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Re: [PATCH v3 2/3] Add an optional "alias" attribute to syscall entries.
> Cc: gdb-patches@sourceware.org
> From: John Baldwin <jhb@FreeBSD.org>
> Date: Fri, 16 Nov 2018 09:43:56 -0800
>
> > IMO, this is very abstract and too vague to be useful. Since we won't
> > have anything more detailed in the manual, would it be possible to
> > make this description more concrete? E.g., how about using some of
> > the text and examples you used in your description of the issue:
>
> Ok. I wasn't too happy with my first attempt either. I've tried to give
> some more detail while not making it too long. Let me know what you think:
>
> * System call catchpoints now support system call aliases on FreeBSD.
> When the ABI of a system call changes in FreeBSD, this is
> implemented by leaving a compatibility system call using the old ABI
> at the existing number and allocating a new system call number for
> the new ABI. For example, FreeBSD 12 altered the layout of 'struct
> kevent' used by the 'kevent' system call. As a result, FreeBSD 12
> kernels ship with both 'kevent' and 'freebsd11_kevent' system calls.
> The 'freebsd11_kevent' system call is assigned an alias of 'kevent'
> so that a system call catchpoint for the 'kevent' system call will
> catch invocations of both the 'kevent' and 'freebsd11_kevent'
> binaries. This ensures that 'kevent' system calls are caught for
> binaries using either the old or new ABIs.
LGTM, thanks.