[lldb] [ObjectFileMachO] BSS segments are loadable segments (#96983) #8943
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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 (cherry picked from commit 91c0ef6)
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JDevlieghere
approved these changes
Jul 2, 2024
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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
(cherry picked from commit 91c0ef6)