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[BPF] Fix .BTF.ext reloc type assigment issue

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Commit f1db33c5c1a9 ("[BPF] Disable relocation for .BTF.ext section")
assigned relocation type R_BPF_NONE if the fixup type
is FK_Data_4 and the symbol is temporary.
The reason is we use FK_Data_4 as a fixup type
for insn offsets in .BTF.ext section.

Just checking whether the symbol is temporary is not enough.
For example, .debug_info may reference some strings whose
fixup is FK_Data_4 with a temporary symbol as well.

To truely reflect the case for .BTF.ext section,
this patch further checks that the section associateed with the symbol
must be SHF_ALLOC and SHF_EXECINSTR, i.e., in the text section.
This fixed the above-mentioned problem.

Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 350637
This commit is contained in:
Yonghong Song 2019-01-08 16:36:06 +00:00
parent 0aed3f8c9d
commit 620741cb36
2 changed files with 43 additions and 2 deletions
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12
lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp
View File

@ -57,8 +57,16 @@ unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
// already been fulfilled by applyFixup(). No
// further relocation is needed.
if (const MCSymbolRefExpr *A = Target.getSymA()) {
if (A->getSymbol().isTemporary())
return ELF::R_BPF_NONE;
if (A->getSymbol().isTemporary()) {
MCSection &Section = A->getSymbol().getSection();
const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
assert(SectionELF && "Null section for reloc symbol");
// The reloc symbol should be in text section.
unsigned Flags = SectionELF->getFlags();
if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_EXECINSTR))
return ELF::R_BPF_NONE;
}
}
return ELF::R_BPF_64_32;
}

33
test/CodeGen/BPF/reloc-btf.ll Normal file
View File

@ -0,0 +1,33 @@
; RUN: llc -march=bpfel -filetype=obj < %s | llvm-objdump -r - | FileCheck --check-prefix=CHECK-RELOC %s
; Function Attrs: norecurse nounwind readnone
define dso_local i32 @test() local_unnamed_addr #0 !dbg !7 {
entry:
ret i32 0, !dbg !11
}
; CHECK-RELOC: file format ELF64-BPF
; CHECK-RELOC: RELOCATION RECORDS FOR [.rel.debug_info]:
; CHECK-RELOC: R_BPF_64_32 .debug_abbrev
; CHECK-RELOC: R_BPF_64_64 .text
; CHECK-RELOC: RELOCATION RECORDS FOR [.rel.BTF.ext]:
; CHECK-RELOC: R_BPF_NONE .text
attributes #0 = { norecurse nounwind readnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5}
!llvm.ident = !{!6}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 8.0.0 (trunk 350573) (llvm/trunk 350569)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
!1 = !DIFile(filename: "tt.c", directory: "/home/yhs/tmp")
!2 = !{}
!3 = !{i32 2, !"Dwarf Version", i32 4}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{i32 1, !"wchar_size", i32 4}
!6 = !{!"clang version 8.0.0 (trunk 350573) (llvm/trunk 350569)"}
!7 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 1, type: !8, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
!8 = !DISubroutineType(types: !9)
!9 = !{!10}
!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!11 = !DILocation(line: 1, column: 14, scope: !7)