[PATCH 24/35] x86: Allow booting a kernel from the EFI app

[Simon Glass]

Hi Heinrich,

On Wed, 8 Sept 2021 at 12:22, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
>
>
> On 9/8/21 3:33 PM, Simon Glass wrote:
> > At present this is disabled, but it should work so long as the kernel does
> > not need EFI services. Enable it and add a note about remaining work.
> >
> > Signed-off-by: Simon Glass <sjg at chromium.org>
> > ---
> >
> >   arch/x86/lib/bootm.c | 11 +++++++----
> >   1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/lib/bootm.c b/arch/x86/lib/bootm.c
> > index 733dd712570..ff0e9f6a085 100644
> > --- a/arch/x86/lib/bootm.c
> > +++ b/arch/x86/lib/bootm.c
> > @@ -179,10 +179,14 @@ int boot_linux_kernel(ulong setup_base, ulong load_address, bool image_64bit)
> >               * U-Boot is setting them up that way for itself in
> >               * arch/i386/cpu/cpu.c.
> >               *
> > -             * Note that we cannot currently boot a kernel while running as
> > -             * an EFI application. Please use the payload option for that.
> > +             * Note: this is incomplete for EFI kernels!
> > +             *
> > +             * This can boot a kernel while running as an EFI application,
> > +             * but if the kernel requires EFI support then that support needs
> > +             * to be enabled first (see EFI_LOADER). Also the EFI information
> > +             * must enabled with setup_efi_info(). See setup_zimage() for
> > +             * how this is done with the stub.
>
> Did you test launching an EFI application with EFI_LOADER from the EFI
> app? If you get it working, please provide a defconfig and a testcase
> that runs helloworld.efi.

No unfortunately that cannot be built at present. This is just for
kernels that don't use EFI_LOADER.

I am pretty sure it could be made to work, perhaps by passing the
original UEFI system table through to the kernel.

Regards,
Simon