ObjectFileMachO::SetLoadAddress sets the address of each segment in a
binary in a Target, but it ignores segments that are not loaded in the
virtual address space. It was marking segments that were purely BSS --
having no content in the file, but in zero-initialized memory when
running in the virtual address space -- as not-loadable, unless they
were named "DATA". This works pretty well for typical userland binaries,
but in less Darwin environments, there may be BSS segments with other
names, that ARE loadable.
I looked at the origin of SectionIsLoadable's check for this, and it was
a cleanup by Greg in 2018 where we had three different implementations
of the idea in ObjectFileMachO and one of them skipped zero-file-size
segments (BSS), which made it into the centralized SectionIsLoadable
method.
Also add some logging to the DynamicLoader log channel when loading a
binary - it's the first place I look when debugging segment address
setting bugs, and it wasn't emitting anything.
rdar://129870649
91c0ef6f67