Support nested rewrite of trace arguments in bpf_trace_printk

There was an issue where the rewrite of bpf_trace_printk combined with conversion of function argument to ctx->$reg was mangling the text. Fix up this case and add a test. Signed-off-by: Brenden Blanco <[email protected]>
linux-kern · Aug 12, 2015 · a328d23 · a328d23
1 parent 4a09dd5
commit a328d23
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Showing 2 changed files with 20 additions and 8 deletions.
diff --git a/src/cc/frontends/clang/b_frontend_action.cc b/src/cc/frontends/clang/b_frontend_action.cc
@@ -227,24 +227,24 @@ bool BTypeVisitor::VisitCallExpr(CallExpr *Call) {
  if (Decl->getName() == "incr_cksum_l3") {
  text = "bpf_l3_csum_replace_(" + fn_args_[0]->getName().str() + ", (u64)";
  text += args[0] + ", " + args[1] + ", " + args[2] + ", sizeof(" + args[2] + "))";
+ rewriter_.ReplaceText(SourceRange(Call->getLocStart(), Call->getLocEnd()), text);
  } else if (Decl->getName() == "incr_cksum_l4") {
  text = "bpf_l4_csum_replace_(" + fn_args_[0]->getName().str() + ", (u64)";
  text += args[0] + ", " + args[1] + ", " + args[2];
  text += ", ((" + args[3] + " & 0x1) << 4) | sizeof(" + args[2] + "))";
+ rewriter_.ReplaceText(SourceRange(Call->getLocStart(), Call->getLocEnd()), text);
  } else if (Decl->getName() == "bpf_trace_printk") {
  // #define bpf_trace_printk(fmt, args...)
  // ({ char _fmt[] = fmt; bpf_trace_printk_(_fmt, sizeof(_fmt), args...); })
  text = "({ char _fmt[] = " + args[0] + "; bpf_trace_printk_(_fmt, sizeof(_fmt)";
- if (args.size() > 1)
- text += ", ";
- for (auto arg = args.begin() + 1; arg != args.end(); ++arg) {
-  text += *arg;
- if (arg + 1 != args.end())
-  text += ", ";
+ if (args.size() <= 1) {
+ text += "); })";
+  rewriter_.ReplaceText(SourceRange(Call->getLocStart(), Call->getLocEnd()), text);
+ } else {
+ rewriter_.ReplaceText(SourceRange(Call->getLocStart(), Call->getArg(0)->getLocEnd()), text);
+ rewriter_.InsertTextAfter(Call->getLocEnd(), "); }");
  }
- text += "); })";
  }
- rewriter_.ReplaceText(SourceRange(Call->getLocStart(), Call->getLocEnd()), text);
  }
  }
  }

diff --git a/tests/cc/test_clang.py b/tests/cc/test_clang.py
@@ -82,6 +82,18 @@ def test_iosnoop(self):
 
  return 0;
 }
+"""
+ b = BPF(text=text, debug=0)
+ fn = b.load_func("do_request", BPF.KPROBE)
+
+ def test_blk_start_request(self):
+ text = """
+#include <linux/blkdev.h>
+#include <uapi/linux/ptrace.h>
+int do_request(struct pt_regs *ctx, int req) {
+ bpf_trace_printk("req ptr: 0x%x\\n", req);
+ return 0;
+}
 """
  b = BPF(text=text, debug=0)
  fn = b.load_func("do_request", BPF.KPROBE)