[DSC] Simplify file mapping to fix intermittent unrelocated pointers

The `FileAccessorCache`'s LRU eviction could discard a file's mapped
data after slide info had already been applied to it. Future accesses to
the file produced a fresh mapping, but failed to reapply the slide info.
This could result in pointers not correctly being slid, such as in
https://github.com/Vector35/binaryninja-api/issues/7689.

The LRU cache existed to stay within OS file descriptor limits, since
the old `MappedFile` held its fd open for the lifetime of the mapping.
There's no real reason for it to hold the file descriptor open like
this. Closing it after `mmap` is sufficient to avoid the file descriptor
limits.

`MappedFileRegion` replaces the combination of `FileAccessorCache`,
`WeakFileAccessor`, and `MappedFileAccessor`. It closes the fd
immediately after mmap, so all files can stay mapped without consuming
descriptors, making the cache unnecessary.

`MappedFileRegion` is owned directly by the `CacheEntry` for its full
lifetime. Slide info is applied exactly once to each `MappedFileRegion`.

1 files changed, 3 insertions, 1 deletions

diff --git a/view/sharedcache/core/MachO.cpp b/view/sharedcache/core/MachO.cpp
index f3f9ec6c..7afcbd8d 100644
--- a/view/sharedcache/core/MachO.cpp
+++ b/view/sharedcache/core/MachO.cpp
@@ -621,7 +621,9 @@ std::vector<CacheSymbol> SharedCacheMachOHeader::ReadExportSymbolTrie(VirtualMem
 		return {};
 	std::vector<CacheSymbol> symbols = {};
 	try {
-		auto [begin, end] = vm.ReadSpan(GetLinkEditFileBase() + exportTrie.dataoff, exportTrie.datasize);
+		auto trieSpan = vm.ReadSpan(GetLinkEditFileBase() + exportTrie.dataoff, exportTrie.datasize);
+		const uint8_t *begin = trieSpan.data();
+		const uint8_t *end = begin + trieSpan.size();
 		const uint8_t *cursor = begin;
 
 		struct Node