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Fri, 18 Oct 2019 09:31:34 +0000 (UTC) Received: from thuth.remote.csb (dhcp-200-228.str.redhat.com [10.33.200.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 02FC65D9D5; Fri, 18 Oct 2019 09:31:20 +0000 (UTC) Subject: Re: [Qemu-devel] [PATCH v2 3/4] trace: forbid use of %m in trace event format strings To: Eric Blake , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= References: <20190118173103.4903-1-berrange@redhat.com> <20190118173103.4903-4-berrange@redhat.com> <20190122143257.GR13143@redhat.com> <20190122172333.GA13143@redhat.com> <9d0997e0-9019-c7c2-56d6-26c70f0d5c7e@redhat.com> From: Thomas Huth Openpgp: preference=signencrypt Autocrypt: addr=thuth@redhat.com; prefer-encrypt=mutual; keydata= mQINBFH7eUwBEACzyOXKU+5Pcs6wNpKzrlJwzRl3VGZt95VCdb+FgoU9g11m7FWcOafrVRwU yYkTm9+7zBUc0sW5AuPGR/dp3pSLX/yFWsA/UB4nJsHqgDvDU7BImSeiTrnpMOTXb7Arw2a2 4CflIyFqjCpfDM4MuTmzTjXq4Uov1giGE9X6viNo1pxyEpd7PanlKNnf4PqEQp06X4IgUacW tSGj6Gcns1bCuHV8OPWLkf4hkRnu8hdL6i60Yxz4E6TqlrpxsfYwLXgEeswPHOA6Mn4Cso9O 0lewVYfFfsmokfAVMKWzOl1Sr0KGI5T9CpmRfAiSHpthhHWnECcJFwl72NTi6kUcUzG4se81 O6n9d/kTj7pzTmBdfwuOZ0YUSqcqs0W+l1NcASSYZQaDoD3/SLk+nqVeCBB4OnYOGhgmIHNW 0CwMRO/GK+20alxzk//V9GmIM2ACElbfF8+Uug3pqiHkVnKqM7W9/S1NH2qmxB6zMiJUHlTH gnVeZX0dgH27mzstcF786uPcdEqS0KJuxh2kk5IvUSL3Qn3ZgmgdxBMyCPciD/1cb7/Ahazr 3ThHQXSHXkH/aDXdfLsKVuwDzHLVSkdSnZdt5HHh75/NFHxwaTlydgfHmFFwodK8y/TjyiGZ zg2Kje38xnz8zKn9iesFBCcONXS7txENTzX0z80WKBhK+XSFJwARAQABtB5UaG9tYXMgSHV0 aCA8dGh1dGhAcmVkaGF0LmNvbT6JAjgEEwECACIFAlVgX6oCGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAAoJEC7Z13T+cC21EbIP/ii9cvT2HHGbFRl8HqGT6+7Wkb+XLMqJBMAIGiQK QIP3xk1HPTsLfVG0ao4hy/oYkGNOP8+ubLnZen6Yq3zAFiMhQ44lvgigDYJo3Ve59gfe99KX EbtB+X95ODARkq0McR6OAsPNJ7gpEUzfkQUUJTXRDQXfG/FX303Gvk+YU0spm2tsIKPl6AmV 1CegDljzjycyfJbk418MQmMu2T82kjrkEofUO2a24ed3VGC0/Uz//XCR2ZTo+vBoBUQl41BD eFFtoCSrzo3yPFS+w5fkH9NT8ChdpSlbNS32NhYQhJtr9zjWyFRf0Zk+T/1P7ECn6gTEkp5k ofFIA4MFBc/fXbaDRtBmPB0N9pqTFApIUI4vuFPPO0JDrII9dLwZ6lO9EKiwuVlvr1wwzsgq zJTPBU3qHaUO4d/8G+gD7AL/6T4zi8Jo/GmjBsnYaTzbm94lf0CjXjsOX3seMhaE6WAZOQQG tZHAO1kAPWpaxne+wtgMKthyPLNwelLf+xzGvrIKvLX6QuLoWMnWldu22z2ICVnLQChlR9d6 WW8QFEpo/FK7omuS8KvvopFcOOdlbFMM8Y/8vBgVMSsK6fsYUhruny/PahprPbYGiNIhKqz7 UvgyZVl4pBFjTaz/SbimTk210vIlkDyy1WuS8Zsn0htv4+jQPgo9rqFE4mipJjy/iboDuQIN BFH7eUwBEAC2nzfUeeI8dv0C4qrfCPze6NkryUflEut9WwHhfXCLjtvCjnoGqFelH/PE9NF4 4VPSCdvD1SSmFVzu6T9qWdcwMSaC+e7G/z0/AhBfqTeosAF5XvKQlAb9ZPkdDr7YN0a1XDfa +NgA+JZB4ROyBZFFAwNHT+HCnyzy0v9Sh3BgJJwfpXHH2l3LfncvV8rgFv0bvdr70U+On2XH 5bApOyW1WpIG5KPJlDdzcQTyptOJ1dnEHfwnABEfzI3dNf63rlxsGouX/NFRRRNqkdClQR3K gCwciaXfZ7ir7fF0u1N2UuLsWA8Ei1JrNypk+MRxhbvdQC4tyZCZ8mVDk+QOK6pyK2f4rMf/ WmqxNTtAVmNuZIwnJdjRMMSs4W4w6N/bRvpqtykSqx7VXcgqtv6eqoDZrNuhGbekQA0sAnCJ VPArerAZGArm63o39me/bRUQeQVSxEBmg66yshF9HkcUPGVeC4B0TPwz+HFcVhheo6hoJjLq knFOPLRj+0h+ZL+D0GenyqD3CyuyeTT5dGcNU9qT74bdSr20k/CklvI7S9yoQje8BeQAHtdV cvO8XCLrpGuw9SgOS7OP5oI26a0548M4KldAY+kqX6XVphEw3/6U1KTf7WxW5zYLTtadjISB X9xsRWSU+Yqs3C7oN5TIPSoj9tXMoxZkCIHWvnqGwZ7JhwARAQABiQIfBBgBAgAJBQJR+3lM AhsMAAoJEC7Z13T+cC21hPAQAIsBL9MdGpdEpvXs9CYrBkd6tS9mbaSWj6XBDfA1AEdQkBOn ZH1Qt7HJesk+qNSnLv6+jP4VwqK5AFMrKJ6IjE7jqgzGxtcZnvSjeDGPF1h2CKZQPpTw890k fy18AvgFHkVk2Oylyexw3aOBsXg6ukN44vIFqPoc+YSU0+0QIdYJp/XFsgWxnFIMYwDpxSHS 5fdDxUjsk3UBHZx+IhFjs2siVZi5wnHIqM7eK9abr2cK2weInTBwXwqVWjsXZ4tq5+jQrwDK cvxIcwXdUTLGxc4/Z/VRH1PZSvfQxdxMGmNTGaXVNfdFZjm4fz0mz+OUi6AHC4CZpwnsliGV ODqwX8Y1zic9viSTbKS01ZNp175POyWViUk9qisPZB7ypfSIVSEULrL347qY/hm9ahhqmn17 Ng255syASv3ehvX7iwWDfzXbA0/TVaqwa1YIkec+/8miicV0zMP9siRcYQkyTqSzaTFBBmqD oiT+z+/E59qj/EKfyce3sbC9XLjXv3mHMrq1tKX4G7IJGnS989E/fg6crv6NHae9Ckm7+lSs IQu4bBP2GxiRQ+NV3iV/KU3ebMRzqIC//DCOxzQNFNJAKldPe/bKZMCxEqtVoRkuJtNdp/5a yXFZ6TfE1hGKrDBYAm4vrnZ4CXFSBDllL59cFFOJCkn4Xboj/aVxxJxF30bn Organization: Red Hat Message-ID: <8e9b4f93-234b-9ae0-0ffc-d96de3ce02cb@redhat.com> Date: Fri, 18 Oct 2019 11:31:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <9d0997e0-9019-c7c2-56d6-26c70f0d5c7e@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="oavsMs1krcPZwOrJzYPfxinbIm5aH64IV" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Fri, 18 Oct 2019 09:31:34 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alex Williamson , qemu-devel@nongnu.org, Stefan Hajnoczi , Gerd Hoffmann Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --oavsMs1krcPZwOrJzYPfxinbIm5aH64IV Content-Type: multipart/mixed; boundary="kdmSty2OLfAjJpCraHdFXrDi9XIN2fyqI"; protected-headers="v1" From: Thomas Huth To: Eric Blake , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= Cc: Alex Williamson , qemu-devel@nongnu.org, Stefan Hajnoczi , Gerd Hoffmann Message-ID: <8e9b4f93-234b-9ae0-0ffc-d96de3ce02cb@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 3/4] trace: forbid use of %m in trace event format strings References: <20190118173103.4903-1-berrange@redhat.com> <20190118173103.4903-4-berrange@redhat.com> <20190122143257.GR13143@redhat.com> <20190122172333.GA13143@redhat.com> <9d0997e0-9019-c7c2-56d6-26c70f0d5c7e@redhat.com> In-Reply-To: <9d0997e0-9019-c7c2-56d6-26c70f0d5c7e@redhat.com> --kdmSty2OLfAjJpCraHdFXrDi9XIN2fyqI Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 22/01/2019 19.10, Eric Blake wrote: > On 1/22/19 11:23 AM, Daniel P. Berrang=C3=A9 wrote: >=20 >> >>>> On this point though, does anyone know of any platforms we support[1= ], >>>> or are likely to support in future, where 'strerror' is *not* thread= >>>> safe ? >>> >>> I'm not coming up with one, and I think the problem is independent of= >>> this series (if we DO have a problem, it's a series all its own to >>> eradicate the use of strerror() in favor of something safer, either >>> picking strerror_l() or dealing with the glibc vs. BSD differences in= >>> strerror_r()). >> >> Agree that its not really something for this series - this just >> made me think of it again. >=20 > Shoot - FreeBSD strerror() is not threadsafe: > https://github.com/freebsd/freebsd/blob/master/lib/libc/string/strerror= =2Ec#L119 >=20 > char * > strerror(int num) > { > static char ebuf[NL_TEXTMAX]; >=20 > if (strerror_r(num, ebuf, sizeof(ebuf)) !=3D 0) > errno =3D EINVAL; > return (ebuf); > } >=20 >> >> We went through the scrubbing in libvirt to use the sane, but still >> tedious to call, variant of strerror_r() many years ago. With luck >> though it is a worry that can be confined the dustbin of ancient >> UNIX history....unless someone can point to evidence to the contrary ?= >=20 > libvirt has it easy - they let gnulib do all the work of futzing around= > with getting a working strerror() despite platform bugs and despite > glibc's insistence on a non-POSIX signature if _GNU_SOURCE is defined. > We'll have to do a bit more legwork. >=20 > That said, I've added it to: > https://wiki.qemu.org/Contribute/BiteSizedTasks#Error_checking >=20 > if someone wants to do the grunt work. I think we should change that task to switch to g_strerror() from glib instead ... as far as I can see, this is a proper wrapper around strerror_r(), so we don't have to deal with the implementation oddities of strerror_r() in QEMU. Thomas --kdmSty2OLfAjJpCraHdFXrDi9XIN2fyqI-- --oavsMs1krcPZwOrJzYPfxinbIm5aH64IV Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEJ7iIR+7gJQEY8+q5LtnXdP5wLbUFAl2phmMACgkQLtnXdP5w LbU5Wg//dUv5ZwZalsdAVgj6u6eJo7WE59nDnBMSPiXQgjFPrF3cFZD2UbljkWfE rmuiwn5wCnlkvawmSsYZs+WALcEAiht8nBVz0qCpQ5hCFvp64/G84HB7JUXkcKdo TQ2Escn22xefESv7WZK2IToqYxLZs7tsoI6+VMVlDmK6c1rJHpxBZTcUfdTo7nW4 qacDDadolf7+dd7opTDP+6drdJdD7YtrYrhNqB1e9pOu06unMu+J0PM62fNegwUm 3GjqSjoU+mrv7SFOHy8gkXpUfWkgqAHYUbF+SvwHHg9CkJRzSQ4wCHc1aVSGrtlB U0QnYzbqgKin7N0Rppy3Plf8Dlkg88OJn5N48oE7nkjHwOWF4i8OR6+zu13vR7Vi xg5ZXqjaT9aV6CDdRD2PSsZDoDEatrn/OXxZdF6Q9wHKsRn5sdE2qMOwUyV0qdpo z/8GCkCGgo01Six8vL5wcP1IVKVgpAOLN95eM1BC4egEe9lxmP9YVvoxYFfFEn5q Be1f0Z8mUBmEYuNzcj3CMkLVPzLPHKzG0TRuTHgO7o0msQ5tlLCI9+HtjXzl1AD7 1i+vXAiUCQSrauzXMA1DaScIYO/b4udQ7jWgkUEjQtOTbSeVvFSRRQbHoHD+Ant0 urQIS8EYt3kjt41tjNFi30t65oSmd4nlj+leBz0IUgXsy0hYHVM= =Ut5Z -----END PGP SIGNATURE----- --oavsMs1krcPZwOrJzYPfxinbIm5aH64IV--