Fix to read correctly even when linkedit does not exist in the same cache #231
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Pull Request Overview
This PR modifies the MachOKit library to properly handle linkedit data when reading from dyld cache files on iOS, where linkedit data is stored in a separate cache file (.0x.linkeditdata) rather than in the same cache as the main Mach-O data.
- Introduces new methods
_fileSliceForLinkEditDataand_readLinkEditDatato handle linkedit data reading from appropriate cache locations - Updates multiple properties to use the new linkedit data reading methods instead of direct file handle operations
- Adds cached properties for
DyldCacheandFullDyldCacheinstances to improve performance
Reviewed Changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 7 comments.
Show a summary per file
| File | Description |
|---|---|
| Sources/MachOKit/MachOFile.swift | Core implementation with new linkedit data handling methods and updated properties |
| Sources/MachOKit/MachOFile+Symbols.swift | Updated symbol loading to use new linkedit data methods |
| Sources/MachOKit/MachOFile+Strings.swift | Added new initializer for Strings class |
| Sources/MachOKit/MachOFile+FunctionStarts.swift | Updated function starts loading to use new linkedit data method |
| Sources/MachOKit/MachOFile+ExportTrie.swift | Updated export trie loading to use new linkedit data method |
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| .deletingPathExtension() | ||
| .deletingPathExtension() | ||
| ) | ||
| } |
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These computed properties will create new cache instances on every access. Consider implementing lazy stored properties or caching mechanisms to avoid repeated initialization overhead, especially since these caches are accessed multiple times throughout the codebase.
| } | |
| internal lazy var cache: DyldCache? = { | |
| try? DyldCache(url: url) | |
| }() | |
| internal lazy var fullCache: FullDyldCache? = { | |
| try? FullDyldCache( | |
| url: url | |
| .deletingPathExtension() | |
| .deletingPathExtension() | |
| ) | |
| }() |
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| length: numericCast(symtab.strsize) | ||
| ) | ||
| )! |
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Force unwrapping with ! can cause crashes if _fileSliceForLinkEditData returns nil. Consider using guard statements or proper error handling instead of force unwrapping.
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| length: numericCast(symtab.nsyms) * MemoryLayout<nlist_64>.size | ||
| ) | ||
| )! |
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Force unwrapping with ! can cause crashes if _fileSliceForLinkEditData returns nil. Consider using guard statements or proper error handling instead of force unwrapping.
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| let stringsSlice = machO._fileSliceForLinkEditData( | ||
| offset: numericCast(symtab.stroff), | ||
| length: numericCast(symtab.strsize) | ||
| )! |
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Force unwrapping with ! can cause crashes if _fileSliceForLinkEditData returns nil. Consider using guard statements or proper error handling instead of force unwrapping.
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| let symbolsSlice = machO._fileSliceForLinkEditData( | ||
| offset: numericCast(symtab.symoff), | ||
| length: numericCast(symtab.nsyms) * MemoryLayout<nlist>.size | ||
| )! |
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Force unwrapping with ! can cause crashes if _fileSliceForLinkEditData returns nil. Consider using guard statements or proper error handling instead of force unwrapping.
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| length: functionStartsSize | ||
| ) | ||
| )! |
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Force unwrapping with ! can cause crashes if _readLinkEditData returns nil. Consider using guard statements or proper error handling instead of force unwrapping.
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| length: exportSize | ||
| ) | ||
| )! |
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Force unwrapping with ! can cause crashes if _readLinkEditData returns nil. Consider using guard statements or proper error handling instead of force unwrapping.
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The linkedit data in iOS is stored together in a separate, independent cache.
(dyld_shared_cache_arm64e.65.dyldreadonly)