[PATCH] D71638: [WIP][BPF] extern BTF_KIND_FUNC to cover global, static and extern funcs

[Yonghong Song via Phabricator via llvm-commits]

yonghong-song created this revision.
yonghong-song added reviewers: ast, anakryiko.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

  Previous extern function is added as BTF_KIND_VAR. This does not work
  well with existing BTF infrastructure as function expected to use
  BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO.
  
  This patch added extern function to BTF_KIND_FUNC. The top two bits
  of btf_type.info are used to indicate what kind of function it is:
    0: static
    1: global
    2: extern
  
  one example:
    -bash-4.4$ cat t.c
    extern int foo(void);
    static __attribute__((noinline)) int test1() { return foo(); }
    int test2() { return test1(); }
    -bash-4.4$ clang -target bpf -O2 -g -S t.c
    ...
          .long   0                       # BTF_KIND_FUNC_PROTO(id = 1)
          .long   218103808               # 0xd000000
          .long   2
          .long   1                       # BTF_KIND_INT(id = 2)
          .long   16777216                # 0x1000000
          .long   4
          .long   16777248                # 0x1000020
          .long   5                       # BTF_KIND_FUNC(id = 3)
          .long   1275068416              # 0x4c000000
          .long   1
          .long   0                       # BTF_KIND_FUNC_PROTO(id = 4)
          .long   218103808               # 0xd000000
          .long   2
          .long   68                      # BTF_KIND_FUNC(id = 5)
          .long   201326592               # 0xc000000
          .long   4
          .long   0                       # BTF_KIND_FUNC_PROTO(id = 6)
          .long   218103808               # 0xd000000
          .long   2
          .long   137                     # BTF_KIND_FUNC(id = 7)
          .long   2348810240              # 0x8c000000
          .long   6
  
          .ascii  "test2"                 # string offset=5
          .ascii  "test1"                 # string offset=68
          .ascii  "foo"                   # string offset=137


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71638

Files:
  llvm/lib/Target/BPF/BTF.h
  llvm/lib/Target/BPF/BTFDebug.cpp
  llvm/lib/Target/BPF/BTFDebug.h


Index: llvm/lib/Target/BPF/BTFDebug.h
===================================================================
--- llvm/lib/Target/BPF/BTFDebug.h
+++ llvm/lib/Target/BPF/BTFDebug.h
@@ -151,7 +151,7 @@
   StringRef Name;
 
 public:
-  BTFTypeFunc(StringRef FuncName, uint32_t ProtoTypeId);
+  BTFTypeFunc(StringRef FuncName, uint32_t ProtoTypeId, uint32_t Scope);
   uint32_t getSize() { return BTFTypeBase::getSize(); }
   void completeType(BTFDebug &BDebug);
   void emitType(MCStreamer &OS);
Index: llvm/lib/Target/BPF/BTFDebug.cpp
===================================================================
--- llvm/lib/Target/BPF/BTFDebug.cpp
+++ llvm/lib/Target/BPF/BTFDebug.cpp
@@ -308,10 +308,11 @@
   }
 }
 
-BTFTypeFunc::BTFTypeFunc(StringRef FuncName, uint32_t ProtoTypeId)
+BTFTypeFunc::BTFTypeFunc(StringRef FuncName, uint32_t ProtoTypeId,
+    uint32_t Scope)
     : Name(FuncName) {
   Kind = BTF::BTF_KIND_FUNC;
-  BTFType.Info = Kind << 24;
+  BTFType.Info = (Scope << 30) | (Kind << 24);
   BTFType.Type = ProtoTypeId;
 }
 
@@ -897,8 +898,9 @@
   visitSubroutineType(SP->getType(), true, FuncArgNames, ProtoTypeId);
 
   // Construct subprogram func type
+  uint8_t Scope = SP->isLocalToUnit() ? BTF::FUNC_STATIC : BTF::FUNC_GLOBAL;
   auto FuncTypeEntry =
-      std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId);
+      std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId, Scope);
   uint32_t FuncTypeId = addType(std::move(FuncTypeEntry));
 
   for (const auto &TypeEntry : TypeEntries)
@@ -1163,20 +1165,10 @@
     const std::unordered_map<uint32_t, StringRef> FuncArgNames;
     visitSubroutineType(SP->getType(), false, FuncArgNames, ProtoTypeId);
 
-    auto VarEntry =
-        std::make_unique<BTFKindVar>(SP->getName(), ProtoTypeId,
-                                     BTF::VAR_GLOBAL_EXTERNAL);
-    uint32_t VarId = addType(std::move(VarEntry));
-
-    StringRef SecName = F.getSection();
-    if (SecName.empty())
-      SecName = ".extern";
-
-    if (DataSecEntries.find(SecName) == DataSecEntries.end()) {
-      DataSecEntries[SecName] = std::make_unique<BTFKindDataSec>(Asm, SecName);
-    }
-
-    DataSecEntries[SecName]->addVar(VarId, Asm->getSymbol(&F), 8);
+    uint8_t Scope = BTF::FUNC_EXTERN;
+    auto FuncTypeEntry =
+        std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId, Scope);
+    addType(std::move(FuncTypeEntry));
   }
 }
 
Index: llvm/lib/Target/BPF/BTF.h
===================================================================
--- llvm/lib/Target/BPF/BTF.h
+++ llvm/lib/Target/BPF/BTF.h
@@ -176,6 +176,13 @@
   uint32_t Type;
 };
 
+/// BTF_KIND_FUNC can be global, static or extern.
+enum : uint8_t {
+  FUNC_STATIC = 0,
+  FUNC_GLOBAL = 1,
+  FUNC_EXTERN = 2,
+};
+
 /// Variable scoping information.
 enum : uint8_t {
   VAR_STATIC = 0,           ///< Linkage: InternalLinkage


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