[U-Boot] [PATCH] efi_loader: variable: support APPEND_WRITE

[Heinrich Schuchardt]

On 9/3/19 7:40 AM, AKASHI Takahiro wrote:
> If EFI_VARIABLE_APPEND_WRITE is specified in attributes at
> efi_set_variable(), specified data will be appended to the variable's
> original value. Attributes other than APPEND_WRITE should not be
> modified.
>
> With this patch, APPEND_WRITE test in 'variables' selftest will pass.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> ---
>   lib/efi_loader/efi_variable.c | 50 +++++++++++++++++++++--------------
>   1 file changed, 30 insertions(+), 20 deletions(-)
>
> diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
> index 6687b69a400d..5d1ee50a606e 100644
> --- a/lib/efi_loader/efi_variable.c
> +++ b/lib/efi_loader/efi_variable.c
> @@ -423,18 +423,17 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
>   				     const efi_guid_t *vendor, u32 attributes,
>   				     efi_uintn_t data_size, const void *data)
>   {
> -	char *native_name = NULL, *val = NULL, *s;
> +	char *native_name = NULL, *oval, *val = NULL, *s;

Please, use old_val install of oval.

> +	size_t oval_size;

Please, use old_val_size.

>   	efi_status_t ret = EFI_SUCCESS;
>   	u32 attr;
>
>   	EFI_ENTRY("\"%ls\" %pUl %x %zu %p", variable_name, vendor, attributes,
>   		  data_size, data);
>
> -	/* TODO: implement APPEND_WRITE */
>   	if (!variable_name || !*variable_name || !vendor ||
>   	    ((attributes & EFI_VARIABLE_RUNTIME_ACCESS) &&
> -	     !(attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS)) ||
> -	    (attributes & EFI_VARIABLE_APPEND_WRITE)) {
> +	     !(attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS))) {
>   		ret = EFI_INVALID_PARAMETER;
>   		goto out;
>   	}

Append with data_size = 0 should not delete the variable. See UEFI 2.8 spec.

If a variable does not exist, trying to delete it should return
EFI_NOT_FOUND.

If a variable is READ_ONLY we have to return EFI_WRITE_PROTECTED and
should not delete it.

I know these deficiencies are not caused by your patch. But as you are
touching the code now, could you, please, consider them.

> @@ -452,28 +451,37 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
>   		goto out;
>   	}
>
> -	val = env_get(native_name);
> -	if (val) {
> -		parse_attr(val, &attr);
> +	oval = env_get(native_name);
> +	if (oval) {
> +		oval = parse_attr(oval, &attr);
>
> -		/* We should not free val */
> -		val = NULL;
>   		if (attr & READ_ONLY) {

>   			ret = EFI_WRITE_PROTECTED;
>   			goto out;
>   		}
>
> -		/*
> -		 * attributes won't be changed
> -		 * TODO: take care of APPEND_WRITE once supported
> -		 */
> -		if (attr != attributes) {
> +		/* attributes won't be changed */
> +		if (attr != (attributes & ~EFI_VARIABLE_APPEND_WRITE)) {
>   			ret = EFI_INVALID_PARAMETER;
>   			goto out;
>   		}
> +
> +		if (attributes & EFI_VARIABLE_APPEND_WRITE) {
> +			if (!prefix(oval, "(blob)")) {
> +				/* TODO: should support utf8? */

If the variable is read_only we should not append to it but return
EFI_WRITE_PROTECTED.

We never stored any data as utf8. We can eliminate all references to the
(utf8) prefix in a future patch.

In lib/efi_selftest/efi_selftest_variables.c we already have a test for
APPEND. We should change the efi_st_todo() into efi_st_error() in a
follow-up patch.

Thanks for taking care of this gap.

Best regards

Heinrich

> +				return EFI_DEVICE_ERROR;
> +				goto out;
> +			}
> +			oval_size = strlen(oval);
> +		} else {
> +			oval_size = 0;
> +		}
> +	} else {
> +		oval_size = 0;
>   	}
>
> -	val = malloc(2 * data_size + strlen("{ro,run,boot,nv}(blob)") + 1);
> +	val = malloc(oval_size + 2 * data_size
> +		     + strlen("{ro,run,boot,nv}(blob)") + 1);
>   	if (!val) {
>   		ret = EFI_OUT_OF_RESOURCES;
>   		goto out;
> @@ -481,10 +489,7 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
>
>   	s = val;
>
> -	/*
> -	 * store attributes
> -	 * TODO: several attributes are not supported
> -	 */
> +	/* store attributes */
>   	attributes &= (EFI_VARIABLE_NON_VOLATILE |
>   		       EFI_VARIABLE_BOOTSERVICE_ACCESS |
>   		       EFI_VARIABLE_RUNTIME_ACCESS);
> @@ -505,8 +510,13 @@ efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
>   	}
>   	s += sprintf(s, "}");
>
> +	if (oval_size)
> +		/* APPEND_WRITE */
> +		s += sprintf(s, oval);
> +	else
> +		s += sprintf(s, "(blob)");
> +
>   	/* store payload: */
> -	s += sprintf(s, "(blob)");
>   	s = bin2hex(s, data, data_size);
>   	*s = '\0';
>
>