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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 66B05C433B4 for ; Tue, 11 May 2021 17:41:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22B7461378 for ; Tue, 11 May 2021 17:41:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231587AbhEKRmR (ORCPT ); Tue, 11 May 2021 13:42:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36112 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231454AbhEKRmR (ORCPT ); Tue, 11 May 2021 13:42:17 -0400 Received: from mail-ej1-x630.google.com (mail-ej1-x630.google.com [IPv6:2a00:1450:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C416C06174A for ; Tue, 11 May 2021 10:41:09 -0700 (PDT) Received: by mail-ej1-x630.google.com with SMTP id b25so30948502eju.5 for ; Tue, 11 May 2021 10:41:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=QcFKWwsZQjmPduID1brcOmkZRMBIxn7KkXSMhmWfN84=; b=bnraoL6UQxTGs4ccEMEF6UJp8+3or2YhhuY9sJ66zaHkd+NSFHpVnfIm+YKpgHYp47 3bRuYeZqAo4y6moDMtHfbd4voPJE0BgJlZmV6qxjEkBeT2gsw0EUCTixHOobrkIAcJdH beuoI1/oneZB8ZNK6w2wGnkDbrMTeJj0oBWDabaQ3JjH55ZkTRy35cq4tMEftXcicJ/A W2Xuuzj/lSJ+Usst8riFY4snpfv+rdpamWKfnQsJ9XkUtyPRVDymjp1ws7Y4HIt+fkAz YXwFrGM4GtWNUXE7fRq8GQrXzLtt/tAv22E0vDz26eBJB7P5xno79MHxejqfGms73+Cm bC7w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-transfer-encoding; bh=QcFKWwsZQjmPduID1brcOmkZRMBIxn7KkXSMhmWfN84=; b=bNIx6QIb1fc24xWv12n5Nlj18RlsouC9JpKrywUCYl2FE6l57Uzf0PtYijpePUqR2f HIhQ5KJ/kKGPlV2MMgvhNLFQQyeb/MStBkYxYCEk9WAf3Jjz7VHSo7kY/DX4vlnAU5Yg lP3Xryo/cr9AO0LRqDvI5Pf6QVXR3crWN/7jMGSxiMMHagGCk7GU2VwzvKD5OOG7j9Un DyGSWBvX7/ezuH2h8UsbiwPL3ilm2ge4GJ6UYLC3NLDtbr3pwEAoF1pxBltldQbtZyuM oN40Kc0f9KRIFCf6AY85RSWzDYnYQdydf7skdTMULahQyrWH/Ro3Z1xDoBnfGBQVH5RL skUw== X-Gm-Message-State: AOAM533e3EHnTH3x19gpusfMvH+IupYTbcjPhWwTKp1vdueAcyf/9H76 txe6QsoySOSlimZs6JGKowJbyfOsoPI= X-Google-Smtp-Source: ABdhPJyov//rnOwePuVhx2EJdtjgAHk2hf/dp+DSDTXoeSvudhZW0deiDLdm45SWhAeQSowrdo2WWA== X-Received: by 2002:a17:906:3544:: with SMTP id s4mr33548521eja.73.1620754868231; Tue, 11 May 2021 10:41:08 -0700 (PDT) Received: from avogadro.redhat.com ([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id v23sm15239073eda.8.2021.05.11.10.41.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 May 2021 10:41:07 -0700 (PDT) Sender: Paolo Bonzini From: Paolo Bonzini To: kvm@vger.kernel.org Cc: Alexandru Elisei Subject: [PATCH kvm-unit-tests 1/2] libcflat: clean up and complete long division routines Date: Tue, 11 May 2021 19:41:05 +0200 Message-Id: <20210511174106.703235-2-pbonzini@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210511174106.703235-1-pbonzini@redhat.com> References: <20210511174106.703235-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Avoid possible uninitialized variables on machines where division by zero does not trap. Add __divmoddi4, and do not use 64-bit math unnecessarily in __moddi3 and __divdi3. Reported-by: Alexandru Elisei Signed-off-by: Paolo Bonzini --- lib/ldiv32.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) diff --git a/lib/ldiv32.c b/lib/ldiv32.c index 96f4b35..c39fccd 100644 --- a/lib/ldiv32.c +++ b/lib/ldiv32.c @@ -1,6 +1,7 @@ #include extern uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t *p_rem); +extern int64_t __divmoddi4(int64_t num, int64_t den, int64_t *p_rem); extern int64_t __moddi3(int64_t num, int64_t den); extern int64_t __divdi3(int64_t num, int64_t den); extern uint64_t __udivdi3(uint64_t num, uint64_t den); @@ -11,8 +12,11 @@ uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t *p_rem) uint64_t quot = 0; /* Trigger a division by zero at run time (trick taken from iPXE). */ - if (den == 0) + if (den == 0) { + if (p_rem) + *p_rem = 0; return 1/((unsigned)den); + } if (num >= den) { /* Align den to num to avoid wasting time on leftmost zero bits. */ @@ -35,9 +39,27 @@ uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t *p_rem) return quot; } +int64_t __divmoddi4(int64_t num, int64_t den, int64_t *p_rem) +{ + int32_t nmask = num < 0 ? -1 : 0; + int32_t qmask = (num ^ den) < 0 ? -1 : 0; + uint64_t quot; + + /* Compute absolute values and do an unsigned division. */ + num = (num + nmask) ^ nmask; + if (den < 0) + den = -den; + + /* Copy sign of num^den into quotient, sign of num into remainder. */ + quot = (__divmoddi4(num, den, p_rem) + qmask) ^ qmask; + if (p_rem) + *p_rem = (*p_rem + nmask) ^ nmask; + return quot; +} + int64_t __moddi3(int64_t num, int64_t den) { - uint64_t mask = num < 0 ? -1 : 0; + int32_t mask = num < 0 ? -1 : 0; /* Compute absolute values and do an unsigned division. */ num = (num + mask) ^ mask; @@ -50,7 +72,7 @@ int64_t __moddi3(int64_t num, int64_t den) int64_t __divdi3(int64_t num, int64_t den) { - uint64_t mask = (num ^ den) < 0 ? -1 : 0; + int32_t mask = (num ^ den) < 0 ? -1 : 0; /* Compute absolute values and do an unsigned division. */ if (num < 0) -- 2.31.1