selftests/seccomp: Support glibc 2.26 siginfo_t.h

The 2.26 release of glibc changed how siginfo_t is defined, and the earlier
work-around to using the kernel definition are no longer needed. The old
way needs to stay around for a while, though.
Reported-by: Seth Forshee <seth.forshee@canonical.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/seccomp/seccomp_bpf.c

@@ -6,10 +6,18 @@
  */
 
 #include <sys/types.h>
-#include <asm/siginfo.h>
-#define __have_siginfo_t 1
-#define __have_sigval_t 1
-#define __have_sigevent_t 1
+
+/*
+ * glibc 2.26 and later have SIGSYS in siginfo_t. Before that,
+ * we need to use the kernel's siginfo.h file and trick glibc
+ * into accepting it.
+ */
+#if !__GLIBC_PREREQ(2, 26)
+# include <asm/siginfo.h>
+# define __have_siginfo_t 1
+# define __have_sigval_t 1
+# define __have_sigevent_t 1
+#endif
 
 #include <errno.h>
 #include <linux/filter.h>
@@ -676,7 +684,7 @@ TEST_F_SIGNAL(TRAP, ign, SIGSYS)
 	syscall(__NR_getpid);
 }
 
-static struct siginfo TRAP_info;
+static siginfo_t TRAP_info;
 static volatile int TRAP_nr;
 static void TRAP_action(int nr, siginfo_t *info, void *void_context)
 {