[RFC PATCH 4/4] selftests: rseq: print rseq extensible size in basic test

From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	"Paul E . McKenney" <paulmck@linux.ibm.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	"H . Peter Anvin" <hpa@zytor.com>, Paul Turner <pjt@google.com>,
	linux-api@vger.kernel.org,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Florian Weimer <fw@deneb.enyo.de>,
	carlos@redhat.com,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: [RFC PATCH 4/4] selftests: rseq: print rseq extensible size in basic test
Date: Mon, 13 Jul 2020 23:03:48 -0400	[thread overview]
Message-ID: <20200714030348.6214-5-mathieu.desnoyers@efficios.com> (raw)
In-Reply-To: <20200714030348.6214-1-mathieu.desnoyers@efficios.com>

Print whether extensible size feature is supported by the kernel
and __rseq_abi definition, along with the contents of the kernel_size
field if it is available.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 tools/testing/selftests/rseq/basic_test.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tools/testing/selftests/rseq/basic_test.c b/tools/testing/selftests/rseq/basic_test.c
index d8efbfb89193..976e040574a1 100644
--- a/tools/testing/selftests/rseq/basic_test.c
+++ b/tools/testing/selftests/rseq/basic_test.c
@@ -10,6 +10,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <sys/time.h>
+#include <inttypes.h>
 
 #include "rseq.h"
 
@@ -35,6 +36,17 @@ void test_cpu_pointer(void)
 	sched_setaffinity(0, sizeof(affinity), &affinity);
 }
 
+static void print_rseq_size(void)
+{
+	bool supported = (__rseq_abi.flags & RSEQ_TLS_FLAG_SIZE) && __rseq_abi.kernel_size != 0;
+
+	printf("extensible struct rseq supported: %s",
+		supported ? "yes" : "no");
+	if (supported)
+		printf(" (kernel_size=%" PRIu16 ")", __rseq_abi.kernel_size);
+	printf("\n");
+}
+
 int main(int argc, char **argv)
 {
 	if (rseq_register_current_thread()) {
@@ -42,6 +54,9 @@ int main(int argc, char **argv)
 			errno, strerror(errno));
 		goto init_thread_error;
 	}
+
+	print_rseq_size();
+
 	printf("testing current cpu\n");
 	test_cpu_pointer();
 	if (rseq_unregister_current_thread()) {
-- 
2.17.1

