Report an error when an ELF file could not be found

When we fail to find a matching ELF file for an mmap event, the
usefulness of the perfparser can be severly impacted:

- unwinding will not work
- symbol resolution will not work
- potentially other things will not work

As such, report an error to the user when this occurs.

Change-Id: I8a47f8725a29684ac11b24dadb20e669a45d3016
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

2 files changed, 16 insertions, 6 deletions

diff --git a/app/perfsymboltable.cpp b/app/perfsymboltable.cpp
index 2193c15..a29cb30 100644
--- a/app/perfsymboltable.cpp
+++ b/app/perfsymboltable.cpp
@@ -211,10 +211,18 @@ void PerfSymbolTable::registerElf(const PerfRecordMmap &mmap, const QByteArray &
                 }
             }
         }
-        if (!found) // last fall-back, try the system root
+        if (!found) {
+            // last fall-back, try the system root
             fullPath.setFile(systemRoot + filePath);
+            found = fullPath.exists();
+        }
 
-        if (!m_firstElfFile.isOpen() && fullPath.exists()) {
+        if (!found) {
+            m_unwind->sendError(PerfUnwind::MissingElfFile,
+                                PerfUnwind::tr("Could not find ELF file for %1. "
+                                               "This can break stack unwinding "
+                                               "and lead to missing symbols.").arg(filePath));
+        } else if (!m_firstElfFile.isOpen()) {
             m_firstElfFile.setFileName(fullPath.absoluteFilePath());
             if (!m_firstElfFile.open(QIODevice::ReadOnly)) {
                 qWarning() << "Failed to open file:" << m_firstElfFile.errorString();
diff --git a/app/perfunwind.h b/app/perfunwind.h
index c7103c6..1894161 100644
--- a/app/perfunwind.h
+++ b/app/perfunwind.h
@@ -147,6 +147,12 @@ public:
 
     PerfKallsymEntry findKallsymEntry(quint64 address) const;
 
+    enum ErrorCode {
+        TimeOrderViolation = 1,
+        MissingElfFile = 2,
+    };
+    void sendError(ErrorCode error, const QString &message);
+
 private:
 
     enum CallchainContext {
@@ -248,10 +254,6 @@ private:
     void sendLocation(qint32 id, const Location &location);
     void sendSymbol(qint32 id, const Symbol &symbol);
     void sendAttributes(qint32 id, const PerfEventAttributes &attributes, const QByteArray &name);
-    enum ErrorCode {
-        TimeOrderViolation = 1
-    };
-    void sendError(ErrorCode error, const QString &message);
 
     template<typename Event>
     void bufferEvent(const Event &event, QList<Event> *buffer, int *eventCounter);