[PATCH 3/6 v2] efi_loader: Introduce helper functions for EFI

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

On 3/13/21 10:47 PM, Ilias Apalodimas wrote:
> A following patch introduces a different logic for loading initrd's
> based on the EFI_LOAD_FILE2_PROTOCOL.
> Since similar logic can be applied in the future for other system files
> (i.e DTBs), let's add some helper functions which will retrieve and
> parse file paths stored in EFI variables.
>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> ---
>   include/efi_helper.h            |  15 ++++
>   include/efi_loader.h            |   2 +
>   lib/efi_loader/Makefile         |   1 +
>   lib/efi_loader/efi_helper.c     | 133 ++++++++++++++++++++++++++++++++
>   lib/efi_loader/efi_var_common.c |  33 ++++++++
>   5 files changed, 184 insertions(+)
>   create mode 100644 include/efi_helper.h
>   create mode 100644 lib/efi_loader/efi_helper.c
>
> diff --git a/include/efi_helper.h b/include/efi_helper.h
> new file mode 100644
> index 000000000000..97492c65b6d2
> --- /dev/null
> +++ b/include/efi_helper.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * Copyright (c) 2020, Linaro Limited
> + */
> +
> +#if !defined _EFI_HELPER_H_
> +#define _EFI_HELPER_H
> +
> +#include <efi.h>
> +#include <efi_api.h>
> +
> +efi_status_t efi_get_file_size(struct efi_file_handle *fh, efi_uintn_t *size);
> +struct efi_device_path *efi_get_dp_from_boot(const efi_guid_t guid);
> +
> +#endif
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index eb11a8c7d4b1..aa812a9a3052 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -717,6 +717,8 @@ efi_status_t EFIAPI efi_query_variable_info(
>   			u64 *remaining_variable_storage_size,
>   			u64 *maximum_variable_size);
>
> +void *efi_get_var(u16 *name, const efi_guid_t *vendor, efi_uintn_t *size);
> +
>   /*
>    * See section 3.1.3 in the v2.7 UEFI spec for more details on
>    * the layout of EFI_LOAD_OPTION.  In short it is:
> diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
> index 10b42e8847bf..da2741adecfa 100644
> --- a/lib/efi_loader/Makefile
> +++ b/lib/efi_loader/Makefile
> @@ -23,6 +23,7 @@ endif
>   obj-$(CONFIG_CMD_BOOTEFI_HELLO) += helloworld_efi.o
>   obj-$(CONFIG_CMD_BOOTEFI_BOOTMGR) += efi_bootmgr.o
>   obj-y += efi_boottime.o
> +obj-y += efi_helper.o
>   obj-$(CONFIG_EFI_HAVE_CAPSULE_SUPPORT) += efi_capsule.o
>   obj-$(CONFIG_EFI_CAPSULE_FIRMWARE) += efi_firmware.o
>   obj-y += efi_console.o
> diff --git a/lib/efi_loader/efi_helper.c b/lib/efi_loader/efi_helper.c
> new file mode 100644
> index 000000000000..df5bdc506dbe
> --- /dev/null
> +++ b/lib/efi_loader/efi_helper.c
> @@ -0,0 +1,133 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (c) 2020, Linaro Limited
> + */
> +
> +#define LOG_CATEGORY LOGC_EFI
> +#include <common.h>
> +#include <env.h>
> +#include <malloc.h>
> +#include <dm.h>
> +#include <fs.h>
> +#include <efi_helper.h>
> +#include <efi_load_initrd.h>
> +#include <efi_loader.h>
> +#include <efi_variable.h>
> +
> +/**
> + * efi_create_current_boot_var() - Return Boot#### name were #### is replaced by
> + *			           the value of BootCurrent
> + *
> + * @var_name:		variable name
> + * @var_name_size:	size of var_name
> + *
> + * Return:	Status code
> + */
> +static efi_status_t efi_create_current_boot_var(u16 var_name[],
> +						size_t var_name_size)
> +{
> +	efi_uintn_t boot_current_size;
> +	efi_status_t ret;
> +	u16 boot_current;
> +	u16 *pos;
> +
> +	boot_current_size = sizeof(boot_current);
> +	ret = efi_get_variable_int(L"BootCurrent",
> +				   &efi_global_variable_guid, NULL,
> +				   &boot_current_size, &boot_current, NULL);
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
> +	pos = efi_create_indexed_name(var_name, var_name_size, "Boot",
> +				      boot_current);
> +	if (!pos) {
> +		ret = EFI_OUT_OF_RESOURCES;
> +		goto out;
> +	}
> +
> +out:
> +	return ret;
> +}
> +
> +/**
> + * efi_get_dp_from_boot() - Retrieve and return a device path from an EFI
> + *			    Boot### variable
> + *
> + * @guid:	Vendor guid of the VenMedia DP
> + *
> + * Return:	device path or NULL. Caller must free the returned value
> + */
> +struct efi_device_path *efi_get_dp_from_boot(const efi_guid_t guid)
> +{
> +	struct efi_device_path *file_path = NULL;
> +	struct efi_device_path *tmp;


struct efi_device_path *tmp = NULL;

