[ASan] Move the sigaltstack() bits to sanitizer_common.

This change is a part of refactoring intended to have common signal handling behavior in all tools.
Note that this particular change doesn't enable use_sigaltstack support in every tool.

llvm-svn: 200310

1 files changed, 28 insertions, 0 deletions

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cc b/compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cc
index 6032f520dee..73b7886c21c 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cc
@@ -20,6 +20,7 @@
 
 #include <errno.h>
 #include <pthread.h>
+#include <signal.h>
 #include <stdlib.h>
 #include <sys/mman.h>
 #include <sys/resource.h>
@@ -89,6 +90,33 @@ int internal_isatty(fd_t fd) {
   return isatty(fd);
 }
 
+// TODO(glider): different tools may require different altstack size.
+static const uptr kAltStackSize = SIGSTKSZ * 4;  // SIGSTKSZ is not enough.
+
+void SetAlternateSignalStack() {
+  stack_t altstack, oldstack;
+  CHECK_EQ(0, sigaltstack(0, &oldstack));
+  // If the alternate stack is already in place, do nothing.
+  if ((oldstack.ss_flags & SS_DISABLE) == 0) return;
+  // TODO(glider): the mapped stack should have the MAP_STACK flag in the
+  // future. It is not required by man 2 sigaltstack now (they're using
+  // malloc()).
+  void* base = MmapOrDie(kAltStackSize, __FUNCTION__);
+  altstack.ss_sp = base;
+  altstack.ss_flags = 0;
+  altstack.ss_size = kAltStackSize;
+  CHECK_EQ(0, sigaltstack(&altstack, 0));
+}
+
+void UnsetAlternateSignalStack() {
+  stack_t altstack, oldstack;
+  altstack.ss_sp = 0;
+  altstack.ss_flags = SS_DISABLE;
+  altstack.ss_size = 0;
+  CHECK_EQ(0, sigaltstack(&altstack, &oldstack));
+  UnmapOrDie(oldstack.ss_sp, oldstack.ss_size);
+}
+
 }  // namespace __sanitizer
 
 #endif