[BPF] Add support for floats and doubles

iii-i · iii-i · commit a7137b238a07 · 2021-03-05T15:10:11.000+01:00
Some BPF programs compiled on s390 fail to load, because s390 arch-specific linux headers contain float and double types. At the moment there is no BTF_KIND for floats and doubles, so the release version of LLVM ends up emitting type id 0 for them, which the in-kernel verifier does not accept. Introduce support for such types to libbpf by representing them using the new BTF_KIND_FLOAT. Reviewed By: yonghong-song Differential Revision: https://reviews.llvm.org/D83289
diff --git a/llvm/lib/Target/BPF/BTF.def b/llvm/lib/Target/BPF/BTF.def
@@ -30,5 +30,6 @@ HANDLE_BTF_KIND(12, FUNC)
 HANDLE_BTF_KIND(13, FUNC_PROTO)
 HANDLE_BTF_KIND(14, VAR)
 HANDLE_BTF_KIND(15, DATASEC)
+HANDLE_BTF_KIND(16, FLOAT)
 
 #undef HANDLE_BTF_KIND
diff --git a/llvm/lib/Target/BPF/BTFDebug.cpp b/llvm/lib/Target/BPF/BTFDebug.cpp
@@ -371,6 +371,21 @@ void BTFKindDataSec::emitType(MCStreamer &OS) {
   }
 }
 
+BTFTypeFloat::BTFTypeFloat(uint32_t SizeInBits, StringRef TypeName)
+    : Name(TypeName) {
+  Kind = BTF::BTF_KIND_FLOAT;
+  BTFType.Info = Kind << 24;
+  BTFType.Size = roundupToBytes(SizeInBits);
+}
+
+void BTFTypeFloat::completeType(BTFDebug &BDebug) {
+  if (IsCompleted)
+    return;
+  IsCompleted = true;
+
+  BTFType.NameOff = BDebug.addString(Name);
+}
+
 uint32_t BTFStringTable::addString(StringRef S) {
   // Check whether the string already exists.
   for (auto &OffsetM : OffsetToIdMap) {
@@ -409,18 +424,28 @@ uint32_t BTFDebug::addType(std::unique_ptr<BTFTypeBase> TypeEntry) {
 }
 
 void BTFDebug::visitBasicType(const DIBasicType *BTy, uint32_t &TypeId) {
-  // Only int types are supported in BTF.
+  // Only int and binary floating point types are supported in BTF.
   uint32_t Encoding = BTy->getEncoding();
-  if (Encoding != dwarf::DW_ATE_boolean && Encoding != dwarf::DW_ATE_signed &&
-      Encoding != dwarf::DW_ATE_signed_char &&
-      Encoding != dwarf::DW_ATE_unsigned &&
-      Encoding != dwarf::DW_ATE_unsigned_char)
+  std::unique_ptr<BTFTypeBase> TypeEntry;
+  switch (Encoding) {
+  case dwarf::DW_ATE_boolean:
+  case dwarf::DW_ATE_signed:
+  case dwarf::DW_ATE_signed_char:
+  case dwarf::DW_ATE_unsigned:
+  case dwarf::DW_ATE_unsigned_char:
+    // Create a BTF type instance for this DIBasicType and put it into
+    // DIToIdMap for cross-type reference check.
+    TypeEntry = std::make_unique<BTFTypeInt>(
+        Encoding, BTy->getSizeInBits(), BTy->getOffsetInBits(), BTy->getName());
+    break;
+  case dwarf::DW_ATE_float:
+    TypeEntry =
+        std::make_unique<BTFTypeFloat>(BTy->getSizeInBits(), BTy->getName());
+    break;
+  default:
     return;
+  }
 
-  // Create a BTF type instance for this DIBasicType and put it into
-  // DIToIdMap for cross-type reference check.
-  auto TypeEntry = std::make_unique<BTFTypeInt>(
-      Encoding, BTy->getSizeInBits(), BTy->getOffsetInBits(), BTy->getName());
   TypeId = addType(std::move(TypeEntry), BTy);
 }
 
diff --git a/llvm/lib/Target/BPF/BTFDebug.h b/llvm/lib/Target/BPF/BTFDebug.h
@@ -195,6 +195,15 @@ class BTFKindDataSec : public BTFTypeBase {
   void emitType(MCStreamer &OS) override;
 };
 
