Disable non-static function calls

Compiled BPF programs must consist of a single contiguous code block, meaning trying to call other function entry points (besides the kernel-defined helpers) is not possible. The bcc frontend didn't explicitly prohibit this, even though the program would fail to compile/load. Add an explicit check and error message. Fixes: iovisor#653 Signed-off-by: Brenden Blanco <[email protected]>
drcwr · Apr 20, 2017 · 3f28e7b · 3f28e7b
1 parent cee6056
commit 3f28e7b
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Showing 4 changed files with 22 additions and 3 deletions.
diff --git a/src/cc/frontends/clang/b_frontend_action.cc b/src/cc/frontends/clang/b_frontend_action.cc
@@ -462,6 +462,15 @@ bool BTypeVisitor::VisitCallExpr(CallExpr *Call) {
  rewriter_.ReplaceText(expansionRange(Call->getSourceRange()), text);
  }
  }
+ } else if (FunctionDecl *F = dyn_cast<FunctionDecl>(Decl)) {
+ if (F->isExternallyVisible() && !F->getBuiltinID()) {
+ auto start_loc = rewriter_.getSourceMgr().getFileLoc(Decl->getLocStart());
+ if (rewriter_.getSourceMgr().getFileID(start_loc)
+ == rewriter_.getSourceMgr().getMainFileID()) {
+ error(Call->getLocStart(), "cannot call non-static helper function");
+ return false;
+ }
+ }
  }
  }
  return true;

diff --git a/tests/python/test_clang.py b/tests/python/test_clang.py
@@ -522,7 +522,17 @@ def test_prog_array_delete(self):
  with self.assertRaises(KeyError):
  b1["dummy"][c_key]
 
-
+ def test_invalid_noninline_call(self):
+ text = """
+int bar(void) {
+ return 0;
+}
+int foo(struct pt_regs *ctx) {
+ return bar();
+}
+"""
+ with self.assertRaises(Exception):
+ b = BPF(text=text)
 
 
 if __name__ == "__main__":

diff --git a/tools/pidpersec.py b/tools/pidpersec.py
@@ -28,7 +28,7 @@
 
 BPF_ARRAY(stats, u64, S_MAXSTAT + 1);
 
-void stats_increment(int key) {
+static void stats_increment(int key) {
  u64 *leaf = stats.lookup(&key);
  if (leaf) (*leaf)++;
 }

diff --git a/tools/vfsstat.py b/tools/vfsstat.py
@@ -51,7 +51,7 @@ def usage():
 
 BPF_ARRAY(stats, u64, S_MAXSTAT + 1);
 
-void stats_increment(int key) {
+static void stats_increment(int key) {
  u64 *leaf = stats.lookup(&key);
  if (leaf) (*leaf)++;
 }