[llvm] r369199 - [BPF] Fix bpf llvm-objdump issues.

Tue Aug 20 02:55:10 PDT 2019

Merged to release_90 in r369359.

On Sun, Aug 18, 2019 at 12:10 AM Yonghong Song via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
>
> Author: yhs
> Date: Sat Aug 17 15:12:00 2019
> New Revision: 369199
>
> URL: http://llvm.org/viewvc/llvm-project?rev=369199&view=rev
> Log:
> [BPF] Fix bpf llvm-objdump issues.
>
> Commit https://reviews.llvm.org/D57939 ("[DWARF] Refactor
> RelocVisitor and fix computation of SHT_RELA-typed relocation entries)
> made a change for relocation resolution when operating
> on an object file.
>
> The change unfortunately broke BPF as given SymbolValue (S) and
> Addent (A), previously relocation is resolved to
>     S + A
> and after the change, it is resolved to
>     S
>
> This patch fixed the issue by resolving relocation correctly.
>
> It looks not all relocation resolution reaches here and I did not
> trace down exactly when. But I do find if the object file includes
> codes in two different ELF sections than default ".text",
> the above bug will be triggered.
>
> This patch included a trivial two function source code to
> demonstrate this issue. The relocation for .debug_loc is resolved
> incorrectly due to this and llvm-objdump cannot display source
> annotated assembly.
>
> Differential Revision: https://reviews.llvm.org/D66372
>
> Added:
>     llvm/trunk/test/CodeGen/BPF/objdump_two_funcs.ll
> Modified:
>     llvm/trunk/lib/Object/RelocationResolver.cpp
>
> Modified: llvm/trunk/lib/Object/RelocationResolver.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Object/RelocationResolver.cpp?rev=369199&r1=369198&r2=369199&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Object/RelocationResolver.cpp (original)
> +++ llvm/trunk/lib/Object/RelocationResolver.cpp Sat Aug 17 15:12:00 2019
> @@ -90,9 +90,9 @@ static bool supportsBPF(uint64_t Type) {
>  static uint64_t resolveBPF(RelocationRef R, uint64_t S, uint64_t A) {
>    switch (R.getType()) {
>    case ELF::R_BPF_64_32:
> -    return S & 0xFFFFFFFF;
> +    return (S + A) & 0xFFFFFFFF;
>    case ELF::R_BPF_64_64:
> -    return S;
> +    return S + A;
>    default:
>      llvm_unreachable("Invalid relocation type");
>    }
>
> Added: llvm/trunk/test/CodeGen/BPF/objdump_two_funcs.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/BPF/objdump_two_funcs.ll?rev=369199&view=auto
> ==============================================================================
> --- llvm/trunk/test/CodeGen/BPF/objdump_two_funcs.ll (added)
> +++ llvm/trunk/test/CodeGen/BPF/objdump_two_funcs.ll Sat Aug 17 15:12:00 2019
> @@ -0,0 +1,69 @@
> +; RUN: llc -march=bpfel -filetype=obj -o - %s | llvm-objdump -S - | FileCheck %s
> +; RUN: llc -march=bpfeb -filetype=obj -o - %s | llvm-objdump -S - | FileCheck %s
> +;
> +; Source code:
> +;   __attribute__((section("s1")))
> +;   int func1(int a) {
> +;       return a * a;
> +;   }
> +;   __attribute__((section("s2")))
> +;   int func2(int a) {
> +;       return a * a * a;
> +;   }
> +; Compiler flag to generate IR:
> +;   clang -target bpf -S -gdwarf-5 -gembed-source -emit-llvm -g -O2 bug.c
> +
> +; Function Attrs: norecurse nounwind readnone
> +define dso_local i32 @func1(i32 %a) local_unnamed_addr #0 section "s1" !dbg !7 {
> +entry:
> +; CHECK: func1:
> +  call void @llvm.dbg.value(metadata i32 %a, metadata !12, metadata !DIExpression()), !dbg !13
> +  %mul = mul nsw i32 %a, %a, !dbg !14
> +  ret i32 %mul, !dbg !15
> +; CHECK: ; return a * a;
> +}
> +
> +; Function Attrs: norecurse nounwind readnone
> +define dso_local i32 @func2(i32 %a) local_unnamed_addr #0 section "s2" !dbg !16 {
> +entry:
> +; CHECK: func2:
> +  call void @llvm.dbg.value(metadata i32 %a, metadata !18, metadata !DIExpression()), !dbg !19
> +  %mul = mul nsw i32 %a, %a, !dbg !20
> +  %mul1 = mul nsw i32 %mul, %a, !dbg !21
> +  ret i32 %mul1, !dbg !22
> +; CHECK: ; return a * a * a;
> +}
> +
> +; Function Attrs: nounwind readnone speculatable
> +declare void @llvm.dbg.value(metadata, metadata, metadata) #1
> +
> +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" }
> +attributes #1 = { nounwind readnone speculatable }
> +
> +!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 9.0.0 (trunk 366422) (llvm/trunk 366423)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
> +!1 = !DIFile(filename: "bug.c", directory: "/tmp/home/yhs/work/tests/llvm/reloc", checksumkind: CSK_MD5, checksum: "c7c9938d4e6989ca33db748213aab194", source: "__attribute__((section(\22s1\22)))\0Aint func1(int a) {\0A    return a * a;\0A}\0A__attribute__((section(\22s2\22)))\0Aint func2(int a) {\0A    return a * a * a;\0A}\0A")
> +!2 = !{}
> +!3 = !{i32 2, !"Dwarf Version", i32 5}
> +!4 = !{i32 2, !"Debug Info Version", i32 3}
> +!5 = !{i32 1, !"wchar_size", i32 4}
> +!6 = !{!"clang version 9.0.0 (trunk 366422) (llvm/trunk 366423)"}
> +!7 = distinct !DISubprogram(name: "func1", scope: !1, file: !1, line: 2, type: !8, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
> +!8 = !DISubroutineType(types: !9)
> +!9 = !{!10, !10}
> +!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
> +!11 = !{!12}
> +!12 = !DILocalVariable(name: "a", arg: 1, scope: !7, file: !1, line: 2, type: !10)
> +!13 = !DILocation(line: 0, scope: !7)
> +!14 = !DILocation(line: 3, column: 14, scope: !7)
> +!15 = !DILocation(line: 3, column: 5, scope: !7)
> +!16 = distinct !DISubprogram(name: "func2", scope: !1, file: !1, line: 6, type: !8, scopeLine: 6, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !17)
> +!17 = !{!18}
> +!18 = !DILocalVariable(name: "a", arg: 1, scope: !16, file: !1, line: 6, type: !10)
> +!19 = !DILocation(line: 0, scope: !16)
> +!20 = !DILocation(line: 7, column: 14, scope: !16)
> +!21 = !DILocation(line: 7, column: 18, scope: !16)
> +!22 = !DILocation(line: 7, column: 5, scope: !16)
>
>
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