[compiler-rt] [compiler-rt][fuchsia] Preallocate a vmar for sanitizer internals (PR #75256)

[via llvm-commits]

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@@ -357,7 +406,7 @@ void *MmapAlignedOrDieOnFatalError(uptr size, uptr alignment,
 }
 
 void UnmapOrDie(void *addr, uptr size) {
-  UnmapOrDieVmar(addr, size, _zx_vmar_root_self());
+  UnmapOrDieVmar(addr, size, gSanitizerHeapVmar);
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PiJoules wrote:

This dispatches to `UnmapOrDieVmar` above which contains that fallback logic. When this is called, it should try unmapping from `gSanitizerHeapVmar` first then try unmapping again in the root.

https://github.com/llvm/llvm-project/pull/75256