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[BPF] Visit nested map array during BTF generation (#150608)
Fixes missing inner map struct type definitions [^1]. We should visit the type of nested array of maps like we do for global maps. This patch adds a boolean to convey the information to visitTypeEntry and visitDerivedType that the pointee is a map definition and should be treated as such. It ressembles and works with commit 0d21c95 ("[BPF] Handle nested wrapper structs in BPF map definition traversal (#144097)") which focused on directly nested wrapper structs. Before that patch, this ARRAY_OF_MAPS definition would lead to the BTF information include the 'missing_type' as "FWD 'missing_type' fwd_kind=struct": struct missing_type { uint64_t foo; }; struct { __uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS); [...] __array( values, struct { [...] __type(value, struct missing_type); }); } map SEC(".maps"); Which lead to errors while trying to load the map: libbpf: map 'outer_map.inner': can't determine value size for type [N]: -22. To solve this issue, users had to use the struct in a dummy variable or in a dummy function for the BTF to be generated correctly [^2]. [^1]: https://lore.kernel.org/netdev/[email protected]/T/#u [^2]: cilium/ebpf#1658 (reply in thread) --------- Signed-off-by: Mahe Tardy <[email protected]> Co-authored-by: Eduard Zingerman <[email protected]>
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-116
lines changed

4 files changed

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lines changed

‎llvm/lib/Target/BPF/BTFDebug.cpp

Lines changed: 37 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -957,47 +957,47 @@ void BTFDebug::visitMapDefType(const DIType *Ty, uint32_t &TypeId) {
957957
return;
958958
}
959959

960-
// MapDef type may be a struct type or a non-pointer derived type
961-
const DIType *OrigTy = Ty;
962-
while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
963-
auto Tag = DTy->getTag();
964-
if (Tag != dwarf::DW_TAG_typedef && Tag != dwarf::DW_TAG_const_type &&
965-
Tag != dwarf::DW_TAG_volatile_type &&
966-
Tag != dwarf::DW_TAG_restrict_type)
967-
break;
968-
Ty = DTy->getBaseType();
969-
}
970-
971-
const auto *CTy = dyn_cast<DICompositeType>(Ty);
972-
if (!CTy)
973-
return;
974-
975-
auto Tag = CTy->getTag();
976-
if (Tag != dwarf::DW_TAG_structure_type || CTy->isForwardDecl())
977-
return;
978-
979-
// Visit all struct members to ensure their types are visited.
980-
const DINodeArray Elements = CTy->getElements();
981-
for (const auto *Element : Elements) {
982-
const auto *MemberType = cast<DIDerivedType>(Element);
983-
const DIType *MemberBaseType = MemberType->getBaseType();
984-
985-
// If the member is a composite type, that may indicate the currently
986-
// visited composite type is a wrapper, and the member represents the
987-
// actual map definition.
988-
// In that case, visit the member with `visitMapDefType` instead of
989-
// `visitTypeEntry`, treating it specifically as a map definition rather
990-
// than as a regular composite type.
991-
const auto *MemberCTy = dyn_cast<DICompositeType>(MemberBaseType);
992-
if (MemberCTy) {
993-
visitMapDefType(MemberBaseType, TypeId);
994-
} else {
995-
visitTypeEntry(MemberBaseType);
960+
uint32_t TmpId;
961+
switch (Ty->getTag()) {
962+
case dwarf::DW_TAG_typedef:
963+
case dwarf::DW_TAG_const_type:
964+
case dwarf::DW_TAG_volatile_type:
965+
case dwarf::DW_TAG_restrict_type:
966+
case dwarf::DW_TAG_pointer_type:
967+
visitMapDefType(dyn_cast<DIDerivedType>(Ty)->getBaseType(), TmpId);
968+
break;
969+
case dwarf::DW_TAG_array_type:
970+
// Visit nested map array and jump to the element type
971+
visitMapDefType(dyn_cast<DICompositeType>(Ty)->getBaseType(), TmpId);
972+
break;
973+
case dwarf::DW_TAG_structure_type: {
974+
// Visit all struct members to ensure their types are visited.
975+
const auto *CTy = cast<DICompositeType>(Ty);
976+
const DINodeArray Elements = CTy->getElements();
977+
for (const auto *Element : Elements) {
978+
const auto *MemberType = cast<DIDerivedType>(Element);
979+
const DIType *MemberBaseType = MemberType->getBaseType();
980+
// If the member is a composite type, that may indicate the currently
981+
// visited composite type is a wrapper, and the member represents the
982+
// actual map definition.
983+
// In that case, visit the member with `visitMapDefType` instead of
984+
// `visitTypeEntry`, treating it specifically as a map definition rather
985+
// than as a regular composite type.
986+
const auto *MemberCTy = dyn_cast<DICompositeType>(MemberBaseType);
987+
if (MemberCTy) {
988+
visitMapDefType(MemberBaseType, TmpId);
989+
} else {
990+
visitTypeEntry(MemberBaseType);
991+
}
996992
}
993+
break;
994+
}
995+
default:
996+
break;
997997
}
998998

999999
// Visit this type, struct or a const/typedef/volatile/restrict type
1000-
visitTypeEntry(OrigTy, TypeId, false, false);
1000+
visitTypeEntry(Ty, TypeId, false, false);
10011001
}
10021002

10031003
/// Read file contents from the actual file or from the source

‎llvm/test/CodeGen/BPF/BTF/map-def-2.ll

Lines changed: 14 additions & 47 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
1-
; RUN: llc -mtriple=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
2-
; RUN: llc -mtriple=bpfeb -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
1+
; RUN: llc -mtriple=bpfel -mcpu=v3 -filetype=obj -o %t1 %s
2+
; RUN: llvm-objcopy --dump-section='.BTF'=%t2 %t1
3+
; RUN: %python %p/print_btf.py %t2 | FileCheck -check-prefixes=CHECK-BTF %s
34
;
45
; Source code:
56
; struct key_type {
@@ -18,51 +19,17 @@
1819

1920
@hash_map = dso_local local_unnamed_addr global %struct.map_type zeroinitializer, section ".maps", align 8, !dbg !0
2021

21-
; CHECK: .long 0 # BTF_KIND_PTR(id = 1)
22-
; CHECK-NEXT: .long 33554432 # 0x2000000
23-
; CHECK-NEXT: .long 2
24-
; CHECK-NEXT: .long 1 # BTF_KIND_STRUCT(id = 2)
25-
; CHECK-NEXT: .long 67108865 # 0x4000001
26-
; CHECK-NEXT: .long 4
27-
; CHECK-NEXT: .long 10
28-
; CHECK-NEXT: .long 3
29-
; CHECK-NEXT: .long 0 # 0x0
30-
; CHECK-NEXT: .long 13 # BTF_KIND_INT(id = 3)
31-
; CHECK-NEXT: .long 16777216 # 0x1000000
32-
; CHECK-NEXT: .long 4
33-
; CHECK-NEXT: .long 16777248 # 0x1000020
34-
; CHECK-NEXT: .long 17 # BTF_KIND_TYPEDEF(id = 4)
35-
; CHECK-NEXT: .long 134217728 # 0x8000000
36-
; CHECK-NEXT: .long 5
37-
; CHECK-NEXT: .long 28 # BTF_KIND_TYPEDEF(id = 5)
38-
; CHECK-NEXT: .long 134217728 # 0x8000000
39-
; CHECK-NEXT: .long 6
40-
; CHECK-NEXT: .long 38 # BTF_KIND_STRUCT(id = 6)
41-
; CHECK-NEXT: .long 67108865 # 0x4000001
42-
; CHECK-NEXT: .long 8
43-
; CHECK-NEXT: .long 47
44-
; CHECK-NEXT: .long 1
45-
; CHECK-NEXT: .long 0 # 0x0
46-
; CHECK-NEXT: .long 51 # BTF_KIND_VAR(id = 7)
47-
; CHECK-NEXT: .long 234881024 # 0xe000000
48-
; CHECK-NEXT: .long 4
49-
; CHECK-NEXT: .long 1
50-
; CHECK-NEXT: .long 60 # BTF_KIND_DATASEC(id = 8)
51-
; CHECK-NEXT: .long 251658241 # 0xf000001
52-
; CHECK-NEXT: .long 0
53-
; CHECK-NEXT: .long 7
54-
; CHECK-NEXT: .long hash_map
55-
; CHECK-NEXT: .long 8
56-
57-
; CHECK: .ascii "key_type" # string offset=1
58-
; CHECK: .ascii "a1" # string offset=10
59-
; CHECK: .ascii "int" # string offset=13
60-
; CHECK: .ascii "__map_type" # string offset=17
61-
; CHECK: .ascii "_map_type" # string offset=28
62-
; CHECK: .ascii "map_type" # string offset=38
63-
; CHECK: .ascii "key" # string offset=47
64-
; CHECK: .ascii "hash_map" # string offset=51
65-
; CHECK: .ascii ".maps" # string offset=60
22+
; CHECK-BTF: [1] PTR '(anon)' type_id=2
23+
; CHECK-BTF-NEXT: [2] STRUCT 'key_type' size=4 vlen=1
24+
; CHECK-BTF-NEXT: 'a1' type_id=3 bits_offset=0
25+
; CHECK-BTF-NEXT: [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
26+
; CHECK-BTF-NEXT: [4] STRUCT 'map_type' size=8 vlen=1
27+
; CHECK-BTF-NEXT: 'key' type_id=1 bits_offset=0
28+
; CHECK-BTF-NEXT: [5] TYPEDEF '_map_type' type_id=4
29+
; CHECK-BTF-NEXT: [6] TYPEDEF '__map_type' type_id=5
30+
; CHECK-BTF-NEXT: [7] VAR 'hash_map' type_id=6, linkage=global
31+
; CHECK-BTF-NEXT: [8] DATASEC '.maps' size=0 vlen=1
32+
; CHECK-BTF-NEXT: type_id=7 offset=0 size=8
6633

