diff mbox series

[1/2] eficonfig: curve out efi_get_next_variable_name_int calls

Message ID 20221208134022.28621-2-masahisa.kojima@linaro.org
State Superseded
Headers show
Series fix eficonfig GetNextVariableName calls handling | expand

Commit Message

Masahisa Kojima Dec. 8, 2022, 1:40 p.m. UTC 
To retrieve the EFI variable name by efi_get_next_variable_name_int(),
the sequence of alloc -> efi_get_next_variable_name_int ->
realloc -> efi_get_next_variable_name_int is required.
In current code, this sequence repeatedly appears in
the several functions. It should be curved out a common function.

This commit also fixes the missing free() of var_name16
in eficonfig_delete_invalid_boot_option().

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
---
 cmd/eficonfig.c             | 62 +++++++++----------------------------
 include/efi_loader.h        |  2 ++
 lib/efi_loader/efi_helper.c | 34 ++++++++++++++++++++
 3 files changed, 51 insertions(+), 47 deletions(-)

Comments

Heinrich Schuchardt Dec. 16, 2022, 1:51 a.m. UTC | #1 
%s/curve/carve/

On 12/8/22 05:40, Masahisa Kojima wrote:
> To retrieve the EFI variable name by efi_get_next_variable_name_int(),
> the sequence of alloc -> efi_get_next_variable_name_int ->
> realloc -> efi_get_next_variable_name_int is required.
> In current code, this sequence repeatedly appears in
> the several functions. It should be curved out a common function.
>
> This commit also fixes the missing free() of var_name16
> in eficonfig_delete_invalid_boot_option().
>
> Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
> ---
>   cmd/eficonfig.c             | 62 +++++++++----------------------------
>   include/efi_loader.h        |  2 ++
>   lib/efi_loader/efi_helper.c | 34 ++++++++++++++++++++
>   3 files changed, 51 insertions(+), 47 deletions(-)
>
> diff --git a/cmd/eficonfig.c b/cmd/eficonfig.c
> index 394ae67cce..cd7a51cc7e 100644
> --- a/cmd/eficonfig.c
> +++ b/cmd/eficonfig.c
> @@ -1683,7 +1683,7 @@ static efi_status_t eficonfig_show_boot_selection(unsigned int *selected)
>   	u32 i;
>   	u16 *bootorder;
>   	efi_status_t ret;
> -	u16 *var_name16 = NULL, *p;
> +	u16 *var_name16 = NULL;
>   	efi_uintn_t num, size, buf_size;

buf_size = 0;
see below

>   	struct efimenu *efi_menu;
>   	struct list_head *pos, *n;
> @@ -1718,24 +1718,12 @@ static efi_status_t eficonfig_show_boot_selection(unsigned int *selected)
>   		int index;
>   		efi_guid_t guid;
>
> -		size = buf_size;
> -		ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
> +		ret = efi_get_variable_name(&buf_size, &var_name16, &guid);
>   		if (ret == EFI_NOT_FOUND)
>   			break;
> -		if (ret == EFI_BUFFER_TOO_SMALL) {
> -			buf_size = size;
> -			p = realloc(var_name16, buf_size);
> -			if (!p) {
> -				free(var_name16);
> -				return EFI_OUT_OF_RESOURCES;
> -			}
> -			var_name16 = p;
> -			ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
> -		}
> -		if (ret != EFI_SUCCESS) {
> -			free(var_name16);
> -			return ret;
> -		}
> +		if (ret != EFI_SUCCESS)
> +			goto out;
> +
>   		if (efi_varname_is_load_option(var_name16, &index)) {
>   			/* If the index is included in the BootOrder, skip it */
>   			if (search_bootorder(bootorder, num, index, NULL))
> @@ -2026,7 +2014,7 @@ static efi_status_t eficonfig_create_change_boot_order_entry(struct efimenu *efi
>   	u32 i;
>   	char *title;
>   	efi_status_t ret;
> -	u16 *var_name16 = NULL, *p;
> +	u16 *var_name16 = NULL;
>   	efi_uintn_t size, buf_size;
>
>   	/* list the load option in the order of BootOrder variable */
> @@ -2054,19 +2042,9 @@ static efi_status_t eficonfig_create_change_boot_order_entry(struct efimenu *efi
>   			break;
>
>   		size = buf_size;
> -		ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
> +		ret = efi_get_variable_name(&buf_size, &var_name16, &guid);
>   		if (ret == EFI_NOT_FOUND)
>   			break;
> -		if (ret == EFI_BUFFER_TOO_SMALL) {
> -			buf_size = size;
> -			p = realloc(var_name16, buf_size);
> -			if (!p) {
> -				ret = EFI_OUT_OF_RESOURCES;
> -				goto out;
> -			}
> -			var_name16 = p;
> -			ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
> -		}
>   		if (ret != EFI_SUCCESS)
>   			goto out;
>
> @@ -2336,10 +2314,10 @@ efi_status_t eficonfig_delete_invalid_boot_option(struct eficonfig_media_boot_op
>   	efi_uintn_t size;
>   	void *load_option;
>   	struct efi_load_option lo;
> -	u16 *var_name16 = NULL, *p;
> +	u16 *var_name16 = NULL;
>   	u16 varname[] = u"Boot####";
>   	efi_status_t ret = EFI_SUCCESS;
> -	efi_uintn_t varname_size, buf_size;
> +	efi_uintn_t buf_size;
>
>   	buf_size = 128;
>   	var_name16 = malloc(buf_size);

