From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 90461C433EF for ; Wed, 20 Apr 2022 23:25:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=9xhiDQEdsvYFYbbTL1ZgXRDn7UGndMkfjsL2DcdVl2I=; b=r5giUtUPRCvw+R ZKqGJpwttEALRriz9l3LsCxoo28KCrjYP0ufRyPsCOcWl9MD4LzdPcRhp718HqtJzFQ83BogQGqMH rfH4IwHFWELgIIhxQzFcjXuURfNUanOD7LH0/eCHCGXCjzf4G6WX3qltz7/cxYqPaNCKysyyljuaB xOkUHSSCvjfc1phO87ixcyiXN2goaiqyh3h0YcBLC9jh/zUaLAIoJge5u6Ek+6wDKup0omEAqby0n MtM6xoI0txyFzOfOarFLOA9E0EQw5hhDSyChBgd4hAWQZh5zAHsGzNpAmMsIt8kLiWf1tDxVrenZl 4cjcL97ZUna2VzMo/7SA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nhJgG-00Aq6x-Kk; Wed, 20 Apr 2022 23:24:16 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nhJgD-00Aq5u-LA for linux-arm-kernel@lists.infradead.org; Wed, 20 Apr 2022 23:24:15 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id F1C96B821AE; Wed, 20 Apr 2022 23:24:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE565C385A1; Wed, 20 Apr 2022 23:24:06 +0000 (UTC) Date: Wed, 20 Apr 2022 19:24:05 -0400 From: Steven Rostedt To: Xu Kuohai Cc: , , , , , Catalin Marinas , Will Deacon , 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 , Mark Rutland , Ard Biesheuvel , Pasha Tatashin , Peter Collingbourne , Daniel Kiss , Sudeep Holla , Steven Price , Marc Zyngier , Mark Brown , Kumar Kartikeya Dwivedi , Delyan Kratunov Subject: Re: [PATCH bpf-next v2 2/6] ftrace: Fix deadloop caused by direct call in ftrace selftest Message-ID: <20220420192405.4e43a966@gandalf.local.home> In-Reply-To: <20220414162220.1985095-3-xukuohai@huawei.com> References: <20220414162220.1985095-1-xukuohai@huawei.com> <20220414162220.1985095-3-xukuohai@huawei.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220420_162414_044283_E07D605A X-CRM114-Status: GOOD ( 26.50 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 14 Apr 2022 12:22:16 -0400 Xu Kuohai wrote: > 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 make trace_direct_tramp() a weak symbol and rewrite it for > arm64. > > To detect this issue directly, call DYN_FTRACE_TEST_NAME() before > register_ftrace_graph(). > > Reported-by: Li Huafei > Signed-off-by: Xu Kuohai > --- > arch/arm64/kernel/entry-ftrace.S | 10 ++++++++++ > kernel/trace/trace_selftest.c | 4 +++- > 2 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S > index dfe62c55e3a2..e58eb06ec9b2 100644 > --- a/arch/arm64/kernel/entry-ftrace.S > +++ b/arch/arm64/kernel/entry-ftrace.S > @@ -357,3 +357,13 @@ SYM_CODE_START(return_to_handler) > ret > SYM_CODE_END(return_to_handler) > #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > + > +#ifdef CONFIG_FTRACE_SELFTEST > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > +SYM_FUNC_START(trace_direct_tramp) > + mov x10, x30 > + mov x30, x9 > + ret x10 > +SYM_FUNC_END(trace_direct_tramp) > +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ > +#endif /* CONFIG_FTRACE_SELFTEST */ > diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c > index abcadbe933bb..38b0d5c9a1e0 100644 > --- a/kernel/trace/trace_selftest.c > +++ b/kernel/trace/trace_selftest.c > @@ -785,7 +785,7 @@ static struct fgraph_ops fgraph_ops __initdata = { > }; > > #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > -noinline __noclone static void trace_direct_tramp(void) { } > +void __weak trace_direct_tramp(void) { } > #endif > > /* > @@ -868,6 +868,8 @@ trace_selftest_startup_function_graph(struct tracer *trace, > if (ret) > goto out; > > + DYN_FTRACE_TEST_NAME(); This doesn't look like it belongs in this patch. -- Steve > + > ret = register_ftrace_graph(&fgraph_ops); > if (ret) { > warn_failed_init_tracer(trace, ret); _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel