[asan] Be more careful and verbose when allocating dynamic shadow memory

FindAvailableMemoryRange can currently overwrite existing memory (by restricting the VM below addresses that are already used). This patch adds a check to make sure we don't restrict the VM space too much. We are also now more explicit about why the lookup failed and print out verbose values.

Differential Revision: https://reviews.llvm.org/D43318



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@326106 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 5 deletions

diff --git a/lib/sanitizer_common/sanitizer_mac.cc b/lib/sanitizer_common/sanitizer_mac.cc
index 8fa61318a..3eb023ebf 100644
--- a/lib/sanitizer_common/sanitizer_mac.cc
+++ b/lib/sanitizer_common/sanitizer_mac.cc
@@ -887,10 +887,9 @@ uptr GetMaxVirtualAddress() {
   return GetMaxUserVirtualAddress();
 }
 
-uptr FindAvailableMemoryRange(uptr shadow_size,
-                              uptr alignment,
-                              uptr left_padding,
-                              uptr *largest_gap_found) {
+uptr FindAvailableMemoryRange(uptr size, uptr alignment, uptr left_padding,
+                              uptr *largest_gap_found,
+                              uptr *max_occupied_addr) {
   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
@@ -902,6 +901,7 @@ uptr FindAvailableMemoryRange(uptr shadow_size,
   mach_vm_address_t free_begin = start_address;
   kern_return_t kr = KERN_SUCCESS;
   if (largest_gap_found) *largest_gap_found = 0;
+  if (max_occupied_addr) *max_occupied_addr = 0;
   while (kr == KERN_SUCCESS) {
     mach_vm_size_t vmsize = 0;
     natural_t depth = 0;
@@ -913,13 +913,15 @@ uptr FindAvailableMemoryRange(uptr shadow_size,
       // No more regions beyond "address", consider the gap at the end of VM.
       address = GetMaxVirtualAddress() + 1;
       vmsize = 0;
+    } else {
+      if (max_occupied_addr) *max_occupied_addr = address + vmsize;
     }
     if (free_begin != address) {
       // We found a free region [free_begin..address-1].
       uptr gap_start = RoundUpTo((uptr)free_begin + left_padding, alignment);
       uptr gap_end = RoundDownTo((uptr)address, alignment);
       uptr gap_size = gap_end > gap_start ? gap_end - gap_start : 0;
-      if (shadow_size < gap_size) {
+      if (size < gap_size) {
         return gap_start;
       }