[lldb] Warn when Mach-O files have overlapping segments

I recently came across a binary that for some reason had overlapping
sections. When debugging it, LLDB was able to get information about one
of the sections but not the other because SectionLoadList assumes that
each address maps to exactly one section. We have the capability to warn
about this, but it was not turned on.

rdar://105751700

Differential Revision: https://reviews.llvm.org/D144528

diff --git a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
index 8485659..eaa4735 100644 (file)
--- a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
+++ b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
@@ -6182,6 +6182,10 @@ bool ObjectFileMachO::SetLoadAddress(Target &target, lldb::addr_t value,
   size_t num_loaded_sections = 0;
   const size_t num_sections = section_list->GetSize();
 
+  // Warn if some top-level segments map to the same address. The binary may be
+  // malformed.
+  const bool warn_multiple = true;
+
   if (value_is_offset) {
     // "value" is an offset to apply to each top level segment
     for (size_t sect_idx = 0; sect_idx < num_sections; ++sect_idx) {
@@ -6190,7 +6194,8 @@ bool ObjectFileMachO::SetLoadAddress(Target &target, lldb::addr_t value,
       SectionSP section_sp(section_list->GetSectionAtIndex(sect_idx));
       if (SectionIsLoadable(section_sp.get()))
         if (target.GetSectionLoadList().SetSectionLoadAddress(
-                section_sp, section_sp->GetFileAddress() + value))
+                section_sp, section_sp->GetFileAddress() + value,
+                warn_multiple))
           ++num_loaded_sections;
     }
   } else {
@@ -6207,7 +6212,7 @@ bool ObjectFileMachO::SetLoadAddress(Target &target, lldb::addr_t value,
                 value, mach_header_section, section_sp.get());
         if (section_load_addr != LLDB_INVALID_ADDRESS) {
           if (target.GetSectionLoadList().SetSectionLoadAddress(
-                  section_sp, section_load_addr))
+                  section_sp, section_load_addr, warn_multiple))
             ++num_loaded_sections;
         }
       }