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=-14.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 B7325C64E7B for ; Mon, 30 Nov 2020 23:28:26 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 40E7920709 for ; Mon, 30 Nov 2020 23:28:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="fenkOp0F" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 40E7920709 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.41522.74724 (Exim 4.92) (envelope-from ) id 1kjsaL-0006oY-LU; Mon, 30 Nov 2020 23:27:57 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 41522.74724; Mon, 30 Nov 2020 23:27:57 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kjsaL-0006oR-Gz; Mon, 30 Nov 2020 23:27:57 +0000 Received: by outflank-mailman (input) for mailman id 41522; Mon, 30 Nov 2020 23:27:55 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kjsaJ-0006oM-Nt for xen-devel@lists.xenproject.org; Mon, 30 Nov 2020 23:27:55 +0000 Received: from mail-wr1-x441.google.com (unknown [2a00:1450:4864:20::441]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 884c9a1d-8b19-42d0-bfb1-7ab34675d380; Mon, 30 Nov 2020 23:27:54 +0000 (UTC) Received: by mail-wr1-x441.google.com with SMTP id t4so18625592wrr.12 for ; Mon, 30 Nov 2020 15:27:54 -0800 (PST) Received: from [192.168.1.7] ([212.22.223.21]) by smtp.gmail.com with ESMTPSA id c2sm30888854wrf.68.2020.11.30.15.27.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Nov 2020 15:27:52 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 884c9a1d-8b19-42d0-bfb1-7ab34675d380 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=+oKm/Ah3AvG9Xr+iFRMsTLDsP/59Ag9EL+r+oaOfy8c=; b=fenkOp0FOx/NUI2txBM85a3ElWiUBpFWSNXeZdZpHu+aRY8Xs8/WC9I+VrU5p1rih6 PgrXie2ockUjfI0MkWZmhVnyk1Cpin8xD3LHry6EAe2K3HWxViavpTMqK+phqqm2ZpiC kre8yOfrHrgiw5ABSzs+wGiOgtuVp8wOyZIBUnSqJFJuKslNa8qu0YF0Atf3jV+PVCdY VCmy5ro4btrBt7zT18HvW2/klsA6o0HibLSlRhFy/z6Zctq5+xwdD0wkgi8xD92nalSM oQJF2MAS0AKSDHxF/vZEsXzeas51AHAGMJustGgwPCv9pk4yfY9kNuvWe/fhBlKFU+Qf ZhZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=+oKm/Ah3AvG9Xr+iFRMsTLDsP/59Ag9EL+r+oaOfy8c=; b=Y9E1t4Divem7wQ47PA74Vy8QKSU6E2SDQjn5pSpqUFjg5udUrw9nFUGz+fvUy8jbYf 26+p2ZHfBVP/CwoHJrecmKN20OrFJSAuUrt0ojF/qRQ5vCOOtmprrpM/BmN5DLmqapNZ BfVkuyQUEi652HZcWCAkeiOWjJm4hIowMKE1nCOEmdO/WajxDOUI6sqI7L1c58lq6VFa S2Ir2wcat9CH9LDyL4+PJj0DUrHi23fHwLjQ7bjE9MYIUoATebfjlmx/vIlUDaCCNJsF Wx4Jf1vLJQssQEj8rRBsY3TFKsF7ojAjuLoEz0fYMDPgTx2dLOf+rxbfFJEP8IXCNlU1 YgGg== X-Gm-Message-State: AOAM533Vu4d+L2c6qHLPE3hhYjWbZsE3sGgD2BufGAL8GdCf6j9SiC7O 3NiLVXAECqoCnSd3jYA01ws= X-Google-Smtp-Source: ABdhPJx4jv+RfJVlXGSo4V/zucNwMx4vQWo4EKNChfWH9mW82KsCz/mIcyipWtCa/EaIPmGFokuJ/A== X-Received: by 2002:adf:9144:: with SMTP id j62mr30951851wrj.419.1606778872847; Mon, 30 Nov 2020 15:27:52 -0800 (PST) Subject: Re: [PATCH V3 19/23] xen/arm: io: Abstract sign-extension To: Volodymyr Babchuk Cc: "xen-devel@lists.xenproject.org" , Oleksandr Tyshchenko , Stefano Stabellini , Julien Grall , Julien Grall References: <1606732298-22107-1-git-send-email-olekstysh@gmail.com> <1606732298-22107-20-git-send-email-olekstysh@gmail.com> <878sai7e1a.fsf@epam.com> From: Oleksandr Message-ID: Date: Tue, 1 Dec 2020 01:27:46 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <878sai7e1a.fsf@epam.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US On 30.11.20 23:03, Volodymyr Babchuk wrote: > Hi, Hi Volodymyr > > Oleksandr Tyshchenko writes: > >> From: Oleksandr Tyshchenko >> >> In order to avoid code duplication (both handle_read() and >> handle_ioserv() contain the same code for the sign-extension) >> put this code to a common helper to be used for both. >> >> Signed-off-by: Oleksandr Tyshchenko >> CC: Julien Grall >> >> --- >> Please note, this is a split/cleanup/hardening of Julien's PoC: >> "Add support for Guest IO forwarding to a device emulator" >> >> Changes V1 -> V2: >> - new patch >> >> Changes V2 -> V3: >> - no changes >> --- >> --- >> xen/arch/arm/io.c | 18 ++---------------- >> xen/arch/arm/ioreq.c | 17 +---------------- >> xen/include/asm-arm/traps.h | 24 ++++++++++++++++++++++++ >> 3 files changed, 27 insertions(+), 32 deletions(-) >> >> diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c >> index f44cfd4..8d6ec6c 100644 >> --- a/xen/arch/arm/io.c >> +++ b/xen/arch/arm/io.c >> @@ -23,6 +23,7 @@ >> #include >> #include >> #include >> +#include >> #include >> >> #include "decode.h" >> @@ -39,26 +40,11 @@ static enum io_state handle_read(const struct mmio_handler *handler, >> * setting r). >> */ >> register_t r = 0; >> - uint8_t size = (1 << dabt.size) * 8; >> >> if ( !handler->ops->read(v, info, &r, handler->priv) ) >> return IO_ABORT; >> >> - /* >> - * Sign extend if required. >> - * Note that we expect the read handler to have zeroed the bits >> - * outside the requested access size. >> - */ >> - if ( dabt.sign && (r & (1UL << (size - 1))) ) >> - { >> - /* >> - * We are relying on register_t using the same as >> - * an unsigned long in order to keep the 32-bit assembly >> - * code smaller. >> - */ >> - BUILD_BUG_ON(sizeof(register_t) != sizeof(unsigned long)); >> - r |= (~0UL) << size; >> - } >> + r = sign_extend(dabt, r); >> >> set_user_reg(regs, dabt.reg, r); >> >> diff --git a/xen/arch/arm/ioreq.c b/xen/arch/arm/ioreq.c >> index f08190c..2f39289 100644 >> --- a/xen/arch/arm/ioreq.c >> +++ b/xen/arch/arm/ioreq.c >> @@ -28,7 +28,6 @@ enum io_state handle_ioserv(struct cpu_user_regs *regs, struct vcpu *v) >> const union hsr hsr = { .bits = regs->hsr }; >> const struct hsr_dabt dabt = hsr.dabt; >> /* Code is similar to handle_read */ >> - uint8_t size = (1 << dabt.size) * 8; >> register_t r = v->io.req.data; >> >> /* We are done with the IO */ >> @@ -37,21 +36,7 @@ enum io_state handle_ioserv(struct cpu_user_regs *regs, struct vcpu *v) >> if ( dabt.write ) >> return IO_HANDLED; >> >> - /* >> - * Sign extend if required. >> - * Note that we expect the read handler to have zeroed the bits >> - * outside the requested access size. >> - */ >> - if ( dabt.sign && (r & (1UL << (size - 1))) ) >> - { >> - /* >> - * We are relying on register_t using the same as >> - * an unsigned long in order to keep the 32-bit assembly >> - * code smaller. >> - */ >> - BUILD_BUG_ON(sizeof(register_t) != sizeof(unsigned long)); >> - r |= (~0UL) << size; >> - } >> + r = sign_extend(dabt, r); >> >> set_user_reg(regs, dabt.reg, r); >> >> diff --git a/xen/include/asm-arm/traps.h b/xen/include/asm-arm/traps.h >> index 997c378..e301c44 100644 >> --- a/xen/include/asm-arm/traps.h >> +++ b/xen/include/asm-arm/traps.h >> @@ -83,6 +83,30 @@ static inline bool VABORT_GEN_BY_GUEST(const struct cpu_user_regs *regs) >> (unsigned long)abort_guest_exit_end == regs->pc; >> } >> >> +/* Check whether the sign extension is required and perform it */ >> +static inline register_t sign_extend(const struct hsr_dabt dabt, register_t r) >> +{ >> + uint8_t size = (1 << dabt.size) * 8; >> + >> + /* >> + * Sign extend if required. >> + * Note that we expect the read handler to have zeroed the bits >> + * outside the requested access size. >> + */ >> + if ( dabt.sign && (r & (1UL << (size - 1))) ) >> + { >> + /* >> + * We are relying on register_t using the same as >> + * an unsigned long in order to keep the 32-bit assembly >> + * code smaller. >> + */ >> + BUILD_BUG_ON(sizeof(register_t) != sizeof(unsigned long)); >> + r |= (~0UL) << size; > If `size` is 64, you will get undefined behavior there. I think, we don't need to worry about undefined behavior here. Having size=64 would be possible with doubleword (dabt.size=3). But if "r" adjustment gets called (I mean Syndrome Sign Extend bit is set) then we deal with byte, halfword or word operations (dabt.size<3). Or I missed something? -- Regards, Oleksandr Tyshchenko