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688f60c786
extern variable usage in BPF is different from traditional
pure user space application. Recent discussion in linux bpf
mailing list has two use cases where debug info types are
required to use extern variables:
- extern types are required to have a suitable interface
in libbpf (bpf loader) to provide kernel config parameters
to bpf programs.
https://lore.kernel.org/bpf/CAEf4BzYCNo5GeVGMhp3fhysQ=_axAf=23PtwaZs-yAyafmXC9g@mail.gmail.com/T/#t
- extern types are required so kernel bpf verifier can
verify program which uses external functions more precisely.
This will make later link with actual external function no
need to reverify.
https://lore.kernel.org/bpf/87eez4odqp.fsf@toke.dk/T/#m8d5c3e87ffe7f2764e02d722cb0d8cbc136880ed
This patch added bpf support to consume such info into BTF,
which can then be used by bpf loader. Function processFuncPrototypes()
only adds extern function definitions into BTF. The functions
with actual definition have been added to BTF in some other places.
Differential Revision: https://reviews.llvm.org/D70697
124 lines
6.5 KiB
LLVM
124 lines
6.5 KiB
LLVM
; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
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; RUN: llc -march=bpfeb -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
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;
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; Source code:
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; extern int global_func(char c) __attribute__((section("abc")));
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; extern char ch __attribute__((section("abc")));
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; int test() {
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; return global_func(0) + ch;
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; }
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; Compilation flag:
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; clang -target bpf -O2 -g -S -emit-llvm test.c
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@ch = external dso_local local_unnamed_addr global i8, section "abc", align 1, !dbg !0
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; Function Attrs: nounwind
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define dso_local i32 @test() local_unnamed_addr #0 !dbg !16 {
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entry:
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%call = tail call i32 @global_func(i8 signext 0) #2, !dbg !19
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%0 = load i8, i8* @ch, align 1, !dbg !20, !tbaa !21
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%conv = sext i8 %0 to i32, !dbg !20
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%add = add nsw i32 %call, %conv, !dbg !24
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ret i32 %add, !dbg !25
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}
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; CHECK: .section .BTF,"",@progbits
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; CHECK-NEXT: .short 60319 # 0xeb9f
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; CHECK-NEXT: .byte 1
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; CHECK-NEXT: .byte 0
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; CHECK-NEXT: .long 24
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; CHECK-NEXT: .long 0
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; CHECK-NEXT: .long 144
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; CHECK-NEXT: .long 144
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; CHECK-NEXT: .long 79
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; CHECK-NEXT: .long 0 # BTF_KIND_FUNC_PROTO(id = 1)
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; CHECK-NEXT: .long 218103808 # 0xd000000
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; CHECK-NEXT: .long 2
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; CHECK-NEXT: .long 1 # BTF_KIND_INT(id = 2)
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; CHECK-NEXT: .long 16777216 # 0x1000000
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; CHECK-NEXT: .long 4
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; CHECK-NEXT: .long 16777248 # 0x1000020
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; CHECK-NEXT: .long 5 # BTF_KIND_FUNC(id = 3)
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; CHECK-NEXT: .long 201326592 # 0xc000000
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; CHECK-NEXT: .long 1
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; CHECK-NEXT: .long 55 # BTF_KIND_INT(id = 4)
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; CHECK-NEXT: .long 16777216 # 0x1000000
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; CHECK-NEXT: .long 1
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; CHECK-NEXT: .long 16777224 # 0x1000008
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; CHECK-NEXT: .long 60 # BTF_KIND_VAR(id = 5)
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; CHECK-NEXT: .long 234881024 # 0xe000000
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; CHECK-NEXT: .long 4
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; CHECK-NEXT: .long 2
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; CHECK-NEXT: .long 0 # BTF_KIND_FUNC_PROTO(id = 6)
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; CHECK-NEXT: .long 218103809 # 0xd000001
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; CHECK-NEXT: .long 2
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; CHECK-NEXT: .long 0
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; CHECK-NEXT: .long 4
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; CHECK-NEXT: .long 63 # BTF_KIND_VAR(id = 7)
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; CHECK-NEXT: .long 234881024 # 0xe000000
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; CHECK-NEXT: .long 6
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; CHECK-NEXT: .long 2
