[compiler-rt] 9faac93 - [sanitizer] Warn if allocator size exceeds max user virtual address (#152428)

[via llvm-commits]

Author: Thurston Dang
Date: 2025-08-07T14:36:45-07:00
New Revision: 9faac938e1b03ea23e7212550860f8b8001757e1

URL: https://github.com/llvm/llvm-project/commit/9faac938e1b03ea23e7212550860f8b8001757e1
DIFF: https://github.com/llvm/llvm-project/commit/9faac938e1b03ea23e7212550860f8b8001757e1.diff

LOG: [sanitizer] Warn if allocator size exceeds max user virtual address (#152428)

This warns the user of incompatible configurations, such as 39-bit and
42-bit VMAs for AArch64 non-Android Linux ASan
(https://github.com/llvm/llvm-project/issues/145259).

Added: 
    

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h

Removed: 
    


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diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h b/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h
index 51ac1b6ae4975..b39eb1538cbcd 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h
@@ -113,6 +113,24 @@ class SizeClassAllocator64 {
   // ~(uptr)0.
   void Init(s32 release_to_os_interval_ms, uptr heap_start = 0) {
     uptr TotalSpaceSize = kSpaceSize + AdditionalSize();
+
+    uptr MaxAddr = GetMaxUserVirtualAddress();
+    // VReport does not call the sanitizer allocator.
+    VReport(3, "Max user virtual address: 0x%zx\n", MaxAddr);
+    VReport(3, "Total space size for primary allocator: 0x%zx\n",
+            TotalSpaceSize);
+    // TODO: revise the check if we ever configure sanitizers to deliberately
+    //       map beyond the 2**48 barrier (note that Linux pretends the VMA is
+    //       limited to 48-bit for backwards compatibility, but allows apps to
+    //       explicitly specify an address beyond that).
+    if (heap_start + TotalSpaceSize >= MaxAddr) {
+      // We can't easily adjust the requested heap size, because kSpaceSize is
+      // const (for optimization) and used throughout the code.
+      VReport(0, "Error: heap size %zx exceeds max user virtual address %zx\n",
+              TotalSpaceSize, MaxAddr);
+      VReport(
+          0, "Try using a kernel that allows a larger virtual address space\n");
+    }
     PremappedHeap = heap_start != 0;
     if (PremappedHeap) {
       CHECK(!kUsingConstantSpaceBeg);