From 62af02e76fe808134b06b75c8108a98c079ac8bc Mon Sep 17 00:00:00 2001
From: Alex Cameron <ascottcameron@gmail.com>
Date: Mon, 9 Mar 2020 11:58:12 +0000
Subject: [PATCH] [XRay] Sanitize DOT labels in graph output

Summary:
Bugzilla: https://bugs.llvm.org/show_bug.cgi?id=39701

This patch is to convert certain characters to their XML escape sequences when generating labels for a DOT graph.

I had trouble reproducing the exact issue described on the tracker. I ran `llvm-xray graph` on a log from a test program that included function templates but wasn't able to get the `dot` tool to complain about the `<` and `>` characters. The documentation also suggests that the escape sequences should only be necessary when using HTML string labels which XRay doesn't use (`label=<...>` as opposed to `label="..."`). Perhaps newer versions of Graphviz silently handle this in the case of quoted-string labels.

In any case, the generated labels still look correct after this patch and should also fix the reporter's issue.

I was a bit unsure how to add a test for this since the existing tests seem to only care about `func-id` rather than giving an actual name. If you could give me a hint on the best way to go about this, that'd be much appreciated!

Reviewers: dberris

Reviewed By: dberris

Subscribers: lebedev.ri, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69461
---
 llvm/tools/llvm-xray/xray-graph.cpp | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/llvm/tools/llvm-xray/xray-graph.cpp b/llvm/tools/llvm-xray/xray-graph.cpp
index f836f9b..522609b 100644
--- a/llvm/tools/llvm-xray/xray-graph.cpp
+++ b/llvm/tools/llvm-xray/xray-graph.cpp
@@ -163,6 +163,30 @@ static void updateStat(GraphRenderer::TimeStat &S, int64_t L) {
   S.Sum += L;
 }
 
+// Labels in a DOT graph must be legal XML strings so it's necessary to escape
+// certain characters.
+static std::string escapeString(StringRef Label) {
+  std::string Str;
+  Str.reserve(Label.size());
+  for (const auto C : Label) {
+    switch (C) {
+    case '&':
+      Str.append("&amp;");
+      break;
+    case '<':
+      Str.append("&lt;");
+      break;
+    case '>':
+      Str.append("&gt;");
+      break;
+    default:
+      Str.push_back(C);
+      break;
+    }
+  }
+  return Str;
+}
+
 // Evaluates an XRay record and performs accounting on it.
 //
 // If the record is an ENTER record it pushes the FuncID and TSC onto a
@@ -398,8 +422,9 @@ void GraphRenderer::exportGraphAsDOT(raw_ostream &OS, StatType ET, StatType EC,
     if (V.first == 0)
       continue;
     OS << "F" << V.first << " [label=\"" << (VT != StatType::NONE ? "{" : "")
-       << (VA.SymbolName.size() > 40 ? VA.SymbolName.substr(0, 40) + "..."
-                                     : VA.SymbolName);
+       << escapeString(VA.SymbolName.size() > 40
+                           ? VA.SymbolName.substr(0, 40) + "..."
+                           : VA.SymbolName);
     if (VT != StatType::NONE)
       OS << "|" << VA.S.getString(VT) << "}\"";
     else
-- 
2.7.4