[U-Boot] [RFC] efi_loader: support for CONFIG_ARMV7_NONSEC

[Mark Kettenis]

> From: Alexander Graf <agraf at suse.de>
> Date: Fri, 6 Apr 2018 09:48:06 +0200
> 
> On 06.04.18 07:43, Heinrich Schuchardt wrote:
> > Booting with SMP fails on the Allwinner A20 CPU.
> > https://gist.github.com/xypron/2524ba898d6905d959c744c2b05da196
> > 
> > When executing bootefi we need to
> > * copy the Power State Coordination Interface (PSCI) code to its
> >   destination address
> > * switch between our hypervisor mode (HYP) and the supervisor mode (SVC)
> >   of the payload (http://linux-sunxi.org/PSCI)
> > 
> > This patch is incomplete. It is just meant to indicate where we could
> > change the entry point.
> > 
> > With the patch iPXE cannot get a network address.
> > 
> > Possibly a better moment for switching to SVC is ExitBootServices.
> > 
> > We also have to consider switching modes at EFI_ENTRY and EFI_EXIT.
> > 
> > Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
> 
> Well, I think it makes perfect sense to switch to HYP mode. We do the
> same on AArch64 when we're in EL3 (MON). The fact that iPXE can not get
> a network address then sounds weird - HYP should have the same privilege
> level as Linux does eventually and there network probably works for you.
> 
> Maybe we also need to do the dcache flushing dance? See efi_run_in_el2().
> 
> Either way, here's a slightly more clean (untested!) version of your
> patch. Because Thunderbird is very good at mangling patches, I'll also
> give you a pastebin link[1].

Since OpenBSD/armv7 requires an EFI implementation I spent some time
investigating this approach.  I just posted a small patch series that
seems to work.  Turns out the dcache flushing dance is indeed
necessary.  Without it, the "global data" pointer sometimes ends up
being uninitialized after the switch into non-secure mode.  The
crucial fix though is making sure we have a usable stack when
returning from HYP mode.  That may very well be the issue that
Heinrich ran into.

> diff --git a/cmd/bootefi.c b/cmd/bootefi.c
> index 5a2a81005f..8107ada52c 100644
> --- a/cmd/bootefi.c
> +++ b/cmd/bootefi.c
> @@ -20,6 +20,11 @@
>  #include <asm-generic/sections.h>
>  #include <linux/linkage.h>
> 
> +#ifdef CONFIG_ARM
> +#include <asm/armv7.h>
> +#include <asm/secure.h>
> +#endif
> +
>  DECLARE_GLOBAL_DATA_PTR;
> 
>  #define OBJ_LIST_NOT_INITIALIZED 1
> @@ -178,6 +183,15 @@ static efi_status_t efi_run_in_el2(EFIAPI
> efi_status_t (*entry)(
>  }
>  #endif
> 
> +#ifdef CONFIG_ARMV7_NONSEC
> +static efi_status_t efi_run_in_hyp(EFIAPI efi_status_t (*entry)(
> +			efi_handle_t image_handle, struct efi_system_table *st),
> +			efi_handle_t image_handle, struct efi_system_table *st)
> +{
> +	return efi_do_enter(image_handle, st, entry);
> +}
> +#endif
> +
>  /* Carve out DT reserved memory ranges */
>  static efi_status_t efi_carve_out_dt_rsv(void *fdt)
>  {
> @@ -327,6 +341,19 @@ static efi_status_t do_bootefi_exec(void *efi,
>  	}
>  #endif
> 
> +#ifdef CONFIG_ARMV7_NONSEC
> +	if (armv7_boot_nonsec()) {
> +		armv7_init_nonsec();
> +		secure_ram_addr(_do_nonsec_entry)(efi_run_in_hyp,
> +				(uintptr_t)entry,
> +				(uintptr_t)&loaded_image_info_obj.handle,
> +				(uintptr_t)&systab);
> +
> +		/* Should never reach here, efi exits with longjmp */
> +		while (1) { }
> +	}
> +#endif
> +
>  	ret = efi_do_enter(loaded_image_info_obj.handle, &systab, entry);
> 
>  exit:
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