+lib/efi_loader/efi_helper.c:79:6: error: variable 'tmp' is used
uninitialized whenever 'if' condition is true
[-Werror,-Wsometimes-uninitialized]
+        if (ret != EFI_SUCCESS)
+            ^~~~~~~~~~~~~~~~~~
+lib/efi_loader/efi_helper.c:90:16: note: uninitialized use occurs here
+        efi_free_pool(tmp);
+                      ^~~

> +	struct efi_load_option lo;
> +	void *var_value = NULL;
> +	efi_uintn_t size;
> +	efi_status_t ret;
> +	u16 var_name[16];
> +
> +	ret = efi_create_current_boot_var(var_name, sizeof(var_name));
> +	if (ret != EFI_SUCCESS)
> +		return NULL;
> +
> +	var_value = efi_get_var(var_name, &efi_global_variable_guid, &size);
> +	if (!var_value)
> +		return NULL;
> +
> +	ret = efi_deserialize_load_option(&lo, var_value, &size);
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
> +	tmp = efi_dp_from_lo(&lo, &size, guid);
> +	if (!tmp)
> +		goto out;
> +
> +	/* efi_dp_dup will just return NULL if efi_dp_next is NULL */
> +	file_path = efi_dp_dup(efi_dp_next(tmp));
> +
> +out:
> +	efi_free_pool(tmp);
> +	free(var_value);
> +
> +	return file_path;
> +}
> +
> +/**
> + * efi_get_file_size() - Get the size of a file using an EFI file handle
> + *
> + * @handle:	EFI file handle
> + * @size:	buffer to fill in the discovered size
> + *
> + * Return:	device path or NULL. Caller must free the returned value
> + */
> +efi_status_t efi_get_file_size(struct efi_file_handle *fh, efi_uintn_t *size)
> +{
> +	struct efi_file_info *info = NULL;
> +	efi_uintn_t bs = 0;
> +	efi_status_t ret;
> +
> +	*size = 0;
> +	ret = EFI_CALL(fh->getinfo(fh, (efi_guid_t *)&efi_file_info_guid, &bs,
> +				   info));
> +	if (ret != EFI_BUFFER_TOO_SMALL) {
> +		ret = EFI_DEVICE_ERROR;
> +		goto out;
> +	}
> +
> +	info = malloc(bs);
> +	if (!info) {
> +		ret = EFI_OUT_OF_RESOURCES;
> +		goto out;
> +	}
> +	ret = EFI_CALL(fh->getinfo(fh, (efi_guid_t *)&efi_file_info_guid, &bs,
> +				   info));
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
> +	*size = info->file_size;
> +
> +out:
> +	free(info);
> +	return ret;
> +}
> diff --git a/lib/efi_loader/efi_var_common.c b/lib/efi_loader/efi_var_common.c
> index 1c7459266a38..b11ed91a74a4 100644
> --- a/lib/efi_loader/efi_var_common.c
> +++ b/lib/efi_loader/efi_var_common.c
> @@ -9,6 +9,7 @@
>   #include <common.h>
>   #include <efi_loader.h>
>   #include <efi_variable.h>
> +#include <stdlib.h>
>
>   enum efi_secure_mode {
>   	EFI_MODE_SETUP,
> @@ -343,3 +344,35 @@ enum efi_auth_var_type efi_auth_var_get_type(u16 *name, const efi_guid_t *guid)
>   	}
>   	return EFI_AUTH_VAR_NONE;
>   }
> +
> +/**
> + * efi_get_var() - read value of an EFI variable
> + *
> + * @name:	variable name
> + * @start:	vendor GUID
> + * @size:	size of allocated buffer
> + *
> + * Return:	buffer with variable data or NULL
> + */
> +void *efi_get_var(u16 *name, const efi_guid_t *vendor, efi_uintn_t *size)
> +{
> +	efi_status_t ret;
> +	void *buf = NULL;
> +
> +	*size = 0;
> +	ret = efi_get_variable_int(name, vendor, NULL, size, buf, NULL);
> +	if (ret == EFI_BUFFER_TOO_SMALL) {
> +		buf = malloc(*size);
> +		if (!buf)
> +			return NULL;
> +		ret = efi_get_variable_int(name, vendor, NULL, size, buf, NULL);
> +	}
> +
> +	if (ret != EFI_SUCCESS) {
> +		free(buf);
> +		*size = 0;
> +		return NULL;
> +	}
> +
> +	return buf;
> +}
>