[U-Boot] [PATCH 1/2] efi_loader: implement GetNextVariableName()

Heinrich Schuchardt xypron.glpk at gmx.de
Thu Jan 17 07:09:57 UTC 2019


On 1/17/19 3:14 AM, AKASHI Takahiro wrote:
> Heinrich,
> 
> Thank you for your quick review.
> 
> On Wed, Jan 16, 2019 at 07:43:47PM +0100, Heinrich Schuchardt wrote:
>> On 12/14/18 10:47 AM, AKASHI Takahiro wrote:
>>> The current GetNextVariableName() is a placeholder.
>>> With this patch, it works well as expected.
>>>
>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
>>> ---
>>>  lib/efi_loader/efi_variable.c | 116 +++++++++++++++++++++++++++++++++-
>>>  1 file changed, 115 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
>>> index 19d9cb865f25..dac2f49aa1cc 100644
>>> --- a/lib/efi_loader/efi_variable.c
>>> +++ b/lib/efi_loader/efi_variable.c
>>> @@ -8,6 +8,9 @@
>>>  #include <malloc.h>
>>>  #include <charset.h>
>>>  #include <efi_loader.h>
>>> +#include <environment.h>
>>> +#include <search.h>
>>> +#include <uuid.h>
>>>  
>>>  #define READ_ONLY BIT(31)
>>>  
>>> @@ -241,14 +244,125 @@ efi_status_t EFIAPI efi_get_variable(u16 *variable_name, efi_guid_t *vendor,
>>>  	return EFI_EXIT(EFI_SUCCESS);
>>>  }
>>>  
>>> +static char *efi_variables_list;
>>> +static char *efi_cur_variable;
>>> +
>>
>> Please, provide a comment describing what this function is meant to do.
> 
> I think that the function name describes itself clearly, but OK.
> 
>> Describe every parameter
>>
>> Clearly state set variable_name_size is in bytes (cf.
>> EmuGetNextVariableName() in EDK2)
> 
> Right.
> 
>> This function duplicates some of the code in efi_get_variable. So,
>> please, use it in efi_get_variable too.
> 
> Which part of code do you mean? I don't think so.

Checking buffer size.
Comparing vendor GUID.
Extracting an EFI variable from a U-Boot variable.

> 
>>> +static efi_status_t parse_uboot_variable(char *variable,
>>> +					 efi_uintn_t *variable_name_size,
>>> +					 u16 *variable_name,
>>> +					 efi_guid_t *vendor,
>>> +					 u32 *attribute)
>>> +{
>>
>>
>>
>>> +	char *guid, *name, *end, c;
>>> +	unsigned long name_size;
>>> +	u16 *p;
>>> +
>>> +	guid = strchr(variable, '_');
>>> +	if (!guid)
>>> +		return EFI_NOT_FOUND;
>>> +	guid++;
>>> +	name = strchr(guid, '_');
>>> +	if (!name)
>>> +		return EFI_NOT_FOUND;
>>> +	name++;
>>> +	end = strchr(name, '=');
>>> +	if (!end)
>>> +		return EFI_NOT_FOUND;
>>> +
>>> +	/* FIXME: size is in byte or u16? */
>>
>> It is in bytes. See comment above.
> 
> OK
> 
>>> +	name_size = end - name;
>>> +	if (*variable_name_size < (name_size + 1)) {
>>> +		*variable_name_size = name_size + 1;
>>> +		return EFI_BUFFER_TOO_SMALL;
>>> +	}
>>> +	end++; /* point to value */
>>> +
>>> +	p = variable_name;
>>> +	utf8_utf16_strncpy(&p, name, name_size);
>>> +	variable_name[name_size] = 0;
>>> +
>>> +	c = *(name - 1);
>>> +	*(name - 1) = '\0'; /* guid need be null-terminated here */
>>> +	uuid_str_to_bin(guid, (unsigned char *)vendor, UUID_STR_FORMAT_GUID);
>>> +	*(name - 1) = c;
>>> +
>>> +	parse_attr(end, attribute);
>>
>> You have to update variable_name_size.
> 
> Right.
> 
>>> +
>>> +	return EFI_SUCCESS;
>>> +}
>>> +
>>>  /* http://wiki.phoenix.com/wiki/index.php/EFI_RUNTIME_SERVICES#GetNextVariableName.28.29 */
>>
>> Please add a description of the function here like we have it in
>> efi_bootefi.c
> 
> OK, but not for efi_get/set_variable() as I didn't touch anything there.

For the other functions we should do it in a separate patch.

