From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754703AbaESPc5 (ORCPT ); Mon, 19 May 2014 11:32:57 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:39247 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751074AbaESPcz (ORCPT ); Mon, 19 May 2014 11:32:55 -0400 Date: Mon, 19 May 2014 16:32:20 +0100 From: Will Deacon To: Larry Bassel Cc: Catalin Marinas , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linaro-kernel@lists.linaro.org" , "khilman@linaro.org" Subject: Re: [PATCH v3 2/2] arm64: enable context tracking Message-ID: <20140519153220.GH15130@arm.com> References: <1399672310-9061-1-git-send-email-larry.bassel@linaro.org> <1399672310-9061-3-git-send-email-larry.bassel@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1399672310-9061-3-git-send-email-larry.bassel@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 09, 2014 at 10:51:50PM +0100, Larry Bassel wrote: > Make calls to ct_user_enter when the kernel is exited > and ct_user_exit when the kernel is entered (in el0_da, > el0_ia, el0_svc, el0_irq and all of the "error" paths). > > These macros expand to function calls which will only work > properly if el0_sync and related code has been rearranged > (in a previous patch of this series). > > The calls to ct_user_exit are made after hw debugging has been > enabled (enable_dbg). > > The call to ct_user_enter is made at the beginning of the > kernel_exit macro. > > This patch is based on earlier work by Kevin Hilman. [...] > diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h > index 720e70b..301ea6a 100644 > --- a/arch/arm64/include/asm/thread_info.h > +++ b/arch/arm64/include/asm/thread_info.h > @@ -108,6 +108,7 @@ static inline struct thread_info *current_thread_info(void) > #define TIF_SINGLESTEP 21 > #define TIF_32BIT 22 /* 32bit process */ > #define TIF_SWITCH_MM 23 /* deferred switch_mm */ > +#define TIF_NOHZ 24 > > #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) > #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index 136bb7d..c839bab 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -30,6 +30,44 @@ > #include > > /* > + * Context tracking subsystem. Used to instrument transitions > + * between user and kernel mode. > + */ > + .macro ct_user_exit, save = 0 > +#ifdef CONFIG_CONTEXT_TRACKING > + bl context_tracking_user_exit > + .if \save == 1 It would be clearer to refer to the parameter as `restore' for the exit case, I reckon. > + /* > + * save/restore needed during syscalls. Restore syscall arguments from > + * the values already saved on stack during kernel_entry > + */ > + ldp x0, x1, [sp] > + ldp x2, x3, [sp, #S_X2] > + ldp x4, x5, [sp, #S_X4] > + ldp x6, x7, [sp, #S_X6] > + .endif > +#endif > + .endm [...] > .macro kernel_exit, el, ret = 0 > ldp x21, x22, [sp, #S_PC] // load ELR, SPSR > .if \el == 0 > + ct_user_enter \ret > ldr x23, [sp, #S_SP] // load return stack pointer > .endif > .if \ret You should check how this patch applies against my debug exception rework: 2a2830703a23 ("arm64: debug: avoid accessing mdscr_el1 on fault paths where possible") in today's next. As well as addressing the conflicts, it's worth nothing that the thread_info becomes available in tsk much earlier for exceptions from userspace with that patch applied. Will