From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-x841.google.com (mail-qt1-x841.google.com [IPv6:2607:f8b0:4864:20::841]) by sourceware.org (Postfix) with ESMTPS id 02173385DC0B for ; Thu, 23 Apr 2020 17:16:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 02173385DC0B Received: by mail-qt1-x841.google.com with SMTP id x8so5466486qtp.13 for ; Thu, 23 Apr 2020 10:16:02 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:autocrypt:subject :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=5BXVGt8IrXWLMSK2GRS/JfPdFF3ur/blx2TC3WrPLDc=; b=PF9ckXLsUS7OF3XVWk2G+NQulk0Tih7lQFTNN5ZibQCTGZjCq11ZnWX6Jf3rbvObSX WZLa1vIsXuA4E05IrdMvL7RCsp0HInwlgIDIyaFQVqDYjGxYqn1kJ9jn22F9solLzjQ+ aom6Dlu+d+jPNbYVM4qMx2d6o9VlNqPDZL6sOGbBsnRGjpy3c8iz/EXFSYLSpgGz5VaR l1lHhtM0hlleEl7sX955eQINh3gFFRXT6INmI4BVZEmyACqQ/dhqmQuN81qs2w+hy3cX V9SgCGQR9R92s3aS4dXgFtlPm/4h1qfLYPL/R9WsWzCMWLuGnBQSL7Pc68pBrB3AFzG+ 9WLw== X-Gm-Message-State: AGi0PuaceVElKTv4FjJDOSG/U2jdsFQyUxpoyZKO/BPrGg57dGwBO7EN uwrkBqEwp54tCeUXe0zhhEOa/g== X-Google-Smtp-Source: APiQypJ6ghAxj1t1MfOfUpTijCGmfnJcMifDuDP5kCXj/wYBQW8Me8D6HPJcxHt0Ndc2HiqoVI6BHw== X-Received: by 2002:ac8:189c:: with SMTP id s28mr5106772qtj.65.1587662162421; Thu, 23 Apr 2020 10:16:02 -0700 (PDT) Received: from [192.168.1.4] ([177.194.48.209]) by smtp.googlemail.com with ESMTPSA id v16sm1875776qkf.80.2020.04.23.10.15.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Apr 2020 10:16:01 -0700 (PDT) To: Rich Felker Cc: Nicholas Piggin , libc-alpha@sourceware.org, libc-dev@lists.llvm.org, linuxppc-dev@lists.ozlabs.org, musl@lists.openwall.com References: <20200420013412.GZ11469@brightrain.aerifal.cx> <1587348538.l1ioqml73m.astroid@bobo.none> <20200420040926.GA11469@brightrain.aerifal.cx> <1587356128.aslvdnmtbw.astroid@bobo.none> <20200420172715.GC11469@brightrain.aerifal.cx> <1587531042.1qvc287tsc.astroid@bobo.none> <20200423023642.GP11469@brightrain.aerifal.cx> <20200423161841.GU11469@brightrain.aerifal.cx> <3fe73604-7c92-e073-cbe7-abb4a8ae7c1a@linaro.org> <20200423164314.GX11469@brightrain.aerifal.cx> From: Adhemerval Zanella Autocrypt: addr=adhemerval.zanella@linaro.org; prefer-encrypt=mutual; keydata= xsFNBFcVGkoBEADiQU2x/cBBmAVf5C2d1xgz6zCnlCefbqaflUBw4hB/bEME40QsrVzWZ5Nq 8kxkEczZzAOKkkvv4pRVLlLn/zDtFXhlcvQRJ3yFMGqzBjofucOrmdYkOGo0uCaoJKPT186L NWp53SACXguFJpnw4ODI64ziInzXQs/rUJqrFoVIlrPDmNv/LUv1OVPKz20ETjgfpg8MNwG6 iMizMefCl+RbtXbIEZ3TE/IaDT/jcOirjv96lBKrc/pAL0h/O71Kwbbp43fimW80GhjiaN2y WGByepnkAVP7FyNarhdDpJhoDmUk9yfwNuIuESaCQtfd3vgKKuo6grcKZ8bHy7IXX1XJj2X/ BgRVhVgMHAnDPFIkXtP+SiarkUaLjGzCz7XkUn4XAGDskBNfbizFqYUQCaL2FdbW3DeZqNIa nSzKAZK7Dm9+0VVSRZXP89w71Y7JUV56xL/PlOE+YKKFdEw+gQjQi0e+DZILAtFjJLoCrkEX w4LluMhYX/X8XP6/C3xW0yOZhvHYyn72sV4yJ1uyc/qz3OY32CRy+bwPzAMAkhdwcORA3JPb kPTlimhQqVgvca8m+MQ/JFZ6D+K7QPyvEv7bQ7M+IzFmTkOCwCJ3xqOD6GjX3aphk8Sr0dq3 4Awlf5xFDAG8dn8Uuutb7naGBd/fEv6t8dfkNyzj6yvc4jpVxwARAQABzUlBZGhlbWVydmFs IFphbmVsbGEgTmV0dG8gKExpbmFybyBWUE4gS2V5KSA8YWRoZW1lcnZhbC56YW5lbGxhQGxp