bcc: Check probe read availabilty and use macros

When bpf_probe_read_kernel is not available, then macros are defined at
the prologue to replace bpf_probe_read_kernel to bpf_prob_read. This
resolves the problem of test_probe_read3 failure in test_clang.py for
 iovisor#2919

Signed-off-by: Sumanth Korikkar <[email protected]>

src/cc/frontends/clang/b_frontend_action.cc

@@ -83,7 +83,7 @@ const char **get_call_conv(void) {
  return ret;
 }
 
-/* Use resolver only once */
+/* Use resolver only once per translation */
 static void *kresolver = NULL;
 static void *get_symbol_resolver(void) {
  if (!kresolver)
@@ -492,7 +492,7 @@ bool ProbeVisitor::VisitUnaryOperator(UnaryOperator *E) {
  memb_visited_.insert(E);
  string pre, post;
  pre = "({ typeof(" + E->getType().getAsString() + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
- pre += " " + check_bpf_probe_read_kernel() + "(&_val, sizeof(_val), (u64)";
+ pre += " bpf_probe_read_kernel(&_val, sizeof(_val), (u64)";
  post = "); _val; })";
  rewriter_.ReplaceText(expansionLoc(E->getOperatorLoc()), 1, pre);
  rewriter_.InsertTextAfterToken(expansionLoc(GET_ENDLOC(sub)), post);
@@ -553,7 +553,7 @@ bool ProbeVisitor::VisitMemberExpr(MemberExpr *E) {
  string base_type = base->getType()->getPointeeType().getAsString();
  string pre, post;
  pre = "({ typeof(" + E->getType().getAsString() + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
- pre += " " + check_bpf_probe_read_kernel() + "(&_val, sizeof(_val), (u64)&";
+ pre += " bpf_probe_read_kernel(&_val, sizeof(_val), (u64)&";
  post = rhs + "); _val; })";
  rewriter_.InsertText(expansionLoc(GET_BEGINLOC(E)), pre);
  rewriter_.ReplaceText(expansionRange(SourceRange(member, GET_ENDLOC(E))), post);
@@ -604,7 +604,7 @@ bool ProbeVisitor::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
  return true;
 
  pre = "({ typeof(" + E->getType().getAsString() + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
- pre += " " + check_bpf_probe_read_kernel() + "(&_val, sizeof(_val), (u64)((";
+ pre += " bpf_probe_read_kernel(&_val, sizeof(_val), (u64)((";
  if (isMemberDereference(base)) {
  pre += "&";
  // If the base of the array subscript is a member dereference, we'll rewrite
@@ -737,7 +737,7 @@ void BTypeVisitor::genParamIndirectAssign(FunctionDecl *D, string& preamble,
  size_t d = idx - 1;
  const char *reg = calling_conv_regs[d];
  preamble += "\n " + text + ";";
- preamble += " " + check_bpf_probe_read_kernel();
+ preamble += " bpf_probe_read_kernel";
  preamble += "(&" + arg->getName().str() + ", sizeof(" +
  arg->getName().str() + "), &" + new_ctx + "->" +
  string(reg) + ");";
@@ -1005,25 +1005,16 @@ bool BTypeVisitor::VisitCallExpr(CallExpr *Call) {
  if (!Decl) return true;
 
  string text;
-
+
+ // Bail out when bpf_probe_read_user is unavailable for overlapping address
+ // space arch.
  bool overlap_addr = false;
  std::string probe = check_bpf_probe_read_user(Decl->getName(),
  overlap_addr);
  if (overlap_addr) {
  error(GET_BEGINLOC(Call), "bpf_probe_read_user not found. Use latest kernel");
  return false;
  }
- if (probe != "") {
- vector<string> probe_args;
-
- for (auto arg : Call->arguments())
- probe_args.push_back(
- rewriter_.getRewrittenText(expansionRange(arg->getSourceRange())));
-
- text = probe + "(" + probe_args[0] + ", " + probe_args[1] + ", " +
- probe_args[2] + ")";
- rewriter_.ReplaceText(expansionRange(Call->getSourceRange()), text);
- }
 
  if (AsmLabelAttr *A = Decl->getAttr<AsmLabelAttr>()) {
  // Functions with the tag asm("llvm.bpf.extra") are implemented in the
@@ -1540,8 +1531,6 @@ void BTypeConsumer::HandleTranslationUnit(ASTContext &Context) {
  btype_visitor_.TraverseDecl(D);
  }
 
- if (kresolver)
- bcc_free_symcache(kresolver, -1);
 }
 
 BFrontendAction::BFrontendAction(llvm::raw_ostream &os, unsigned flags,
@@ -1577,8 +1566,21 @@ void BFrontendAction::DoMiscWorkAround() {
  // to guard certain fields. The workaround here intends to define
  // CONFIG_CC_STACKPROTECTOR properly based on other configs, so it relieved any bpf
  // program (using task_struct, etc.) of patching the below code.
- rewriter_->getEditBuffer(rewriter_->getSourceMgr().getMainFileID()).InsertText(0,
- "#if defined(BPF_LICENSE)\n"
+ std::string probefunc = check_bpf_probe_read_kernel();
+ if (kresolver) {
+ bcc_free_symcache(kresolver, -1);
+ kresolver = NULL;
+ }
+ if (probefunc == "bpf_probe_read") {
+ probefunc = "#define bpf_probe_read_kernel bpf_probe_read\n"
+ "#define bpf_probe_read_kernel_str bpf_probe_read_str\n"
+ "#define bpf_probe_read_user bpf_probe_read\n"
+ "#define bpf_probe_read_user_str bpf_probe_read_str\n";
+ }
+ else {
+ probefunc = "";
+ }
+ std::string prologue = "#if defined(BPF_LICENSE)\n"
  "#error BPF_LICENSE cannot be specified through cflags\n"
  "#endif\n"
  "#if !defined(CONFIG_CC_STACKPROTECTOR)\n"
@@ -1587,7 +1589,10 @@ void BFrontendAction::DoMiscWorkAround() {
  " || defined(CONFIG_CC_STACKPROTECTOR_STRONG)\n"
  "#define CONFIG_CC_STACKPROTECTOR\n"
  "#endif\n"
- "#endif\n",
+ "#endif\n";
+ prologue = prologue + probefunc;
+ rewriter_->getEditBuffer(rewriter_->getSourceMgr().getMainFileID()).InsertText(0,
+ prologue,
  false);
 
  rewriter_->getEditBuffer(rewriter_->getSourceMgr().getMainFileID()).InsertTextAfter(