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

AKASHI Takahiro takahiro.akashi at linaro.org
Thu Jan 17 08:15:53 UTC 2019 

On Thu, Jan 17, 2019 at 08:09:57AM +0100, Heinrich Schuchardt wrote:
> 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.

Please specify exact line numbers on both side.
Otherwise, I don't get you.

> > 
> >>> +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.

Not me.

> > 
> >>>  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.

What about this?

> > 
> >>> +		/* 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.

The code below behaves exactly as you mention:
	/* search for the last-returned variable */
	ret = efi_to_native(&native_name, variable_name, vendor);

	name_len = strlen(native_name);

	for (variable = efi_variables_list; variable && *variable;) {
		...
	}
	free(native_name);
	if (!(variable && *variable))
		return EFI_EXIT(EFI_INVALID_PARAMETER);

-Takahiro Akashi

> 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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