[PATCH] D43351: Relax relocation type checking in a non-ALLOC section.
Rafael Avila de Espindola via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 15 17:07:04 PST 2018
LGTM
Rui Ueyama via Phabricator <reviews at reviews.llvm.org> writes:
> ruiu updated this revision to Diff 134531.
> ruiu added a comment.
>
> - keep reporting errors if not R_ABS nor R_PC
> - restore the original test for an unknown relocation type
>
>
> https://reviews.llvm.org/D43351
>
> Files:
> lld/ELF/InputSection.cpp
> lld/test/ELF/i386-debug-noabs.test
> lld/test/ELF/non-abs-reloc.s
>
>
> Index: lld/test/ELF/non-abs-reloc.s
> ===================================================================
> --- lld/test/ELF/non-abs-reloc.s
> +++ lld/test/ELF/non-abs-reloc.s
> @@ -1,11 +1,19 @@
> // REQUIRES: x86
> // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
> -// RUN: not ld.lld %t.o -o %t.so -shared 2>&1 | FileCheck %s
> -// CHECK: {{.*}}:(.dummy+0x0): has non-ABS relocation R_X86_64_GOTPCREL against symbol 'foo'
> +// RUN: ld.lld %t.o -o %t 2>&1 | FileCheck %s
> +// CHECK: (.nonalloc+0x1): has non-ABS relocation R_X86_64_PC32 against symbol '_start'
> +// CHECK: (.nonalloc+0x6): has non-ABS relocation R_X86_64_PC32 against symbol '_start'
> +
> +// RUN: llvm-objdump -D %t | FileCheck --check-prefix=DISASM %s
> +// DISASM: Disassembly of section .nonalloc:
> +// DISASM-NEXT: .nonalloc:
> +// DISASM-NEXT: 0: {{.*}} callq {{.*}} <_start>
> +// DISASM-NEXT: 5: {{.*}} callq {{.*}} <_start>
>
> .globl _start
> _start:
> nop
>
> -.section .dummy
> - .long foo at gotpcrel
> +.section .nonalloc
> + call _start
> + call _start
> Index: lld/test/ELF/i386-debug-noabs.test
> ===================================================================
> --- lld/test/ELF/i386-debug-noabs.test
> +++ lld/test/ELF/i386-debug-noabs.test
> @@ -1,7 +1,7 @@
> # REQUIRES: x86
>
> # RUN: yaml2obj %s -o %t.o
> -# RUN: ld.lld %t.o -o %t.exe
> +# RUN: ld.lld %t.o -o %t.exe --entry 0 --fatal-warnings
>
> ## This is for https://bugs.llvm.org//show_bug.cgi?id=34852. GCC 8.0 or
> ## earlier have a bug which creates non-absolute R_386_GOTPC relocations
> Index: lld/ELF/InputSection.cpp
> ===================================================================
> --- lld/ELF/InputSection.cpp
> +++ lld/ELF/InputSection.cpp
> @@ -641,6 +641,14 @@
>
> for (const RelTy &Rel : Rels) {
> RelType Type = Rel.getType(Config->IsMips64EL);
> +
> + // GCC 8.0 or earlier have a bug that they emit R_386_GOTPC relocations
> + // against _GLOBAL_OFFSET_TABLE_ for .debug_info. The bug has been fixed
> + // in 2017 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82630), but we
> + // need to keep this bug-compatible code for a while.
> + if (Config->EMachine == EM_386 && Type == R_386_GOTPC)
> + continue;
> +
> uint64_t Offset = getOffset(Rel.r_offset);
> uint8_t *BufLoc = Buf + Offset;
> int64_t Addend = getAddend<ELFT>(Rel);
> @@ -651,17 +659,27 @@
> RelExpr Expr = Target->getRelExpr(Type, Sym, BufLoc);
> if (Expr == R_NONE)
> continue;
> +
> if (Expr != R_ABS) {
> - // GCC 8.0 or earlier have a bug that it emits R_386_GOTPC relocations
> - // against _GLOBAL_OFFSET_TABLE for .debug_info. The bug seems to have
> - // been fixed in 2017: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82630,
> - // but we need to keep this bug-compatible code for a while.
> - if (Config->EMachine == EM_386 && Type == R_386_GOTPC)
> - continue;
> + std::string Msg = getLocation<ELFT>(Offset) +
> + ": has non-ABS relocation " + toString(Type) +
> + " against symbol '" + toString(Sym) + "'";
> + if (Expr != R_PC) {
> + error(Msg);
> + return;
> + }
>
> - error(getLocation<ELFT>(Offset) + ": has non-ABS relocation " +
> - toString(Type) + " against symbol '" + toString(Sym) + "'");
> - return;
> + // If the control reaches here, we found a PC-relative relocation in a
> + // non-ALLOC section. Since non-ALLOC section is not loaded into memory
> + // at runtime, the notion of PC-relative doesn't make sense here. So,
> + // this is a usage error. However, GNU linkers historically accept such
> + // relocations without any errors and relocate them as if they were at
> + // address 0. For bug-compatibilty, we accepts them with warnings. We
> + // know Steel Bank Common Lisp as of 2018 have this bug.
