Re: [PATCH 2/2] efi/x86: Add a quirk to support command line arguments on Dell EFI firmware

[Ard Biesheuvel <ardb@kernel.org>]

On Tue, 15 Sep 2020 at 00:35, Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> At least some versions of Dell EFI firmware pass the entire
> EFI_LOAD_OPTION descriptor, rather than just the OptionalData part, to
> the loaded image. This was verified with firmware revision 2.15.0 on a
> Dell Precision T3620 by Jacobo Pontaja.
>
> To handle this, add a quirk to check if the options look like a valid
> EFI_LOAD_OPTION descriptor, and if so, use the OptionalData part as the
> command line.
>
> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
> Reported-by: Jacobo Pantoja <jacobopantoja@gmail.com>
> Link: https://lore.kernel.org/linux-efi/20200907170021.GA2284449@rani.riverdale.lan/

I'll queue these up for v5.10

Thanks all

> ---
>  .../firmware/efi/libstub/efi-stub-helper.c    | 101 +++++++++++++++++-
>  drivers/firmware/efi/libstub/efistub.h        |  31 ++++++
>  drivers/firmware/efi/libstub/file.c           |   5 +-
>  3 files changed, 135 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
> index f735db55adc0..aa8da0a49829 100644
> --- a/drivers/firmware/efi/libstub/efi-stub-helper.c
> +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
> @@ -238,6 +238,102 @@ efi_status_t efi_parse_options(char const *cmdline)
>         return EFI_SUCCESS;
>  }
>
> +/*
> + * The EFI_LOAD_OPTION descriptor has the following layout:
> + *     u32 Attributes;
> + *     u16 FilePathListLength;
> + *     u16 Description[];
> + *     efi_device_path_protocol_t FilePathList[];
> + *     u8 OptionalData[];
> + *
> + * This function validates and unpacks the variable-size data fields.
> + */
> +static
> +bool efi_load_option_unpack(efi_load_option_unpacked_t *dest,
> +                           const efi_load_option_t *src, size_t size)
> +{
> +       const void *pos;
> +       u16 c;
> +       efi_device_path_protocol_t header;
> +       const efi_char16_t *description;
> +       const efi_device_path_protocol_t *file_path_list;
> +
> +       if (size < offsetof(efi_load_option_t, variable_data))
> +               return false;
> +       pos = src->variable_data;
> +       size -= offsetof(efi_load_option_t, variable_data);
> +
> +       if ((src->attributes & ~EFI_LOAD_OPTION_MASK) != 0)
> +               return false;
> +
> +       /* Scan description. */
> +       description = pos;
> +       do {
> +               if (size < sizeof(c))
> +                       return false;
> +               c = *(const u16 *)pos;
> +               pos += sizeof(c);
> +               size -= sizeof(c);
> +       } while (c != L'\0');
> +
> +       /* Scan file_path_list. */
> +       file_path_list = pos;
> +       do {
> +               if (size < sizeof(header))
> +                       return false;
> +               header = *(const efi_device_path_protocol_t *)pos;
> +               if (header.length < sizeof(header))
> +                       return false;
> +               if (size < header.length)
> +                       return false;
> +               pos += header.length;
> +               size -= header.length;
> +       } while ((header.type != EFI_DEV_END_PATH && header.type != EFI_DEV_END_PATH2) ||
> +                (header.sub_type != EFI_DEV_END_ENTIRE));
> +       if (pos != (const void *)file_path_list + src->file_path_list_length)
> +               return false;
> +
> +       dest->attributes = src->attributes;
> +       dest->file_path_list_length = src->file_path_list_length;
> +       dest->description = description;
> +       dest->file_path_list = file_path_list;
> +       dest->optional_data_size = size;
> +       dest->optional_data = size ? pos : NULL;
> +
> +       return true;
> +}
> +
> +/*
> + * At least some versions of Dell firmware pass the entire contents of the
> + * Boot#### variable, i.e. the EFI_LOAD_OPTION descriptor, rather than just the
> + * OptionalData field.
> + *
> + * Detect this case and extract OptionalData.
> + */
> +void efi_apply_loadoptions_quirk(const void **load_options, int *load_options_size)
> +{
> +       const efi_load_option_t *load_option = *load_options;
> +       efi_load_option_unpacked_t load_option_unpacked;
> +
> +       if (!IS_ENABLED(CONFIG_X86))
> +               return;
> +       if (!load_option)
> +               return;
> +       if (*load_options_size < sizeof(*load_option))
