[PATCH] D43920: Set DF_TEXTREL instead of creating an empty DT_TEXTREL.

[Rafael Avila de Espindola via llvm-commits]

Looks like OpenBSD only supports DT_TEXTREL.

Brad, any particular reason for that?

Cheers,
Rafael

Rui Ueyama via Phabricator <reviews at reviews.llvm.org> writes:

> ruiu created this revision.
> ruiu added a reviewer: rafael.
> Herald added subscribers: arichardson, emaste.
>
> Generic ABI as of 2000 [1] mentioned that "Its [DT_TEXTREL's] use
> has been superseded by the DF_TEXTREL flag". We currently create only
> DT_TEXTREL and don't set the DF_TEXTREL flag.
>
> This patch is to let the linker to set the flag instead of creating
> a DT_TEXTREL marker segment.
>
> With this patch, lld no longer emits DT_TEXTREL. I believe that's not
> an issue because it is a very old option and text relocation is rare.
> If you want to keep it, we can set both DT_TEXTREL and DF_TEXTREL though.
> But I'm not comfortable with supporting only the old way.
>
> [1] http://www.sco.com/developers/gabi/2000-07-17/ch5.dynamic.html
>
>
> https://reviews.llvm.org/D43920
>
> Files:
>   lld/ELF/SyntheticSections.cpp
>   lld/test/ELF/Inputs/ztext-text-notext.s
>   lld/test/ELF/Inputs/ztext.s
>   lld/test/ELF/ztext-text-notext.s
>   lld/test/ELF/ztext.s
>
>
> Index: lld/test/ELF/ztext.s
> ===================================================================
> --- lld/test/ELF/ztext.s
> +++ lld/test/ELF/ztext.s
> @@ -1,13 +1,13 @@
>  # REQUIRES: x86
>  # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
> -# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/ztext-text-notext.s -o %t2.o
> +# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/ztext.s -o %t2.o
>  # RUN: ld.lld %t2.o -o %t2.so -shared
>  # RUN: ld.lld -z notext %t.o %t2.so -o %t -shared
> -# RUN: llvm-readobj  -dynamic-table -r %t | FileCheck %s
> +# RUN: llvm-readobj -dynamic-table -r %t | FileCheck %s
>  # RUN: ld.lld -z notext %t.o %t2.so -o %t2 -pie
> -# RUN: llvm-readobj  -dynamic-table -r %t2 | FileCheck %s
> +# RUN: llvm-readobj -dynamic-table -r %t2 | FileCheck %s
>  # RUN: ld.lld -z notext %t.o %t2.so -o %t3
> -# RUN: llvm-readobj  -dynamic-table -r %t3 | FileCheck --check-prefix=STATIC %s
> +# RUN: llvm-readobj -dynamic-table -r %t3 | FileCheck --check-prefix=STATIC %s
>  
>  # If the preference is to have text relocations, don't create plt of copy relocations.
>  
> @@ -19,16 +19,16 @@
>  # CHECK-NEXT:    }
>  # CHECK-NEXT:  ]
>  # CHECK: DynamicSection [
> -# CHECK: 0x0000000000000016 TEXTREL 0x0
> +# CHECK: FLAGS TEXTREL
>  
>  # STATIC:      Relocations [
>  # STATIC-NEXT:    Section {{.*}} .rela.dyn {
>  # STATIC-NEXT:      0x201008 R_X86_64_64 bar 0x0
>  # STATIC-NEXT:      0x201010 R_X86_64_PC64 zed 0x0
>  # STATIC-NEXT:    }
>  # STATIC-NEXT:  ]
>  # STATIC: DynamicSection [
> -# STATIC: 0x0000000000000016 TEXTREL 0x0
> +# STATIC: FLAGS TEXTREL
>  
>  foo:
>  .quad foo
> Index: lld/test/ELF/Inputs/ztext-text-notext.s
> ===================================================================
> --- /dev/null
> +++ lld/test/ELF/Inputs/ztext-text-notext.s
> @@ -1,10 +0,0 @@
> -        .global bar
> -        .type bar, @object
> -        .size bar, 8
> -bar:
> -        .quad 0
> -
> -        .global zed
> -        .type zed, @function
> -zed:
> -        nop
> Index: lld/ELF/SyntheticSections.cpp
