[SharedCache] Fix handling of relative selectors in macOS shared caches #6192
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`BackingCache` now tracks the `dyld_cache_mapping_info` for its mappings so it has access to the memory protections for the region. This means it can avoid marking some regions as containing code when they don't, reducing the amount of analysis work that has to be done. Using `dyld_cache_mapping_info` also makes references to mappings easier to understand due to its named fields vs the nested `std::pair`s that were previously in use.
Find the relative selector base address in the Objective-C optimization data pointed to by the shared cache header, rather than via `__objc_scoffs`. This is only present on iOS, and not for every iOS version that encodes selectors via direct offsets. This also includes some related improvements: 1. Direct selectors get their own pointer type so they're rendered correctly in the view. 2. Method lists encoded as lists of lists are now handled. 3. The `dyld_cache_header` type added to the view is truncated to the length in the loaded cache. This ensures it is applied to the view. 4. A couple of methods that process method IMPs and selectors are updated to check whether the address is valid before attempting to process them. They would otherwise fail by throwing an exception if they proceed, but checking for validity is quicker and makes exception breakpoints usable.
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This requires the fixes from #6172. Without those fixes a lot of the class / method data hasn't been rebased appropriately and so is impossible to correctly interpret. |
This was referenced Nov 26, 2024
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Find the relative selector base address in the Objective-C optimization data pointed to by the shared cache header, rather than via
__objc_scoffs. That section is only present on iOS, and not for every iOS version that encodes selectors via direct offsets.This also includes some related improvements:
dyld_cache_headertype added to the view is truncated to the length of the header in the loaded cache. This ensures it is correctly applied to the view.Additionally,
SharedCachenow tracks whether non-image regions are data vs code. This means it can avoid marking some regions as containing code when they don't, reducing the amount of analysis work that has to be done.