[compiler-rt] [sanitizer-common] [Darwin] Fix overlapping dyld segment addresses (PR #166005)

[Paddy McDonald via llvm-commits]

================
@@ -255,16 +257,16 @@ static bool NextSegmentLoad(MemoryMappedSegment *segment,
   layout_data->current_load_cmd_count--;
   if (((const load_command *)lc)->cmd == kLCSegment) {
     const SegmentCommand* sc = (const SegmentCommand *)lc;
+    if (strncmp(sc->segname, "__LINKEDIT", sizeof("__LINKEDIT")) == 0) {
+      // The LINKEDIT sections alias, so we ignore these sections to
+      // ensure our mappings are disjoint.
+      return false;
+    }
+
     uptr base_virt_addr, addr_mask;
     if (layout_data->current_image == kDyldImageIdx) {
-      base_virt_addr = (uptr)get_dyld_hdr();
-      // vmaddr is masked with 0xfffff because on macOS versions < 10.12,
-      // it contains an absolute address rather than an offset for dyld.
-      // To make matters even more complicated, this absolute address
-      // isn't actually the absolute segment address, but the offset portion
-      // of the address is accurate when combined with the dyld base address,
-      // and the mask will give just this offset.
-      addr_mask = 0xfffff;
+      base_virt_addr = (uptr)_dyld_get_image_slide(get_dyld_hdr());
+      addr_mask = ~0;
----------------
padriff wrote:

Seems like removing addr_mask would simplify the code

https://github.com/llvm/llvm-project/pull/166005