Re: [U-Boot] [PATCH 6/9] efi_loader: Add runtime services

On Tue, Dec 22, 2015 at 02:57:53PM +0100, Alexander Graf wrote:

After booting has finished, EFI allows firmware to still interact with the OS using the "runtime services". These callbacks live in a separate address space, since they are available long after U-Boot has been overwritten by the OS.

However, since U-Boot has no notion of RTS, we just create an extremely minimal RTS stub that just declares all functions as unsupported. We could in the future map U-boot environment variables to EFI variables here.

Signed-off-by: Alexander Graf agraf@suse.de

arch/arm/cpu/armv8/u-boot.lds | 8 ++++++ arch/arm/cpu/u-boot.lds | 13 ++++++++++ arch/arm/lib/sections.c | 2 ++ include/efi_loader.h | 3 +++ lib/efi_loader/efi_runtime.c | 59 +++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 85 insertions(+) create mode 100644 lib/efi_loader/efi_runtime.c

diff --git a/arch/arm/cpu/armv8/u-boot.lds b/arch/arm/cpu/armv8/u-boot.lds index 4c12222..7c5b032 100644 --- a/arch/arm/cpu/armv8/u-boot.lds +++ b/arch/arm/cpu/armv8/u-boot.lds @@ -42,6 +42,14 @@ SECTIONS

. = ALIGN(8);

• .efi_runtime : {

•            __efi_runtime_start = .;
  

• *(efi_runtime)
  

•            __efi_runtime_stop = .;
  

• }
• . = ALIGN(8);
• .image_copy_end : { *(.__image_copy_end)

diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds index d48a905..b5198d0 100644 --- a/arch/arm/cpu/u-boot.lds +++ b/arch/arm/cpu/u-boot.lds @@ -89,6 +89,19 @@ SECTIONS

. = ALIGN(4);

• .__efi_runtime_start : {

• *(.__efi_runtime_start)
  

• }
• .efi_runtime : {

• *(efi_runtime)
  

• }
• .__efi_runtime_stop : {

• *(.__efi_runtime_stop)
  

• }
• . = ALIGN(4);
• .image_copy_end : { *(.__image_copy_end)

diff --git a/arch/arm/lib/sections.c b/arch/arm/lib/sections.c index a1205c3..21b3066 100644 --- a/arch/arm/lib/sections.c +++ b/arch/arm/lib/sections.c @@ -27,4 +27,6 @@ char __rel_dyn_start[0] __attribute__((section(".__rel_dyn_start"))); char __rel_dyn_end[0] __attribute__((section(".__rel_dyn_end"))); char __secure_start[0] __attribute__((section(".__secure_start"))); char __secure_end[0] __attribute__((section(".__secure_end"))); +char __efi_runtime_start[0] __attribute__((section(".__efi_runtime_start"))); +char __efi_runtime_stop[0] __attribute__((section(".__efi_runtime_stop"))); char _end[0] __attribute__((section(".__end"))); diff --git a/include/efi_loader.h b/include/efi_loader.h index 7fb2106..af1c88f 100644 --- a/include/efi_loader.h +++ b/include/efi_loader.h @@ -39,6 +39,7 @@

#define EFI_EXIT(ret) efi_exit_func(ret);

+extern const struct efi_runtime_services efi_runtime_services; extern struct efi_system_table systab;

extern const struct efi_simple_text_output_protocol efi_con_out; @@ -49,6 +50,8 @@ extern const efi_guid_t efi_guid_console_control; extern const efi_guid_t efi_guid_device_path; extern const efi_guid_t efi_guid_loaded_image;

+extern unsigned int __efi_runtime_start, __efi_runtime_stop;

struct efi_class_map { const efi_guid_t *guid; const void *interface; diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c new file mode 100644 index 0000000..214e1f5 --- /dev/null +++ b/lib/efi_loader/efi_runtime.c @@ -0,0 +1,59 @@ +/*

• • EFI application runtime services
• • Copyright (c) 2015 Alexander Graf
• • This library is free software; you can redistribute it and/or
• • modify it under the terms of the GNU Lesser General Public
• • License as published by the Free Software Foundation; either
• • version 2.1 of the License, or (at your option) any later version.
• • This library is distributed in the hope that it will be useful,
• • but WITHOUT ANY WARRANTY; without even the implied warranty of
• • MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
• • Lesser General Public License for more details.
• • You should have received a copy of the GNU Lesser General Public
• • License along with this library; if not, write to the Free Software
• • Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
• • SPDX-License-Identifier: LGPL-2.1+
• */

+#include <common.h> +#include <efi_loader.h>

+/*

• • EFI Runtime code is still alive when U-Boot is long overwritten. To isolate
• • this code from the rest, we put it into a special section.

• •    !!WARNING!!
    

• • This means that we can not rely on any code outside of this file at runtime.
• • Please keep it fully self-contained.
• */

+asm(".section efi_runtime,"a"");

+static efi_status_t efi_unimplemented(void) +{

• return EFI_UNSUPPORTED;

Again, EFI_UNSUPPORTED is not necessarily a valid return value for all runtime services.

+}

+const struct efi_runtime_services efi_runtime_services = {

• .hdr = {

• .signature = EFI_RUNTIME_SERVICES_SIGNATURE,
  

• .revision = EFI_RUNTIME_SERVICES_REVISION,
  

• .headersize = sizeof(struct efi_table_hdr),
  

• },
• .get_time = (void *)&efi_unimplemented,

EFI_DEVICE_ERROR

• .set_time = (void *)&efi_unimplemented,

EFI_DEVICE_ERROR

• .get_wakeup_time = (void *)&efi_unimplemented,
• .set_wakeup_time = (void *)&efi_unimplemented,

Both of these are fine, and correct, to return EFI_UNSUPPORTED.

• .set_virtual_address_map = (void *)&efi_unimplemented,
• .convert_pointer = (void *)&efi_unimplemented,

There really isn't a way to gracefully decline these two functions. All valid error codes refer to invalid inputs.

• .get_variable = (void *)&efi_unimplemented,

EFI_DEVICE_ERROR would probably be the closest thing to a correct return code in this instance.

• .get_next_variable = (void *)&efi_unimplemented,

(get_next_variable_name?) Again, EFI_DEVICE_ERROR, is probably the least wrong return value.

• .set_variable = (void *)&efi_unimplemented,

EFI_DEVICE_ERROR

• .get_next_high_mono_count = (void *)&efi_unimplemented,

EFI_DEVICE_ERROR

• .reset_system = (void *)&efi_unimplemented,

"The ResetSystem() function does not return."

+};

2.1.4