Fix elf core file VMA-contiguous region collapsing.

Elf core files were collapsing core segments when the virtual memory
addresses were contiguous without checking if the core-file-backed
memory region was the same size as the segment's VMA region. Without
this extra check, any time regions were collapsed but the core-backed
region was smaller (and thus had a zero-filled hole at the end), the
collapse operation would break VMA to core file lookups for subsequent
collapsed regions.

This change fixes the following bug:
http://llvm.org/bugs/show_bug.cgi?id=18769

llvm-svn: 201214

1 files changed, 8 insertions, 3 deletions

diff --git a/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp b/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
index 93641ede1bc..a2b02d26d82 100644
--- a/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
+++ b/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
@@ -131,7 +131,8 @@ ProcessElfCore::AddAddressRangeFromLoadSegment(const elf::ELFProgramHeader *head
     VMRangeToFileOffset::Entry *last_entry = m_core_aranges.Back();
     if (last_entry &&
         last_entry->GetRangeEnd() == range_entry.GetRangeBase() &&
-        last_entry->data.GetRangeEnd() == range_entry.data.GetRangeBase())
+        last_entry->data.GetRangeEnd() == range_entry.data.GetRangeBase() &&
+        last_entry->GetByteSize() == last_entry->data.GetByteSize())
     {
         last_entry->SetRangeEnd (range_entry.GetRangeEnd());
         last_entry->data.SetRangeEnd (range_entry.data.GetRangeEnd());
@@ -294,9 +295,13 @@ ProcessElfCore::DoReadMemory (lldb::addr_t addr, void *buf, size_t size, Error &
     size_t zero_fill_size = 0;   // Padding
     lldb::addr_t bytes_left = 0; // Number of bytes available in the core file from the given address
 
-    if (file_end > offset)
-        bytes_left = file_end - offset;
+    // Figure out how many on-disk bytes remain in this segment
+    // starting at the given offset
+    if (file_end > file_start + offset)
+        bytes_left = file_end - (file_start + offset);
 
+    // Figure out how many bytes we need to zero-fill if we are
+    // reading more bytes than available in the on-disk segment
     if (bytes_to_read > bytes_left)
     {
         zero_fill_size = bytes_to_read - bytes_left;