linux-kernel - Re: [PATCH] binfmt_misc: pass binfmt

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Date:   Fri, 6 Mar 2020 19:29:57 +0800
From:   YunQiang Su <syq@...ian.org>
To:     Laurent Vivier <laurent@...ier.eu>
Cc:     Florian Weimer <fw@...eb.enyo.de>, torvalds@...ux-foundation.org,
        Greg KH <gregkh@...uxfoundation.org>,
        akpm@...ux-foundation.org, Al Viro <viro@...iv.linux.org.uk>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        libc-alpha@...rceware.org
Subject: Re: [PATCH] binfmt_misc: pass binfmt_misc P flag to the interpreter

Laurent Vivier <laurent@...ier.eu> 于2020年3月6日周五 下午7:13写道：
>
> Le 06/03/2020 à 09:37, Florian Weimer a écrit :
> > * Laurent Vivier:
> >
> >> Le 06/03/2020 à 09:13, Florian Weimer a écrit :
> >>> * YunQiang Su:
> >>>
> >>>> +  if (bprm->interp_flags & BINPRM_FLAGS_PRESERVE_ARGV0)
> >>>> +          flags |= AT_FLAGS_PRESERVE_ARGV0;
> >>>> +  NEW_AUX_ENT(AT_FLAGS, flags);
> >>>
> >>> Is it necessary to reuse AT_FLAGS?  I think it's cleaner to define a
> >>> separate AT_ tag dedicated to binfmt_misc.
> >>
> >> Not necessary, but it seemed simpler and cleaner to re-use a flag that
> >> is marked as unused and with a name matching the new role. It avoids to
> >> patch other packages (like glibc) to add it as it is already defined.
> >
> > You still need to define AT_FLAGS_PRESERVE_ARGV0.  At that point, you
> > might as well define AT_BINFMT and AT_BINFMT_PRESERVE_ARGV0.
> >
>
> Yes, you're right.
>
> But is there any reason to not reuse AT_FLAGS?

AT_* only has 32 slot and now. I was afraid that maybe we shouldn't take one.
   /* AT_* values 18 through 22 are reserved */
   27,28,29,30 are not used now.
Which should we use?

>
> Thanks,
> Laurent