+/// Handle binary floating point type.
+class BTFTypeFloat : public BTFTypeBase {
+  StringRef Name;
+
+public:
+  BTFTypeFloat(uint32_t SizeInBits, StringRef TypeName);
+  void completeType(BTFDebug &BDebug) override;
+};
+
 /// String table.
 class BTFStringTable {
   /// String table size in bytes.
diff --git a/llvm/test/CodeGen/BPF/BTF/double.ll b/llvm/test/CodeGen/BPF/BTF/double.ll
@@ -0,0 +1,58 @@
+; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
+; RUN: llc -march=bpfeb -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
+
+; Source code:
+;   double a;
+; Compilation flag:
+;   clang -target bpf -O2 -g -S -emit-llvm t.c
+
+@a = dso_local local_unnamed_addr global double 0.000000e+00, align 8, !dbg !0
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9}
+!llvm.ident = !{!10}
+
+; CHECK:             .section .BTF,"",@progbits
+; CHECK-NEXT:        .short 60319 # 0xeb9f
+; CHECK-NEXT:        .byte 1
+; CHECK-NEXT:        .byte 0
+; CHECK-NEXT:        .long 24
+; CHECK-NEXT:        .long 0
+; CHECK-NEXT:        .long 52
+; CHECK-NEXT:        .long 52
+; CHECK-NEXT:        .long 15
+; [1] double, size=8 bytes (64 bits)
+; CHECK-NEXT:        .long 1 # BTF_KIND_FLOAT(id = 1)
+; CHECK-NEXT:        .long 268435456 # 0x10000000
+; CHECK-NEXT:        .long 8
+; [2] a, type=double (1), global
+; CHECK-NEXT:        .long 8 # BTF_KIND_VAR(id = 2)
+; CHECK-NEXT:        .long 234881024 # 0xe000000
+; CHECK-NEXT:        .long 1
+; CHECK-NEXT:        .long 1
+; [3] .bss, 1 var, {a, offset=&a, size=8 bytes}
+; CHECK-NEXT:        .long 10 # BTF_KIND_DATASEC(id = 3)
+; CHECK-NEXT:        .long 251658241 # 0xf000001
+; CHECK-NEXT:        .long 0
+; CHECK-NEXT:        .long 2
+; CHECK-NEXT:        .long a
+; CHECK-NEXT:        .long 8
+; CHECK-NEXT:        .byte 0 # string offset=0
+; CHECK-NEXT:        .ascii "double" # string offset=1
+; CHECK-NEXT:        .byte 0
+; CHECK-NEXT:        .byte 97 # string offset=8
+; CHECK-NEXT:        .byte 0
+; CHECK-NEXT:        .ascii ".bss" # string offset=10
+; CHECK-NEXT:        .byte 0
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 11.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "t.c", directory: "/home/yhs/tmp")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "double", size: 64, encoding: DW_ATE_float)
+!7 = !{i32 7, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!10 = !{!"clang version 11.0.0 "}
diff --git a/llvm/test/CodeGen/BPF/BTF/float.ll b/llvm/test/CodeGen/BPF/BTF/float.ll
@@ -0,0 +1,58 @@
+; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
+; RUN: llc -march=bpfeb -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
+
+; Source code:
+;   float a;
+; Compilation flag:
+;   clang -target bpf -O2 -g -S -emit-llvm t.c
+
+@a = dso_local local_unnamed_addr global float 0.000000e+00, align 4, !dbg !0
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9}
+!llvm.ident = !{!10}
+
+; CHECK:             .section .BTF,"",@progbits
+; CHECK-NEXT:        .short 60319 # 0xeb9f
+; CHECK-NEXT:        .byte 1
+; CHECK-NEXT:        .byte 0
+; CHECK-NEXT:        .long 24
+; CHECK-NEXT:        .long 0
+; CHECK-NEXT:        .long 52
+; CHECK-NEXT:        .long 52
+; CHECK-NEXT:        .long 14
+; [1] float, size=4 bytes (32 bits)
+; CHECK-NEXT:        .long 1 # BTF_KIND_FLOAT(id = 1)
+; CHECK-NEXT:        .long 268435456 # 0x10000000
+; CHECK-NEXT:        .long 4
+; [2] a, type=float (1), global
+; CHECK-NEXT:        .long 7 # BTF_KIND_VAR(id = 2)
+; CHECK-NEXT:        .long 234881024 # 0xe000000
+; CHECK-NEXT:        .long 1
+; CHECK-NEXT:        .long 1
+; [3] .bss, 1 var, {a, offset=&a, size=4 bytes}
+; CHECK-NEXT:        .long 9 # BTF_KIND_DATASEC(id = 3)
+; CHECK-NEXT:        .long 251658241 # 0xf000001
+; CHECK-NEXT:        .long 0
+; CHECK-NEXT:        .long 2
+; CHECK-NEXT:        .long a
+; CHECK-NEXT:        .long 4
+; CHECK-NEXT:        .byte 0 # string offset=0
+; CHECK-NEXT:        .ascii "float" # string offset=1
+; CHECK-NEXT:        .byte 0
+; CHECK-NEXT:        .byte 97 # string offset=7
+; CHECK-NEXT:        .byte 0
+; CHECK-NEXT:        .ascii ".bss" # string offset=9
+; CHECK-NEXT:        .byte 0
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 11.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "t.c", directory: "/home/yhs/tmp")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "float", size: 32, encoding: DW_ATE_float)
+!7 = !{i32 7, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!10 = !{!"clang version 11.0.0 "}
