Autodetect hwasan support

Added a C source that checks if the kernel has Aarch64 tagged address
ABI. CMake will then enable or disable hwasan tests depending on the
result of that test in configure time.

CMakeLists.txt

@@ -45,6 +45,24 @@ option(ENABLE_LIBCXX "assume libc++ is available" ON)
 option(ENABLE_STATIC_LIBCXX "assume libc++.a is available" ON)
 option(ENABLE_LIBUNWIND "assume libunwind is available" ON)
 
+message(STATUS "Checking kernel support for tagged address ABI")
+try_run(
+    _TEST_RUN_RESULT
+    _BUILD_RESULT_UNUSED
+    ${CMAKE_BINARY_DIR}
+    ${CMAKE_CURRENT_SOURCE_DIR}/test_tagged_addr_abi_support.c
+    )
+if(DEFINED _TEST_RUN_RESULT AND _TEST_RUN_RESULT EQUAL 0)
+    set(SUPPORT_HWASAN ON)
+else()
+    message(STATUS "Tagged address ABI disabled, disabling hwasan test(s)")
+    set(SUPPORT_HWASAN OFF)
+endif()
+option(ENABLE_HWASAN
+    "The host supports Aarch64 tagged address ABI"
+    ${SUPPORT_HWASAN}
+    )
+
 configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/tests/lit.site.cfg.in
     ${CMAKE_BINARY_DIR}/tests/lit.site.cfg

README.rst

@@ -40,6 +40,7 @@ Sensible configuration variables
 - ``ENABLE_COMPILER_RT``: ON (the default) if we assume compiler-rt is available
 - ``ENABLE_LIBCXX``: ON (the default) if we assume libc++ is available
 - ``ENABLE_UNWIND``: ON (the default) if we assume libunwind is available
+- ``ENABLE_HWASAN``: Run hwasan tests. Autodetected based on the host system.
 
 Writing new tests
 -----------------

test_tagged_addr_abi_support.c

@@ -0,0 +1,14 @@
+/*
+ * This simple program checks if the kernel running the testsuite has support
+ * for tagged address ABI, needed to test hardware assisted address sanitizer.
+ * https://www.kernel.org/doc/html/next/arm64/tagged-address-abi.html
+ *
+ * The program returns 0 if the kernel supports tagged address ABI.
+ */
+
+#include <sys/prctl.h>
+int main(void)
+{
+    return prctl(PR_GET_TAGGED_ADDR_CTRL, 0,0,0,0);
+}
+

tests/lit.site.cfg.in

@@ -51,3 +51,4 @@ enable_feature("compiler-rt", "@ENABLE_COMPILER_RT@")
 enable_feature("libc++", "@ENABLE_LIBCXX@")
 enable_feature("static-libc++", "@ENABLE_STATIC_LIBCXX@")
 enable_feature("libunwind", "@ENABLE_LIBUNWIND@")
+enable_feature("support_hwasan", "@ENABLE_HWASAN@")

tests/test_hwasan.c

@@ -1,6 +1,6 @@
 // Test hwasan use after free -- aarch64 only.
 //
-// REQUIRES: clang, compiler-rt, aarch64
+// REQUIRES: clang, compiler-rt, support_hwasan
 // RUN: %clang -o %t -fsanitize=hwaddress -g %s
 // RUN: env HWASAN_OPTIONS="log_path=stdout:exitcode=0"  %t 2>&1 > %t.out
 // RUN: grep -q "HWAddressSanitizer: tag-mismatch" %t.out