[compiler-rt] Add support for the dynamic shadow allocation

Summary:
This patch is adding support for dynamic shadow allocation.

This is a merge and re-commit of the following patches.

```
[compiler-rt] Fix Asan build on Android
  https://reviews.llvm.org/D24768
[compiler-rt] Add support for the dynamic shadow allocation
  https://reviews.llvm.org/D23363
```

This patch needed to re-land at the same time:
```
[asan] Support dynamic shadow address instrumentation
  https://reviews.llvm.org/D23354
```

Reviewers: rnk, zaks.anna

Subscribers: tberghammer, danalbert, kubabrecka, dberris, chrisha, llvm-commits

Differential Revision: https://reviews.llvm.org/D25104

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@282882 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 24 insertions, 6 deletions

diff --git a/lib/asan/asan_rtl.cc b/lib/asan/asan_rtl.cc
index 5a1128d6e..462867be0 100644
--- a/lib/asan/asan_rtl.cc
+++ b/lib/asan/asan_rtl.cc
@@ -32,6 +32,7 @@
 #include "ubsan/ubsan_init.h"
 #include "ubsan/ubsan_platform.h"
 
+uptr __asan_shadow_memory_dynamic_address;  // Global interface symbol.
 int __asan_option_detect_stack_use_after_return;  // Global interface symbol.
 uptr *__asan_test_only_reported_buggy_pointer;  // Used only for testing asan.
 
@@ -460,7 +461,30 @@ static void AsanInitInternal() {
 
   ReplaceSystemMalloc();
 
+  // Set the shadow memory address to uninitialized.
+  __asan_shadow_memory_dynamic_address = kDefaultShadowSentinel;
+
   uptr shadow_start = kLowShadowBeg;
+  // Detect if a dynamic shadow address must used and find a available location
+  // when necessary. When dynamic address is used, the macro |kLowShadowBeg|
+  // expands to |__asan_shadow_memory_dynamic_address| which is
+  // |kDefaultShadowSentinel|.
+  if (shadow_start == kDefaultShadowSentinel) {
+    __asan_shadow_memory_dynamic_address = 0;
+    CHECK_EQ(0, kLowShadowBeg);
+
+    uptr granularity = GetMmapGranularity();
+    uptr alignment = 8 * granularity;
+    uptr left_padding = granularity;
+    uptr space_size = kHighShadowEnd + left_padding;
+
+    shadow_start = FindAvailableMemoryRange(space_size, alignment, granularity);
+    CHECK_NE((uptr)0, shadow_start);
+    CHECK(IsAligned(shadow_start, alignment));
+  }
+  // Update the shadow memory address (potentially) used by instrumentation.
+  __asan_shadow_memory_dynamic_address = shadow_start;
+
   if (kLowShadowBeg)
     shadow_start -= GetMmapGranularity();
   bool full_shadow_is_available =
@@ -472,12 +496,6 @@ static void AsanInitInternal() {
     kMidMemBeg = kLowMemEnd < 0x3000000000ULL ? 0x3000000000ULL : 0;
     kMidMemEnd = kLowMemEnd < 0x3000000000ULL ? 0x4fffffffffULL : 0;
   }
-#elif SANITIZER_WINDOWS64
-  // Disable the "mid mem" shadow layout.
-  if (!full_shadow_is_available) {
-    kMidMemBeg = 0;
-    kMidMemEnd = 0;
-  }
 #endif
 
   if (Verbosity()) PrintAddressSpaceLayout();