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=-6.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 F3849C282C7 for ; Thu, 31 Jan 2019 10:20:47 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 78C2B218AF for ; Thu, 31 Jan 2019 10:20:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="SIRd5y6K" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 78C2B218AF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 43qx8C5RCQzDqbq for ; Thu, 31 Jan 2019 21:20:43 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=c-s.fr (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@c-s.fr; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=c-s.fr header.i=@c-s.fr header.b="SIRd5y6K"; dkim-atps=neutral Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 43qwtc3CS8zDqTT for ; Thu, 31 Jan 2019 21:08:56 +1100 (AEDT) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 43qwtX1y3Rz9tyxD; Thu, 31 Jan 2019 11:08:52 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=SIRd5y6K; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id dg1E1baNvEeN; Thu, 31 Jan 2019 11:08:52 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 43qwtX0wJkz9tyxB; Thu, 31 Jan 2019 11:08:52 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1548929332; bh=yMq6si7jSH6bQUbdVukf4mkG8sOf1bePhLPx15JBPBI=; h=In-Reply-To:References:From:Subject:To:Cc:Date:From; b=SIRd5y6KTz59S6MR0NxmvTvQnbh0EppDwx+cUqIvuKIgn3iwerFhyJ9ng4B1INBAj TXaVhccbqh3kuEnbcUAQ5mW+HdTJBMRlkvL+sGlYkNnOTPZwNaYlZK/1uAor3xnAKo Nq3LMd9nwv0fFdoaOzpyJVZFU1CxMX9GP1/1cpQc= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 437C28B814; Thu, 31 Jan 2019 11:08:53 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id zql9HpmPwQCG; Thu, 31 Jan 2019 11:08:53 +0100 (CET) Received: from po16846vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 05CB58B78D; Thu, 31 Jan 2019 11:08:53 +0100 (CET) Received: by po16846vm.idsi0.si.c-s.fr (Postfix, from userid 0) id 9AFEA72E14; Thu, 31 Jan 2019 10:08:52 +0000 (UTC) Message-Id: <38755f11005b121f1483736f565f6fd24c827e14.1548852243.git.christophe.leroy@c-s.fr> In-Reply-To: References: From: Christophe Leroy Subject: [PATCH v15 05/13] powerpc: prep stack walkers for THREAD_INFO_IN_TASK To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Nicholas Piggin Date: Thu, 31 Jan 2019 10:08:52 +0000 (UTC) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" [text copied from commit 9bbd4c56b0b6 ("arm64: prep stack walkers for THREAD_INFO_IN_TASK")] When CONFIG_THREAD_INFO_IN_TASK is selected, task stacks may be freed before a task is destroyed. To account for this, the stacks are refcounted, and when manipulating the stack of another task, it is necessary to get/put the stack to ensure it isn't freed and/or re-used while we do so. This patch reworks the powerpc stack walking code to account for this. When CONFIG_THREAD_INFO_IN_TASK is not selected these perform no refcounting, and this should only be a structural change that does not affect behaviour. Acked-by: Mark Rutland Signed-off-by: Christophe Leroy --- arch/powerpc/kernel/process.c | 23 +++++++++++++++++++++-- arch/powerpc/kernel/stacktrace.c | 29 ++++++++++++++++++++++++++--- 2 files changed, 47 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index ce393df243aa..4ffbb677c9f5 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -2027,7 +2027,7 @@ int validate_sp(unsigned long sp, struct task_struct *p, EXPORT_SYMBOL(validate_sp); -unsigned long get_wchan(struct task_struct *p) +static unsigned long __get_wchan(struct task_struct *p) { unsigned long ip, sp; int count = 0; @@ -2053,6 +2053,20 @@ unsigned long get_wchan(struct task_struct *p) return 0; } +unsigned long get_wchan(struct task_struct *p) +{ + unsigned long ret; + + if (!try_get_task_stack(p)) + return 0; + + ret = __get_wchan(p); + + put_task_stack(p); + + return ret; +} + static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH; void show_stack(struct task_struct *tsk, unsigned long *stack) @@ -2067,6 +2081,9 @@ void show_stack(struct task_struct *tsk, unsigned long *stack) int curr_frame = 0; #endif + if (!try_get_task_stack(tsk)) + return; + sp = (unsigned long) stack; if (tsk == NULL) tsk = current; @@ -2081,7 +2098,7 @@ void show_stack(struct task_struct *tsk, unsigned long *stack) printk("Call Trace:\n"); do { if (!validate_sp(sp, tsk, STACK_FRAME_OVERHEAD)) - return; + break; stack = (unsigned long *) sp; newsp = stack[0]; @@ -2121,6 +2138,8 @@ void show_stack(struct task_struct *tsk, unsigned long *stack) sp = newsp; } while (count++ < kstack_depth_to_print); + + put_task_stack(tsk); } #ifdef CONFIG_PPC64 diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c index e2c50b55138f..f80e1129c0f2 100644 --- a/arch/powerpc/kernel/stacktrace.c +++ b/arch/powerpc/kernel/stacktrace.c @@ -67,12 +67,17 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) { unsigned long sp; + if (!try_get_task_stack(tsk)) + return; + if (tsk == current) sp = current_stack_pointer(); else sp = tsk->thread.ksp; save_context_stack(trace, sp, tsk, 0); + + put_task_stack(tsk); } EXPORT_SYMBOL_GPL(save_stack_trace_tsk); @@ -84,9 +89,8 @@ save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace) EXPORT_SYMBOL_GPL(save_stack_trace_regs); #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE -int -save_stack_trace_tsk_reliable(struct task_struct *tsk, - struct stack_trace *trace) +static int __save_stack_trace_tsk_reliable(struct task_struct *tsk, + struct stack_trace *trace) { unsigned long sp; unsigned long stack_page = (unsigned long)task_stack_page(tsk); @@ -193,6 +197,25 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk, } return 0; } + +int save_stack_trace_tsk_reliable(struct task_struct *tsk, + struct stack_trace *trace) +{ + int ret; + + /* + * If the task doesn't have a stack (e.g., a zombie), the stack is + * "reliably" empty. + */ + if (!try_get_task_stack(tsk)) + return 0; + + ret = __save_stack_trace_tsk_reliable(tsk, trace); + + put_task_stack(tsk); + + return ret; +} EXPORT_SYMBOL_GPL(save_stack_trace_tsk_reliable); #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */ -- 2.13.3