bmFyby5vcmc+wsF3BBMBCAAhBQJXFRpKAhsDBQsJCAcDBRUKCQgLBRYCAwEAAh4BAheAAAoJ EKqx7BSnlIjv0e8P/1YOYoNkvJ+AJcNUaM5a2SA9oAKjSJ/M/EN4Id5Ow41ZJS4lUA0apSXW NjQg3VeVc2RiHab2LIB4MxdJhaWTuzfLkYnBeoy4u6njYcaoSwf3g9dSsvsl3mhtuzm6aXFH /Qsauav77enJh99tI4T+58rp0EuLhDsQbnBic/ukYNv7sQV8dy9KxA54yLnYUFqH6pfH8Lly sTVAMyi5Fg5O5/hVV+Z0Kpr+ZocC1YFJkTsNLAW5EIYSP9ftniqaVsim7MNmodv/zqK0IyDB GLLH1kjhvb5+6ySGlWbMTomt/or/uvMgulz0bRS+LUyOmlfXDdT+t38VPKBBVwFMarNuREU2 69M3a3jdTfScboDd2ck1u7l+QbaGoHZQ8ZNUrzgObltjohiIsazqkgYDQzXIMrD9H19E+8fw kCNUlXxjEgH/Kg8DlpoYJXSJCX0fjMWfXywL6ZXc2xyG/hbl5hvsLNmqDpLpc1CfKcA0BkK+ k8R57fr91mTCppSwwKJYO9T+8J+o4ho/CJnK/jBy1pWKMYJPvvrpdBCWq3MfzVpXYdahRKHI ypk8m4QlRlbOXWJ3TDd/SKNfSSrWgwRSg7XCjSlR7PNzNFXTULLB34sZhjrN6Q8NQZsZnMNs TX8nlGOVrKolnQPjKCLwCyu8PhllU8OwbSMKskcD1PSkG6h3r0AqzsFNBFcVGkoBEACgAdbR Ck+fsfOVwT8zowMiL3l9a2DP3Eeak23ifdZG+8Avb/SImpv0UMSbRfnw/N81IWwlbjkjbGTu oT37iZHLRwYUFmA8fZX0wNDNKQUUTjN6XalJmvhdz9l71H3WnE0wneEM5ahu5V1L1utUWTyh VUwzX1lwJeV3vyrNgI1kYOaeuNVvq7npNR6t6XxEpqPsNc6O77I12XELic2+36YibyqlTJIQ V1SZEbIy26AbC2zH9WqaKyGyQnr/IPbTJ2Lv0dM3RaXoVf+CeK7gB2B+w1hZummD21c1Laua +VIMPCUQ+EM8W9EtX+0iJXxI+wsztLT6vltQcm+5Q7tY+HFUucizJkAOAz98YFucwKefbkTp eKvCfCwiM1bGatZEFFKIlvJ2QNMQNiUrqJBlW9nZp/k7pbG3oStOjvawD9ZbP9e0fnlWJIsj 6c7pX354Yi7kxIk/6gREidHLLqEb/otuwt1aoMPg97iUgDV5mlNef77lWE8vxmlY0FBWIXuZ yv0XYxf1WF6dRizwFFbxvUZzIJp3spAao7jLsQj1DbD2s5+S1BW09A0mI/1DjB6EhNN+4bDB SJCOv/ReK3tFJXuj/HbyDrOdoMt8aIFbe7YFLEExHpSk+HgN05Lg5TyTro8oW7TSMTk+8a5M kzaH4UGXTTBDP/g5cfL3RFPl79ubXwARAQABwsFfBBgBCAAJBQJXFRpKAhsMAAoJEKqx7BSn lIjvI/8P/jg0jl4Tbvg3B5kT6PxJOXHYu9OoyaHLcay6Cd+ZrOd1VQQCbOcgLFbf4Yr+rE9l mYsY67AUgq2QKmVVbn9pjvGsEaz8UmfDnz5epUhDxC6yRRvY4hreMXZhPZ1pbMa6A0a/WOSt AgFj5V6Z4dXGTM/lNManr0HjXxbUYv2WfbNt3/07Db9T+GZkpUotC6iknsTA4rJi6u2ls0W9 1UIvW4o01vb4nZRCj4rni0g6eWoQCGoVDk/xFfy7ZliR5B+3Z3EWRJcQskip/QAHjbLa3pml xAZ484fVxgeESOoaeC9TiBIp0NfH8akWOI0HpBCiBD5xaCTvR7ujUWMvhsX2n881r/hNlR9g fcE6q00qHSPAEgGr1bnFv74/1vbKtjeXLCcRKk3Ulw0bY1OoDxWQr86T2fZGJ/HIZuVVBf3+ gaYJF92GXFynHnea14nFFuFgOni0Mi1zDxYH/8yGGBXvo14KWd8JOW0NJPaCDFJkdS5hu0VY 7vJwKcyHJGxsCLU+Et0mryX8qZwqibJIzu7kUJQdQDljbRPDFd/xmGUFCQiQAncSilYOcxNU EMVCXPAQTteqkvA+gNqSaK1NM9tY0eQ4iJpo+aoX8HAcn4sZzt2pfUB9vQMTBJ2d4+m/qO6+ cFTAceXmIoFsN8+gFN3i8Is3u12u8xGudcBPvpoy4OoG Subject: Re: [musl] Powerpc Linux 'scv' system call ABI proposal take 2 Message-ID: <64d82a23-1f6e-2e6a-b7a9-0eeab8a53435@linaro.org> Date: Thu, 23 Apr 2020 14:15:58 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200423164314.GX11469@brightrain.aerifal.cx> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-12.