[compiler-rt] [hwasan] Add fixed_shadow_base flag (PR #73980)

[Vitaly Buka via llvm-commits]

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+// Test fixed shadow base functionality.
+//
+// Default compiler instrumentation works with any shadow base (dynamic or fixed).
+// RUN: %clang_hwasan %s -o %t && %run %t
+// RUN: %clang_hwasan %s -o %t && HWASAN_OPTIONS=fixed_shadow_base=263878495698944 %run %t
+// RUN: %clang_hwasan %s -o %t && HWASAN_OPTIONS=fixed_shadow_base=4398046511104 %run %t
+//
+// If -hwasan-mapping-offset is set, then the fixed_shadow_base needs to match.
+// RUN: %clang_hwasan %s -mllvm -hwasan-mapping-offset=263878495698944 -o %t && HWASAN_OPTIONS=fixed_shadow_base=263878495698944 %run %t
+// RUN: %clang_hwasan %s -mllvm -hwasan-mapping-offset=4398046511104 -o %t && HWASAN_OPTIONS=fixed_shadow_base=4398046511104 %run %t
+// RUN: %clang_hwasan %s -mllvm -hwasan-mapping-offset=263878495698944 -o %t && HWASAN_OPTIONS=fixed_shadow_base=4398046511104 not %run %t
+// RUN: %clang_hwasan %s -mllvm -hwasan-mapping-offset=4398046511104 -o %t && HWASAN_OPTIONS=fixed_shadow_base=263878495698944 not %run %t
+//
+// Note: if fixed_shadow_base is not set, compiler-rt will dynamically choose a
+// shadow base, which has a tiny but non-zero probability of matching the
+// compiler instrumentation. To avoid test flake, we do not test this case.
+//
+// Assume 48-bit VMA
+// REQUIRES: aarch64-target-arch
+//
+// UNSUPPORTED: android
+
+#include <assert.h>
+#include <sanitizer/allocator_interface.h>
+#include <sanitizer/hwasan_interface.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+
+int main() {
+  __hwasan_enable_allocator_tagging();
+
+  void **mmaps[256];
+  // 48-bit VMA
+  for (int i = 0; i < 256; i++) {
+    unsigned long long addr = (i * (1ULL << 40));
+
+    void *p = mmap((void *)addr, 4096, PROT_READ | PROT_WRITE,
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vitalybuka wrote:

Also there is DumpProcessMap(), maybe it's easy to see shadow there?

https://github.com/llvm/llvm-project/pull/73980