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; CHECK-NEXT: .long 75 # BTF_KIND_DATASEC(id = 8)
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; CHECK-NEXT: .long 251658242 # 0xf000002
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; CHECK-NEXT: .long 0
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; CHECK-NEXT: .long 5
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; CHECK-NEXT: .long ch
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; CHECK-NEXT: .long 1
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; CHECK-NEXT: .long 7
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; CHECK-NEXT: .long global_func
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; CHECK-NEXT: .long 8
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; CHECK-NEXT: .byte 0 # string offset=0
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; CHECK-NEXT: .ascii "int" # string offset=1
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; CHECK-NEXT: .byte 0
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; CHECK-NEXT: .ascii "test" # string offset=5
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; CHECK-NEXT: .byte 0
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; CHECK-NEXT: .ascii ".text" # string offset=10
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; CHECK-NEXT: .byte 0
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; CHECK-NEXT: .ascii "/tmp/home/yhs/work/tests/extern/test.c" # string offset=16
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; CHECK-NEXT: .byte 0
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; CHECK-NEXT: .ascii "char" # string offset=55
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; CHECK-NEXT: .byte 0
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; CHECK-NEXT: .ascii "ch" # string offset=60
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; CHECK-NEXT: .byte 0
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; CHECK-NEXT: .ascii "global_func" # string offset=63
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; CHECK-NEXT: .byte 0
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; CHECK-NEXT: .ascii "abc" # string offset=75
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; CHECK-NEXT: .byte 0
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declare !dbg !6 dso_local i32 @global_func(i8 signext) local_unnamed_addr #1 section "abc"
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attributes #0 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "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" }
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attributes #1 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "no-infs-fp-math"="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" }
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attributes #2 = { nounwind }
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!llvm.dbg.cu = !{!2}
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!llvm.module.flags = !{!12, !13, !14}
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!llvm.ident = !{!15}
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!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
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!1 = distinct !DIGlobalVariable(name: "ch", scope: !2, file: !3, line: 2, type: !10, isLocal: false, isDefinition: false)
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!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 10.0.0 (https://github.com/llvm/llvm-project.git 0ad024346185b3f0b5167438e126568982b1168d)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, retainedTypes: !5, globals: !11, nameTableKind: None)
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!3 = !DIFile(filename: "test.c", directory: "/tmp/home/yhs/work/tests/extern")
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!4 = !{}
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!5 = !{!6}
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!6 = !DISubprogram(name: "global_func", scope: !3, file: !3, line: 1, type: !7, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !4)
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!7 = !DISubroutineType(types: !8)
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!8 = !{!9, !10}
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!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!10 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
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!11 = !{!0}
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!12 = !{i32 2, !"Dwarf Version", i32 4}
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!13 = !{i32 2, !"Debug Info Version", i32 3}
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!14 = !{i32 1, !"wchar_size", i32 4}
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!15 = !{!"clang version 10.0.0 (https://github.com/llvm/llvm-project.git 0ad024346185b3f0b5167438e126568982b1168d)"}
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!16 = distinct !DISubprogram(name: "test", scope: !3, file: !3, line: 3, type: !17, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !4)
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!17 = !DISubroutineType(types: !18)
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!18 = !{!9}
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!19 = !DILocation(line: 4, column: 10, scope: !16)
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!20 = !DILocation(line: 4, column: 27, scope: !16)
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!21 = !{!22, !22, i64 0}
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!22 = !{!"omnipotent char", !23, i64 0}
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!23 = !{!"Simple C/C++ TBAA"}
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!24 = !DILocation(line: 4, column: 25, scope: !16)
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!25 = !DILocation(line: 4, column: 3, scope: !16)
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