Fix btf_type_tag issue with llvm 15

With llvm15, the tool 'execsnoop.py' failed the compilation with
the following error messages:

  ...
  /virtual/main.c:103:157: error: expected ')'
      data.ppid = ({ typeof(pid_t) _val; __builtin_memset(&_val, 0, sizeof(_val));
         bpf_probe_read(&_val, sizeof(_val), (void *)&({ typeof(struct task_struct  btf_type_tag(rcu)*) _val;
          __builtin_memset(&_val, 0, sizeof(_val));
          bpf_probe_read(&_val, sizeof(_val), (void *)&task->real_parent); _val; })->tgid); _val; });
  ...

The main reason is incorrect type string
  btf_type_tag(rcu)
btf_type_tag is introduced in llvm15 is an attribute. The correct type representation
should be
  __attribute__((btf_type_tag("rcu")))

The bug is fixed in llvm16 with [1]. Unfortunately the patch cannot be backported to llvm15 since
at that time llvm15 has been freezed.

This patch manually fixed this issue for bcc.

  [1] llvm/llvm-project@82b4446

Signed-off-by: Yonghong Song <[email protected]>

src/cc/frontends/clang/b_frontend_action.cc

@@ -520,6 +520,27 @@ bool ProbeVisitor::VisitBinaryOperator(BinaryOperator *E) {
  }
  return true;
 }
+
+static std::string FixBTFTypeTag(std::string TypeStr)
+{
+#if LLVM_VERSION_MAJOR == 15
+ std::map<std::string, std::string> TypePair =
+ {{"btf_type_tag(user)", "__attribute__((btf_type_tag(\"user\")))"},
+ {"btf_type_tag(rcu)", "__attribute__((btf_type_tag(\"rcu\")))"},
+ {"btf_type_tag(percpu)", "__attribute__((btf_type_tag(\"percpu\")))"}};
+
+ for (auto T: TypePair) {
+ size_t index;
+ index = TypeStr.find(T.first, 0);
+ if (index != std::string::npos) {
+ TypeStr.replace(index, T.first.size(), T.second);
+ return TypeStr;
+ }
+ }
+#endif
+ return TypeStr;
+}
+
 bool ProbeVisitor::VisitUnaryOperator(UnaryOperator *E) {
  if (E->getOpcode() == UO_AddrOf) {
  addrof_stmt_ = E;
@@ -598,7 +619,7 @@ bool ProbeVisitor::VisitMemberExpr(MemberExpr *E) {
  string rhs = rewriter_.getRewrittenText(expansionRange(SourceRange(rhs_start, GET_ENDLOC(E))));
  string base_type = base->getType()->getPointeeType().getAsString();
  string pre, post;
- pre = "({ typeof(" + E->getType().getAsString() + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
+ pre = "({ typeof(" + FixBTFTypeTag(E->getType().getAsString()) + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
  if (cannot_fall_back_safely)
  pre += " bpf_probe_read_kernel(&_val, sizeof(_val), (void *)&";
  else
@@ -652,7 +673,7 @@ bool ProbeVisitor::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
  if (rewriter_.getRewrittenText(lbracket_range).size() == 0)
  return true;
 
- pre = "({ typeof(" + E->getType().getAsString() + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
+ pre = "({ typeof(" + FixBTFTypeTag(E->getType().getAsString()) + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
  if (cannot_fall_back_safely)
  pre += " bpf_probe_read_kernel(&_val, sizeof(_val), (void *)((";
  else