> +               return;
> +       if ((load_option->attributes & ~EFI_LOAD_OPTION_BOOT_MASK) != 0)
> +               return;
> +
> +       if (!efi_load_option_unpack(&load_option_unpacked, load_option, *load_options_size))
> +               return;
> +
> +       efi_warn_once(FW_BUG "LoadOptions is an EFI_LOAD_OPTION descriptor\n");
> +       efi_warn_once(FW_BUG "Using OptionalData as a workaround\n");
> +
> +       *load_options = load_option_unpacked.optional_data;
> +       *load_options_size = load_option_unpacked.optional_data_size;
> +}
> +
>  /*
>   * Convert the unicode UEFI command line to ASCII to pass to kernel.
>   * Size of memory allocated return in *cmd_line_len.
> @@ -247,12 +343,15 @@ char *efi_convert_cmdline(efi_loaded_image_t *image, int *cmd_line_len)
>  {
>         const u16 *s2;
>         unsigned long cmdline_addr = 0;
> -       int options_chars = efi_table_attr(image, load_options_size) / 2;
> +       int options_chars = efi_table_attr(image, load_options_size);
>         const u16 *options = efi_table_attr(image, load_options);
>         int options_bytes = 0, safe_options_bytes = 0;  /* UTF-8 bytes */
>         bool in_quote = false;
>         efi_status_t status;
>
> +       efi_apply_loadoptions_quirk((const void **)&options, &options_chars);
> +       options_chars /= sizeof(*options);
> +
>         if (options) {
>                 s2 = options;
>                 while (options_bytes < COMMAND_LINE_SIZE && options_chars--) {
> diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
> index e33b9395bc23..7997890c756d 100644
> --- a/drivers/firmware/efi/libstub/efistub.h
> +++ b/drivers/firmware/efi/libstub/efistub.h
> @@ -711,6 +711,35 @@ union efi_load_file_protocol {
>         } mixed_mode;
>  };
>
> +typedef struct {
> +       u32 attributes;
> +       u16 file_path_list_length;
> +       u8 variable_data[];
> +       // efi_char16_t description[];
> +       // efi_device_path_protocol_t file_path_list[];
> +       // u8 optional_data[];
> +} __packed efi_load_option_t;
> +
> +#define EFI_LOAD_OPTION_ACTIVE         0x0001U
> +#define EFI_LOAD_OPTION_FORCE_RECONNECT        0x0002U
> +#define EFI_LOAD_OPTION_HIDDEN         0x0008U
> +#define EFI_LOAD_OPTION_CATEGORY       0x1f00U
> +#define   EFI_LOAD_OPTION_CATEGORY_BOOT        0x0000U
> +#define   EFI_LOAD_OPTION_CATEGORY_APP 0x0100U
> +
> +#define EFI_LOAD_OPTION_BOOT_MASK \
> +       (EFI_LOAD_OPTION_ACTIVE|EFI_LOAD_OPTION_HIDDEN|EFI_LOAD_OPTION_CATEGORY)
> +#define EFI_LOAD_OPTION_MASK (EFI_LOAD_OPTION_FORCE_RECONNECT|EFI_LOAD_OPTION_BOOT_MASK)
> +
> +typedef struct {
> +       u32 attributes;
> +       u16 file_path_list_length;
> +       const efi_char16_t *description;
> +       const efi_device_path_protocol_t *file_path_list;
> +       size_t optional_data_size;
> +       const void *optional_data;
> +} efi_load_option_unpacked_t;
> +
>  void efi_pci_disable_bridge_busmaster(void);
>
>  typedef efi_status_t (*efi_exit_boot_map_processing)(
> @@ -753,6 +782,8 @@ __printf(1, 2) int efi_printk(char const *fmt, ...);
>
>  void efi_free(unsigned long size, unsigned long addr);
>
> +void efi_apply_loadoptions_quirk(const void **load_options, int *load_options_size);
> +
>  char *efi_convert_cmdline(efi_loaded_image_t *image, int *cmd_line_len);
>
>  efi_status_t efi_get_memory_map(struct efi_boot_memmap *map);
> diff --git a/drivers/firmware/efi/libstub/file.c b/drivers/firmware/efi/libstub/file.c
> index 630caa6b1f4c..4e81c6077188 100644
> --- a/drivers/firmware/efi/libstub/file.c
> +++ b/drivers/firmware/efi/libstub/file.c
> @@ -136,7 +136,7 @@ efi_status_t handle_cmdline_files(efi_loaded_image_t *image,
>                                   unsigned long *load_size)
>  {
>         const efi_char16_t *cmdline = image->load_options;
> -       int cmdline_len = image->load_options_size / 2;
> +       int cmdline_len = image->load_options_size;
>         unsigned long efi_chunk_size = ULONG_MAX;
>         efi_file_protocol_t *volume = NULL;
>         efi_file_protocol_t *file;
> @@ -148,6 +148,9 @@ efi_status_t handle_cmdline_files(efi_loaded_image_t *image,
>         if (!load_addr || !load_size)
>                 return EFI_INVALID_PARAMETER;
>
> +       efi_apply_loadoptions_quirk((const void **)&cmdline, &cmdline_len);
> +       cmdline_len /= sizeof(*cmdline);
> +
>         if (IS_ENABLED(CONFIG_X86) && !efi_nochunk)
>                 efi_chunk_size = EFI_READ_CHUNK_SIZE;
>
> --
> 2.26.2
>