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[BPF] handle typedef of struct/union for CO-RE relocations

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Linux commit
  1cf5b23988 (diff-289313b9fec99c6f0acfea19d9cfd949)
uses "#pragma clang attribute push (__attribute__((preserve_access_index)),
      apply_to = record)"
to apply CO-RE relocations to all records including the following pattern:
  #pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)
  typedef struct {
    int a;
  } __t;
  #pragma clang attribute pop
  int test(__t *arg) { return arg->a; }

The current approach to use struct/union type in the relocation record will
result in an anonymous struct, which make later type matching difficult
in bpf loader. In fact, current BPF backend will fail the above program
with assertion:
  clang: ../lib/Target/BPF/BPFAbstractMemberAccess.cpp:796: ...
     Assertion `TypeName.size()' failed.

clang will change to use the type of the base of the member access
which will preserve the typedef modifier for the
preserve_{struct,union}_access_index intrinsics in the above example.
Here we adjust BPF backend to accept that the debuginfo
type metadata may be 'typedef' and handle them properly.

Differential Revision: https://reviews.llvm.org/D73902
This commit is contained in:
Yonghong Song 2020-02-01 21:00:00 -08:00
parent 3a4ded6113
commit aa49707128
3 changed files with 192 additions and 10 deletions
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25
lib/Target/BPF/BPFAbstractMemberAccess.cpp
View File

@ -189,18 +189,20 @@ bool BPFAbstractMemberAccess::runOnModule(Module &M) {
return doTransformation(M);
}
static bool SkipDIDerivedTag(unsigned Tag) {
static bool SkipDIDerivedTag(unsigned Tag, bool skipTypedef) {
if (Tag != dwarf::DW_TAG_typedef && Tag != dwarf::DW_TAG_const_type &&
Tag != dwarf::DW_TAG_volatile_type &&
Tag != dwarf::DW_TAG_restrict_type &&
Tag != dwarf::DW_TAG_member)
return false;
return false;
if (Tag == dwarf::DW_TAG_typedef && !skipTypedef)
return false;
return true;
}
static DIType * stripQualifiers(DIType *Ty) {
static DIType * stripQualifiers(DIType *Ty, bool skipTypedef = true) {
while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
if (!SkipDIDerivedTag(DTy->getTag()))
if (!SkipDIDerivedTag(DTy->getTag(), skipTypedef))
break;
Ty = DTy->getBaseType();
}
@ -209,7 +211,7 @@ static DIType * stripQualifiers(DIType *Ty) {
static const DIType * stripQualifiers(const DIType *Ty) {
while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
if (!SkipDIDerivedTag(DTy->getTag()))
if (!SkipDIDerivedTag(DTy->getTag(), true))
break;
Ty = DTy->getBaseType();
}
@ -710,7 +712,7 @@ Value *BPFAbstractMemberAccess::computeBaseAndAccessKey(CallInst *Call,
// calculated here as all debuginfo types are available.
// Get type name and calculate the first index.
// We only want to get type name from structure or union.
// We only want to get type name from typedef, structure or union.
// If user wants a relocation like
// int *p; ... __builtin_preserve_access_index(&p[4]) ...
// or
@ -727,12 +729,15 @@ Value *BPFAbstractMemberAccess::computeBaseAndAccessKey(CallInst *Call,
if (!Base)
Base = CInfo.Base;
DIType *Ty = stripQualifiers(cast<DIType>(CInfo.Metadata));
DIType *PossibleTypeDef = stripQualifiers(cast<DIType>(CInfo.Metadata),
false);
DIType *Ty = stripQualifiers(PossibleTypeDef);
if (CInfo.Kind == BPFPreserveUnionAI ||
CInfo.Kind == BPFPreserveStructAI) {
// struct or union type
TypeName = std::string(Ty->getName());
TypeMeta = Ty;
// struct or union type. If the typedef is in the metadata, always
// use the typedef.
TypeName = std::string(PossibleTypeDef->getName());
TypeMeta = PossibleTypeDef;
PatchImm += FirstIndex * (Ty->getSizeInBits() >> 3);
break;
}