Why allocate anything here? We already have a realloc() in
efi_get_variable_name() which will do the job. Just start with
var_name16 = NULL, buf_size = 0.

> @@ -2352,24 +2330,12 @@ efi_status_t eficonfig_delete_invalid_boot_option(struct eficonfig_media_boot_op
>   		efi_guid_t guid;
>   		efi_uintn_t tmp;
>
> -		varname_size = buf_size;
> -		ret = efi_get_next_variable_name_int(&varname_size, var_name16, &guid);
> +		ret = efi_get_variable_name(&buf_size, &var_name16, &guid);
>   		if (ret == EFI_NOT_FOUND)
>   			break;
> -		if (ret == EFI_BUFFER_TOO_SMALL) {
> -			buf_size = varname_size;
> -			p = realloc(var_name16, buf_size);
> -			if (!p) {
> -				free(var_name16);
> -				return EFI_OUT_OF_RESOURCES;
> -			}
> -			var_name16 = p;
> -			ret = efi_get_next_variable_name_int(&varname_size, var_name16, &guid);
> -		}
> -		if (ret != EFI_SUCCESS) {
> -			free(var_name16);
> -			return ret;
> -		}
> +		if (ret != EFI_SUCCESS)
> +			goto out;
> +
>   		if (!efi_varname_is_load_option(var_name16, &index))
>   			continue;
>
> @@ -2407,6 +2373,8 @@ next:
>   	}
>
>   out:
> +	free(var_name16);
> +
>   	return ret;
>   }
>
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index 0899e293e5..f80a16108a 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -708,6 +708,8 @@ int algo_to_len(const char *algo);
>   int efi_link_dev(efi_handle_t handle, struct udevice *dev);
>   int efi_unlink_dev(efi_handle_t handle);
>   bool efi_varname_is_load_option(u16 *var_name16, int *index);
> +efi_status_t efi_get_variable_name(efi_uintn_t *size, u16 **buf,
> +				   efi_guid_t *guid);
>
>   /**
>    * efi_size_in_pages() - convert size in bytes to size in pages
> diff --git a/lib/efi_loader/efi_helper.c b/lib/efi_loader/efi_helper.c
> index 788cb9faec..ca9854ec79 100644
> --- a/lib/efi_loader/efi_helper.c
> +++ b/lib/efi_loader/efi_helper.c
> @@ -223,3 +223,37 @@ bool efi_varname_is_load_option(u16 *var_name16, int *index)
>
>   	return false;
>   }
> +
> +/**
> + * efi_get_variable_name_() - get variable name
> + *
> + * This function is a wrapper of efi_get_next_variable_name_int().
> + * If efi_get_next_variable_name_int() returns EFI_BUFFER_TOO_SMALL,
> + * @size and @buf are updated by new buffer size and realloced buffer.
> + *
> + * @size:	pointer to the buffer size
> + * @buf:	pointer to the buffer
> + * @guid:	pointer to the guid
> + * Return:	status code
> + */
> +efi_status_t efi_get_variable_name(efi_uintn_t *size, u16 **buf, efi_guid_t *guid)

We should have next in the function name, e.g. "efi_next_variable_name".

