Add getauxval() compat for NetBSD

Summary:
getauxval() is not available on NetBSD and there is no a direct equivalent.

Add a function that implements the same semantics with NetBSD internals.

Reorder the GetPageSize() functions to prefer the sysctl approach for NetBSD.
It no longer makes a difference which approach is better. Avoid changing
conditional code path.

Reviewers: vitalybuka, dvyukov, mgorny, joerg

Reviewed By: vitalybuka

Subscribers: llvm-commits, #sanitizers

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D67329

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@371758 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 21 insertions, 3 deletions

diff --git a/lib/sanitizer_common/sanitizer_getauxval.h b/lib/sanitizer_common/sanitizer_getauxval.h
index f1ca0be43..777b1212d 100644
--- a/lib/sanitizer_common/sanitizer_getauxval.h
+++ b/lib/sanitizer_common/sanitizer_getauxval.h
@@ -9,6 +9,7 @@
 // Common getauxval() guards and definitions.
 // getauxval() is not defined until glibc version 2.16, or until API level 21
 // for Android.
+// Implement the getauxval() compat function for NetBSD.
 //
 //===----------------------------------------------------------------------===//
 
@@ -41,6 +42,23 @@
 extern "C" SANITIZER_WEAK_ATTRIBUTE unsigned long getauxval(unsigned long type);
 # endif
 
-#endif // SANITIZER_LINUX || SANITIZER_FUCHSIA
+#elif SANITIZER_NETBSD
+
+#define SANITIZER_USE_GETAUXVAL 1
+
+#include <dlfcn.h>
+#include <elf.h>
+
+static inline decltype(AuxInfo::a_v) getauxval(decltype(AuxInfo::a_type) type) {
+  for (const AuxInfo *aux = (const AuxInfo *)_dlauxinfo();
+       aux->a_type != AT_NULL; ++aux) {
+    if (type == aux->a_type)
+      return aux->a_v;
+  }
+
+  return 0;
+}
+
+#endif
 
 #endif // SANITIZER_GETAUXVAL_H
diff --git a/lib/sanitizer_common/sanitizer_linux.cpp b/lib/sanitizer_common/sanitizer_linux.cpp
index e666290fc..d23009075 100644
--- a/lib/sanitizer_common/sanitizer_linux.cpp
+++ b/lib/sanitizer_common/sanitizer_linux.cpp
@@ -1062,8 +1062,6 @@ uptr GetMaxUserVirtualAddress() {
 uptr GetPageSize() {
 #if SANITIZER_LINUX && (defined(__x86_64__) || defined(__i386__))
   return EXEC_PAGESIZE;
-#elif SANITIZER_USE_GETAUXVAL
-  return getauxval(AT_PAGESZ);
 #elif SANITIZER_FREEBSD || SANITIZER_NETBSD
 // Use sysctl as sysconf can trigger interceptors internally.
   int pz = 0;
@@ -1072,6 +1070,8 @@ uptr GetPageSize() {
   int rv = internal_sysctl(mib, 2, &pz, &pzl, nullptr, 0);
   CHECK_EQ(rv, 0);
   return (uptr)pz;
+#elif SANITIZER_USE_GETAUXVAL
+  return getauxval(AT_PAGESZ);
 #else
   return sysconf(_SC_PAGESIZE);  // EXEC_PAGESIZE may not be trustworthy.
 #endif