BPF: add extern func to data sections if specified

This permits extern function (BTF_KIND_FUNC) be added
to BTF_KIND_DATASEC if a section name is specified.
For example,

-bash-4.4$ cat t.c
void foo(int) __attribute__((section(".kernel.funcs")));
int test(void) {
  foo(5);
  return 0;
}

The extern function foo (BTF_KIND_FUNC) will be put into
BTF_KIND_DATASEC with name ".kernel.funcs".

This will help to differentiate two kinds of external functions,
functions in kernel and functions defined in other bpf programs.

Differential Revision: https://reviews.llvm.org/D93563

(cherry picked from commit 886f9ff53155075bd5f1e994f17b85d1e1b7470c)

5 files changed, 38 insertions, 13 deletions

diff --git a/llvm/lib/Target/BPF/BTFDebug.cpp b/llvm/lib/Target/BPF/BTFDebug.cpp
index da7ec32703a5..bedf159430dc 100644
--- a/llvm/lib/Target/BPF/BTFDebug.cpp
+++ b/llvm/lib/Target/BPF/BTFDebug.cpp
@@ -1224,8 +1224,8 @@ void BTFDebug::processGlobals(bool ProcessingMapDef) {
     const DataLayout &DL = Global.getParent()->getDataLayout();
     uint32_t Size = DL.getTypeAllocSize(Global.getType()->getElementType());
 
-    DataSecEntries[std::string(SecName)]->addVar(VarId, Asm->getSymbol(&Global),
-                                                 Size);
+    DataSecEntries[std::string(SecName)]->addDataSecEntry(VarId,
+        Asm->getSymbol(&Global), Size);
   }
 }
 
@@ -1303,7 +1303,19 @@ void BTFDebug::processFuncPrototypes(const Function *F) {
   uint8_t Scope = BTF::FUNC_EXTERN;
   auto FuncTypeEntry =
       std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId, Scope);
-  addType(std::move(FuncTypeEntry));
+  uint32_t FuncId = addType(std::move(FuncTypeEntry));
+  if (F->hasSection()) {
+    StringRef SecName = F->getSection();
+
+    if (DataSecEntries.find(std::string(SecName)) == DataSecEntries.end()) {
+      DataSecEntries[std::string(SecName)] =
+          std::make_unique<BTFKindDataSec>(Asm, std::string(SecName));
+    }
+
+    // We really don't know func size, set it to 0.
+    DataSecEntries[std::string(SecName)]->addDataSecEntry(FuncId,
+        Asm->getSymbol(F), 0);
+  }
 }
 
 void BTFDebug::endModule() {
diff --git a/llvm/lib/Target/BPF/BTFDebug.h b/llvm/lib/Target/BPF/BTFDebug.h
index fb20ec59574b..76f1901779bb 100644
--- a/llvm/lib/Target/BPF/BTFDebug.h
+++ b/llvm/lib/Target/BPF/BTFDebug.h
@@ -187,7 +187,7 @@ public:
   uint32_t getSize() override {
     return BTFTypeBase::getSize() + BTF::BTFDataSecVarSize * Vars.size();
   }
-  void addVar(uint32_t Id, const MCSymbol *Sym, uint32_t Size) {
+  void addDataSecEntry(uint32_t Id, const MCSymbol *Sym, uint32_t Size) {
     Vars.push_back(std::make_tuple(Id, Sym, Size));
   }
   std::string getName() { return Name; }
diff --git a/llvm/test/CodeGen/BPF/BTF/extern-var-func-weak-section.ll b/llvm/test/CodeGen/BPF/BTF/extern-var-func-weak-section.ll
index 23332c9d9aa1..d47a9d6c504a 100644
--- a/llvm/test/CodeGen/BPF/BTF/extern-var-func-weak-section.ll
+++ b/llvm/test/CodeGen/BPF/BTF/extern-var-func-weak-section.ll
@@ -23,9 +23,9 @@ declare !dbg !4 extern_weak dso_local i32 @global_func(i8 signext) local_unnamed
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .long   24
 ; CHECK-NEXT:        .long   0
-; CHECK-NEXT:        .long   88
-; CHECK-NEXT:        .long   88
-; CHECK-NEXT:        .long   72
+; CHECK-NEXT:        .long   112
+; CHECK-NEXT:        .long   112
+; CHECK-NEXT:        .long   76
 ; CHECK-NEXT:        .long   0                       # BTF_KIND_FUNC_PROTO(id = 1)
 ; CHECK-NEXT:        .long   218103808               # 0xd000000
 ; CHECK-NEXT:        .long   2
@@ -48,6 +48,12 @@ declare !dbg !4 extern_weak dso_local i32 @global_func(i8 signext) local_unnamed
 ; CHECK-NEXT:        .long   60                      # BTF_KIND_FUNC(id = 6)
 ; CHECK-NEXT:        .long   201326594               # 0xc000002
 ; CHECK-NEXT:        .long   4
+; CHECK-NEXT:        .long   72                      # BTF_KIND_DATASEC(id = 7)
+; CHECK-NEXT:        .long   251658241               # 0xf000001
+; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   6
+; CHECK-NEXT:        .long   global_func
+; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .byte   0                       # string offset=0
 ; CHECK-NEXT:        .ascii  "int"                   # string offset=1
 ; CHECK-NEXT:        .byte   0
@@ -61,6 +67,7 @@ declare !dbg !4 extern_weak dso_local i32 @global_func(i8 signext) local_unnamed
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .ascii  "global_func"           # string offset=60
 ; CHECK-NEXT:        .byte   0
+; CHECK-NEXT:        .ascii  "abc"                   # string offset=72
 
