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

[AKASHI Takahiro]

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.

> > +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.

> >  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.


> > +			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