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

[Heinrich Schuchardt]

On 3/14/21 8:34 AM, Ilias Apalodimas wrote:
> Hi Heinrich,
>
> On Sun, Mar 14, 2021 at 08:31:20AM +0100, Heinrich Schuchardt wrote:
>> 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.
>>> +/**
>>> + * 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)
>>
>> Should this function be in lib/efi_loader/efi_file?
>
> there's already a statically defined efi_get_file_size() in that file.  I can
> rename that, just let me know what you prefer.

Unfortunately we cannot call the efi_get_file_size() function in
lib/efi_loader/efi_file.c directly because a driver might have installed
a different implementation of a simple file protocol.

We should have different names for the functions, e.g. efi_file_size()
and efi_get_file_size().

But still I think lib/efi_loader/efi_file.c would be a better place for
the new function. We will be able to reuse it in:

* efi_capsule_read_file()
* efi_load_image_from_file()

Best regards

Heinrich

>
>>
>> Best regards
>>
>> Heinrich
>>
>>> +{
>>> +	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;
>>> +}
>>>
>>