From: John Baldwin <jhb@FreeBSD.org>
To: Pedro Alves <palves@redhat.com>, Eli Zaretskii <eliz@gnu.org>
Cc: gdb-patches@sourceware.org
Subject: Re: [PATCH v3 2/3] Add an optional "alias" attribute to syscall entries.
Date: Wed, 28 Nov 2018 17:22:00 -0000 [thread overview]
Message-ID: <766d8293-d021-ce40-219e-f5a832b46fa7@FreeBSD.org> (raw)
In-Reply-To: <34fcc769-4533-31bf-d258-36c6110037e0@redhat.com>
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
next prev parent reply other threads:[~2018-11-28 17:22 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-09 20:04 [PATCH v3 0/3] Update FreeBSD's syscall table John Baldwin
2018-11-09 20:04 ` [PATCH v3 1/3] Change get_syscalls_by_group to append to an existing vector of integers John Baldwin
2018-11-09 20:04 ` [PATCH v3 2/3] Add an optional "alias" attribute to syscall entries John Baldwin
2018-11-09 20:18 ` Eli Zaretskii
2018-11-16 17:44 ` John Baldwin
2018-11-16 19:37 ` Eli Zaretskii
2018-11-27 17:13 ` Pedro Alves
2018-11-27 21:54 ` John Baldwin
2018-11-28 6:31 ` Eli Zaretskii
2018-11-28 12:19 ` Pedro Alves
2018-11-28 17:22 ` John Baldwin [this message]
2018-11-28 17:44 ` Eli Zaretskii
2018-11-28 18:00 ` John Baldwin
2018-11-28 18:31 ` Eli Zaretskii
2018-11-28 18:34 ` Pedro Alves
2018-11-28 19:15 ` John Baldwin
2018-11-28 19:21 ` Eli Zaretskii
2018-11-09 20:04 ` [PATCH v3 3/3] Update the FreeBSD system call table to match FreeBSD 12.0 John Baldwin
2018-11-26 20:31 ` [PATCH v3 0/3] Update FreeBSD's syscall table John Baldwin
2018-11-27 17:20 ` Pedro Alves
2018-11-27 20:00 ` John Baldwin
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