On Tue, Aug 29, 2023 at 2:28 PM Richard Henderson <
richard.hender...@linaro.org> wrote:
> On 8/27/23 08:57, Karim Taha wrote:
> > From: Stacey Son<s...@freebsd.org>
> >
> > Signed-off-by: Stacey Son<s...@freebsd.org>
> > Signed-off-by: Karim Taha<kariem.taha...@gmail.com>
> > ---
> > bsd-user/freebsd/os-proc.c | 177 +++++++++++++++++++++++++++++++++++++
> > 1 file changed, 177 insertions(+)
>
> Acked-by: Richard Henderson <richard.hender...@linaro.org>
>
> > + if (do_fexec) {
> > + if (((int)path_or_fd > 0 &&
> > + is_target_elf_binary((int)path_or_fd)) == 1) {
> > + char execpath[PATH_MAX];
> > +
> > + /*
> > + * The executable is an elf binary for the target
> > + * arch. execve() it using the emulator if we can
> > + * determine the filename path from the fd.
> > + */
> > + if (get_filename_from_fd(getpid(), (int)path_or_fd,
> execpath,
> > + sizeof(execpath)) != NULL) {
> > + memmove(qarg1 + 2, qarg1, (qargend-qarg1) *
> sizeof(*qarg1));
> > + qarg1[1] = qarg1[0];
> > + qarg1[0] = (char *)"-0";
> > + qarg1 += 2;
> > + qargend += 2;
> > + *qarg1 = execpath;
> > +#ifndef DONT_INHERIT_INTERP_PREFIX
> > + memmove(qarg1 + 2, qarg1, (qargend-qarg1) *
> sizeof(*qarg1));
> > + *qarg1++ = (char *)"-L";
> > + *qarg1++ = (char *)interp_prefix;
> > +#endif
>
> I'm not especailly keen on the ifdef, but I'll let that go.
>
> As for get_filename_from_fd, perhaps it would be cleaner to add a
> command-line parameter
> which would allow qemu to run from an open file descriptor? Although
> perhaps that has
> CLOEXEC implications too...
>
This is one area that's in transition in the bsd-user stuff, but we've not
yet finished
that transition. Doug Rabson has created something that caches a reference
to
the interpreter, and if we exec the same kind of binary, it will reuse that
reference.
In a jail that Doug's code runs, this allows the interpreter to be running
a binary
from outside the jail, while restricting the emulated binary's reach to the
jail.
This eliminates, in some cases, the need to inherit this prefix. However,
in other
cases, it still seems to be needed (like when I'm not in a chroot
environment and
wanting to pull the shared libraries from a different location). How to
resolve
these two cases is an on-going area of discussions. And all the work may not
yet be merged with the upstream tree.
Warner
