Re: [RFC v2 6/6] *-user: move safe-syscall.* to common-user

[Warner Losh <imp@bsdimp.com>]

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On Wed, Nov 10, 2021 at 10:04 AM Richard Henderson <
richard.henderson@linaro.org> wrote:

> On 11/10/21 5:31 PM, Warner Losh wrote:
> > Move linux-user/safe-syscall.S to common-user/common-safe-syscall.S and
> > replace it with a #include "common-safe-syscall.S" so that bsd-user can
> > also use it. Also move safe-syscall.h so that it can define a few more
> > externs.
> >
> > Signed-off-by: Warner Losh <imp@bsdimp.com>
> > ---
> >   common-user/common-safe-syscall.S          | 30 +++++++++++++++++++++
> >   {linux-user => common-user}/safe-syscall.h |  0
> >   linux-user/safe-syscall.S                  | 31 +---------------------
> >   linux-user/signal.c                        |  1 +
> >   meson.build                                |  1 +
> >   5 files changed, 33 insertions(+), 30 deletions(-)
> >   create mode 100644 common-user/common-safe-syscall.S
> >   rename {linux-user => common-user}/safe-syscall.h (100%)
> >
> > diff --git a/common-user/common-safe-syscall.S
> b/common-user/common-safe-syscall.S
> > new file mode 100644
> > index 0000000000..42ea7c40ba
> > --- /dev/null
> > +++ b/common-user/common-safe-syscall.S
> > @@ -0,0 +1,30 @@
> > +/*
> > + * safe-syscall.S : include the host-specific assembly fragment
> > + * to handle signals occurring at the same time as system calls.
> > + *
> > + * Written by Peter Maydell <peter.maydell@linaro.org>
> > + *
> > + * Copyright (C) 2016 Linaro Limited
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or
> later.
> > + * See the COPYING file in the top-level directory.
> > + */
> > +
> > +#include "hostdep.h"
> > +#include "target_errno_defs.h"
> > +
> > +/* We have the correct host directory on our include path
> > + * so that this will pull in the right fragment for the architecture.
> > + */
> > +#ifdef HAVE_SAFE_SYSCALL
> > +#include "safe-syscall.inc.S"
> > +#endif
> > +
> > +/* We must specifically say that we're happy for the stack to not be
> > + * executable, otherwise the toolchain will default to assuming our
> > + * assembly needs an executable stack and the whole QEMU binary will
> > + * needlessly end up with one. This should be the last thing in this
> file.
> > + */
> > +#if defined(__linux__) && defined(__ELF__)
> > +.section        .note.GNU-stack, "", %progbits
> > +#endif
>
> Hmm.  If we're going to split this file into safe-syscall.S and
> common-safe-syscall.S, we
> shouldn't do the ifdef thing here.  (Why it was present at all for
> linux-user is a mystery.)
>

Yea, the #ifdef dates from the earliest days of the safe syscall stuff. I
think it can be dropped,
though I'm unsure if the the whole thing should be dropped, or just the
ifdef.


> What do you have planned for bsd-user that would be more than
>
> > +#include "common-safe-syscall.S"
>
> this?
>

Yes. I had that in mind. I wasn't sure how to do this with meson directly,
or I'd have
compiled it out of common-user tree.

Warner

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