Date: Wed, 26 Apr 2023 15:15:09 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Hans Petter Selasky <hselasky@freebsd.org> Cc: Zhenlei Huang <zlei@freebsd.org>, FreeBSD CURRENT <freebsd-current@freebsd.org>, Gleb Smirnoff <glebius@freebsd.org> Subject: Re: Link modules to DYN type Message-ID: <ZEkVzcdYuh_MkDZm@kib.kiev.ua> In-Reply-To: <f200bce7-add8-6aff-38cf-2ee15dc35411@freebsd.org> References: <97390FE1-1DF5-43A1-A3F4-2B945D681437@FreeBSD.org> <2bb66cac-c7f1-e45b-693a-8afbda05cfa6@freebsd.org> <ZEkHKJ_BRhV22gf_@kib.kiev.ua> <f200bce7-add8-6aff-38cf-2ee15dc35411@freebsd.org>
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On Wed, Apr 26, 2023 at 01:38:32PM +0200, Hans Petter Selasky wrote:
> On 4/26/23 13:12, Konstantin Belousov wrote:
> > No, in-kernel linker does not behave this way.
> > Modules need to contain explicit reference to all modules they depend upon,
> > using the MODULE_DEPEND() macro. Only symbols from the dependencies are
> > resolved.
> >
> > All modules get an implicit reference to kernel.
>
> Hi Konstantin,
>
> Maybe I wasn't so clear. Trying again:
>
> > diff --git a/sys/tests/ktest.c b/sys/tests/ktest.c
> > index 495fedf95dde..eb42cf062487 100644
> > --- a/sys/tests/ktest.c
> > +++ b/sys/tests/ktest.c
> > @@ -409,6 +409,12 @@ static moduledata_t ktestmod = {
> > 0
> > };
> > +int
> > +printf(const char *fmt, ...)
> > +{
> > + return (0);
> > +}
> > +
> > DECLARE_MODULE(ktestmod, ktestmod, SI_SUB_PSEUDO, SI_ORDER_ANY);
> > MODULE_VERSION(ktestmod, 1);
> > MODULE_DEPEND(ktestmod, netlink, 1, 1, 1);
>
> Then kldload ktest.ko . Which printf() function will be used if ktest.c
> calls printf() ?
My best guess is that printf is resolved locally by the static linker,
even before the module is loaded. In other words, it would be ktest.c
printf.
>
> I would expect a warning from the kernel at least ...
This is not how ELF behaves, even in such not fully compliant env as kernel.
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