> +{
> +	u16 *p;
> +	efi_status_t ret;
> +	efi_uintn_t buf_size = *size;
> +
> +	ret = efi_get_next_variable_name_int(&buf_size, *buf, guid);
> +	if (ret == EFI_NOT_FOUND)
> +		return ret;
> +	if (ret == EFI_BUFFER_TOO_SMALL) {
> +		p = realloc(*buf, buf_size);
> +		if (!p)

*buf should be freed here and set to NULL.

Best regards

Heinrich

> +			return EFI_OUT_OF_RESOURCES;
> +
> +		*buf = p;
> +		*size = buf_size;
> +		ret = efi_get_next_variable_name_int(&buf_size, *buf, guid);
> +	}
> +
> +	return ret;
> +}
Masahisa Kojima Dec. 16, 2022, 6:22 a.m. UTC | #2 
On Fri, 16 Dec 2022 at 10:51, Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:
>
> %s/curve/carve/

Thank you for pointing out the typo.

>
> On 12/8/22 05:40, Masahisa Kojima wrote:
> > To retrieve the EFI variable name by efi_get_next_variable_name_int(),
> > the sequence of alloc -> efi_get_next_variable_name_int ->
> > realloc -> efi_get_next_variable_name_int is required.
> > In current code, this sequence repeatedly appears in
> > the several functions. It should be curved out a common function.
> >
> > This commit also fixes the missing free() of var_name16
> > in eficonfig_delete_invalid_boot_option().
> >
> > Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
> > ---
> >   cmd/eficonfig.c             | 62 +++++++++----------------------------
> >   include/efi_loader.h        |  2 ++
> >   lib/efi_loader/efi_helper.c | 34 ++++++++++++++++++++
> >   3 files changed, 51 insertions(+), 47 deletions(-)
> >
> > diff --git a/cmd/eficonfig.c b/cmd/eficonfig.c
> > index 394ae67cce..cd7a51cc7e 100644
> > --- a/cmd/eficonfig.c
> > +++ b/cmd/eficonfig.c
> > @@ -1683,7 +1683,7 @@ static efi_status_t eficonfig_show_boot_selection(unsigned int *selected)
> >       u32 i;
> >       u16 *bootorder;
> >       efi_status_t ret;
> > -     u16 *var_name16 = NULL, *p;
> > +     u16 *var_name16 = NULL;
> >       efi_uintn_t num, size, buf_size;
>
> buf_size = 0;
> see below
>
> >       struct efimenu *efi_menu;
> >       struct list_head *pos, *n;
> > @@ -1718,24 +1718,12 @@ static efi_status_t eficonfig_show_boot_selection(unsigned int *selected)
> >               int index;
> >               efi_guid_t guid;
> >
> > -             size = buf_size;
> > -             ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
> > +             ret = efi_get_variable_name(&buf_size, &var_name16, &guid);
> >               if (ret == EFI_NOT_FOUND)
> >                       break;
> > -             if (ret == EFI_BUFFER_TOO_SMALL) {
> > -                     buf_size = size;
> > -                     p = realloc(var_name16, buf_size);
> > -                     if (!p) {
> > -                             free(var_name16);
> > -                             return EFI_OUT_OF_RESOURCES;
> > -                     }
> > -                     var_name16 = p;
> > -                     ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
> > -             }
> > -             if (ret != EFI_SUCCESS) {
> > -                     free(var_name16);
> > -                     return ret;
> > -             }
> > +             if (ret != EFI_SUCCESS)
> > +                     goto out;
> > +
> >               if (efi_varname_is_load_option(var_name16, &index)) {
> >                       /* If the index is included in the BootOrder, skip it */
> >                       if (search_bootorder(bootorder, num, index, NULL))
> > @@ -2026,7 +2014,7 @@ static efi_status_t eficonfig_create_change_boot_order_entry(struct efimenu *efi
> >       u32 i;
> >       char *title;
> >       efi_status_t ret;
> > -     u16 *var_name16 = NULL, *p;
> > +     u16 *var_name16 = NULL;
> >       efi_uintn_t size, buf_size;
> >
> >       /* list the load option in the order of BootOrder variable */
> > @@ -2054,19 +2042,9 @@ static efi_status_t eficonfig_create_change_boot_order_entry(struct efimenu *efi
> >                       break;
> >
> >               size = buf_size;
> > -             ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
> > +             ret = efi_get_variable_name(&buf_size, &var_name16, &guid);
> >               if (ret == EFI_NOT_FOUND)
> >                       break;
> > -             if (ret == EFI_BUFFER_TOO_SMALL) {
> > -                     buf_size = size;
> > -                     p = realloc(var_name16, buf_size);
> > -                     if (!p) {
> > -                             ret = EFI_OUT_OF_RESOURCES;
> > -                             goto out;
> > -                     }
> > -                     var_name16 = p;
> > -                     ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
> > -             }
> >               if (ret != EFI_SUCCESS)
> >                       goto out;
> >
> > @@ -2336,10 +2314,10 @@ efi_status_t eficonfig_delete_invalid_boot_option(struct eficonfig_media_boot_op
> >       efi_uintn_t size;
> >       void *load_option;
> >       struct efi_load_option lo;
> > -     u16 *var_name16 = NULL, *p;
> > +     u16 *var_name16 = NULL;
> >       u16 varname[] = u"Boot####";
> >       efi_status_t ret = EFI_SUCCESS;
> > -     efi_uintn_t varname_size, buf_size;
> > +     efi_uintn_t buf_size;
> >
> >       buf_size = 128;
> >       var_name16 = malloc(buf_size);
>
> Why allocate anything here? We already have a realloc() in
> efi_get_variable_name() which will do the job. Just start with
> var_name16 = NULL, buf_size = 0.

