[PATCH] efi_loader: Disable devices before handing over control

[Ilias Apalodimas]

Hi Heinrich,

On Wed, Oct 21, 2020 at 12:17:29PM +0200, Heinrich Schuchardt wrote:
> On 10/21/20 9:32 AM, Ilias Apalodimas wrote:
> > U-Boot Driver Model is supposed to remove devices with either
> > DM_REMOVE_ACTIVE_DMA or DM_REMOVE_OS_PREPARE flags set, before exiting.
> > Our bootm command does that by explicitly calling calling
> > "dm_remove_devices_flags(DM_REMOVE_ACTIVE_ALL);" and we also disable any
> > USB devices.
> >
> > The EFI equivalent is doing none of those at the moment. As a result
> > probing an fTPM driver now renders it unusable in Linux. During our
> > (*probe) callback we open a session with OP-TEE, which is supposed to
> > close with our (*remove) callback. Since the (*remove) is never called,
> > once we boot into Linux and try to probe the device again we are getting
> > a busy error response. We also never free
> >
> > So let's fix this by mimicking what bootm does and disconnect devices
> > when efi_exit_boot_services() is called. Note that for the OP-TEE case
> > and in particular any subsequent bootloader that wants to use a device
> > (e.g GRUB) will need to call exit_boot_services() in order to close the
> > session.
> 
> Hello Ilias,
> 
> thanks for the patch. Adding the function calls looks correct to me,

Well the only doubt I have is what if GRUB has to extend some PCRs before 
calling Linux? Any idea if it's currently calling ExitBootSevices?
I was considering if it would be a better idea to call the device unbinding during
some kind of "exit" from U-boot's EFI code. (i.e before StartImage)

> but
> sandbox_spl_defconfig gives me a compile time error with this patch, cf.
> https://gitlab.denx.de/u-boot/custodians/u-boot-efi/-/jobs/166842
> 
> You might want to use Travis CI before resubmitting.

Ok will do.

Thanks
/Ilias

> 
> Best regards
> 
> Heinrich
> 
> 
> >
> > Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> > ---
> >  lib/efi_loader/efi_boottime.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> > index bf78176217c6..25e6cf0fe719 100644
> > --- a/lib/efi_loader/efi_boottime.c
> > +++ b/lib/efi_loader/efi_boottime.c
> > @@ -18,6 +18,8 @@
> >  #include <pe.h>
> >  #include <u-boot/crc.h>
> >  #include <watchdog.h>
> > +#include <dm/device.h>
> > +#include <dm/root.h>
> >
> >  DECLARE_GLOBAL_DATA_PTR;
> >
> > @@ -1994,7 +1996,10 @@ static efi_status_t EFIAPI efi_exit_boot_services(efi_handle_t image_handle,
> >  			list_del(&evt->link);
> >  	}
> >
> > +	if IS_ENABLED(CONFIG_USB_DEVICE)
> > +		udc_disconnect();
> >  	board_quiesce_devices();
> > +	dm_remove_devices_flags(DM_REMOVE_ACTIVE_ALL);
> >
> >  	/* Patch out unsupported runtime function */
> >  	efi_runtime_detach();
> >
>