 attributes #0 = { nounwind "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 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "no-infs-fp-math"="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" }
diff --git a/llvm/test/CodeGen/BPF/BTF/extern-var-section.ll b/llvm/test/CodeGen/BPF/BTF/extern-var-section.ll
index e01da7e209fd..520847449950 100644
--- a/llvm/test/CodeGen/BPF/BTF/extern-var-section.ll
+++ b/llvm/test/CodeGen/BPF/BTF/extern-var-section.ll
@@ -28,8 +28,8 @@ entry:
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .long   24
 ; CHECK-NEXT:        .long   0
-; CHECK-NEXT:        .long   128
-; CHECK-NEXT:        .long   128
+; CHECK-NEXT:        .long   140
+; CHECK-NEXT:        .long   140
 ; CHECK-NEXT:        .long   79
 ; CHECK-NEXT:        .long   0                       # BTF_KIND_FUNC_PROTO(id = 1)
 ; CHECK-NEXT:        .long   218103808               # 0xd000000
@@ -58,7 +58,10 @@ entry:
 ; CHECK-NEXT:        .long   5
 ; CHECK-NEXT:        .long   2
 ; CHECK-NEXT:        .long   75                      # BTF_KIND_DATASEC(id = 8)
-; CHECK-NEXT:        .long   251658241               # 0xf000001
+; CHECK-NEXT:        .long   251658242               # 0xf000002
+; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   6
+; CHECK-NEXT:        .long   global_func
 ; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .long   7
 ; CHECK-NEXT:        .long   ch
diff --git a/llvm/test/CodeGen/BPF/BTF/extern-var-weak-section.ll b/llvm/test/CodeGen/BPF/BTF/extern-var-weak-section.ll
index 6e64d9b4e482..bdf7fb49c560 100644
--- a/llvm/test/CodeGen/BPF/BTF/extern-var-weak-section.ll
+++ b/llvm/test/CodeGen/BPF/BTF/extern-var-weak-section.ll
@@ -28,8 +28,8 @@ declare !dbg !6 extern_weak dso_local i32 @global_func(i8 signext) local_unnamed
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .long   24
 ; CHECK-NEXT:        .long   0
-; CHECK-NEXT:        .long   128
-; CHECK-NEXT:        .long   128
+; CHECK-NEXT:        .long   140
+; CHECK-NEXT:        .long   140
 ; CHECK-NEXT:        .long   79
 ; CHECK-NEXT:        .long   0                       # BTF_KIND_FUNC_PROTO(id = 1)
 ; CHECK-NEXT:        .long   218103808               # 0xd000000
@@ -58,7 +58,10 @@ declare !dbg !6 extern_weak dso_local i32 @global_func(i8 signext) local_unnamed
 ; CHECK-NEXT:        .long   5
 ; CHECK-NEXT:        .long   2
 ; CHECK-NEXT:        .long   75                      # BTF_KIND_DATASEC(id = 8)
-; CHECK-NEXT:        .long   251658241               # 0xf000001
+; CHECK-NEXT:        .long   251658242               # 0xf000002
+; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   6
+; CHECK-NEXT:        .long   global_func
 ; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .long   7
 ; CHECK-NEXT:        .long   ch