89
test/CodeGen/BPF/CORE/offset-reloc-typedef-struct-2.ll Normal file
View File

@ -0,0 +1,89 @@
; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck %s
; RUN: llc -march=bpfel -mattr=+alu32 -filetype=asm -o - %s | FileCheck %s
;
; Source code:
; #pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)
; typedef struct {
; int a;
; } __t;
; #pragma clang attribute pop
;
; int test(__t *arg) { return arg->a; }
; Compiler flag to generate IR:
; clang -target bpf -S -O2 -g -emit-llvm test.c
%struct.__t = type { i32 }
; Function Attrs: nounwind readonly
define dso_local i32 @test(%struct.__t* readonly %arg) local_unnamed_addr #0 !dbg !13 {
entry:
call void @llvm.dbg.value(metadata %struct.__t* %arg, metadata !18, metadata !DIExpression()), !dbg !19
%0 = tail call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.__ts(%struct.__t* %arg, i32 0, i32 0), !dbg !20, !llvm.preserve.access.index !4
%1 = load i32, i32* %0, align 4, !dbg !20, !tbaa !21
ret i32 %1, !dbg !26
}
; CHECK: .long 1 # BTF_KIND_TYPEDEF(id = 2)
; CHECK-NEXT: .long 134217728 # 0x8000000
; CHECK-NEXT: .long 3
; CHECK-NEXT: .long 0 # BTF_KIND_STRUCT(id = 3)
; CHECK-NEXT: .long 67108865 # 0x4000001
; CHECK-NEXT: .long 4
; CHECK-NEXT: .long 5
; CHECK-NEXT: .long 4
; CHECK-NEXT: .long 0 # 0x0
;
; CHECK: .ascii "__t" # string offset=1
; CHECK: .byte 97 # string offset=5
; CHECK: .ascii ".text" # string offset=20
; CHECK: .ascii "0:0" # string offset=26
;
; CHECK: .long 16 # FieldReloc
; CHECK-NEXT: .long 20 # Field reloc section string offset=20
; CHECK-NEXT: .long 1
; CHECK-NEXT: .long .Ltmp{{[0-9]+}}
; CHECK-NEXT: .long 2
; CHECK-NEXT: .long 26
; CHECK-NEXT: .long 0
; Function Attrs: nounwind readnone
declare i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.__ts(%struct.__t*, i32, i32) #1
; Function Attrs: nounwind readnone speculatable
declare void @llvm.dbg.value(metadata, metadata, metadata) #2
attributes #0 = { nounwind readonly "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" }
attributes #1 = { nounwind readnone }
attributes #2 = { nounwind readnone speculatable}
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!9, !10, !11}
!llvm.ident = !{!12}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 11.0.0 (https://github.com/llvm/llvm-project.git 5125d1c934efa69ffc1902ce3b8f2f288653a92f)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.c", directory: "/tmp/home/yhs/work/tests/core_bug")
!2 = !{}
!3 = !{!4}
!4 = !DIDerivedType(tag: DW_TAG_typedef, name: "__t", file: !1, line: 4, baseType: !5)
!5 = distinct !DICompositeType(tag: DW_TAG_structure_type, file: !1, line: 2, size: 32, elements: !6)
!6 = !{!7}
!7 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !5, file: !1, line: 3, baseType: !8, size: 32)
!8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!9 = !{i32 7, !"Dwarf Version", i32 4}
!10 = !{i32 2, !"Debug Info Version", i32 3}
!11 = !{i32 1, !"wchar_size", i32 4}
!12 = !{!"clang version 11.0.0 (https://github.com/llvm/llvm-project.git 5125d1c934efa69ffc1902ce3b8f2f288653a92f)"}
!13 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 7, type: !14, scopeLine: 7, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, isDefinition: true, isOptimized: true, unit: !0, retainedNodes: !17)
!14 = !DISubroutineType(types: !15)
!15 = !{!8, !16}
!16 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !4, size: 64)
!17 = !{!18}
!18 = !DILocalVariable(name: "arg", arg: 1, scope: !13, file: !1, line: 7, type: !16)
!19 = !DILocation(line: 0, scope: !13)
!20 = !DILocation(line: 7, column: 34, scope: !13)
!21 = !{!22, !23, i64 0}
!22 = !{!"", !23, i64 0}
!23 = !{!"int", !24, i64 0}
!24 = !{!"omnipotent char", !25, i64 0}
!25 = !{!"Simple C/C++ TBAA"}
!26 = !DILocation(line: 7, column: 22, scope: !13)

