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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 BC3F7C433E0 for ; Fri, 15 Jan 2021 07:11:39 +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 6694D22D50 for ; Fri, 15 Jan 2021 07:11:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6694D22D50 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.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.67689.120948 (Exim 4.92) (envelope-from ) id 1l0JGK-0008SZ-Vk; Fri, 15 Jan 2021 07:11:12 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 67689.120948; Fri, 15 Jan 2021 07:11:12 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l0JGK-0008SS-SL; Fri, 15 Jan 2021 07:11:12 +0000 Received: by outflank-mailman (input) for mailman id 67689; Fri, 15 Jan 2021 07:11:11 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l0JGJ-0008SN-CR for xen-devel@lists.xenproject.org; Fri, 15 Jan 2021 07:11:11 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 347cfaf8-8a0a-484c-9a98-9efaa0ec038b; Fri, 15 Jan 2021 07:11:09 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0CA13AB7A; Fri, 15 Jan 2021 07:11:08 +0000 (UTC) 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: 347cfaf8-8a0a-484c-9a98-9efaa0ec038b X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1610694668; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=FPYYUNXR3uCVIaBn0lurWALGM5JsyzYXK93n/ui6d7A=; b=gmaPjyMZAICqvvGH0NlmOj14tq+leqDLPL9TrNMkuL0VXBCPVQB7PuhogCjMlu3/i4uZvo R23CpKlcjnqXCQkZNSVWJq2qckPAa0qfEMD5Lolo6+CINwc14xmoKoOIbpOJa/zNPiye+D UtvCkozvv2vvy7K3cTHsnzhqV39UyEE= To: Andrew Cooper , xen-devel@lists.xenproject.org Cc: Ian Jackson , Wei Liu , Julien Grall References: <20210114153803.2591-1-jgross@suse.com> <20210114153803.2591-6-jgross@suse.com> <21c113c0-9118-8c22-7c3b-50ffccb4db8c@citrix.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Subject: Re: [PATCH v11 05/27] tools/libxenevtchn: add possibility to not close file descriptor on exec Message-ID: Date: Fri, 15 Jan 2021 08:11:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <21c113c0-9118-8c22-7c3b-50ffccb4db8c@citrix.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="uWZYBBcJKy9I3ATVk0OvSsPaK9uUe2dCy" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --uWZYBBcJKy9I3ATVk0OvSsPaK9uUe2dCy Content-Type: multipart/mixed; boundary="K1FqjKGGmABY4mPW4fq7IFNml4VIXkI7m"; protected-headers="v1" From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= To: Andrew Cooper , xen-devel@lists.xenproject.org Cc: Ian Jackson , Wei Liu , Julien Grall Message-ID: Subject: Re: [PATCH v11 05/27] tools/libxenevtchn: add possibility to not close file descriptor on exec References: <20210114153803.2591-1-jgross@suse.com> <20210114153803.2591-6-jgross@suse.com> <21c113c0-9118-8c22-7c3b-50ffccb4db8c@citrix.com> In-Reply-To: <21c113c0-9118-8c22-7c3b-50ffccb4db8c@citrix.com> --K1FqjKGGmABY4mPW4fq7IFNml4VIXkI7m Content-Type: multipart/mixed; boundary="------------331E962FC3FA629F4E6330F8" Content-Language: en-US This