> + warn(Msg);
> + Target->relocateOne(BufLoc, Type,
> + SignExtend64<Bits>(Sym.getVA(Addend - Offset)));
> + continue;
> }
>
> if (Sym.isTls() && !Out::TlsPhdr)
>
>
> Index: lld/test/ELF/non-abs-reloc.s
> ===================================================================
> --- lld/test/ELF/non-abs-reloc.s
> +++ lld/test/ELF/non-abs-reloc.s
> @@ -1,11 +1,19 @@
> // REQUIRES: x86
> // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
> -// RUN: not ld.lld %t.o -o %t.so -shared 2>&1 | FileCheck %s
> -// CHECK: {{.*}}:(.dummy+0x0): has non-ABS relocation R_X86_64_GOTPCREL against symbol 'foo'
> +// RUN: ld.lld %t.o -o %t 2>&1 | FileCheck %s
> +// CHECK: (.nonalloc+0x1): has non-ABS relocation R_X86_64_PC32 against symbol '_start'
> +// CHECK: (.nonalloc+0x6): has non-ABS relocation R_X86_64_PC32 against symbol '_start'
> +
> +// RUN: llvm-objdump -D %t | FileCheck --check-prefix=DISASM %s
> +// DISASM: Disassembly of section .nonalloc:
> +// DISASM-NEXT: .nonalloc:
> +// DISASM-NEXT: 0: {{.*}} callq {{.*}} <_start>
> +// DISASM-NEXT: 5: {{.*}} callq {{.*}} <_start>
>
> .globl _start
> _start:
> nop
>
> -.section .dummy
> - .long foo at gotpcrel
> +.section .nonalloc
> + call _start
> + call _start
> Index: lld/test/ELF/i386-debug-noabs.test
> ===================================================================
> --- lld/test/ELF/i386-debug-noabs.test
> +++ lld/test/ELF/i386-debug-noabs.test
> @@ -1,7 +1,7 @@
> # REQUIRES: x86
>
> # RUN: yaml2obj %s -o %t.o
> -# RUN: ld.lld %t.o -o %t.exe
> +# RUN: ld.lld %t.o -o %t.exe --entry 0 --fatal-warnings
>
> ## This is for https://bugs.llvm.org//show_bug.cgi?id=34852. GCC 8.0 or
> ## earlier have a bug which creates non-absolute R_386_GOTPC relocations
> Index: lld/ELF/InputSection.cpp
> ===================================================================
> --- lld/ELF/InputSection.cpp
> +++ lld/ELF/InputSection.cpp
> @@ -641,6 +641,14 @@
>
> for (const RelTy &Rel : Rels) {
> RelType Type = Rel.getType(Config->IsMips64EL);
> +
> + // GCC 8.0 or earlier have a bug that they emit R_386_GOTPC relocations
> + // against _GLOBAL_OFFSET_TABLE_ for .debug_info. The bug has been fixed
> + // in 2017 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82630), but we
> + // need to keep this bug-compatible code for a while.
> + if (Config->EMachine == EM_386 && Type == R_386_GOTPC)
> + continue;
> +
> uint64_t Offset = getOffset(Rel.r_offset);
> uint8_t *BufLoc = Buf + Offset;
> int64_t Addend = getAddend<ELFT>(Rel);
> @@ -651,17 +659,27 @@
> RelExpr Expr = Target->getRelExpr(Type, Sym, BufLoc);
> if (Expr == R_NONE)
> continue;
> +
> if (Expr != R_ABS) {
> - // GCC 8.0 or earlier have a bug that it emits R_386_GOTPC relocations
> - // against _GLOBAL_OFFSET_TABLE for .debug_info. The bug seems to have
> - // been fixed in 2017: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82630,
> - // but we need to keep this bug-compatible code for a while.
> - if (Config->EMachine == EM_386 && Type == R_386_GOTPC)
> - continue;
> + std::string Msg = getLocation<ELFT>(Offset) +
> + ": has non-ABS relocation " + toString(Type) +
> + " against symbol '" + toString(Sym) + "'";
> + if (Expr != R_PC) {
> + error(Msg);
> + return;
> + }
>
> - error(getLocation<ELFT>(Offset) + ": has non-ABS relocation " +
> - toString(Type) + " against symbol '" + toString(Sym) + "'");
> - return;
> + // If the control reaches here, we found a PC-relative relocation in a
> + // non-ALLOC section. Since non-ALLOC section is not loaded into memory
> + // at runtime, the notion of PC-relative doesn't make sense here. So,
> + // this is a usage error. However, GNU linkers historically accept such
> + // relocations without any errors and relocate them as if they were at
> + // address 0. For bug-compatibilty, we accepts them with warnings. We
> + // know Steel Bank Common Lisp as of 2018 have this bug.
> + warn(Msg);
> + Target->relocateOne(BufLoc, Type,
> + SignExtend64<Bits>(Sym.getVA(Addend - Offset)));
> + continue;
> }
>
> if (Sym.isTls() && !Out::TlsPhdr)
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