Deduce the perf header sizes from the actual data

The magic constants will only work as long as the header doesn't grow.

Change-Id: Ib931363b440da83646bbb57e8b3ea574b303a52f
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>

2 files changed, 41 insertions, 10 deletions

diff --git a/app/perfheader.cpp b/app/perfheader.cpp
index d08d6c3..369b611 100644
--- a/app/perfheader.cpp
+++ b/app/perfheader.cpp
@@ -36,14 +36,13 @@ void PerfHeader::read()
 
     QDataStream stream(m_source);
     if (m_size == 0) {
-        const auto expectedSize = static_cast<qint64>(sizeof(m_magic) + sizeof(m_size));
-        if (!m_source->isSequential() && m_source->size() < expectedSize) {
+        if (!m_source->isSequential() && m_source->size() < pipeHeaderFixedLength()) {
             qWarning() << "File is too small for perf header.";
             emit error();
             return;
         }
 
-        if (m_source->bytesAvailable() < expectedSize)
+        if (m_source->bytesAvailable() < pipeHeaderFixedLength())
             return;
 
         stream >> m_magic;
@@ -59,15 +58,21 @@ void PerfHeader::read()
         stream >> m_size;
     }
 
-    if (m_size == s_perfHeaderSize) {
-        if (!m_source->isSequential() && m_source->size() < static_cast<qint64>(m_size)) {
+    if (m_size < pipeHeaderFixedLength()) {
+        qWarning() << "Header claims to be smaller than magic + size:" << m_size;
+        emit error();
+        return;
+    } else if (m_size > pipeHeaderFixedLength()) {
+        // read extended header information only available in perf.data files,
+        // not in piped perf streams
+
+        if (!m_source->isSequential() && m_source->size() < fileHeaderFixedLength()) {
             qWarning() << "File is too small for perf header.";
             emit error();
             return;
         }
 
-        if (m_source->bytesAvailable()
-                < m_size - static_cast<qint64>(sizeof(m_magic) + sizeof(m_size)))
+        if (m_source->bytesAvailable() < fileHeaderFixedLength() - pipeHeaderFixedLength())
             return;
 
         // file header
@@ -96,6 +101,16 @@ void PerfHeader::read()
             emit error();
             return;
         }
+
+        if (m_size > fileHeaderFixedLength()) {
+            if (m_size > std::numeric_limits<int>::max()) {
+                qWarning() << "Excessively large perf file header:" << m_size;
+                emit error();
+                return;
+            }
+            qWarning() << "Header not completely read.";
+            stream.skipRawData(static_cast<int>(m_size) - fileHeaderFixedLength());
+        }
     } else {
         // pipe header, anything to do here?
     }
@@ -105,6 +120,19 @@ void PerfHeader::read()
     emit finished();
 }
 
+quint16 PerfHeader::pipeHeaderFixedLength()
+{
+    return sizeof(m_magic) + sizeof(m_size);
+}
+
+quint16 PerfHeader::fileHeaderFixedLength()
+{
+    return pipeHeaderFixedLength()
+            + sizeof(m_attrSize)
+            + 3 * PerfFileSection::fixedLength() // m_attrs, m_data, m_eventTypes
+            + sizeof(m_features);
+}
+
 QDataStream::ByteOrder PerfHeader::byteOrder() const
 {
     // magic is read in QDataStream's default big endian mode
diff --git a/app/perfheader.h b/app/perfheader.h
index 47d7a5f..32e41b4 100644
--- a/app/perfheader.h
+++ b/app/perfheader.h
@@ -69,7 +69,9 @@ public:
     qint64 featureOffset() const { return m_data.offset + m_data.size; }
     qint64 dataOffset() const { return m_data.offset; }
     qint64 dataSize() const { return m_data.size; }
-    bool isPipe() const { return m_size == s_pipeHeaderSize; }
+    bool isPipe() const { return m_size == pipeHeaderFixedLength(); }
+
+    qint64 size() const { return m_size; }
 
 public slots:
     void read();
@@ -79,6 +81,9 @@ signals:
     void error();
 
 private:
+    static quint16 fileHeaderFixedLength();
+    static quint16 pipeHeaderFixedLength();
+
     QIODevice *m_source;
 
     qint64 m_magic;
@@ -93,6 +98,4 @@ private:
 
     static const qint64 s_magicSame = 0x32454c4946524550LL;
     static const qint64 s_magicSwitched = 0x50455246494c4532LL;
-    static const qint64 s_pipeHeaderSize = 16LL;
-    static const qint64 s_perfHeaderSize = 104LL;
 };