is a multi-part message in MIME format. --------------331E962FC3FA629F4E6330F8 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 15.01.21 02:01, Andrew Cooper wrote: > On 14/01/2021 15:37, Juergen Gross wrote: >> diff --git a/tools/include/xenevtchn.h b/tools/include/xenevtchn.h >> index 3e9b6e7323..b6dd8f3186 100644 >> --- a/tools/include/xenevtchn.h >> +++ b/tools/include/xenevtchn.h >> @@ -64,11 +64,25 @@ struct xentoollog_logger; >> * >> * Calling xenevtchn_close() is the only safe operation on a >> * xenevtchn_handle which has been inherited. >> + * >> + * Setting XENEVTCHN_NO_CLOEXEC allows to keep the file descriptor us= ed >> + * for the event channel driver open across exec(2). In order to be a= ble >> + * to use that file descriptor the new binary activated via exec(2) h= as >> + * to call xenevtchn_fdopen() with that file descriptor as parameter = in >> + * order to associate it with a new handle. The file descriptor can b= e >> + * obtained via xenevtchn_fd() before calling exec(2). >> */ >=20 > Earlier commentary in this block is already wrong (refer to gnttab, and= > making what appear to be false claims), and/or made stale by this chang= e. >=20 > How about: >=20 > /* > =C2=A0* Opens the evtchn device node.=C2=A0 Return a handle to the eve= nt channel > =C2=A0* driver, or NULL on failure, in which case errno will be set > =C2=A0* appropriately. > =C2=A0* > =C2=A0* On fork(2): > =C2=A0* > =C2=A0*=C2=A0=C2=A0 After fork, a child process must not use any opene= d evtchn handle > =C2=A0*=C2=A0=C2=A0 inherited from their parent.=C2=A0 This includes o= perations such as > =C2=A0*=C2=A0=C2=A0 poll() on the underlying file descriptor.=C2=A0 Ca= lling xenevtchn_close() > =C2=A0*=C2=A0=C2=A0 is the only safe operation on a xenevtchn_handle w= hich has been > =C2=A0*=C2=A0=C2=A0 inherited. > =C2=A0* > =C2=A0*=C2=A0=C2=A0 The child must open a new handle if they want to i= nteract with > =C2=A0*=C2=A0=C2=A0 evtchn. > =C2=A0* > =C2=A0* On exec(2): > =C2=A0* > =C2=A0*=C2=A0=C2=A0 Wherever possible, the device node will be opened = with O_CLOEXEC, > =C2=A0*=C2=A0=C2=A0 so it is not inherited by the subsequent program. > =C2=A0* > =C2=A0*=C2=A0=C2=A0 However the XENEVTCHN_NO_CLOEXEC flag may be used = to avoid opening > =C2=A0*=C2=A0=C2=A0 the device node with O_CLOEXEC.=C2=A0 This is inte= nded for use by > =C2=A0*=C2=A0=C2=A0 daemons which support a self-reexec method of upda= ting themselves. > =C2=A0* > =C2=A0*=C2=A0=C2=A0 In this case, the updated daemon should pass the u= nderlying file > =C2=A0*=C2=A0=C2=A0 descriptor it inherited to xenevtchn_fdopen() to r= econstruct the > =C2=A0*=C2=A0=C2=A0 library handle. > =C2=A0*/ >=20 > which I think is somewhat more concise? Yes, I'll change it. >=20 >=20 >> -/* Currently no flags are defined */ >> + >> +/* Don't set O_CLOEXEC when opening event channel driver node. */ >> +#define XENEVTCHN_NO_CLOEXEC 0x01 >=20 > Do we really want an byte-looking constant?=C2=A0 Wouldn't (1 << 0) be = a more > normal way of writing this? Fine with me. >=20 >> + >> xenevtchn_handle *xenevtchn_open(struct xentoollog_logger *logger, >> unsigned int flags); >> =20 >> +/* Flag XENEVTCHN_NO_CLOEXEC is ignored by xenevtchn_fdopen(). */ >> +xenevtchn_handle *xenevtchn_fdopen(struct xentoollog_logger *logger, >> + int fd, unsigned open_flags); >=20 > True, but see below... >=20 >> + >> /* >> * Close a handle previously allocated with xenevtchn_open(). >=20 > xenevtchn_{,fd}open(), now. Ah, right. >=20 >> diff --git a/tools/libs/evtchn/core.c b/tools/libs/evtchn/core.c >> index c069d5da71..f2ab27384b 100644 >> --- a/tools/libs/evtchn/core.c >> +++ b/tools/libs/evtchn/core.c >> >> +xenevtchn_handle *xenevtchn_fdopen(struct xentoollog_logger *logger, >> + int fd, unsigned int flags) >> +{ >> + xenevtchn_handle *xce; >> + >> + if ( flags & ~XENEVTCHN_NO_CLOEXEC ) >> + { >> + errno =3D EINVAL; >> + return NULL; >> + } >=20 > Do we really want to tolerate XENEVTCHN_NO_CLOEXEC here?=C2=A0 I'd sugg= est > rejecting it, because nothing good can come of a caller thinking it has= > avoided setting O_CLOEXEC when in fact it hasn't. Fine with me. >=20 >> diff --git a/tools/libs/evtchn/freebsd.c b/tools/libs/evtchn/freebsd.c= >> index bb601f350f..ed2baf3c95 100644 >> --- a/tools/libs/evtchn/freebsd.c >> +++ b/tools/libs/evtchn/freebsd.c >> @@ -33,8 +33,12 @@ >> =20 >> int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int flags) >> { >> - int fd =3D open(EVTCHN_DEV, O_RDWR|O_CLOEXEC); >> + int open_flags =3D O_RDWR; >> + int fd; >> =20 >> + if ( !(flags & XENEVTCHN_NO_CLOEXEC) ) >> + open_flags |=3D O_CLOEXEC; >=20 > As we're now consistently using hypervisor style, we ought to have an > extra newline here and in equivalent positions. Yes. >=20 > If you're happy with the suggestions, I'm happy folding them on commit,= > to avoid yet another posting. I'll post v12 today. Juergen --------------331E962FC3FA629F4E6330F8 Content-Type: application/pgp-keys; name="OpenPGP_0xB0DE9DD628BF132F.asc" Content-Transfer-Encoding: quoted-printable Content-Disposition: attachment; filename="OpenPGP_0xB0DE9DD628BF132F.asc" -----BEGIN PGP PUBLIC KEY BLOCK----- xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOBy= cWx w3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJvedYm8O= f8Z d621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJNwQpd369y= 9bf IhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvxXP3FAp2pkW0xq= G7/ 377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEBAAHNHEp1ZXJnZW4gR= 3Jv c3MgPGpnQHBmdXBmLm5ldD7CwHkEEwECACMFAlOMcBYCGwMHCwkIBwMCAQYVCAIJCgsEFgIDA= QIe AQIXgAAKCRCw3p3WKL8TL0KdB/93FcIZ3GCNwFU0u3EjNbNjmXBKDY4FUGNQH2lvWAUy+dnyT= hpw dtF/jQ6j9RwE8VP0+NXcYpGJDWlNb9/JmYqLiX2Q3TyevpB0CA3dbBQp0OW0fgCetToGIQrg0= MbD 1C/sEOv8Mr4NAfbauXjZlvTj30H2jO0u+6WGM6nHwbh2l5O8ZiHkH32iaSTfN7Eu5RnNVUJbv= oPH Z8SlM4KWm8rG+lIkGurqqu5gu8q8ZMKdsdGC4bBxdQKDKHEFExLJK/nRPFmAuGlId1E3fe10v= 5QL +qHI3EIPtyfE7i9Hz6rVwi7lWKgh7pe0ZvatAudZ+JNIlBKptb64FaiIOAWDCx1SzR9KdWVyZ= 2Vu