[asan] add flag uar_noreserve to use noreserve mmap for fake stack. uar_noreserve=1 will save some memory but also negatively affect performance

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@197233 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 3 deletions

diff --git a/lib/asan/asan_fake_stack.cc b/lib/asan/asan_fake_stack.cc
index 7301c9afd..00fe2fe59 100644
--- a/lib/asan/asan_fake_stack.cc
+++ b/lib/asan/asan_fake_stack.cc
@@ -42,13 +42,17 @@ FakeStack *FakeStack::Create(uptr stack_size_log) {
     stack_size_log = kMinStackSizeLog;
   if (stack_size_log > kMaxStackSizeLog)
     stack_size_log = kMaxStackSizeLog;
+  uptr size = RequiredSize(stack_size_log);
   FakeStack *res = reinterpret_cast<FakeStack *>(
-      MmapOrDie(RequiredSize(stack_size_log), "FakeStack"));
+      flags()->uar_noreserve ? MmapNoReserveOrDie(size, "FakeStack")
+                             : MmapOrDie(size, "FakeStack"));
   res->stack_size_log_ = stack_size_log;
   u8 *p = reinterpret_cast<u8 *>(res);
-  VReport(1, "T%d: FakeStack created: %p -- %p stack_size_log: %zd \n",
+  VReport(1, "T%d: FakeStack created: %p -- %p stack_size_log: %zd; "
+          "noreserve=%d \n",
           GetCurrentTidOrInvalid(), p,
-          p + FakeStack::RequiredSize(stack_size_log), stack_size_log);
+          p + FakeStack::RequiredSize(stack_size_log), stack_size_log,
+          flags()->uar_noreserve);
   return res;
 }