To start the EFI variable search with GetNextVariableName(), the first call of
efi_get_next_variable_name_int() requires a pointer to the
Null-terminated string
and non-zero buffer size.
So var_name16 = NULL, buf_size = 0 setup will not work as expected,
efi_get_next_variable_name_int() returns EFI_INVALID_PARAMETER in this case.

>
> > @@ -2352,24 +2330,12 @@ efi_status_t eficonfig_delete_invalid_boot_option(struct eficonfig_media_boot_op
> >               efi_guid_t guid;
> >               efi_uintn_t tmp;
> >
> > -             varname_size = buf_size;
> > -             ret = efi_get_next_variable_name_int(&varname_size, var_name16, &guid);
> > +             ret = efi_get_variable_name(&buf_size, &var_name16, &guid);
> >               if (ret == EFI_NOT_FOUND)
> >                       break;
> > -             if (ret == EFI_BUFFER_TOO_SMALL) {
> > -                     buf_size = varname_size;
> > -                     p = realloc(var_name16, buf_size);
> > -                     if (!p) {
> > -                             free(var_name16);
> > -                             return EFI_OUT_OF_RESOURCES;
> > -                     }
> > -                     var_name16 = p;
> > -                     ret = efi_get_next_variable_name_int(&varname_size, var_name16, &guid);
> > -             }
> > -             if (ret != EFI_SUCCESS) {
> > -                     free(var_name16);
> > -                     return ret;
> > -             }
> > +             if (ret != EFI_SUCCESS)
> > +                     goto out;
> > +
> >               if (!efi_varname_is_load_option(var_name16, &index))
> >                       continue;
> >
> > @@ -2407,6 +2373,8 @@ next:
> >       }
> >
> >   out:
> > +     free(var_name16);
> > +
> >       return ret;
> >   }
> >
> > diff --git a/include/efi_loader.h b/include/efi_loader.h
> > index 0899e293e5..f80a16108a 100644
> > --- a/include/efi_loader.h
> > +++ b/include/efi_loader.h
> > @@ -708,6 +708,8 @@ int algo_to_len(const char *algo);
> >   int efi_link_dev(efi_handle_t handle, struct udevice *dev);
> >   int efi_unlink_dev(efi_handle_t handle);
> >   bool efi_varname_is_load_option(u16 *var_name16, int *index);
> > +efi_status_t efi_get_variable_name(efi_uintn_t *size, u16 **buf,
> > +                                efi_guid_t *guid);
> >
> >   /**
> >    * efi_size_in_pages() - convert size in bytes to size in pages
> > diff --git a/lib/efi_loader/efi_helper.c b/lib/efi_loader/efi_helper.c
> > index 788cb9faec..ca9854ec79 100644
> > --- a/lib/efi_loader/efi_helper.c
> > +++ b/lib/efi_loader/efi_helper.c
> > @@ -223,3 +223,37 @@ bool efi_varname_is_load_option(u16 *var_name16, int *index)
> >
> >       return false;
> >   }
> > +
> > +/**
> > + * efi_get_variable_name_() - get variable name
> > + *
> > + * This function is a wrapper of efi_get_next_variable_name_int().
> > + * If efi_get_next_variable_name_int() returns EFI_BUFFER_TOO_SMALL,
> > + * @size and @buf are updated by new buffer size and realloced buffer.
> > + *
> > + * @size:    pointer to the buffer size
> > + * @buf:     pointer to the buffer
> > + * @guid:    pointer to the guid
> > + * Return:   status code
> > + */
> > +efi_status_t efi_get_variable_name(efi_uintn_t *size, u16 **buf, efi_guid_t *guid)
>
> We should have next in the function name, e.g. "efi_next_variable_name".