IEdyb3NzIDxqZ3Jvc3NAc3VzZS5jb20+wsB5BBMBAgAjBQJTjHCvAhsDBwsJCAcDAgEGFQgCC= QoL BBYCAwECHgECF4AACgkQsN6d1ii/Ey/HmQf/RtI7kv5A2PS4RF7HoZhPVPogNVbC4YA6lW7Dr= Wf0 teC0RR3MzXfy6pJ+7KLgkqMlrAbN/8Dvjoz78X+5vhH/rDLa9BuZQlhFmvcGtCF8eR0T1v0nC= /nu AFVGy+67q2DH8As3KPu0344TBDpAvr2uYM4tSqxK4DURx5INz4ZZ0WNFHcqsfvlGJALDeE0Lh= ITT d9jLzdDad1pQSToCnLl6SBJZjDOX9QQcyUigZFtCXFst4dlsvddrxyqT1f17+2cFSdu7+ynLm= XBK 7abQ3rwJY8SbRO2iRulogc5vr/RLMMlscDAiDkaFQWLoqHHOdfO9rURssHNN8WkMnQfvUewRz= 80h SnVlcmdlbiBHcm9zcyA8amdyb3NzQG5vdmVsbC5jb20+wsB5BBMBAgAjBQJTjHDXAhsDBwsJC= AcD AgEGFQgCCQoLBBYCAwECHgECF4AACgkQsN6d1ii/Ey8PUQf/ehmgCI9jB9hlgexLvgOtf7PJn= FOX gMLdBQgBlVPO3/D9R8LtF9DBAFPNhlrsfIG/SqICoRCqUcJ96Pn3P7UUinFG/I0ECGF4EvTE1= jnD kfJZr6jrbjgyoZHiw/4BNwSTL9rWASyLgqlA8u1mf+c2yUwcGhgkRAd1gOwungxcwzwqgljf0= N51 N5JfVRHRtyfwq/ge+YEkDGcTU6Y0sPOuj4Dyfm8fJzdfHNQsWq3PnczLVELStJNdapwPOoE+l= otu fe3AM2vAEYJ9rTz3Cki4JFUsgLkHFqGZarrPGi1eyQcXeluldO3m91NK/1xMI3/+8jbO0tsn1= tqS EUGIJi7ox80eSnVlcmdlbiBHcm9zcyA8amdyb3NzQHN1c2UuZGU+wsB5BBMBAgAjBQJTjHDrA= hsD BwsJCAcDAgEGFQgCCQoLBBYCAwECHgECF4AACgkQsN6d1ii/Ey+LhQf9GL45eU5vOowA2u5N3= g3O ZUEBmDHVVbqMtzwlmNC4k9Kx39r5s2vcFl4tXqW7g9/ViXYuiDXb0RfUpZiIUW89siKrkzmQ5= dM7 wRqzgJpJwK8Bn2MIxAKArekWpiCKvBOB/Cc+3EXE78XdlxLyOi/NrmSGRIov0karw2RzMNOu5= D+j LRZQd1Sv27AR+IP3I8U4aqnhLpwhK7MEy9oCILlgZ1QZe49kpcumcZKORmzBTNh30FVKK1Evm= V2x AKDoaEOgQB4iFQLhJCdP1I5aSgM5IVFdn7v5YgEYuJYx37IoN1EblHI//x/e2AaIHpzK5h88N= Eaw QsaNRpNSrcfbFmAg987ATQRTjHAWAQgAyzH6AOODMBjgfWE9VeCgsrwH3exNAU32gLq2xvjpW= nHI s98ndPUDpnoxWQugJ6MpMncr0xSwFmHEgnSEjK/PAjppgmyc57BwKII3sV4on+gDVFJR6Y8ZR= wgn BC5mVM6JjQ5xDk8WRXljExRfUX9pNhdE5eBOZJrDRoLUmmjDtKzWaDhIg/+1Hzz93X4fCQkNV= bVF LELU9bMaLPBG/x5q4iYZ2k2ex6d47YE1ZFdMm6YBYMOljGkZKwYde5ldM9mo45mmwe0icXKLk= pEd IXKTZeKDO+Hdv1aqFuAcccTg9RXDQjmwhC3yEmrmcfl0+rPghO0Iv3OOImwTEe4co3c1mwARA= QAB wsBfBBgBAgAJBQJTjHAWAhsMAAoJELDendYovxMvQ/gH/1ha96vm4P/L+bQpJwrZ/dneZcmEw= Tbe 8YFsw2V/Buv6Z4Mysln3nQK5ZadD534CF7TDVft7fC4tU4PONxF5D+/tvgkPfDAfF77zy2AH1= vJz Q1fOU8lYFpZXTXIHb+559UqvIB8AdgR3SAJGHHt4RKA0F7f5ipYBBrC6cyXJyyoprT10EMvU8= VGi wXvTyJz3fjoYsdFzpWPlJEBRMedCot60g5dmbdrZ5DWClAr0yau47zpWj3enf1tLWaqcsuylW= svi uGjKGw7KHQd3bxALOknAp4dN3QwBYCKuZ7AddY9yjynVaD5X7nF9nO5BjR/i1DG86lem3iBDX= zXs ZDn8R38=3D =3D2wuH -----END PGP PUBLIC KEY BLOCK----- --------------331E962FC3FA629F4E6330F8-- --K1FqjKGGmABY4mPW4fq7IFNml4VIXkI7m-- --uWZYBBcJKy9I3ATVk0OvSsPaK9uUe2dCy Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature" -----BEGIN PGP SIGNATURE----- wsB5BAABCAAjFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAmABQAsFAwAAAAAACgkQsN6d1ii/Ey+Y cAgAlP5nkU1XofmefEiQlhDNAOqOe3uHeO/mbVsW0YJlpuEmNghpo2BPQ0HVnRBUR8XtWat8LaqQ F3JoLRhzLqX2Px7ARgUqULLiGIKFYaGbsu3rlWc9lTF2cNMwGOJMfDb8YxrftPGomaLLMniZSKsV zZYxKlX2OPEa3pYyOmv5pJJDVq+GXJUPW8pND8SUAtoWMA9Uk3ALxzobniSYmW2Yj4Kb+eTwG3OR /nYQsCQjBVH4mf8XXoQoyYWHM00EKfqdo4kONuY/HA5S/CRm0vQejzxnfkvO0TPVXHmMX7wPtwUW 7+61Udfzy9iwcv1/Z/vdx+cP9ALb6BzeiL5RKJsY6g== =T+tq -----END PGP SIGNATURE----- --uWZYBBcJKy9I3ATVk0OvSsPaK9uUe2dCy--