[PATCH] [ASan] Add use_madv_dontdump flag.

[Yury Gribov]

Hi kcc, samsonov,

This patch implements use_madv_dontdump flag suggested in https://code.google.com/p/address-sanitizer/issues/detail?id=345 . The flag disables dumping of shadow memory to corefile (which takes hours on 64-bit platforms). Tested on Linux x64.

I didn't add a testcase - generating a predictable corefile is hard given the zoo of modern crash reporters. E.g. see https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1346497 (Apport from stock Ubuntu 14 multiples core limit by 1000).

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D7294

Files:
  lib/asan/asan_flags.inc
  lib/asan/asan_rtl.cc
  lib/sanitizer_common/sanitizer_common.h
  lib/sanitizer_common/sanitizer_posix_libcdep.cc
  lib/sanitizer_common/sanitizer_win.cc

Index: lib/asan/asan_flags.inc
===================================================================
--- lib/asan/asan_flags.inc
+++ lib/asan/asan_flags.inc
@@ -77,6 +77,9 @@
           "295.*.")
 ASAN_FLAG(bool, unmap_shadow_on_exit, false,
           "If set, explicitly unmaps the (huge) shadow at exit.")
+ASAN_FLAG(bool, use_madv_dontdump, true,
+          "If set, instructs kernel to not store the (huge) shadow "
+          "in core file.")
 ASAN_FLAG(
     bool, abort_on_error, false,
     "If set, the tool calls abort() instead of _exit() after printing the "
Index: lib/asan/asan_rtl.cc
===================================================================
--- lib/asan/asan_rtl.cc
+++ lib/asan/asan_rtl.cc
@@ -100,6 +100,8 @@
   }
   if (common_flags()->no_huge_pages_for_shadow)
     NoHugePagesInRegion(beg, size);
+  if (flags()->use_madv_dontdump)
+    DontDumpShadowMemory(beg, size);
 }
 
 // --------------- LowLevelAllocateCallbac ---------- {{{1
Index: lib/sanitizer_common/sanitizer_common.h
===================================================================
--- lib/sanitizer_common/sanitizer_common.h
+++ lib/sanitizer_common/sanitizer_common.h
@@ -77,6 +77,7 @@
 void DecreaseTotalMmap(uptr size);
 uptr GetRSS();
 void NoHugePagesInRegion(uptr addr, uptr length);
+void DontDumpShadowMemory(uptr addr, uptr length);
 
 // InternalScopedBuffer can be used instead of large stack arrays to
 // keep frame size low.
Index: lib/sanitizer_common/sanitizer_posix_libcdep.cc
===================================================================
--- lib/sanitizer_common/sanitizer_posix_libcdep.cc
+++ lib/sanitizer_common/sanitizer_posix_libcdep.cc
@@ -50,6 +50,12 @@
 #endif  // MADV_NOHUGEPAGE
 }
 
+void DontDumpShadowMemory(uptr addr, uptr length) {
+#ifdef MADV_DONTDUMP
+  madvise((void *)addr, length, MADV_DONTDUMP);
+#endif
+}
+
 static rlim_t getlim(int res) {
   rlimit rlim;
   CHECK_EQ(0, getrlimit(res, &rlim));
Index: lib/sanitizer_common/sanitizer_win.cc
===================================================================
--- lib/sanitizer_common/sanitizer_win.cc
+++ lib/sanitizer_common/sanitizer_win.cc
@@ -129,13 +129,18 @@
 
 void FlushUnneededShadowMemory(uptr addr, uptr size) {
   // This is almost useless on 32-bits.
-  // FIXME: add madvice-analog when we move to 64-bits.
+  // FIXME: add madvise-analog when we move to 64-bits.
 }
 
 void NoHugePagesInRegion(uptr addr, uptr size) {
   // FIXME: probably similar to FlushUnneededShadowMemory.
 }
 
+void DontDumpShadowMemory(uptr addr, uptr length) {
+  // This is almost useless on 32-bits.
+  // FIXME: add madvise-analog when we move to 64-bits.
+}
+
 bool MemoryRangeIsAvailable(uptr range_start, uptr range_end) {
   MEMORY_BASIC_INFORMATION mbi;
   CHECK(VirtualQuery((void *)range_start, &mbi, sizeof(mbi)));

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