Yes, I agree.

>
> > +{
> > +     u16 *p;
> > +     efi_status_t ret;
> > +     efi_uintn_t buf_size = *size;
> > +
> > +     ret = efi_get_next_variable_name_int(&buf_size, *buf, guid);
> > +     if (ret == EFI_NOT_FOUND)
> > +             return ret;
> > +     if (ret == EFI_BUFFER_TOO_SMALL) {
> > +             p = realloc(*buf, buf_size);
> > +             if (!p)
>
> *buf should be freed here and set to NULL.

var_name16 should be allocated by a caller as described above,
let me keep the current code.

Thanks,
Masahisa Kojima

>
> Best regards
>
> Heinrich
>
> > +                     return EFI_OUT_OF_RESOURCES;
> > +
> > +             *buf = p;
> > +             *size = buf_size;
> > +             ret = efi_get_next_variable_name_int(&buf_size, *buf, guid);
> > +     }
> > +
> > +     return ret;
> > +}
>
diff mbox series

Patch

diff --git a/cmd/eficonfig.c b/cmd/eficonfig.c
index 394ae67cce..cd7a51cc7e 100644
--- a/cmd/eficonfig.c
+++ b/cmd/eficonfig.c
@@ -1683,7 +1683,7 @@  static efi_status_t eficonfig_show_boot_selection(unsigned int *selected)
 	u32 i;
 	u16 *bootorder;
 	efi_status_t ret;
-	u16 *var_name16 = NULL, *p;
+	u16 *var_name16 = NULL;
 	efi_uintn_t num, size, buf_size;
 	struct efimenu *efi_menu;
 	struct list_head *pos, *n;
@@ -1718,24 +1718,12 @@  static efi_status_t eficonfig_show_boot_selection(unsigned int *selected)
 		int index;
 		efi_guid_t guid;
 
-		size = buf_size;
-		ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
+		ret = efi_get_variable_name(&buf_size, &var_name16, &guid);
 		if (ret == EFI_NOT_FOUND)
 			break;
-		if (ret == EFI_BUFFER_TOO_SMALL) {
-			buf_size = size;
-			p = realloc(var_name16, buf_size);
-			if (!p) {
-				free(var_name16);
-				return EFI_OUT_OF_RESOURCES;
-			}
-			var_name16 = p;
-			ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
-		}
-		if (ret != EFI_SUCCESS) {
-			free(var_name16);
-			return ret;
-		}
+		if (ret != EFI_SUCCESS)
+			goto out;
+
 		if (efi_varname_is_load_option(var_name16, &index)) {
 			/* If the index is included in the BootOrder, skip it */
 			if (search_bootorder(bootorder, num, index, NULL))
@@ -2026,7 +2014,7 @@  static efi_status_t eficonfig_create_change_boot_order_entry(struct efimenu *efi
 	u32 i;
 	char *title;
 	efi_status_t ret;
-	u16 *var_name16 = NULL, *p;
+	u16 *var_name16 = NULL;
 	efi_uintn_t size, buf_size;
 
 	/* list the load option in the order of BootOrder variable */
@@ -2054,19 +2042,9 @@  static efi_status_t eficonfig_create_change_boot_order_entry(struct efimenu *efi
 			break;
 
 		size = buf_size;
-		ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
+		ret = efi_get_variable_name(&buf_size, &var_name16, &guid);
 		if (ret == EFI_NOT_FOUND)
 			break;
-		if (ret == EFI_BUFFER_TOO_SMALL) {
-			buf_size = size;
-			p = realloc(var_name16, buf_size);
-			if (!p) {
-				ret = EFI_OUT_OF_RESOURCES;
-				goto out;
-			}
-			var_name16 = p;
-			ret = efi_get_next_variable_name_int(&size, var_name16, &guid);
-		}
 		if (ret != EFI_SUCCESS)
 			goto out;
 
