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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 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 D8322C74A42 for ; Thu, 11 Jul 2019 03:25:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD34C21019 for ; Thu, 11 Jul 2019 03:25:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727927AbfGKDZB (ORCPT ); Wed, 10 Jul 2019 23:25:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:46430 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725977AbfGKDZB (ORCPT ); Wed, 10 Jul 2019 23:25:01 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 81CB0206B8; Thu, 11 Jul 2019 03:24:59 +0000 (UTC) Date: Wed, 10 Jul 2019 23:24:56 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: tglx@linutronix.de, bp@alien8.de, mingo@kernel.org, luto@kernel.org, torvalds@linux-foundation.org, hpa@zytor.com, dave.hansen@linux.intel.com, jgross@suse.com, linux-kernel@vger.kernel.org, zhe.he@windriver.com, joel@joelfernandes.org, devel@etsukata.com Subject: Re: [PATCH v2 6/7] x86/entry/64: Remove TRACE_IRQS_*_DEBUG Message-ID: <20190710232456.5f2de961@oasis.local.home> In-Reply-To: <20190704200050.591915266@infradead.org> References: <20190704195555.580363209@infradead.org> <20190704200050.591915266@infradead.org> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 04 Jul 2019 21:56:01 +0200 Peter Zijlstra wrote: > Since INT3/#BP no longer runs on an IST, this workaround is no longer > required. > > Tested by running lockdep+ftrace as described in the initial commit: > > 5963e317b1e9 ("ftrace/x86: Do not change stacks in DEBUG when calling lockdep") It looks like a clean revert, and it passed my ftrace smoke tests with lockdep enabled (although I triggered a locked warning unrelated to this, with the text_mutex and module_mutex, but I'm hoping my tree has the fixes for that). Reviewed-by: Steven Rostedt (VMware) Hmm, does this mean we can remove the IDT switching in the NMI handler as well? -- Steve > > Signed-off-by: Peter Zijlstra (Intel) > --- > arch/x86/entry/entry_64.S | 46 ++-------------------------------------------- > 1 file changed, 2 insertions(+), 44 deletions(-) > > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -68,44 +68,6 @@ END(native_usergs_sysret64) > .endm > > /* > - * When dynamic function tracer is enabled it will add a breakpoint > - * to all locations that it is about to modify, sync CPUs, update > - * all the code, sync CPUs, then remove the breakpoints. In this time > - * if lockdep is enabled, it might jump back into the debug handler > - * outside the updating of the IST protection. (TRACE_IRQS_ON/OFF). > - * > - * We need to change the IDT table before calling TRACE_IRQS_ON/OFF to > - * make sure the stack pointer does not get reset back to the top > - * of the debug stack, and instead just reuses the current stack. > - */ > -#if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_TRACE_IRQFLAGS) > - > -.macro TRACE_IRQS_OFF_DEBUG > - call debug_stack_set_zero > - TRACE_IRQS_OFF > - call debug_stack_reset > -.endm > - > -.macro TRACE_IRQS_ON_DEBUG > - call debug_stack_set_zero > - TRACE_IRQS_ON > - call debug_stack_reset > -.endm > - > -.macro TRACE_IRQS_IRETQ_DEBUG > - btl $9, EFLAGS(%rsp) /* interrupts off? */ > - jnc 1f > - TRACE_IRQS_ON_DEBUG > -1: > -.endm > - > -#else > -# define TRACE_IRQS_OFF_DEBUG TRACE_IRQS_OFF > -# define TRACE_IRQS_ON_DEBUG TRACE_IRQS_ON > -# define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ > -#endif > - > -/* > * 64-bit SYSCALL instruction entry. Up to 6 arguments in registers. > * > * This is the only entry point used for 64-bit system calls. The > @@ -879,11 +841,7 @@ apicinterrupt IRQ_WORK_VECTOR irq_work > GET_CR2_INTO(%rdx); /* can clobber %rax */ > .endif > > - .if \shift_ist != -1 > - TRACE_IRQS_OFF_DEBUG /* reload IDT in case of recursion */ > - .else > TRACE_IRQS_OFF > - .endif > > .if \paranoid == 0 > testb $3, CS(%rsp) > @@ -1292,7 +1250,7 @@ END(paranoid_entry) > ENTRY(paranoid_exit) > UNWIND_HINT_REGS > DISABLE_INTERRUPTS(CLBR_ANY) > - TRACE_IRQS_OFF_DEBUG > + TRACE_IRQS_OFF > > /* Handle GS depending on FSGSBASE availability */ > ALTERNATIVE "jmp .Lparanoid_exit_checkgs", "nop",X86_FEATURE_FSGSBASE > @@ -1312,7 +1270,7 @@ ENTRY(paranoid_exit) > jmp .Lparanoid_exit_restore > > .Lparanoid_exit_no_swapgs: > - TRACE_IRQS_IRETQ_DEBUG > + TRACE_IRQS_IRETQ > /* Always restore stashed CR3 value (see paranoid_entry) */ > RESTORE_CR3 scratch_reg=%rbx save_reg=%r14 > >