[asan] Reapply: Switch to using dynamic shadow offset on iOS

The VM layout is not stable between iOS version releases, so switch to dynamic shadow offset.

Differential Revision: https://reviews.llvm.org/D25218

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@283375 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 49 insertions, 1 deletions

diff --git a/lib/sanitizer_common/sanitizer_mac.cc b/lib/sanitizer_common/sanitizer_mac.cc
index 6b513486c..0de994ae2 100644
--- a/lib/sanitizer_common/sanitizer_mac.cc
+++ b/lib/sanitizer_common/sanitizer_mac.cc
@@ -72,12 +72,23 @@ extern "C" {
 #include <unistd.h>
 #include <util.h>
 
-// from <crt_externs.h>, but we don't have that file on iOS
+// From <crt_externs.h>, but we don't have that file on iOS.
 extern "C" {
   extern char ***_NSGetArgv(void);
   extern char ***_NSGetEnviron(void);
 }
 
+// From <mach/mach_vm.h>, but we don't have that file on iOS.
+extern "C" {
+  extern kern_return_t mach_vm_region_recurse (
+    vm_map_t target_task,
+    mach_vm_address_t *address,
+    mach_vm_size_t *size,
+    natural_t *nesting_depth,
+    vm_region_recurse_info_t info,
+    mach_msg_type_number_t *infoCnt);
+}
+
 namespace __sanitizer {
 
 #include "sanitizer_syscall_generic.inc"
@@ -742,6 +753,43 @@ char **GetArgv() {
   return *_NSGetArgv();
 }
 
+uptr FindAvailableMemoryRange(uptr shadow_size,
+                              uptr alignment,
+                              uptr left_padding) {
+  typedef vm_region_submap_short_info_data_64_t RegionInfo;
+  enum { kRegionInfoSize = VM_REGION_SUBMAP_SHORT_INFO_COUNT_64 };
+  // Start searching for available memory region past PAGEZERO, which is
+  // 4KB on 32-bit and 4GB on 64-bit.
+  mach_vm_address_t start_address =
+    (SANITIZER_WORDSIZE == 32) ? 0x000000001000 : 0x000100000000;
+
+  mach_vm_address_t address = start_address;
+  mach_vm_address_t free_begin = start_address;
+  kern_return_t kr = KERN_SUCCESS;
+  while (kr == KERN_SUCCESS) {
+    mach_vm_size_t vmsize = 0;
+    natural_t depth = 0;
+    RegionInfo vminfo;
+    mach_msg_type_number_t count = kRegionInfoSize;
+    kr = mach_vm_region_recurse(mach_task_self(), &address, &vmsize, &depth,
+                                (vm_region_info_t)&vminfo, &count);
+    if (free_begin != address) {
+      // We found a free region [free_begin..address-1].
+      uptr shadow_address = RoundUpTo((uptr)free_begin + left_padding,
+                                      alignment);
+      if (shadow_address + shadow_size < (uptr)address) {
+        return shadow_address;
+      }
+    }
+    // Move to the next region.
+    address += vmsize;
+    free_begin = address;
+  }
+
+  // We looked at all free regions and could not find one large enough.
+  return 0;
+}
+
 // FIXME implement on this platform.
 void GetMemoryProfile(fill_profile_f cb, uptr *stats, uptr stats_size) { }