[compiler-rt] [sanitizer_common] Introduce SANITIZER_MMAP_BEGIN macro (PR #147645)

[Jake Egan via llvm-commits]

https://github.com/jakeegan created https://github.com/llvm/llvm-project/pull/147645

To prepare for other platforms, such as 64-bit AIX, that have a non-zero mmap beginning address. 

>From 01ac087bd0f6614b1586cdfb7a7b0f16c97f10b7 Mon Sep 17 00:00:00 2001
From: Jake Egan <jake.egan at ibm.com>
Date: Tue, 8 Jul 2025 23:50:37 -0400
Subject: [PATCH] Introduce SANITIZER_MMAP_BEGIN

---
 compiler-rt/lib/asan/asan_allocator.h                          | 2 +-
 compiler-rt/lib/lsan/lsan_allocator.h                          | 2 +-
 compiler-rt/lib/msan/msan_allocator.cpp                        | 2 +-
 .../lib/sanitizer_common/sanitizer_allocator_internal.h        | 2 +-
 compiler-rt/lib/sanitizer_common/sanitizer_platform.h          | 3 +++
 compiler-rt/lib/tsan/rtl/tsan_rtl.h                            | 2 +-
 6 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/compiler-rt/lib/asan/asan_allocator.h b/compiler-rt/lib/asan/asan_allocator.h
index a94ef958aa75e..247d8bb77c984 100644
--- a/compiler-rt/lib/asan/asan_allocator.h
+++ b/compiler-rt/lib/asan/asan_allocator.h
@@ -239,7 +239,7 @@ using PrimaryAllocator = PrimaryAllocatorASVT<LocalAddressSpaceView>;
 typedef CompactSizeClassMap SizeClassMap;
 template <typename AddressSpaceViewTy>
 struct AP32 {
-  static const uptr kSpaceBeg = 0;
+  static const uptr kSpaceBeg = SANITIZER_MMAP_BEGIN;
   static const u64 kSpaceSize = SANITIZER_MMAP_RANGE_SIZE;
   static const uptr kMetadataSize = 0;
   typedef __asan::SizeClassMap SizeClassMap;
diff --git a/compiler-rt/lib/lsan/lsan_allocator.h b/compiler-rt/lib/lsan/lsan_allocator.h
index 2342f11fb5d0d..556b9f56a4a4a 100644
--- a/compiler-rt/lib/lsan/lsan_allocator.h
+++ b/compiler-rt/lib/lsan/lsan_allocator.h
@@ -53,7 +53,7 @@ struct ChunkMetadata {
 #if !SANITIZER_CAN_USE_ALLOCATOR64
 template <typename AddressSpaceViewTy>
 struct AP32 {
-  static const uptr kSpaceBeg = 0;
+  static const uptr kSpaceBeg = SANITIZER_MMAP_BEGIN;
   static const u64 kSpaceSize = SANITIZER_MMAP_RANGE_SIZE;
   static const uptr kMetadataSize = sizeof(ChunkMetadata);
   typedef __sanitizer::CompactSizeClassMap SizeClassMap;
diff --git a/compiler-rt/lib/msan/msan_allocator.cpp b/compiler-rt/lib/msan/msan_allocator.cpp
index d7d4967c94985..2b543db49d36e 100644
--- a/compiler-rt/lib/msan/msan_allocator.cpp
+++ b/compiler-rt/lib/msan/msan_allocator.cpp
@@ -56,7 +56,7 @@ struct MsanMapUnmapCallback {
 const uptr kMaxAllowedMallocSize = 2UL << 30;
 
 struct AP32 {
-  static const uptr kSpaceBeg = 0;
+  static const uptr kSpaceBeg = SANITIZER_MMAP_BEGIN;
   static const u64 kSpaceSize = SANITIZER_MMAP_RANGE_SIZE;
   static const uptr kMetadataSize = sizeof(Metadata);
   using SizeClassMap = __sanitizer::CompactSizeClassMap;
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_allocator_internal.h b/compiler-rt/lib/sanitizer_common/sanitizer_allocator_internal.h
index 62523c7ae187c..6c2020e6373c0 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_allocator_internal.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_allocator_internal.h
@@ -23,7 +23,7 @@ namespace __sanitizer {
 typedef CompactSizeClassMap InternalSizeClassMap;
 
 struct AP32 {
-  static const uptr kSpaceBeg = 0;
+  static const uptr kSpaceBeg = SANITIZER_MMAP_BEGIN;
   static const u64 kSpaceSize = SANITIZER_MMAP_RANGE_SIZE;
   static const uptr kMetadataSize = 0;
   typedef InternalSizeClassMap SizeClassMap;
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_platform.h b/compiler-rt/lib/sanitizer_common/sanitizer_platform.h
index 4c8d9a9b86bed..484006bf851a6 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_platform.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_platform.h
@@ -318,6 +318,9 @@
 #  endif
 #endif
 
+// The beginning of mmap range of addresses.
+#define SANITIZER_MMAP_BEGIN 0
+
 // The range of addresses which can be returned my mmap.
 // FIXME: this value should be different on different platforms.  Larger values
 // will still work but will consume more memory for TwoLevelByteMap.
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl.h b/compiler-rt/lib/tsan/rtl/tsan_rtl.h
index 0be53599b6a49..dc32980e905f2 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl.h
@@ -62,7 +62,7 @@ struct MapUnmapCallback;
       defined(__powerpc__) || SANITIZER_RISCV64
 
 struct AP32 {
-  static const uptr kSpaceBeg = 0;
+  static const uptr kSpaceBeg = SANITIZER_MMAP_BEGIN;
   static const u64 kSpaceSize = SANITIZER_MMAP_RANGE_SIZE;
   static const uptr kMetadataSize = 0;
   typedef __sanitizer::CompactSizeClassMap SizeClassMap;