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Subject[tip: efi/core] efi/x86: Add a quirk to support command line arguments on Dell EFI firmware
The following commit has been merged into the efi/core branch of tip:

Commit-ID: 4a568ce29d3f48df95919f82a80e4b9be7ea0dc1
Gitweb: https://git.kernel.org/tip/4a568ce29d3f48df95919f82a80e4b9be7ea0dc1
Author: Arvind Sankar <nivedita@alum.mit.edu>
AuthorDate: Mon, 14 Sep 2020 17:35:35 -04:00
Committer: Ard Biesheuvel <ardb@kernel.org>
CommitterDate: Thu, 17 Sep 2020 10:19:53 +03:00

efi/x86: Add a quirk to support command line arguments on Dell EFI firmware

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 Pantoja.

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/
Link: https://lore.kernel.org/r/20200914213535.933454-2-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
drivers/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 6bca70b..4dbf04c 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -231,6 +231,102 @@ efi_status_t efi_parse_options(char const *cmdline)
}

/*
+ * 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.
* Returns NULL on error.
@@ -239,12 +335,15 @@ 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 9ea87a2..2d7abcd 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -708,6 +708,35 @@ 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)(
@@ -750,6 +779,8 @@ __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 630caa6..4e81c60 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;

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