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=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 DC371C10F0E for ; Mon, 8 Apr 2019 00:33:30 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id AD6E420B1F for ; Mon, 8 Apr 2019 00:33:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ughl4cGr"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="j04YICGE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD6E420B1F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Mime-Version:References:In-Reply-To: Message-Id:Subject: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=jsdILaWU/Y2eRQ0MecfdbdiNMb4W56m696KnWaeohEg=; b=ughl4cGrUb6ClA L08wURq57eUzNMQemUFpzDWXisRCPVUGGJ6wXTZ2gyNhPxkJICHpyc75/sbV5zhTypk6WFMlC34E2 IeVMv+Nj10AezzfzeQd/cLaXRGoKusLn6OG+vOzFu9n2L01z1GCDJ5bPvXU7MqhGWRNXX7z5rKUco J3l6LwHOSI3n0HzmQHVcKgBtpnycFMHX+VjPSmsB0xAQrOyFOP/lsGKwiLQw2fxojViPKAaKWGouw 6HUk2UV9Nlm79nkZvv0aTxsGEIr9gtkTyPAASDCQ1uwmzEtxO1yPCfpfmtkkNN0iKcMCOcjiL8ZID eqXmlRNZkXHqIbGyQXxg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hDIE4-0001BD-So; Mon, 08 Apr 2019 00:33:28 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hDIE1-0001Ag-87 for linux-arm-kernel@lists.infradead.org; Mon, 08 Apr 2019 00:33:26 +0000 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 CF06C20883; Mon, 8 Apr 2019 00:33:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554683604; bh=4WjgolGb0uGqjgZKtZxFbvcwldWnc+OxMCHji4IyQjc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=j04YICGEIQR+3gYHPAhTjMXqr2YlQ+BpriV9SACWLm1+zU8lEO1uPzretrQU8NXv1 7xBegn5c3BXlhpZMMOgpv7rg+npHzTktE+rR7c3IZVgAcQUCBJLF+IgL3115X/Q0AV BahsrmPbUL2F609hVNzoXOkHjb50ORQYX5YTYUIk= Date: Mon, 8 Apr 2019 09:33:20 +0900 From: Masami Hiramatsu To: Will Deacon Subject: Re: [PATCH] arm64: ptrace: Add function argument access API Message-Id: <20190408093320.35f4050788937c995ca56a6b@kernel.org> In-Reply-To: <20190403120649.GB29409@fuggles.cambridge.arm.com> References: <155289594227.10570.1879705446198840331.stgit@devnote2> <20190403120649.GB29409@fuggles.cambridge.arm.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190407_173325_323329_21B4FDE4 X-CRM114-Status: GOOD ( 23.30 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Oleg Nesterov , Steven Rostedt , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Will, On Wed, 3 Apr 2019 13:06:49 +0100 Will Deacon wrote: > On Mon, Mar 18, 2019 at 04:59:02PM +0900, Masami Hiramatsu wrote: > > Add regs_get_argument() which returns N th argument of the function > > call. On arm64, it supports up to 8th argument. > > Note that this chooses most probably assignment, in some case > > it can be incorrect (e.g. passing data structure or floating > > point etc.) > > > > This enables ftrace kprobe events to access kernel function > > arguments via $argN syntax. > > > > Signed-off-by: Masami Hiramatsu > > --- > > arch/arm64/Kconfig | 1 + > > arch/arm64/include/asm/ptrace.h | 18 ++++++++++++++++++ > > 2 files changed, 19 insertions(+) > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > index 117b2541ef3d..6ba0da4be73c 100644 > > --- a/arch/arm64/Kconfig > > +++ b/arch/arm64/Kconfig > > @@ -148,6 +148,7 @@ config ARM64 > > select HAVE_PERF_REGS > > select HAVE_PERF_USER_STACK_DUMP > > select HAVE_REGS_AND_STACK_ACCESS_API > > + select HAVE_FUNCTION_ARG_ACCESS_API > > select HAVE_RCU_TABLE_FREE > > select HAVE_RCU_TABLE_INVALIDATE > > select HAVE_RSEQ > > diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h > > index ec60174c8c18..cfa1bc9b8b70 100644 > > --- a/arch/arm64/include/asm/ptrace.h > > +++ b/arch/arm64/include/asm/ptrace.h > > @@ -305,6 +305,24 @@ static inline unsigned long regs_return_value(struct pt_regs *regs) > > return regs->regs[0]; > > } > > > > +/** > > + * regs_get_kernel_argument() - get Nth function argument in kernel > > + * @regs: pt_regs of that context > > + * @n: function argument number (start from 0) > > + * > > + * regs_get_argument() returns @n th argument of the function call. > > + * Note that this chooses most probably assignment, in some case > > + * it can be incorrect. > > In which cases would it be incorrect? I can imagine varargs causing > problems, but are there others? As far as I can read "Procedure Call Standard for the ARM 64-bit Architecture(AArch64) 5.4.2 Parameter Passing Rules", it may not return correct data if the target function has a parameter which is 16bytes or bigger size. Of course that is just a limitation of this interface. But anyway, it can return wrong data for the parameter after such big parameters. I think, for func(data-struct-128bits p1, u64 p2), p1 is stored into r0 and r1, and p2 is stored r2, is that correct? (Of course any SIMD/float parameter passed to the function, it also can not correctly get, but in the kernel we can ignore it.) > > +static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs, > > + unsigned int n) > > +{ > > +#define NR_REG_ARGUMENTS 8 > > + if (n < NR_REG_ARGUMENTS) > > + return regs_get_register(regs, n << 3); > > You can use pt_regs_read_reg() to avoid the shift here. Ah, right! Thank you, -- Masami Hiramatsu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel