cf56b536bf
Currently, to avoid generating too much BTF types, for a struct type
like
```
struct foo {
int val;
struct bar *ptr;
};
```
if the BTF generation reaches 'struct foo', it will not generate actual
type for 'struct bar' and instead a forward decl is generated. The
'struct bar' is actual generated in BTF unless it is reached through a
non-struct pointer member.
Such a limitation forces bpf developer to hack and workaround this
problem. See [1] and [2]. For example in [1], we have
```
struct map_value {
struct prog_test_ref_kfunc *not_kptr;
struct prog_test_ref_kfunc __kptr *val;
struct node_data __kptr *node;
};
```
The BTF type for 'struct node_data' is not generated. Note that we have
a '__kptr' annotation. Similar problem for [2] with a '__uptr'
annotation. Note that the issue in [1] has been resolved later but the
hack in [2] is still needed.
This patch relaxed the struct type (with struct pointer member) BTF
generation if the struct pointer has a btf_type_tag annotation.
[1] https://lore.kernel.org/r/20230310230743.2320707-4-davemarchevsky@fb.com
[2] https://lore.kernel.org/r/20241023234759.860539-9-martin.lau@linux.dev
87 lines
4.3 KiB
LLVM
87 lines
4.3 KiB
LLVM
; RUN: llc -mtriple=bpfel -mcpu=v3 -filetype=obj -o %t1 %s
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; RUN: llvm-objcopy --dump-section='.BTF'=%t2 %t1
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; RUN: %python %p/print_btf.py %t2 | FileCheck -check-prefixes=CHECK-BTF %s
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; Source:
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; #define __tag1 __attribute__((btf_type_tag("tag1")))
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;
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; struct t1 {
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; int a;
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; };
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; struct t2 {
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; struct t1 *p1;
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; struct t1 __tag1 *p2;
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; int b;
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; };
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; int foo(struct t2 *arg) {
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; return arg->b;
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; }
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; Compilation flags:
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; clang -target bpf -O2 -g -S -emit-llvm t.c
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; Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(argmem: read)
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define dso_local i32 @foo(ptr nocapture noundef readonly %0) local_unnamed_addr #0 !dbg !8 {
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#dbg_value(ptr %0, !26, !DIExpression(), !27)
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%2 = getelementptr inbounds nuw i8, ptr %0, i64 16, !dbg !28
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%3 = load i32, ptr %2, align 8, !dbg !28, !tbaa !29
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ret i32 %3, !dbg !36
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}
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; CHECK-BTF: [1] PTR '(anon)' type_id=2
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; CHECK-BTF: [2] STRUCT 't2' size=24 vlen=3
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; CHECK-BTF: 'p1' type_id=3 bits_offset=0
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; CHECK-BTF: 'p2' type_id=5 bits_offset=64
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; CHECK-BTF: 'b' type_id=7 bits_offset=128
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; CHECK-BTF: [3] PTR '(anon)' type_id=6
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; CHECK-BTF: [4] TYPE_TAG 'tag1' type_id=6
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; CHECK-BTF: [5] PTR '(anon)' type_id=4
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; CHECK-BTF: [6] STRUCT 't1' size=4 vlen=1
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; CHECK-BTF: 'a' type_id=7 bits_offset=0
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; CHECK-BTF: [7] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
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; CHECK-BTF: [8] FUNC_PROTO '(anon)' ret_type_id=7 vlen=1
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; CHECK-BTF: 'arg' type_id=1
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; CHECK-BTF: [9] FUNC 'foo' type_id=8 linkage=global
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attributes #0 = { mustprogress nofree norecurse nosync nounwind willreturn memory(argmem: read) "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!2, !3, !4, !5, !6}
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!llvm.ident = !{!7}
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!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 20.1.6 (https://github.com/llvm/llvm-project.git aa804fd3e624cb92c6e7665182504c6049387f35)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
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!1 = !DIFile(filename: "t.c", directory: "/tmp/home/yhs/tmp3/tests", checksumkind: CSK_MD5, checksum: "73ef5b93654cc4e2667f383d5c3a9cd3")
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!2 = !{i32 7, !"Dwarf Version", i32 5}
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!3 = !{i32 2, !"Debug Info Version", i32 3}
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!4 = !{i32 1, !"wchar_size", i32 4}
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!5 = !{i32 7, !"frame-pointer", i32 2}
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!6 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
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!7 = !{!"clang version 20.1.6 (https://github.com/llvm/llvm-project.git aa804fd3e624cb92c6e7665182504c6049387f35)"}
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!8 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 11, type: !9, scopeLine: 11, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !25)
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!9 = !DISubroutineType(types: !10)
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!10 = !{!11, !12}
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!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!12 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 64)
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!13 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "t2", file: !1, line: 6, size: 192, elements: !14)
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!14 = !{!15, !20, !24}
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!15 = !DIDerivedType(tag: DW_TAG_member, name: "p1", scope: !13, file: !1, line: 7, baseType: !16, size: 64)
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!16 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !17, size: 64)
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!17 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "t1", file: !1, line: 3, size: 32, elements: !18)
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!18 = !{!19}
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!19 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !17, file: !1, line: 4, baseType: !11, size: 32)
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!20 = !DIDerivedType(tag: DW_TAG_member, name: "p2", scope: !13, file: !1, line: 8, baseType: !21, size: 64, offset: 64)
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!21 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !17, size: 64, annotations: !22)
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!22 = !{!23}
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!23 = !{!"btf_type_tag", !"tag1"}
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!24 = !DIDerivedType(tag: DW_TAG_member, name: "b", scope: !13, file: !1, line: 9, baseType: !11, size: 32, offset: 128)
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!25 = !{!26}
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!26 = !DILocalVariable(name: "arg", arg: 1, scope: !8, file: !1, line: 11, type: !12)
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!27 = !DILocation(line: 0, scope: !8)
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!28 = !DILocation(line: 12, column: 15, scope: !8)
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!29 = !{!30, !35, i64 16}
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!30 = !{!"t2", !31, i64 0, !31, i64 8, !35, i64 16}
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!31 = !{!"p1 _ZTS2t1", !32, i64 0}
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!32 = !{!"any pointer", !33, i64 0}
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!33 = !{!"omnipotent char", !34, i64 0}
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!34 = !{!"Simple C/C++ TBAA"}
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!35 = !{!"int", !33, i64 0}
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!36 = !DILocation(line: 12, column: 3, scope: !8)
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