Date: Tue, 1 Apr 2003 18:42:30 -0500 (EST) From: Daniel Eischen <eischen@pcnet1.pcnet.com> To: Jake Burkholder <jake@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern kern_context.c Message-ID: <Pine.GSO.4.10.10304011827200.9020-100000@pcnet1.pcnet.com> In-Reply-To: <200304012325.h31NPI3p086961@repoman.freebsd.org>
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On Tue, 1 Apr 2003, Jake Burkholder wrote:
> jake 2003/04/01 15:25:18 PST
>
> FreeBSD src repository
>
> Modified files:
> sys/kern kern_context.c
> Log:
> - Fix UC_COPY_SIZE. Adding up the size of structure fields doesn't take
> alignment into account.
> - Return EJUSTRETURN from set_context on success to avoid clobbering the
> first 2 out registers with td_retval on sparc64.
Oh shit. I forgot I have some local changes lying around
to fix being able to set/swapcontext on an interrupted
context (not formed by getcontext). When getcontext()
is called, the return value registers need to be cleared
so that 0 is returned after a subsequent setcontext():
ret = getcontext(&uc);
...
setcontext(&uc);
The above should work as well as:
void
sighandler(int sig, siginfo_t *info, ucontext_t *ucp)
{
...
setcontext(ucp);
}
The latter case doesn't want to return 0 in the syscall;
it wants to return EJUSTRETURN. In the former case, you
need to be able to return 0.
I think you need to fix get_mcontext() so that it clears
the return values or it breaks the first case.
My changes add a third parameter to
get_mcontext(struct thread *td, mcontext_t *mcp, int clear_retval)
so that you can tell it to clear the return values.
When getcontext() calls get_mcontext() you want to clear
the return values in the context, but when get_mcontext()
is called by sendsig() or by the KSE system, you don't
want to clear the return values.
Is this making any sense?
--
Dan Eischen
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