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 X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C70BC433E6 for ; Thu, 18 Mar 2021 03:24:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BC14E64EEC for ; Thu, 18 Mar 2021 03:24:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230226AbhCRDYO convert rfc822-to-8bit (ORCPT ); Wed, 17 Mar 2021 23:24:14 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:3042 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231352AbhCRDYE (ORCPT ); Wed, 17 Mar 2021 23:24:04 -0400 Received: from DGGEMM402-HUB.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4F1C3H1sczzWMfX; Thu, 18 Mar 2021 11:20:59 +0800 (CST) Received: from dggpemm500002.china.huawei.com (7.185.36.229) by DGGEMM402-HUB.china.huawei.com (10.3.20.210) with Microsoft SMTP Server (TLS) id 14.3.498.0; Thu, 18 Mar 2021 11:24:01 +0800 Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500002.china.huawei.com (7.185.36.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Thu, 18 Mar 2021 11:24:01 +0800 Received: from dggpemm500006.china.huawei.com ([7.185.36.236]) by dggpemm500006.china.huawei.com ([7.185.36.236]) with mapi id 15.01.2106.013; Thu, 18 Mar 2021 11:24:01 +0800 From: "chenjun (AM)" To: Mark Rutland , Catalin Marinas CC: "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "akpm@linux-foundation.org" , "will@kernel.org" , "Xiangrui (Euler)" , Mark Brown , "Wangkefeng (OS Kernel Lab)" Subject: Re: [PATCH 2/2] arm64: stacktrace: Add skip when task == current Thread-Topic: [PATCH 2/2] arm64: stacktrace: Add skip when task == current Thread-Index: AQHXGzmzVCWLNYUND0iAKn2NT1sSPA== Date: Thu, 18 Mar 2021 03:24:01 +0000 Message-ID: <75f39d3e2a38438fab5a3ca79e296d73@huawei.com> References: <20210317142050.57712-1-chenjun102@huawei.com> <20210317142050.57712-3-chenjun102@huawei.com> <20210317183636.GG12269@arm.com> <20210317193416.GB9786@C02TD0UTHF1T.local> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.174.178.53] Content-Type: text/plain; charset="iso-2022-jp" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/3/18 3:34, Mark Rutland 写道: > On Wed, Mar 17, 2021 at 06:36:36PM +0000, Catalin Marinas wrote: >> On Wed, Mar 17, 2021 at 02:20:50PM +0000, Chen Jun wrote: >>> On ARM64, cat /sys/kernel/debug/page_owner, all pages return the same >>> stack: >>> stack_trace_save+0x4c/0x78 >>> register_early_stack+0x34/0x70 >>> init_page_owner+0x34/0x230 >>> page_ext_init+0x1bc/0x1dc >>> >>> The reason is that: >>> check_recursive_alloc always return 1 because that >>> entries[0] is always equal to ip (__set_page_owner+0x3c/0x60). >>> >>> The root cause is that: >>> commit 5fc57df2f6fd ("arm64: stacktrace: Convert to ARCH_STACKWALK") >>> make the save_trace save 2 more entries. >>> >>> Add skip in arch_stack_walk when task == current. >>> >>> Fixes: 5fc57df2f6fd ("arm64: stacktrace: Convert to ARCH_STACKWALK") >>> Signed-off-by: Chen Jun >>> --- >>> arch/arm64/kernel/stacktrace.c | 5 +++-- >>> 1 file changed, 3 insertions(+), 2 deletions(-) >>> >>> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c >>> index ad20981..c26b0ac 100644 >>> --- a/arch/arm64/kernel/stacktrace.c >>> +++ b/arch/arm64/kernel/stacktrace.c >>> @@ -201,11 +201,12 @@ void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, >>> >>> if (regs) >>> start_backtrace(&frame, regs->regs[29], regs->pc); >>> - else if (task == current) >>> + else if (task == current) { >>> + ((struct stacktrace_cookie *)cookie)->skip += 2; >>> start_backtrace(&frame, >>> (unsigned long)__builtin_frame_address(0), >>> (unsigned long)arch_stack_walk); >>> - else >>> + } else >>> start_backtrace(&frame, thread_saved_fp(task), >>> thread_saved_pc(task)); >> >> I don't like abusing the cookie here. It's void * as it's meant to be an >> opaque type. I'd rather skip the first two frames in walk_stackframe() >> instead before invoking fn(). > > I agree that we shouldn't touch cookie here. > > I don't think that it's right to bodge this inside walk_stackframe(), > since that'll add bogus skipping for the case starting with regs in the > current task. If we need a bodge, it has to live in arch_stack_walk() > where we set up the initial unwinding state. > > In another thread, we came to the conclusion that arch_stack_walk() > should start at its parent, and its parent should add any skipping it > requires. > > Currently, arch_stack_walk() is off-by-one, and we can bodge that by > using __builtin_frame_address(1), though I'm waiting for some compiler > folk to confirm that's sound. Otherwise we need to add an assembly > trampoline to snapshot the FP, which is unfortunastely convoluted. > > This report suggests that a caller of arch_stack_walk() is off-by-one > too, which suggests a larger cross-architecture semantic issue. I'll try > to take a look tomorrow. > > Thanks, > Mark. > >> >> Prior to the conversion to ARCH_STACKWALK, we were indeed skipping two >> more entries in __save_stack_trace() if tsk == current. Something like >> below, completely untested: >> >> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c >> index ad20981dfda4..2a9f759aa41a 100644 >> --- a/arch/arm64/kernel/stacktrace.c >> +++ b/arch/arm64/kernel/stacktrace.c >> @@ -115,10 +115,15 @@ NOKPROBE_SYMBOL(unwind_frame); >> void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame, >> bool (*fn)(void *, unsigned long), void *data) >> { >> + /* for the current task, we don't want this function nor its caller */ >> + int skip = tsk == current ? 2 : 0; >> + >> while (1) { >> int ret; >> >> - if (!fn(data, frame->pc)) >> + if (skip) >> + skip--; >> + else if (!fn(data, frame->pc)) >> break; >> ret = unwind_frame(tsk, frame); >> if (ret < 0) >> >> >> -- >> Catalin > This change will make kmemleak broken. Maybe the reason is what Mark pointed out. I will try to check out. -- Regards Chen Jun