6734
!llvm.dbg.cu = !{!2}
6835
!llvm.module.flags = !{!16, !17, !18}

‎llvm/test/CodeGen/BPF/BTF/map-def-3.ll

Lines changed: 10 additions & 32 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
1-
; RUN: llc -mtriple=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
2-
; RUN: llc -mtriple=bpfeb -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
1+
; RUN: llc -mtriple=bpfel -mcpu=v3 -filetype=obj -o %t1 %s
2+
; RUN: llvm-objcopy --dump-section='.BTF'=%t2 %t1
3+
; RUN: %python %p/print_btf.py %t2 | FileCheck -check-prefixes=CHECK-BTF %s
34
;
45
; Source code:
56
; struct key_type {
@@ -13,36 +14,13 @@
1314

1415
@hash_map = dso_local local_unnamed_addr constant %struct.key_type zeroinitializer, section ".maps", align 4, !dbg !0
1516

16-
; CHECK: .long 1 # BTF_KIND_INT(id = 1)
17-
; CHECK-NEXT: .long 16777216 # 0x1000000
18-
; CHECK-NEXT: .long 4
19-
; CHECK-NEXT: .long 16777248 # 0x1000020
20-
; CHECK-NEXT: .long 0 # BTF_KIND_CONST(id = 2)
21-
; CHECK-NEXT: .long 167772160 # 0xa000000
22-
; CHECK-NEXT: .long 3
23-
; CHECK-NEXT: .long 5 # BTF_KIND_STRUCT(id = 3)
24-
; CHECK-NEXT: .long 67108865 # 0x4000001
25-
; CHECK-NEXT: .long 4
26-
; CHECK-NEXT: .long 14
27-
; CHECK-NEXT: .long 1
28-
; CHECK-NEXT: .long 0 # 0x0
29-
; CHECK-NEXT: .long 17 # BTF_KIND_VAR(id = 4)
30-
; CHECK-NEXT: .long 234881024 # 0xe000000
31-
; CHECK-NEXT: .long 2
32-
; CHECK-NEXT: .long 1
33-
; CHECK-NEXT: .long 26 # BTF_KIND_DATASEC(id = 5)
34-
; CHECK-NEXT: .long 251658241 # 0xf000001
35-
; CHECK-NEXT: .long 0
36-
; CHECK-NEXT: .long 4
37-
; CHECK-NEXT: .long hash_map
38-
; CHECK-NEXT: .long 4
39-
40-
; CHECK: .ascii "int" # string offset=1
41-
; CHECK: .ascii "key_type" # string offset=5
42-
; CHECK: .ascii "a1" # string offset=14
43-
; CHECK: .ascii "hash_map" # string offset=17
44-
; CHECK: .ascii ".maps" # string offset=26
45-
17+
; CHECK-BTF: [1] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
18+
; CHECK-BTF-NEXT: [2] STRUCT 'key_type' size=4 vlen=1
19+
; CHECK-BTF-NEXT: 'a1' type_id=1 bits_offset=0
20+
; CHECK-BTF-NEXT: [3] CONST '(anon)' type_id=2
21+
; CHECK-BTF-NEXT: [4] VAR 'hash_map' type_id=3, linkage=global
22+
; CHECK-BTF-NEXT: [5] DATASEC '.maps' size=0 vlen=1
23+
; CHECK-BTF-NEXT: type_id=4 offset=0 size=4
4624

4725
!llvm.dbg.cu = !{!2}
4826
!llvm.module.flags = !{!11, !12, !13}

‎llvm/test/CodeGen/BPF/BTF/map-def-nested-array.ll

Lines changed: 75 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,75 @@
1+
; RUN: llc -mtriple=bpfel -mcpu=v3 -filetype=obj -o %t1 %s
2+
; RUN: llvm-objcopy --dump-section='.BTF'=%t2 %t1
3+
; RUN: %python %p/print_btf.py %t2 | FileCheck -check-prefixes=CHECK-BTF-SHORT %s
4+
; RUN: %python %p/print_btf.py %t2 | FileCheck -check-prefixes=CHECK-BTF %s
5+
; Source:
6+
; struct nested_value_type {
7+
; int a1;
8+
; };
9+
; struct map_type {
10+
; struct {
11+
; struct nested_value_type *value;
12+
; } *values[];
13+
; };
14+
; Compilation flags:
15+
; clang -target bpf -g -O2 -S -emit-llvm prog.c
16+
17+
; ModuleID = 'prog.c'
18+
source_filename = "prog.c"
19+
target datalayout = "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128"
20+
target triple = "bpf"
21+
22+
%struct.map_type = type { [0 x ptr] }
23+
24+
@array_of_maps = dso_local local_unnamed_addr global %struct.map_type zeroinitializer, section ".maps", align 8, !dbg !0
25+
26+
; We expect no forward declarations.
27+
;
28+
; CHECK-BTF-SHORT-NOT: FWD
29+
30+
; Assert the whole BTF.
31+
;
32+
; CHECK-BTF: [1] PTR '(anon)' type_id=2
33+
; CHECK-BTF-NEXT: [2] STRUCT 'nested_value_type' size=4 vlen=1
34+
; CHECK-BTF-NEXT: 'a1' type_id=3 bits_offset=0
35+
; CHECK-BTF-NEXT: [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
36+
; CHECK-BTF-NEXT: [4] STRUCT '(anon)' size=8 vlen=1
37+
; CHECK-BTF-NEXT: 'value' type_id=1 bits_offset=0
38+
; CHECK-BTF-NEXT: [5] PTR '(anon)' type_id=4
39+
; CHECK-BTF-NEXT: [6] ARRAY '(anon)' type_id=5 index_type_id=7 nr_elems=0
40+
; CHECK-BTF-NEXT: [7] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
41+
; CHECK-BTF-NEXT: [8] STRUCT 'map_type' size=0 vlen=1
42+
; CHECK-BTF-NEXT: 'values' type_id=6 bits_offset=0
43+
; CHECK-BTF-NEXT: [9] VAR 'array_of_maps' type_id=8, linkage=global
44+
; CHECK-BTF-NEXT: [10] DATASEC '.maps' size=0 vlen=1
45+
; CHECK-BTF-NEXT: type_id=9 offset=0 size=0
46+
47+
!llvm.dbg.cu = !{!2}
48+
!llvm.module.flags = !{!20, !21, !22, !23}
49+
!llvm.ident = !{!24}
50+
51+
!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
52+
!1 = distinct !DIGlobalVariable(name: "array_of_maps", scope: !2, file: !3, line: 9, type: !5, isLocal: false, isDefinition: true)
53+
!2 = distinct !DICompileUnit(language: DW_LANG_C11, file: !3, producer: "clang version 22.0.0git ([email protected]:llvm/llvm-project.git ed93eaa421b714028b85cc887d80c45991d7207f)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: None)
54+
!3 = !DIFile(filename: "prog.c", directory: "/home/mtardy/llvm-bug-repro", checksumkind: CSK_MD5, checksum: "9381d9e83e9c0b235a14704224815e96")
55+
!4 = !{!0}
56+
!5 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "map_type", file: !3, line: 4, elements: !6)
57+
!6 = !{!7}
58+
!7 = !DIDerivedType(tag: DW_TAG_member, name: "values", scope: !5, file: !3, line: 7, baseType: !8)
59+
!8 = !DICompositeType(tag: DW_TAG_array_type, baseType: !9, elements: !18)
60+
!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64)
61+
!10 = distinct !DICompositeType(tag: DW_TAG_structure_type, scope: !5, file: !3, line: 5, size: 64, elements: !11)
62+
!11 = !{!12}
63+
!12 = !DIDerivedType(tag: DW_TAG_member, name: "value", scope: !10, file: !3, line: 6, baseType: !13, size: 64)
64+
!13 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !14, size: 64)
65+
!14 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "nested_value_type", file: !3, line: 1, size: 32, elements: !15)
66+
!15 = !{!16}
67+
!16 = !DIDerivedType(tag: DW_TAG_member, name: "a1", scope: !14, file: !3, line: 2, baseType: !17, size: 32)
68+
!17 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
69+
!18 = !{!19}
70+
!19 = !DISubrange(count: -1)
71+
!20 = !{i32 7, !"Dwarf Version", i32 5}
72+
!21 = !{i32 2, !"Debug Info Version", i32 3}
73+
!22 = !{i32 1, !"wchar_size", i32 4}
74+
!23 = !{i32 7, !"frame-pointer", i32 2}
75+
!24 = !{!"clang version 22.0.0git ([email protected]:llvm/llvm-project.git ed93eaa421b714028b85cc887d80c45991d7207f)"}

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