[llvm] [lldb][llvm] Return an error instead of crashing when parsing a line table prologue. (PR #80769)

[David Blaikie via llvm-commits]

================
@@ -372,26 +372,56 @@ Error DWARFDebugLine::Prologue::parse(
   std::tie(TotalLength, FormParams.Format) =
       DebugLineData.getInitialLength(Cursor);
 
+  // Report an error, but also make sure the cursor is not in a bad state. If
+  // the cursor is in a bad state, return its error instead. Many times during
+  // parsing we might end up bailing if we don't like what we see, but often
+  // times when we decode items with a bad cursor, we will get zero back which
+  // might not be valid data to extract.
+  auto ReportErrorOrCursor = [&](llvm::Error Error) -> llvm::Error {
+    if (Cursor)
+      return Error;
+    llvm::consumeError(std::move(Error));
+    *OffsetPtr = Cursor.tell();
+    std::string CursorErrorStr = llvm::toString(Cursor.takeError());
+    return createStringError(
+        errc::not_supported,
+        "parsing line table prologue at offset 0x%8.8" PRIx64 ": %s",
+        PrologueOffset, CursorErrorStr.c_str());
+  };
+
   DebugLineData =
       DWARFDataExtractor(DebugLineData, Cursor.tell() + TotalLength);
   FormParams.Version = DebugLineData.getU16(Cursor);
-  if (Cursor && !versionIsSupported(getVersion())) {
+  if (!versionIsSupported(getVersion())) {
     // Treat this error as unrecoverable - we cannot be sure what any of
     // the data represents including the length field, so cannot skip it or make
     // any reasonable assumptions.
-    *OffsetPtr = Cursor.tell();
-    return createStringError(
+    return ReportErrorOrCursor(createStringError(
         errc::not_supported,
         "parsing line table prologue at offset 0x%8.8" PRIx64
         ": unsupported version %" PRIu16,
-        PrologueOffset, getVersion());
+        PrologueOffset, getVersion()));
   }
 
   if (getVersion() >= 5) {
     FormParams.AddrSize = DebugLineData.getU8(Cursor);
-    assert((!Cursor || DebugLineData.getAddressSize() == 0 ||
-            DebugLineData.getAddressSize() == getAddressSize()) &&
-           "Line table header and data extractor disagree");
+    const uint8_t DataAddrSize = DebugLineData.getAddressSize();
+    const uint8_t PrologueAddrSize = FormParams.AddrSize;
+    if (DataAddrSize == 0) {
+      if (PrologueAddrSize != 4 && PrologueAddrSize != 8) {
+        return ReportErrorOrCursor(createStringError(
+            errc::not_supported,
+            "parsing line table prologue at offset 0x%8.8" PRIx64
+            ": invalid address size %" PRIu8, PrologueOffset,
+            PrologueAddrSize));
+      }
+    } else if (DataAddrSize != getAddressSize()) {
+      return ReportErrorOrCursor(createStringError(
+          errc::not_supported,
+          "parsing line table prologue at offset 0x%8.8" PRIx64 ": address "
+          "size %" PRIu8 " doesn't match architecture address size %" PRIu8,
+          PrologueOffset, PrologueAddrSize, DataAddrSize));
+    }
     SegSelectorSize = DebugLineData.getU8(Cursor);
   }
----------------
dwblaikie wrote:

These should be recoverable errors, because we can skip this line table and read the next one.

https://github.com/llvm/llvm-project/pull/80769