> ===================================================================
> --- lld/ELF/SyntheticSections.cpp
> +++ lld/ELF/SyntheticSections.cpp
> @@ -1046,6 +1046,8 @@
>      DtFlags |= DF_ORIGIN;
>      DtFlags1 |= DF_1_ORIGIN;
>    }
> +  if (!Config->ZText)
> +    DtFlags |= DF_TEXTREL;
>  
>    if (DtFlags)
>      addInt(DT_FLAGS, DtFlags);
> @@ -1108,8 +1110,6 @@
>    addInt(DT_SYMENT, sizeof(Elf_Sym));
>    addInSec(DT_STRTAB, InX::DynStrTab);
>    addInt(DT_STRSZ, InX::DynStrTab->getSize());
> -  if (!Config->ZText)
> -    addInt(DT_TEXTREL, 0);
>    if (InX::GnuHashTab)
>      addInSec(DT_GNU_HASH, InX::GnuHashTab);
>    if (InX::HashTab)
>
>
> Index: lld/test/ELF/ztext.s
> ===================================================================
> --- lld/test/ELF/ztext.s
> +++ lld/test/ELF/ztext.s
> @@ -1,13 +1,13 @@
>  # REQUIRES: x86
>  # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
> -# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/ztext-text-notext.s -o %t2.o
> +# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/ztext.s -o %t2.o
>  # RUN: ld.lld %t2.o -o %t2.so -shared
>  # RUN: ld.lld -z notext %t.o %t2.so -o %t -shared
> -# RUN: llvm-readobj  -dynamic-table -r %t | FileCheck %s
> +# RUN: llvm-readobj -dynamic-table -r %t | FileCheck %s
>  # RUN: ld.lld -z notext %t.o %t2.so -o %t2 -pie
> -# RUN: llvm-readobj  -dynamic-table -r %t2 | FileCheck %s
> +# RUN: llvm-readobj -dynamic-table -r %t2 | FileCheck %s
>  # RUN: ld.lld -z notext %t.o %t2.so -o %t3
> -# RUN: llvm-readobj  -dynamic-table -r %t3 | FileCheck --check-prefix=STATIC %s
> +# RUN: llvm-readobj -dynamic-table -r %t3 | FileCheck --check-prefix=STATIC %s
>  
>  # If the preference is to have text relocations, don't create plt of copy relocations.
>  
> @@ -19,16 +19,16 @@
>  # CHECK-NEXT:    }
>  # CHECK-NEXT:  ]
>  # CHECK: DynamicSection [
> -# CHECK: 0x0000000000000016 TEXTREL 0x0
> +# CHECK: FLAGS TEXTREL
>  
>  # STATIC:      Relocations [
>  # STATIC-NEXT:    Section {{.*}} .rela.dyn {
>  # STATIC-NEXT:      0x201008 R_X86_64_64 bar 0x0
>  # STATIC-NEXT:      0x201010 R_X86_64_PC64 zed 0x0
>  # STATIC-NEXT:    }
>  # STATIC-NEXT:  ]
>  # STATIC: DynamicSection [
> -# STATIC: 0x0000000000000016 TEXTREL 0x0
> +# STATIC: FLAGS TEXTREL
>  
>  foo:
>  .quad foo
> Index: lld/test/ELF/Inputs/ztext-text-notext.s
> ===================================================================
> --- /dev/null
> +++ lld/test/ELF/Inputs/ztext-text-notext.s
> @@ -1,10 +0,0 @@
> -        .global bar
> -        .type bar, @object
> -        .size bar, 8
> -bar:
> -        .quad 0
> -
> -        .global zed
> -        .type zed, @function
> -zed:
> -        nop
> Index: lld/ELF/SyntheticSections.cpp
> ===================================================================
> --- lld/ELF/SyntheticSections.cpp
> +++ lld/ELF/SyntheticSections.cpp
> @@ -1046,6 +1046,8 @@
>      DtFlags |= DF_ORIGIN;
>      DtFlags1 |= DF_1_ORIGIN;
>    }
> +  if (!Config->ZText)
> +    DtFlags |= DF_TEXTREL;
>  
>    if (DtFlags)
>      addInt(DT_FLAGS, DtFlags);
> @@ -1108,8 +1110,6 @@
>    addInt(DT_SYMENT, sizeof(Elf_Sym));
>    addInSec(DT_STRTAB, InX::DynStrTab);
>    addInt(DT_STRSZ, InX::DynStrTab->getSize());
> -  if (!Config->ZText)
> -    addInt(DT_TEXTREL, 0);
>    if (InX::GnuHashTab)
>      addInSec(DT_GNU_HASH, InX::GnuHashTab);
>    if (InX::HashTab)