[lldb][Mach-O] Handle shared cache binaries correctly (#117832) #9672
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The Mach-O load commands have an LC_SYMTAB / struct symtab_command which represents the offset of the symbol table (nlist records) and string table for this binary. In a mach-o binary on disk, these are file offsets. If a mach-o binary is loaded in memory with all segments consecutive, the `symoff` and `stroff` are the offsets from the TEXT segment (aka the mach-o header) virtual address to the virtual address of the start of these tables. However, if a Mach-O binary is a part of the shared cache, then the segments will be separated -- they will have different slide values. And it is possible for the LINKEDIT segment to be greater than 4GB away from the TEXT segment in the virtual address space, so these 32-bit offsets cannot express the offset from TEXT segment to these tables. Create separate uint64_t variables to track the offset to the symbol table and string table, instead of reusing the 32-bit ones in the symtab_command structure. rdar://140432279 (cherry picked from commit 448ac7d)
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JDevlieghere
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Nov 28, 2024
jasonmolenda
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The Mach-O load commands have an LC_SYMTAB / struct symtab_command which represents the offset of the symbol table (nlist records) and string table for this binary. In a mach-o binary on disk, these are file offsets. If a mach-o binary is loaded in memory with all segments consecutive, the
symoffandstroffare the offsets from the TEXT segment (aka the mach-o header) virtual address to the virtual address of the start of these tables.However, if a Mach-O binary is a part of the shared cache, then the segments will be separated -- they will have different slide values. And it is possible for the LINKEDIT segment to be greater than 4GB away from the TEXT segment in the virtual address space, so these 32-bit offsets cannot express the offset from TEXT segment to these tables.
Create separate uint64_t variables to track the offset to the symbol table and string table, instead of reusing the 32-bit ones in the symtab_command structure.
rdar://140432279
(cherry picked from commit 448ac7d)