implementation uses _end to find the initial value of
> brk, so it has to be defined in the main binary.
>
> This should fix the emacs build.
>
> Added:
>     lld/trunk/test/ELF/Inputs/resolution-end.s
>     lld/trunk/test/ELF/resolution-end.s
> Modified:
>     lld/trunk/ELF/SymbolTable.cpp
>
> Modified: lld/trunk/ELF/SymbolTable.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SymbolTable.cpp?rev=292512&r1=292511&r2=292512&view=diff
> ==============================================================================
> --- lld/trunk/ELF/SymbolTable.cpp (original)
> +++ lld/trunk/ELF/SymbolTable.cpp Thu Jan 19 13:43:34 2017
> @@ -140,7 +140,7 @@ template <class ELFT>
>  DefinedRegular<ELFT> *SymbolTable<ELFT>::addIgnored(StringRef Name,
>                                                      uint8_t Visibility) {
>    SymbolBody *S = find(Name);
> -  if (!S || !S->isUndefined())
> +  if (!S || S->isInCurrentDSO())
>      return nullptr;
>    return addAbsolute(Name, Visibility);
>  }
>
> Added: lld/trunk/test/ELF/Inputs/resolution-end.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/Inputs/resolution-end.s?rev=292512&view=auto
> ==============================================================================
> --- lld/trunk/test/ELF/Inputs/resolution-end.s (added)
> +++ lld/trunk/test/ELF/Inputs/resolution-end.s Thu Jan 19 13:43:34 2017
> @@ -0,0 +1,2 @@
> +.data
> +        .quad _end
>
> Added: lld/trunk/test/ELF/resolution-end.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/resolution-end.s?rev=292512&view=auto
> ==============================================================================
> --- lld/trunk/test/ELF/resolution-end.s (added)
> +++ lld/trunk/test/ELF/resolution-end.s Thu Jan 19 13:43:34 2017
> @@ -0,0 +1,39 @@
> +# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t1.o
> +# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/resolution-end.s -o %t2.o
> +# RUN: ld.lld -shared -o %t2.so %t2.o
> +# RUN: ld.lld %t1.o %t2.so -o %t
> +# RUN: llvm-readobj -t -s -section-data  %t | FileCheck %s
> +# REQUIRES: x86
> +
> +# Test that we resolve _end to the this executable.
> +
> +# CHECK:      Name: .text
> +# CHECK-NEXT: Type: SHT_PROGBITS
> +# CHECK-NEXT: Flags [
> +# CHECK-NEXT:   SHF_ALLOC
> +# CHECK-NEXT:   SHF_EXECINSTR
> +# CHECK-NEXT: ]
> +# CHECK-NEXT: Address:
> +# CHECK-NEXT: Offset:
> +# CHECK-NEXT: Size:
> +# CHECK-NEXT: Link:
> +# CHECK-NEXT: Info:
> +# CHECK-NEXT: AddressAlignment:
> +# CHECK-NEXT: EntrySize:
> +# CHECK-NEXT: SectionData (
> +# CHECK-NEXT:   0000: 80202000 00000000
> +# CHECK-NEXT: )
> +
> +# CHECK:      Symbol {
> +# CHECK:        Name: _end
> +# CHECK-NEXT:   Value: 0x202080
> +# CHECK-NEXT:   Size:
> +# CHECK-NEXT:   Binding: Global
> +# CHECK-NEXT:   Type:
> +# CHECK-NEXT:   Other:
> +# CHECK-NEXT:   Section:
> +# CHECK-NEXT: }
> +
> +.global _start
> +_start:
> +.quad _end
>
>
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