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, KAM_NUMSUBJECT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=no autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Apr 2020 17:16:04 -0000 On 23/04/2020 13:43, Rich Felker wrote: > On Thu, Apr 23, 2020 at 01:35:01PM -0300, Adhemerval Zanella wrote: >> >> >> On 23/04/2020 13:18, Rich Felker wrote: >>> On Thu, Apr 23, 2020 at 09:13:57AM -0300, Adhemerval Zanella wrote: >>>> >>>> >>>> On 22/04/2020 23:36, Rich Felker wrote: >>>>> On Wed, Apr 22, 2020 at 04:18:36PM +1000, Nicholas Piggin wrote: >>>>>> Yeah I had a bit of a play around with musl (which is very nice code I >>>>>> must say). The powerpc64 syscall asm is missing ctr clobber by the way. >>>>>> Fortunately adding it doesn't change code generation for me, but it >>>>>> should be fixed. glibc had the same bug at one point I think (probably >>>>>> due to syscall ABI documentation not existing -- something now lives in >>>>>> linux/Documentation/powerpc/syscall64-abi.rst). >>>>> >>>>> Do you know anywhere I can read about the ctr issue, possibly the >>>>> relevant glibc bug report? I'm not particularly familiar with ppc >>>>> register file (at least I have to refamiliarize myself every time I >>>>> work on this stuff) so it'd be nice to understand what's >>>>> potentially-wrong now. >>>> >>>> My understanding is the ctr issue only happens for vDSO calls where it >>>> fallback to a syscall in case an error (invalid argument, etc. and >>>> assuming if vDSO does not fallback to a syscall it always succeed). >>>> This makes the vDSO call on powerpc to have same same ABI constraint >>>> as a syscall, where it clobbers CR0. >>> >>> I think you mean "vsyscall", the old thing glibc used where there are >>> in-userspace implementations of some syscalls with call interfaces >>> roughly equivalent to a syscall. musl has never used this. It only >>> uses the actual exported functions from the vdso which have normal >>> external function call ABI. >> >> I wasn't thinking in vsyscall in fact, which afaik it is a x86 thing. >> The issue is indeed when calling the powerpc provided functions in >> vDSO, which musl might want to do eventually. > > AIUI (at least this is true for all other archs) the functions have > normal external function call ABI and calling them has nothing to do > with syscall mechanisms. My point is powerpc specifically does not follow it, since it issues a syscall in fallback and its semantic follow kernel syscalls (error signalled in cr0, r3 being always a positive value): -- V_FUNCTION_BEGIN(__kernel_clock_gettime) .cfi_startproc [...] /* * syscall fallback */ 99: li r0,__NR_clock_gettime .cfi_restore lr sc blr .cfi_endproc V_FUNCTION_END(__kernel_clock_gettime) > > It looks like we're not using them right now and I'm not sure why. It > could be that there are ABI mismatch issues (are 32-bit ones > compatible with secure-plt? are 64-bit ones compatible with ELFv2?) or > just that nobody proposed adding them. Also as of 5.4 32-bit ppc > lacked time64 versions of them; not sure if this is fixed yet. For 64-bit it also have an issue where vDSO does not provide an OPD for ELFv1, which has bitten glibc while trying to implement an ifunc optimization. I don't recall any issue for ELFv2. For 32-bit I am not sure secure-plt will change anything, at least not on powerpc where we use the same strategy for 64-bit and use a mtctr/bctr directly.