88
test/CodeGen/BPF/CORE/offset-reloc-typedef-union-2.ll Normal file
View File

@ -0,0 +1,88 @@
; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck %s
; RUN: llc -march=bpfel -mattr=+alu32 -filetype=asm -o - %s | FileCheck %s
;
; Source code:
; #pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)
; typedef union {
; int a;
; } __t;
; #pragma clang attribute pop
;
; int test(__t *arg) { return arg->a; }
; Compiler flag to generate IR:
; clang -target bpf -S -O2 -g -emit-llvm test.c
%union.__t = type { i32 }
; Function Attrs: nounwind readonly
define dso_local i32 @test(%union.__t* readonly %arg) local_unnamed_addr #0 !dbg !13 {
entry:
call void @llvm.dbg.value(metadata %union.__t* %arg, metadata !18, metadata !DIExpression()), !dbg !19
%0 = tail call %union.__t* @llvm.preserve.union.access.index.p0s_union.__ts.p0s_union.__ts(%union.__t* %arg, i32 0), !dbg !20, !llvm.preserve.access.index !4
%a = getelementptr %union.__t, %union.__t* %0, i64 0, i32 0, !dbg !20
%1 = load i32, i32* %a, align 4, !dbg !20, !tbaa !21
ret i32 %1, !dbg !24
}
; CHECK: .long 1 # BTF_KIND_TYPEDEF(id = 2)
; CHECK-NEXT: .long 134217728 # 0x8000000
; CHECK-NEXT: .long 3
; CHECK-NEXT: .long 0 # BTF_KIND_UNION(id = 3)
; CHECK-NEXT: .long 83886081 # 0x5000001
; CHECK-NEXT: .long 4
; CHECK-NEXT: .long 5
; CHECK-NEXT: .long 4
; CHECK-NEXT: .long 0 # 0x0
;
; CHECK: .ascii "__t" # string offset=1
; CHECK: .byte 97 # string offset=5
; CHECK: .ascii ".text" # string offset=20
; CHECK: .ascii "0:0" # string offset=26
;
; CHECK: .long 16 # FieldReloc
; CHECK-NEXT: .long 20 # Field reloc section string offset=20
; CHECK-NEXT: .long 1
; CHECK-NEXT: .long .Ltmp{{[0-9]+}}
; CHECK-NEXT: .long 2
; CHECK-NEXT: .long 26
; CHECK-NEXT: .long 0
; Function Attrs: nounwind readnone
declare %union.__t* @llvm.preserve.union.access.index.p0s_union.__ts.p0s_union.__ts(%union.__t*, i32) #1
; Function Attrs: nounwind readnone speculatable
declare void @llvm.dbg.value(metadata, metadata, metadata) #2
attributes #0 = { nounwind readonly "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" }
attributes #1 = { nounwind readnone }
attributes #2 = { nounwind readnone speculatable}
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!9, !10, !11}
!llvm.ident = !{!12}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 11.0.0 (https://github.com/llvm/llvm-project.git 5125d1c934efa69ffc1902ce3b8f2f288653a92f)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.c", directory: "/tmp/home/yhs/work/tests/core_bug")
!2 = !{}
!3 = !{!4}
!4 = !DIDerivedType(tag: DW_TAG_typedef, name: "__t", file: !1, line: 4, baseType: !5)
!5 = distinct !DICompositeType(tag: DW_TAG_union_type, file: !1, line: 2, size: 32, elements: !6)
!6 = !{!7}
!7 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !5, file: !1, line: 3, baseType: !8, size: 32)
!8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!9 = !{i32 7, !"Dwarf Version", i32 4}
!10 = !{i32 2, !"Debug Info Version", i32 3}
!11 = !{i32 1, !"wchar_size", i32 4}
!12 = !{!"clang version 11.0.0 (https://github.com/llvm/llvm-project.git 5125d1c934efa69ffc1902ce3b8f2f288653a92f)"}
!13 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 7, type: !14, scopeLine: 7, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, isDefinition: true, isOptimized: true, unit: !0, retainedNodes: !17)
!14 = !DISubroutineType(types: !15)
!15 = !{!8, !16}
!16 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !4, size: 64)
!17 = !{!18}
!18 = !DILocalVariable(name: "arg", arg: 1, scope: !13, file: !1, line: 7, type: !16)
!19 = !DILocation(line: 0, scope: !13)
!20 = !DILocation(line: 7, column: 34, scope: !13)
!21 = !{!22, !22, i64 0}
!22 = !{!"omnipotent char", !23, i64 0}
!23 = !{!"Simple C/C++ TBAA"}
!24 = !DILocation(line: 7, column: 22, scope: !13)