[PATCH] cmd: bootefi: restore ability to boot arbitrary blob

[Kyle Evans]

On Sat, Apr 9, 2022 at 5:37 AM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 4/6/22 07:04, kevans at FreeBSD.org wrote:
> > From: Kyle Evans <kevans at FreeBSD.org>
> >
> > Up until commit 5f59518a7b1ae ("efi_loader: setting boot device"), we
> > could boot an arbitrary blob with bootefi.  Indeed, efi_run_image() even
> > has a special case for missing device paths indicating a payload that
> > was directly loaded via JTAG, for example.
> >
> > Restore the ability to inject a UEFI payload into memory and `bootefi`
> > it.  If the address passed isn't the last PE-COFF loaded, then we'll
> > wipe out the pre-existing DP/Image information and let efi_run_image()
> > synthesize a memory device path.
> >
> > An image size is required if we're booting an arbitrary payload, and
> > the FDT argument has been changed to accept `-`.  The size could be
> > deduced from the image header, but it's required anyways as an explicit
> > acknowledgment that one's trying to boot an arbitrary payload rather
> > than accidentally using the wrong address in the single-addr form.
> >
> > Signed-off-by: Kyle Evans <kevans at FreeBSD.org>
>
> I have tested at follows:
>
> host bind 0 ../sandbox.img
> load host 0:1 $kernel_addr_r helloworld.efi
> bootefi $fdt_add_r
>
> Expected result is a message
> No UEFI binary known at 0xc00000
>
> With your patch the message is not shown. Instead the help text for
> bootefi is displayed.
>

I can certainly pare down how often the help text is shown, I kind of
threw it everywhere thinking it'd be helpful because a lot of these
are "you're using it wrong" (including the above), but I'm a little
more awake now and could also see how this is more correct as "No UEFI
binary known" and the latter is more correct as "Incorrect size
specified".

> > ---
> >
> >   cmd/bootefi.c | 36 ++++++++++++++++++++++++++++--------
> >   1 file changed, 28 insertions(+), 8 deletions(-)
> >
> > diff --git a/cmd/bootefi.c b/cmd/bootefi.c
> > index 53d9f0e0dc..1dac74781e 100644
> > --- a/cmd/bootefi.c
> > +++ b/cmd/bootefi.c
> > @@ -425,7 +425,7 @@ static int do_efibootmgr(void)
> >    * @image_opt:      string of image start address
> >    * Return:  status code
> >    */
> > -static int do_bootefi_image(const char *image_opt)
> > +static int do_bootefi_image(const char *image_opt, const char *size_opt)
> >   {
> >       void *image_buf;
> >       unsigned long addr, size;
> > @@ -444,13 +444,29 @@ static int do_bootefi_image(const char *image_opt)
> >               if (!addr)
> >                       return CMD_RET_USAGE;
> >
> > +             size = 0;
> > +             if (size_opt) {
> > +                     size = strtoul(size_opt, NULL, 16);
> > +                     /* Check that a numeric value was passed */
> > +                     if (!size)
> > +                             return CMD_RET_USAGE;
> > +             }
> > +
> >               image_buf = map_sysmem(addr, 0);
> >
> >               if (image_buf != image_addr) {
> > -                     log_err("No UEFI binary known at %s\n", image_opt);
> > -                     return CMD_RET_FAILURE;
> > +                     /* Fake device path -- we must have a size. */
> > +
> > +                     if (image_addr)
> > +                             efi_clear_bootdev();
> > +
> > +                     if (size == 0)
> > +                             return CMD_RET_USAGE;
> > +             } else {
> > +                     if (size != 0)
> > +                             return CMD_RET_USAGE;
> > +                     size = image_size;
> >               }
> > -             size = image_size;
> >       }
> >       ret = efi_run_image(image_buf, size);
> >
> > @@ -654,7 +670,7 @@ static int do_bootefi(struct cmd_tbl *cmdtp, int flag, int argc,
> >               return CMD_RET_FAILURE;
> >       }
> >
> > -     if (argc > 2) {
> > +     if (argc > 2 && strcmp(argv[2], "-") != 0) {
> >               uintptr_t fdt_addr;
> >
> >               fdt_addr = hextoul(argv[2], NULL);
> > @@ -677,15 +693,19 @@ static int do_bootefi(struct cmd_tbl *cmdtp, int flag, int argc,
> >               return do_efi_selftest();
> >   #endif
> >
> > -     return do_bootefi_image(argv[1]);
> > +     return do_bootefi_image(argv[1], argc > 3 ? argv[3] : NULL);
> >   }
> >
> >   #ifdef CONFIG_SYS_LONGHELP
> >   static char bootefi_help_text[] =
> > -     "<image address> [fdt address]\n"
> > +     "<image address> [fdt address [image size]]\n"
> >       "  - boot EFI payload stored at address <image address>.\n"
> >       "    If specified, the device tree located at <fdt address> gets\n"
> >       "    exposed as EFI configuration table.\n"
> > +     "    The image size is required if this is not a preloaded image, but\n"
> > +     "    it must be omitted if the image was preloaded.\n"
>
> Why must the image size be omitted?
>
> I expect the following to work fine:
>
> load host 0:1 $kernel_addr_r foo.efi
> bootefi $kernel_addr_r - $filesize
>

I'll change this to allow omission and require a match if it's
specified and the address matches last loaded.

> Best regards
>
> Heinrich
>
> > +     "    The <fdt address> parameter accepts '-' to indicate FDT already\n"
> > +     "    installed or pre-specified in fdt_addr or fdtcontroladdr.\n"
> >   #ifdef CONFIG_CMD_BOOTEFI_HELLO
> >       "bootefi hello\n"
> >       "  - boot a sample Hello World application stored within U-Boot\n"
> > @@ -707,7 +727,7 @@ static char bootefi_help_text[] =
> >   #endif
> >
> >   U_BOOT_CMD(
> > -     bootefi, 3, 0, do_bootefi,
> > +     bootefi, 4, 0, do_bootefi,
> >       "Boots an EFI payload from memory",
> >       bootefi_help_text
> >   );
>