From patchwork Sun Apr 24 15:40:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xu Kuohai X-Patchwork-Id: 12824932 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E76FBC433FE for ; Sun, 24 Apr 2022 15:34:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232361AbiDXPhE (ORCPT ); Sun, 24 Apr 2022 11:37:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36888 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240449AbiDXPbX (ORCPT ); Sun, 24 Apr 2022 11:31:23 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CAEC8171C03; Sun, 24 Apr 2022 08:28:20 -0700 (PDT) Received: from kwepemi500013.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KmX8l38tLzhYWb; Sun, 24 Apr 2022 23:28:07 +0800 (CST) Received: from huawei.com (10.67.174.197) by kwepemi500013.china.huawei.com (7.221.188.120) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sun, 24 Apr 2022 23:28:16 +0800 From: Xu Kuohai To: , , , , CC: Catalin Marinas , Will Deacon , Steven Rostedt , Ingo Molnar , Daniel Borkmann , Alexei Starovoitov , Zi Shen Lim , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , "David S . Miller" , Hideaki YOSHIFUJI , David Ahern , Thomas Gleixner , Borislav Petkov , Dave Hansen , , , Shuah Khan , Jakub Kicinski , Jesper Dangaard Brouer , Mark Rutland , Pasha Tatashin , Ard Biesheuvel , Daniel Kiss , Steven Price , Sudeep Holla , Marc Zyngier , Peter Collingbourne , Mark Brown , Delyan Kratunov , Kumar Kartikeya Dwivedi Subject: [PATCH bpf-next v3 2/7] ftrace: Fix deadloop caused by direct call in ftrace selftest Date: Sun, 24 Apr 2022 11:40:23 -0400 Message-ID: <20220424154028.1698685-3-xukuohai@huawei.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220424154028.1698685-1-xukuohai@huawei.com> References: <20220424154028.1698685-1-xukuohai@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.67.174.197] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemi500013.china.huawei.com (7.221.188.120) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net After direct call is enabled for arm64, ftrace selftest enters a dead loop: : 00 bti c 01 mov x9, x30 : 02 bl ----------> ret | lr/x30 is 03, return to 03 | 03 mov w0, #0x0 <-----------------------------| | | | dead loop! | | | 04 ret ---- lr/x30 is still 03, go back to 03 ----| The reason is that when the direct caller trace_direct_tramp() returns to the patched function trace_selftest_dynamic_test_func(), lr is still the address after the instrumented instruction in the patched function, so when the patched function exits, it returns to itself! To fix this issue, we need to restore lr before trace_direct_tramp() exits, so rewrite a dedicated trace_direct_tramp() for arm64. Reported-by: Li Huafei Signed-off-by: Xu Kuohai --- kernel/trace/trace_selftest.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c index abcadbe933bb..d2eff2b1d743 100644 --- a/kernel/trace/trace_selftest.c +++ b/kernel/trace/trace_selftest.c @@ -785,8 +785,24 @@ static struct fgraph_ops fgraph_ops __initdata = { }; #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS +#ifdef CONFIG_ARM64 +extern void trace_direct_tramp(void); + +asm ( +" .pushsection .text, \"ax\", @progbits\n" +" .type trace_direct_tramp, %function\n" +" .global trace_direct_tramp\n" +"trace_direct_tramp:" +" mov x10, x30\n" +" mov x30, x9\n" +" ret x10\n" +" .size trace_direct_tramp, .-trace_direct_tramp\n" +" .popsection\n" +); +#else noinline __noclone static void trace_direct_tramp(void) { } #endif +#endif /* * Pretty much the same than for the function tracer from which the selftest