From patchwork Thu Jan 30 16:08:39 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christophe Leroy X-Patchwork-Id: 11358263 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DD853112B for ; Thu, 30 Jan 2020 16:10:20 +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 9B0B620707 for ; Thu, 30 Jan 2020 16:10:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="hs+jYURo"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="k1nV5HNo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9B0B620707 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.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:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Date:To:Subject: From:References:In-Reply-To:Message-Id:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=DXDYKTDnoT+u0dLoi/Km4fVuZMsGGxdzpoNTV00vEBI=; b=hs+jYURo+V4adlFk08w/MsoLld CCQd5CcWWIBqznwlvUilLkzGHd5BwPGX7QytWc+5vHDGEcWY+SQKjxrbdlmmZJRndkwww2/gevNyv /fLlhkAf5eDV0ZnWM4frNDbtc6PfpUkiKgLD/rhM1U6HNM0NVqAs2VeZ+MNZT6A5qZYjPwpYTEUWJ hqrtgk8T8v/6u0AdQL1yGdSvO48k4avsTBilPK9zfIG48fgY4n9rsknOSvQSqSqPsc2AoAXgYqyZ3 ocDYB3UVvIG1a8SMVRDLwEsEy/IjjSN1olVF/rSCSHxUoDi0iCVZyXSkPQLmIwxinXmdbuWrze8WR /D0GYP7w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1ixCOX-00038b-HW; Thu, 30 Jan 2020 16:10:17 +0000 Received: from pegase1.c-s.fr ([93.17.236.30]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1ixCN1-0000ZR-45 for linux-arm-kernel@lists.infradead.org; Thu, 30 Jan 2020 16:08:47 +0000 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 487ldf4nKzz9v6KS; Thu, 30 Jan 2020 17:08:38 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=k1nV5HNo; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id zEchKtxoY4H7; Thu, 30 Jan 2020 17:08:38 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 487ldf3KlDz9v6KL; Thu, 30 Jan 2020 17:08:38 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1580400518; bh=4Kvsye4EMnIWruMrubU2uEdzOim6m1UTTTl/5OsNwDs=; h=In-Reply-To:References:From:Subject:To:Cc:Date:From; b=k1nV5HNo6Z2IrIBX+SaaIKQiwfqmxiGqGobyiJMGtGs/qsVlUVN6uqGFGqCXCQBBX oYi0dvc9bnGnv2gGUmnZDs/rlVHOXIphaNA3L790NbL4gYT4lQFP/lWLd3BOJcHwdr Z34gMu3hoEcwW/wmPHOdvX3sxhvVNl4WXKQxEebM= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id DFEE78B87B; Thu, 30 Jan 2020 17:08:39 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id OdXw842o2kSJ; Thu, 30 Jan 2020 17:08:39 +0100 (CET) Received: from po14934vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 8723C8B877; Thu, 30 Jan 2020 17:08:39 +0100 (CET) Received: by po14934vm.idsi0.si.c-s.fr (Postfix, from userid 0) id 53A6765283; Thu, 30 Jan 2020 16:08:39 +0000 (UTC) Message-Id: In-Reply-To: References: From: Christophe Leroy Subject: [PATCH v5 5/6] lib/vdso: Allow architectures to override the ns shift operation To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , nathanl@linux.ibm.com, arnd@arndb.de, tglx@linutronix.de, vincenzo.frascino@arm.com, luto@kernel.org Date: Thu, 30 Jan 2020 16:08:39 +0000 (UTC) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200130_080843_506825_CE6A2E97 X-CRM114-Status: UNSURE ( 9.40 ) X-CRM114-Notice: Please train this message. X-Spam-Score: -0.2 (/) X-Spam-Report: SpamAssassin version 3.4.3 on bombadil.infradead.org summary: Content analysis details: (-0.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [93.17.236.30 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org On powerpc/32, GCC (8.1) generates pretty bad code for the ns >>= vd->shift operation taking into account that the shift is always <= 32 and the upper part of the result is likely to be nul. GCC makes reversed assumptions considering the shift to be likely >= 32 and the upper part to be like not nul. unsigned long long shift(unsigned long long x, unsigned char s) { return x >> s; } results in: 00000018 : 18: 35 25 ff e0 addic. r9,r5,-32 1c: 41 80 00 10 blt 2c 20: 7c 64 4c 30 srw r4,r3,r9 24: 38 60 00 00 li r3,0 28: 4e 80 00 20 blr 2c: 54 69 08 3c rlwinm r9,r3,1,0,30 30: 21 45 00 1f subfic r10,r5,31 34: 7c 84 2c 30 srw r4,r4,r5 38: 7d 29 50 30 slw r9,r9,r10 3c: 7c 63 2c 30 srw r3,r3,r5 40: 7d 24 23 78 or r4,r9,r4 44: 4e 80 00 20 blr Even when forcing the shift with an &= 31, it still considers the shift as likely >= 32. Define a vdso_shift_ns() macro that can be overriden by architectures. Signed-off-by: Christophe Leroy --- lib/vdso/gettimeofday.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c index 0b4b71880f22..a5ee53d1ecee 100644 --- a/lib/vdso/gettimeofday.c +++ b/lib/vdso/gettimeofday.c @@ -38,6 +38,13 @@ u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult) } #endif +#ifndef vdso_shift_ns +static __always_inline u64 vdso_shift_ns(u64 ns, unsigned long shift) +{ + return ns >> shift; +} +#endif + #ifdef CONFIG_TIME_NS static int do_hres_timens(const struct vdso_data *vdns, clockid_t clk, struct __kernel_timespec *ts) @@ -134,7 +141,7 @@ static __always_inline int do_hres(const struct vdso_data *vd, clockid_t clk, #endif ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult); - ns >>= vd->shift; + ns = vdso_shift_ns(ns, vd->shift); sec = vdso_ts->sec; } while (unlikely(vdso_read_retry(vd, seq)));