From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 105019 invoked by alias); 28 Nov 2018 17:22:31 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 104514 invoked by uid 89); 28 Nov 2018 17:22:28 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-1.2 required=5.0 tests=BAYES_00,SPF_HELO_PASS,SPF_SOFTFAIL autolearn=no version=3.3.2 spammy=HContent-Transfer-Encoding:8bit X-HELO: mail.baldwin.cx Received: from bigwig.baldwin.cx (HELO mail.baldwin.cx) (96.47.65.170) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 28 Nov 2018 17:22:25 +0000 Received: from John-Baldwins-MacBook-Pro-2.local (ralph.baldwin.cx [66.234.199.215]) by mail.baldwin.cx (Postfix) with ESMTPSA id F001010AFCD; Wed, 28 Nov 2018 12:22:22 -0500 (EST) Subject: Re: [PATCH v3 2/3] Add an optional "alias" attribute to syscall entries. To: Pedro Alves , Eli Zaretskii References: <20181109200432.84491-1-jhb@FreeBSD.org> <20181109200432.84491-3-jhb@FreeBSD.org> <83efbuattx.fsf@gnu.org> <650590ef-3036-57a8-6cd5-abaa5654add3@FreeBSD.org> <34fcc769-4533-31bf-d258-36c6110037e0@redhat.com> Cc: gdb-patches@sourceware.org From: John Baldwin Openpgp: preference=signencrypt Message-ID: <766d8293-d021-ce40-219e-f5a832b46fa7@FreeBSD.org> Date: Wed, 28 Nov 2018 17:22:00 -0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <34fcc769-4533-31bf-d258-36c6110037e0@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-IsSubscribed: yes X-SW-Source: 2018-11/txt/msg00516.txt.bz2 On 11/28/18 4:19 AM, Pedro Alves wrote: > On 11/27/2018 09:53 PM, John Baldwin wrote: >> +On some operating systems, a system call name may map to more than one >> +system call number. For example, the FreeBSD kernel allocates new >> +system call numbers when changing the ABI of an existing system call. >> +The kernel also includes a compatibility system call using the old ABI >> +and number. FreeBSD's system call XML file includes aliases for >> +compatibility system calls that are used to catch all versions of a >> +system call. For example, FreeBSD 12 introduced a new variant of the >> +@code{kevent} system call. Both system calls are caught when catching >> +the @code{kevent} system call: >> + >> +@smallexample >> +(@value{GDBP}) catch syscall kevent >> +Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560]) >> +(@value{GDBP}) >> +@end smallexample >> + > > I'd suggest replacing "FreeBSD's system call XML file includes" with > something else that isn't so implementor-speak. Users needn't > be aware of the XML file. Maybe something along the lines of > "GDB is aware of aliases for compatibility system calls that > are used to catch ..." Or maybe remove the sentence altogether. > Maybe simplify it a bit further, as users don't really need > to be told that that's what FreeBSD does for all new syscalls, > just that some syscalls are like that. I think. Thus, something > like this is enough, IMHO: > > > On some operating systems, a system call name may map to more than one > system call number. > > For example, FreeBSD 12 introduced a new variant of the @code{kevent} system > call, and included a compatibility system call using the old ABI and number. > As convenience, both system calls are caught when catching the @code{kevent} > system call by name: > > @smallexample > (@value{GDBP}) catch syscall kevent > Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560]) > (@value{GDBP}) > @end smallexample Yes, I think this is better as well. Eli, I don't know if other OS's will make use of this feature. Given Pedro's new text above, do you think it should still be moved into a native section or should it stay in the the syscall section? -- John Baldwin                                                                            Â