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 309FCC433EF for ; Thu, 6 Jan 2022 20:15:20 +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:Date: Message-ID:From:References:Cc:To:Subject:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=B7tCmisWUHiip/lHs1lbnig3IHIJkEyYefOh+QBkyk4=; b=dGLJ92i37XxX204b0wh+sSLHSI zFZTPHeD9Wo9GHbknwj52emg8exJLh2DewEpIR9NF2E+HBg8Q9JQVsNUzVtDpnQE2ASy4jdNRMpbp HkMn2gBjBViVNkKC45R9Ep9mS55D9a9PpibDoYDrMilg3nhr6quZ/ZDu30OGTzGIfWtrJvW71dkTL AEHpaW6tXyUzh0qphR4u7rydBJy5kcts8RGUaDcuyhVdybMeyj5+LZh8STUwFGLn0xLqt0gOAhFhb RIn36AKWd2DVA9VRV8b/Sr1dpWXEUz39y5ki2VIJPknGi+v52sbmh0zNt4mbIMGPO0/ZFxZKUsvBJ 75gsKy4A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1n5Z8g-001JCe-Jb; Thu, 06 Jan 2022 20:13:34 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1n5Z8c-001JCE-Vf for linux-arm-kernel@lists.infradead.org; Thu, 06 Jan 2022 20:13:32 +0000 Received: from [192.168.254.32] (unknown [47.187.212.181]) by linux.microsoft.com (Postfix) with ESMTPSA id 43ADE20B7179; Thu, 6 Jan 2022 12:13:28 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 43ADE20B7179 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1641500009; bh=ekYj3DAX7k1otTJH+CiC8/gklCIU2B9Xe1JBuVI/sBw=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=Oiu2my5rBcJoSQH5pZo+oeVgXcfU6fE1kjfMtvHqiQErYDow6cHMNYuCHZ9sVEBoh umkUgGZAAIG8LVQx6IaLpywvNxfl5C0u0hs5U+Inz6BCHNIUzt0SSi5FmPvBurdaKp jwDotueSyJv9cjmoRpbJ2orrSTgOIdtIKLPbpnPE= Subject: Re: [PATCH v12 04/10] arm64: Split unwind_init() To: Mark Rutland Cc: broonie@kernel.org, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org References: <0d0eb36f348fb5a6af6eb592c0525f6e94007328> <20220103165212.9303-1-madvenka@linux.microsoft.com> <20220103165212.9303-5-madvenka@linux.microsoft.com> From: "Madhavan T. Venkataraman" Message-ID: <5e527aab-955f-00f6-c326-3a1e3ed6fcff@linux.microsoft.com> Date: Thu, 6 Jan 2022 14:13:27 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220106_121331_159342_E2B4755E X-CRM114-Status: GOOD ( 29.04 ) 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 1/6/22 10:31 AM, Mark Rutland wrote: > On Mon, Jan 03, 2022 at 10:52:06AM -0600, madvenka@linux.microsoft.com wrote: >> From: "Madhavan T. Venkataraman" >> >> unwind_init() is currently a single function that initializes all of the >> unwind state. Split it into the following functions and call them >> appropriately: >> >> - unwind_init_regs() - initialize from regs passed by caller. >> >> - unwind_init_current() - initialize for the current task from the >> caller of arch_stack_walk(). >> >> - unwind_init_from_task() - initialize from the saved state of a >> task other than the current task. In this case, the other >> task must not be running. >> >> - unwind_init_common() - initialize fields that are common across >> the above 3 cases. >> >> This is done so that specialized initialization can be added to each case >> in the future. >> >> Signed-off-by: Madhavan T. Venkataraman >> --- >> arch/arm64/kernel/stacktrace.c | 50 +++++++++++++++++++++++++++------- >> 1 file changed, 40 insertions(+), 10 deletions(-) >> >> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c >> index a1a7ff93b84f..bd797e3f7789 100644 >> --- a/arch/arm64/kernel/stacktrace.c >> +++ b/arch/arm64/kernel/stacktrace.c >> @@ -33,11 +33,8 @@ >> */ >> >> >> -static void unwind_init(struct unwind_state *state, unsigned long fp, >> - unsigned long pc) >> +static void unwind_init_common(struct unwind_state *state) >> { >> - state->fp = fp; >> - state->pc = pc; >> #ifdef CONFIG_KRETPROBES >> state->kr_cur = NULL; >> #endif >> @@ -56,6 +53,40 @@ static void unwind_init(struct unwind_state *state, unsigned long fp, >> state->prev_type = STACK_TYPE_UNKNOWN; >> } >> >> +/* >> + * TODO: document requirements here. >> + */ >> +static inline void unwind_init_regs(struct unwind_state *state, >> + struct pt_regs *regs) >> +{ >> + state->fp = regs->regs[29]; >> + state->pc = regs->pc; >> +} > > When I suggested this back in: > > https://lore.kernel.org/linux-arm-kernel/20211123193723.12112-1-madvenka@linux.microsoft.com/T/#md91fbfe08ceab2a02d9f5c326e17997786e53208 > > ... my intent was that each unwind_init_from_*() helpers was the sole > initializer of the structure, and the caller only had to call one function. > That way it's not possible to construct an object with an erroneous combination > of arguments because the prototype enforces the set of arguments, and the > helper function can operate on a consistent snapshot of those arguments. > > So I'd much prefer that each of these helpers called unwind_init_common(), > rather than leaving that to the caller to do. I don't mind if those pass > arguments to unwind_init_common(), or explciitly initialize their respective > fields, but I don' think the caller should have to care about unwind_init_common(). > > I'd also prefer the unwind_init_from*() naming I'd previously suggested, so > that it's clear which direction information is flowing. > OK. No problem. >> >> + >> +/* >> + * TODO: document requirements here. >> + * >> + * Note: this is always inlined, and we expect our caller to be a noinline >> + * function, such that this starts from our caller's caller. >> + */ >> +static __always_inline void unwind_init_current(struct unwind_state *state) >> +{ >> + state->fp = (unsigned long)__builtin_frame_address(1); >> + state->pc = (unsigned long)__builtin_return_address(0); >> +} >> + >> +/* >> + * TODO: document requirements here. >> + * >> + * The caller guarantees that the task is not running. >> + */ >> +static inline void unwind_init_task(struct unwind_state *state, >> + struct task_struct *task) >> +{ >> + state->fp = thread_saved_fp(task); >> + state->pc = thread_saved_pc(task); >> +} >> + >> /* >> * Unwind from one frame record (A) to the next frame record (B). >> * >> @@ -194,15 +225,14 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry, >> { >> struct unwind_state state; >> >> + unwind_init_common(&state); > > As above, I really don't like that the caller has to call both the common > initializer and a specialized initializer here. > OK. Will change this. Thanks. Madhavan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel