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[BPF] generate R_BPF_NONE relocation for BTF DataSec variables 

The variables in BTF DataSec type encode in-section offset.
R_BPF_NONE should be generated instead of R_BPF_64_32.

Signed-off-by: Yonghong Song <yhs@fb.com>

Differential Revision: https://reviews.llvm.org/D62460

llvm-svn: 361742
This commit is contained in:
Yonghong Song 2019-05-26 21:26:06 +00:00
parent ba447bae74
commit e698958ad8
2 changed files with 82 additions and 10 deletions
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32
llvm/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp
View File

@ -50,21 +50,33 @@ unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
case FK_Data_8:
return ELF::R_BPF_64_64;
case FK_Data_4:
// .BTF.ext generates FK_Data_4 relocations for
// insn offset by creating temporary labels.
// The insn offset is within the code section and
// already been fulfilled by applyFixup(). No
// further relocation is needed.
if (const MCSymbolRefExpr *A = Target.getSymA()) {
if (A->getSymbol().isTemporary()) {
MCSection &Section = A->getSymbol().getSection();
const MCSymbol &Sym = A->getSymbol();
if (Sym.isDefined()) {
MCSection &Section = Sym.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;
if (Sym.isTemporary()) {
// .BTF.ext generates FK_Data_4 relocations for
// insn offset by creating temporary labels.
// The insn offset is within the code section and
// already been fulfilled by applyFixup(). No
// further relocation is needed.
// The reloc symbol should be in text section.
if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_EXECINSTR))
return ELF::R_BPF_NONE;
} else {
// .BTF generates FK_Data_4 relocations for variable
// offset in DataSec kind. Similar to the above .BTF.ext
// insn offset, no further relocation is needed.
// The reloc symbol should be in data section.
if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_WRITE))
return ELF::R_BPF_NONE;
}
}
}
return ELF::R_BPF_64_32;

60
llvm/test/CodeGen/BPF/reloc-btf-2.ll Normal file
View File

@ -0,0 +1,60 @@
; RUN: llc -march=bpfel -filetype=obj < %s | llvm-objdump -r - | FileCheck --check-prefix=CHECK-RELOC %s
; RUN: llc -march=bpfeb -filetype=obj < %s | llvm-objdump -r - | FileCheck --check-prefix=CHECK-RELOC %s
; source code:
; int g __attribute__((section("ids"))) = 4;
; static volatile int s = 0;
; int test() {
; return g + s;
; }
; compilation flag:
; clang -target bpf -g -O2 -emit-llvm -S test.c
@g = dso_local local_unnamed_addr global i32 4, section "ids", align 4, !dbg !0
@s = internal global i32 0, align 4, !dbg !6
; Function Attrs: norecurse nounwind
define dso_local i32 @test() local_unnamed_addr #0 !dbg !14 {
%1 = load i32, i32* @g, align 4, !dbg !17, !tbaa !18
%2 = load volatile i32, i32* @s, align 4, !dbg !22, !tbaa !18
%3 = add nsw i32 %2, %1, !dbg !23
ret i32 %3, !dbg !24
}
; CHECK-RELOC: file format ELF64-BPF
; CHECK-RELOC: RELOCATION RECORDS FOR [.BTF]:
; CHECK-RELOC: R_BPF_NONE .bss
; CHECK-RELOC: R_BPF_NONE g
; CHECK-RELOC: RELOCATION RECORDS FOR [.BTF.ext]:
attributes #0 = { norecurse nounwind "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 = !{!2}
!llvm.module.flags = !{!10, !11, !12}
!llvm.ident = !{!13}
!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = distinct !DIGlobalVariable(name: "g", scope: !2, file: !3, line: 1, type: !9, isLocal: false, isDefinition: true)
!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 9.0.0 (trunk 360739) (llvm/trunk 360747)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
!3 = !DIFile(filename: "test.c", directory: "/tmp/home/yhs/work/tests/llvm/relocation")
!4 = !{}
!5 = !{!0, !6}
!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
!7 = distinct !DIGlobalVariable(name: "s", scope: !2, file: !3, line: 2, type: !8, isLocal: true, isDefinition: true)
!8 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !9)
!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!10 = !{i32 2, !"Dwarf Version", i32 4}
!11 = !{i32 2, !"Debug Info Version", i32 3}
!12 = !{i32 1, !"wchar_size", i32 4}
!13 = !{!"clang version 9.0.0 (trunk 360739) (llvm/trunk 360747)"}
!14 = distinct !DISubprogram(name: "test", scope: !3, file: !3, line: 3, type: !15, scopeLine: 3, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !4)
!15 = !DISubroutineType(types: !16)
!16 = !{!9}
!17 = !DILocation(line: 4, column: 10, scope: !14)
!18 = !{!19, !19, i64 0}
!19 = !{!"int", !20, i64 0}
!20 = !{!"omnipotent char", !21, i64 0}
!21 = !{!"Simple C/C++ TBAA"}
!22 = !DILocation(line: 4, column: 14, scope: !14)
!23 = !DILocation(line: 4, column: 12, scope: !14)
!24 = !DILocation(line: 4, column: 3, scope: !14)