[PATCH v2] bootstd: Make efi_mgr bootmeth work for non-sandbox setups

[Mark Kettenis]

> From: Simon Glass <sjg at chromium.org>
> Date: Thu, 7 Sep 2023 06:23:10 -0600
> 
> Hi Mark,
> 
> On Sun, 3 Sept 2023 at 14:40, Mark Kettenis <kettenis at openbsd.org> wrote:
> >
> > Enable the bootflow based on this bootmeth if the BootOrder EFI
> > variable is set.
> >
> > Signed-off-by: Mark Kettenis <kettenis at openbsd.org>
> > ---
> >
> > ChangeLog:
> >
> > v2: - Initialize EFI subsystem to populate EFI variables
> >
> >
> >  boot/bootmeth_efi_mgr.c | 17 ++++++++++++++++-
> >  1 file changed, 16 insertions(+), 1 deletion(-)
> >
> > diff --git a/boot/bootmeth_efi_mgr.c b/boot/bootmeth_efi_mgr.c
> > index e9d973429f..e6c42d41fb 100644
> > --- a/boot/bootmeth_efi_mgr.c
> > +++ b/boot/bootmeth_efi_mgr.c
> > @@ -14,6 +14,8 @@
> >  #include <bootmeth.h>
> >  #include <command.h>
> >  #include <dm.h>
> > +#include <efi_loader.h>
> > +#include <efi_variable.h>
> >
> >  /**
> >   * struct efi_mgr_priv - private info for the efi-mgr driver
> > @@ -46,13 +48,26 @@ static int efi_mgr_check(struct udevice *dev, struct bootflow_iter *iter)
> >  static int efi_mgr_read_bootflow(struct udevice *dev, struct bootflow *bflow)
> >  {
> >         struct efi_mgr_priv *priv = dev_get_priv(dev);
> > +       efi_status_t ret;
> > +       efi_uintn_t size;
> > +       u16 *bootorder;
> >
> >         if (priv->fake_dev) {
> >                 bflow->state = BOOTFLOWST_READY;
> >                 return 0;
> >         }
> >
> > -       /* To be implemented */
> > +       ret = efi_init_obj_list();
> 
> Doesn't this start up the whole EFI system? Is there a cheaper way to
> see if the variable subsystem exists, or can work?

A fair bit of it at least.  With the possible exception of launching
EFI capsules (which shouldn't happen for a "normal" boot), I don't
think this is very expensive though.

There currently isn't a way to only initialize the variable subsystem;
we can't just call efi_init_variables() here since we have to also
call efi_disks_register() and a later efi_init_obj_list() call would
call efi_init_variables() again, which would leak memory.

Alternatively we could just unconditionally declare the efi_mgr
bootmeth as "ready" (like you already do for sandbox).  That would
postpone initialization of the EFI subsystem until we actually execute
this bootmeth.

But we need to do something before we switch more targets to standard
boot since otherwise booting through the EFI boot manager is just
plain broken.

> > +       if (ret)
> > +               return log_msg_ret("init", ret);
> > +
> > +       /* Enable this method if the "BootOrder" UEFI exists. */
> > +       bootorder = efi_get_var(u"BootOrder", &efi_global_variable_guid,
> > +                               &size);
> > +       if (bootorder) {
> > +               bflow->state = BOOTFLOWST_READY;
> > +               return 0;
> > +       }
> >
> >         return -EINVAL;
> >  }
> > --
> > 2.42.0
> >
> 
> Regards,
> Simon
>