[PATCH] D35032: [sanitizer] Use TASK_VM_INFO to get the maximum VM address on iOS/AArch64

[Kuba (Brecka) Mracek via Phabricator via llvm-commits]

kubamracek created this revision.
kubamracek added a project: Sanitizers.
Herald added subscribers: kristof.beyls, rengolin, aemerson.

We currently hardcode the maximum VM address on iOS/AArch64, which is not really correct and this value changes between device configurations.  Let's use TASK_VM_INFO to retrieve the maximum VM address dynamically.

The patch manually declares some constants, which would normally be provided in a header file by the SDK, but since this API is only declared in a recent SDK and we want to continue supporting building against older SDKs, the patch declares the constants manually.


Repository:
  rL LLVM

https://reviews.llvm.org/D35032

Files:
  lib/sanitizer_common/sanitizer_mac.cc


Index: lib/sanitizer_common/sanitizer_mac.cc
===================================================================
--- lib/sanitizer_common/sanitizer_mac.cc
+++ lib/sanitizer_common/sanitizer_mac.cc
@@ -798,13 +798,32 @@
 char **GetArgv() {
   return *_NSGetArgv();
 }
+  
+// These constants are normally provided by the macOS SDK, but only in 10.12+.
+// We want to be able to build against older SDKs, so declare them manually.
+static const int kTaskVmInfoCount = 42;
+static const int kTaskVmInfoMaxAddressOffset = 40;
+    
+uptr GetTaskInfoMaxAddress() {
+  integer_t vm_info[kTaskVmInfoCount] = {0};
+  mach_msg_type_number_t count = kTaskVmInfoCount;
+  int err = task_info(mach_task_self(), TASK_VM_INFO, vm_info, &count);
+  if (err == 0) {
+    return *(uptr *)(&vm_info[kTaskVmInfoMaxAddressOffset]) - 1;
+  } else {
+    // xnu cannot provide vm address limit
+    return 0x200000000 - 1;
+  }
+}
 
 uptr GetMaxVirtualAddress() {
 #if SANITIZER_WORDSIZE == 64
 # if defined(__aarch64__) && SANITIZER_IOS && !SANITIZER_IOSSIM
-  // Ideally, we would derive the upper bound from MACH_VM_MAX_ADDRESS. The
-  // upper bound can change depending on the device.
-  return 0x200000000 - 1;
+  // Get the maximum VM address
+  static uptr max_vm = 0;
+  if (max_vm == 0) max_vm = GetTaskInfoMaxAddress();
+  CHECK(max_vm);
+  return max_vm;
 # else
   return (1ULL << 47) - 1;  // 0x00007fffffffffffUL;
 # endif


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