> 
>>>  efi_status_t EFIAPI efi_get_next_variable_name(efi_uintn_t *variable_name_size,
>>>  					       u16 *variable_name,
>>>  					       efi_guid_t *vendor)
>>>  {
>>> +	char *native_name, *variable;
>>> +	ssize_t name_len, list_len;
>>> +	char regex[256];
>>> +	char * const regexlist[] = {regex};
>>> +	u32 attribute;
>>> +	int i;
>>> +	efi_status_t ret;
>>> +
>>>  	EFI_ENTRY("%p \"%ls\" %pUl", variable_name_size, variable_name, vendor);
>>>  
>>> -	return EFI_EXIT(EFI_DEVICE_ERROR);
>>> +	if (!variable_name_size || !variable_name || !vendor)
>>> +		EFI_EXIT(EFI_INVALID_PARAMETER);
>>> +
>>> +	if (variable_name[0]) {
>>
>> This code partially duplicates code in in efi_get_variable. Please,
>> carve out a common function.
> 
> Which part of code do you mean? I don't see any duplication.
> 
>>> +		/* check null-terminated string */
>>> +		for (i = 0; i < *variable_name_size; i++)
>>> +			if (!variable_name[i])
>>> +				break;
>>> +		if (i >= *variable_name_size)
>>> +			return EFI_EXIT(EFI_INVALID_PARAMETER);
>>> +
>>> +		/* search for the last-returned variable */
>>> +		ret = efi_to_native(&native_name, variable_name, vendor);
>>> +		if (ret)
>>> +			return EFI_EXIT(ret);
>>> +
>>> +		name_len = strlen(native_name);
>>> +		for (variable = efi_variables_list; variable && *variable;) {
>>> +			if (!strncmp(variable, native_name, name_len) &&
>>> +			    variable[name_len] == '=')
>>> +				break;
>>> +
>>
>> You miss to compare the GUID.
> 
> No, "native_name" already contains a given guid.
> 
>> Consider the case that the GUID changes between two calls.
> 
> UEFI specification, section 8.2, clearly describes;
>    When VariableName is a pointer to a Null character, VendorGuid is ignored.
>    etNextVariableName() cannot be used as a filter to return variable names
>    with a specific GUID. Instead, the entire list of variables must be
>    retrieved, and the caller may act as a filter if it chooses.
> 

Look at the list of error codes. EFI_INVALID_PARAMETER has to be
returned if name or GUID does not match an existing variable.

Regards

Heinrich

> 
>>> +			variable = strchr(variable, '\n');
>>> +			if (variable)
>>> +				variable++;
>>> +		}
>>> +
>>> +		free(native_name);
>>> +		if (!(variable && *variable))
>>
>> With less parentheses I can read the logic more easily:
>>
>> if (!variable || !*variable)
>>
>> But that is just a question of taste.
> 
> Well, this "if" clause corresponds with a termination condition of
> the previous "for" clause and checks whether a for loop has been exhausted.
> So my expression would be better IMO.
> 
>> Please, consider the case that the variable is not on the list because
>> the variable has already been deleted.
> 
> ditto
> 
>>
>>> +			return EFI_EXIT(EFI_INVALID_PARAMETER);
>>> +
>>> +		/* next variable */
>>> +		variable = strchr(variable, '\n');
>>> +		if (variable)
>>> +			variable++;
>>> +		if (!(variable && *variable))
>>> +			return EFI_EXIT(EFI_NOT_FOUND);
>>> +	} else {
>>> +		/* new search */
>>
>> Please, put a comment here explaining that the list of the preceding
>> search is freed here.
> 
> OK
> 
>>> +		free(efi_variables_list);
>>> +		efi_variables_list = NULL;
>>> +		efi_cur_variable = NULL;
>>> +
>>> +		snprintf(regex, 256, "efi_.*-.*-.*-.*-.*_.*");
>>> +		list_len = hexport_r(&env_htab, '\n',
>>> +				     H_MATCH_REGEX | H_MATCH_KEY,
>>> +				     &efi_variables_list, 0, 1, regexlist);
>>> +		if (list_len <= 0)
>>> +			return EFI_EXIT(EFI_NOT_FOUND);
>>
>> You miss to compare the vendor GUIDs.
> 
> No. Please see UEFI specification quoted above.
> 
> Thanks,
> -Takahiro Akashi
> 
>> Please, assume that variables are deleted or inserted while the caller
>> loops over the variables.
>>> +
>>> +		variable = efi_variables_list;
>>> +	}
>>> +
>>> +	ret = parse_uboot_variable(variable, variable_name_size, variable_name,
>>> +				   vendor, &attribute);
>>> +
>>> +	return EFI_EXIT(ret);
>>>  }
>>>  
>>>  /* http://wiki.phoenix.com/wiki/index.php/EFI_RUNTIME_SERVICES#SetVariable.28.29 */
>>>
>>
>> Thanks a lot for filling this gap in our EFI implementation.
>>
>> Best regards
>>
>> Heinrich
> 



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