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 C0E6CC433FE for ; Fri, 18 Nov 2022 12:33:06 +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:In-Reply-To:MIME-Version:References: 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=i6nMiK2YpuUB4frOyguCj/XuCqZO4jjfbXQ9T8JD384=; b=OZ35sCTj4vsjYF tv1wPS4en6nykX/c1HHQaumpBV+tpW9OHBPKy62e38H78Bno7saKDgpgRpNSIQXB0SY7jiwy9XENl Oh5XBIxeUFPVwY6cJGrfQz5Tv3qWs2sQNSjZoHAZpKs1CXdBB9D6enPCkWt3Kvju5TXjw2juah0sy 2xGgvLfTJu7uUK2MLlKrGog59BcI/vFwVo02ITE3FWrugrHFn3TcJpQ6FDJbUNrM8WmimhoXPkw0p rBtdb2r3T3buCasNAApW+LlBdBkCiWeSF/y5JYYsxyDa/Jj7oJtRFiZOZoLLlJM7nJZoNsu2n4+Bp tsY85ikDxfmZd1x9B4ng==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ow0XI-003teS-CP; Fri, 18 Nov 2022 12:32:00 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ow0XF-003tdE-RE for linux-arm-kernel@lists.infradead.org; Fri, 18 Nov 2022 12:31:59 +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 dfw.source.kernel.org (Postfix) with ESMTPS id DC02E624C6; Fri, 18 Nov 2022 12:31:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0EFBC433D6; Fri, 18 Nov 2022 12:31:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668774715; bh=Nh3NzJbEfvZTCSH3QvtCEwh5yBDVeSLUhz1ZQCC1KD8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=K9ZdtXF0U/keAUEDERBh8h2v7ZUwV9O2Wl5Gm68a5Hh3izm3vmUk8+H7cySeSRaJR SCU4lz5MX5ZNV0AwMNMa2mdARmapdZQqVXBURVYmCnvF1E4vaAaQPFPCnalw/fCw0L k+0qrMksCEUxmf8abkMcEpMrtOzpS1+wN0zN0jRuTyuRtid7j10AgjUueQILI3n+sp SQiFgrRctAuICj63oYSxdnHOZhOi45c9JjJ/iAFA0Sekk1RlXOtRSQQfY02KxeWmJd AopymhGU0kiiTHI+IaTJk7xEM3JdEjzVLrRG5dDOHhdSyN6a59WOBpDUfi3wYwMxyw am7cLpmdiq8bQ== Date: Fri, 18 Nov 2022 12:31:50 +0000 From: Will Deacon To: Mark Rutland Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, mhiramat@kernel.org, revest@chromium.org, rostedt@goodmis.org Subject: Re: [PATCH v2 4/4] ftrace: arm64: move from REGS to ARGS Message-ID: <20221118123149.GB3697@willie-the-truck> References: <20221103170520.931305-1-mark.rutland@arm.com> <20221103170520.931305-5-mark.rutland@arm.com> <20221115112701.GB32523@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221118_043157_976624_5F17A834 X-CRM114-Status: GOOD ( 23.71 ) 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, Nov 17, 2022 at 10:52:15AM +0000, Mark Rutland wrote: > On Tue, Nov 15, 2022 at 11:27:03AM +0000, Will Deacon wrote: > > On Thu, Nov 03, 2022 at 05:05:20PM +0000, Mark Rutland wrote: > > > This commit replaces arm64's support for FTRACE_WITH_REGS with support > > > for FTRACE_WITH_ARGS. This removes some overhead and complexity, and > > > removes some latent issues with inconsistent presentation of struct > > > pt_regs (which can only be reliably saved/restored at exception > > > boundaries). > > > > [...] > > > > > @@ -78,10 +77,71 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) > > > return addr; > > > } > > > > > > -#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS > > > struct dyn_ftrace; > > > struct ftrace_ops; > > > -struct ftrace_regs; > > > + > > > +#define arch_ftrace_get_regs(regs) NULL > > > + > > > +struct ftrace_regs { > > > + /* x0 - x8 */ > > > + unsigned long regs[9]; > > > + unsigned long __unused; > > > + > > > + unsigned long fp; > > > + unsigned long lr; > > > + > > > + unsigned long sp; > > > + unsigned long pc; > > > +}; > > > + > > > +static __always_inline unsigned long > > > +ftrace_regs_get_instruction_pointer(const struct ftrace_regs *fregs) > > > +{ > > > + return fregs->pc; > > > +} > > > + > > > +static __always_inline void > > > +ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs, > > > + unsigned long pc) > > > +{ > > > + fregs->pc = pc; > > > +} > > > + > > > +static __always_inline unsigned long > > > +ftrace_regs_get_stack_pointer(const struct ftrace_regs *fregs) > > > +{ > > > + return fregs->sp; > > > +} > > > + > > > +static __always_inline unsigned long > > > +ftrace_regs_get_argument(struct ftrace_regs *fregs, unsigned int n) > > > +{ > > > + if (n < 8) > > > + return fregs->regs[n]; > > > > Where does this '8' come from? > > Because in AAPCS64 the arguments are in x0 to x7, as mentioned in the commit > message: > > | Per AAPCS64, all function call argument and return values are held in > | the following GPRs: > | > | * X0 - X7 : parameter / result registers > | * X8 : indirect result location register > | * SP : stack pointer (AKA SP) > > The 'indirect result location register' would be used when returning large > structures, and isn't a function argument as such. Ah gotcha, I was mainly wondering about the role of x8 in 'struct ftrace_regs', but now I see that the FETCH_OP_REG might want to get at that. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel