Date: Fri, 12 Mar 2010 11:29:32 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Jung-uk Kim <jkim@freebsd.org> Cc: freebsd-hackers@freebsd.org, Marcel Moolenaar <xcllnt@mac.com> Subject: Re: [RFC] Saving the latest errno from syscalls. Message-ID: <20100312092932.GJ2489@deviant.kiev.zoral.com.ua> In-Reply-To: <201003111815.10186.jkim@FreeBSD.org> References: <201003111624.51018.jkim@FreeBSD.org> <8EE3605E-6E39-44A1-9E3A-5A37E1921D27@mac.com> <201003111815.10186.jkim@FreeBSD.org>
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--7epHAAa1/vAPJ6LR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Mar 11, 2010 at 06:15:07PM -0500, Jung-uk Kim wrote: > On Thursday 11 March 2010 04:55 pm, Marcel Moolenaar wrote: > > On Mar 11, 2010, at 1:24 PM, Jung-uk Kim wrote: > > > While I was debugging syscalls, I found a very useful field in > > > struct thread, td_errno. It seems it was added for dtrace but it > > > is only populated on amd64 and i386. Is the attached patch > > > acceptable for maintainers of other platforms? > > > > Isn't it better to do it in cpu_set_syscall_retval()? > > That way you catch all cases, plus you can save the > > translated error as well... >=20 > I just took amd64/i386 as an example and I was not sure whether it was=20 > meant to store translated error or not. Does anyone with DTrace=20 > internal knowledge answer the question? I do not know that much about DTrace, but it seems that setting td_errno in cpu_set_syscall_retval() is too late. Dtrace has a probe after the syscall return, and it is called right before cpu_set_syscall_retval() can be reasonably called. The probe only issued for syscall that goes into sysent. --7epHAAa1/vAPJ6LR Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkuaCXwACgkQC3+MBN1Mb4iYGQCfbxmtBnBDez8DMbLGZLKuXcYj SRQAoNdLRhK4xmEf5VRk6OJBJauQjvAQ =W5iU -----END PGP SIGNATURE----- --7epHAAa1/vAPJ6LR--
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