@@ -2336,10 +2314,10 @@  efi_status_t eficonfig_delete_invalid_boot_option(struct eficonfig_media_boot_op
 	efi_uintn_t size;
 	void *load_option;
 	struct efi_load_option lo;
-	u16 *var_name16 = NULL, *p;
+	u16 *var_name16 = NULL;
 	u16 varname[] = u"Boot####";
 	efi_status_t ret = EFI_SUCCESS;
-	efi_uintn_t varname_size, buf_size;
+	efi_uintn_t buf_size;
 
 	buf_size = 128;
 	var_name16 = malloc(buf_size);
@@ -2352,24 +2330,12 @@  efi_status_t eficonfig_delete_invalid_boot_option(struct eficonfig_media_boot_op
 		efi_guid_t guid;
 		efi_uintn_t tmp;
 
-		varname_size = buf_size;
-		ret = efi_get_next_variable_name_int(&varname_size, var_name16, &guid);
+		ret = efi_get_variable_name(&buf_size, &var_name16, &guid);
 		if (ret == EFI_NOT_FOUND)
 			break;
-		if (ret == EFI_BUFFER_TOO_SMALL) {
-			buf_size = varname_size;
-			p = realloc(var_name16, buf_size);
-			if (!p) {
-				free(var_name16);
-				return EFI_OUT_OF_RESOURCES;
-			}
-			var_name16 = p;
-			ret = efi_get_next_variable_name_int(&varname_size, var_name16, &guid);
-		}
-		if (ret != EFI_SUCCESS) {
-			free(var_name16);
-			return ret;
-		}
+		if (ret != EFI_SUCCESS)
+			goto out;
+
 		if (!efi_varname_is_load_option(var_name16, &index))
 			continue;
 
@@ -2407,6 +2373,8 @@  next:
 	}
 
 out:
+	free(var_name16);
+
 	return ret;
 }
 
diff --git a/include/efi_loader.h b/include/efi_loader.h
index 0899e293e5..f80a16108a 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -708,6 +708,8 @@  int algo_to_len(const char *algo);
 int efi_link_dev(efi_handle_t handle, struct udevice *dev);
 int efi_unlink_dev(efi_handle_t handle);
 bool efi_varname_is_load_option(u16 *var_name16, int *index);
+efi_status_t efi_get_variable_name(efi_uintn_t *size, u16 **buf,
+				   efi_guid_t *guid);
 
 /**
  * efi_size_in_pages() - convert size in bytes to size in pages
diff --git a/lib/efi_loader/efi_helper.c b/lib/efi_loader/efi_helper.c
index 788cb9faec..ca9854ec79 100644
--- a/lib/efi_loader/efi_helper.c
+++ b/lib/efi_loader/efi_helper.c
@@ -223,3 +223,37 @@  bool efi_varname_is_load_option(u16 *var_name16, int *index)
 
 	return false;
 }
+
+/**
+ * efi_get_variable_name_() - get variable name
+ *
+ * This function is a wrapper of efi_get_next_variable_name_int().
+ * If efi_get_next_variable_name_int() returns EFI_BUFFER_TOO_SMALL,
+ * @size and @buf are updated by new buffer size and realloced buffer.
+ *
+ * @size:	pointer to the buffer size
+ * @buf:	pointer to the buffer
+ * @guid:	pointer to the guid
+ * Return:	status code
+ */
+efi_status_t efi_get_variable_name(efi_uintn_t *size, u16 **buf, efi_guid_t *guid)
+{
+	u16 *p;
+	efi_status_t ret;
+	efi_uintn_t buf_size = *size;
+
+	ret = efi_get_next_variable_name_int(&buf_size, *buf, guid);
+	if (ret == EFI_NOT_FOUND)
+		return ret;
+	if (ret == EFI_BUFFER_TOO_SMALL) {
+		p = realloc(*buf, buf_size);
+		if (!p)
+			return EFI_OUT_OF_RESOURCES;
+
+		*buf = p;
+		*size = buf_size;
+		ret = efi_get_next_variable_name_int(&buf_size, *buf, guid);
+	}
+
+	return ret;
+}