[PATCH 15/16] efi_loader: enable UEFI variables at runtime

Heinrich Schuchardt
2020-04-01T06:26:24Z

On 4/1/20 3:41 AM, AKASHI Takahiro wrote:
> On Tue, Mar 31, 2020 at 08:05:40AM +0200, Heinrich Schuchardt wrote:
>> Enable UEFI variables at runtime.
>>
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
>> ---
>> lib/efi_loader/efi_runtime.c | 6 +++++-
>> lib/efi_loader/efi_variable.c | 23 +++++++++++++++++------
>> 2 files changed, 22 insertions(+), 7 deletions(-)
>>
>> diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c
>> index 664a0422e2..acd644202d 100644
>> --- a/lib/efi_loader/efi_runtime.c
>> +++ b/lib/efi_loader/efi_runtime.c
>> @@ -120,8 +120,12 @@ efi_status_t efi_init_runtime_supported(void)
>> rt_table->version = EFI_RT_PROPERTIES_TABLE_VERSION;
>> rt_table->length = sizeof(struct efi_rt_properties_table);
>> rt_table->runtime_services_supported =
>> + EFI_RT_SUPPORTED_GET_VARIABLE |
>> + EFI_RT_SUPPORTED_GET_NEXT_VARIABLE_NAME |
>> + EFI_RT_SUPPORTED_SET_VARIABLE |
>> EFI_RT_SUPPORTED_SET_VIRTUAL_ADDRESS_MAP |
>> - EFI_RT_SUPPORTED_CONVERT_POINTER;
>> + EFI_RT_SUPPORTED_CONVERT_POINTER |
>> + EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO;
>>
>> /*
>> * This value must be synced with efi_runtime_detach_list
>> diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
>> index 7c39542968..cf8b44c535 100644
>> --- a/lib/efi_loader/efi_variable.c
>> +++ b/lib/efi_loader/efi_variable.c
>> @@ -326,15 +326,13 @@ efi_status_t __efi_runtime EFIAPI efi_query_variable_info(
>> u64 *remaining_variable_storage_size,
>> u64 *maximum_variable_size)
>> {
>> - /*
>> *maximum_variable_storage_size = EFI_VAR_BUF_SIZE -
>> sizeof(struct efi_var_file);
>> *remaining_variable_storage_size = efi_var_mem_free();
>> *maximum_variable_size = EFI_VAR_BUF_SIZE -
>> sizeof(struct efi_var_file) -
>> sizeof(struct efi_var_entry);
>> - */
>> - return EFI_UNSUPPORTED;
>> + return EFI_SUCCESS;
>> }
>>
>> /**
>> @@ -351,7 +349,8 @@ static efi_status_t __efi_runtime EFIAPI
>> efi_get_variable_runtime(u16 *variable_name, const efi_guid_t *vendor,
>> u32 *attributes, efi_uintn_t *data_size, void *data)
>> {
>> - return EFI_UNSUPPORTED;
>> + return efi_get_variable_int(variable_name, vendor, attributes,
>> + data_size, data);
>> }
>>
>> /**
>> @@ -367,7 +366,8 @@ static efi_status_t __efi_runtime EFIAPI
>> efi_get_next_variable_name_runtime(efi_uintn_t *variable_name_size,
>> u16 *variable_name, efi_guid_t *vendor)
>> {
>> - return EFI_UNSUPPORTED;
>> + return efi_get_next_variable_name_int(variable_name_size, variable_name,
>> + vendor);
>> }
>>
>> /**
>> @@ -385,7 +385,18 @@ efi_set_variable_runtime(u16 *variable_name, const efi_guid_t *vendor,
>> u32 attributes, efi_uintn_t data_size,
>> const void *data)
>> {
>> - return EFI_UNSUPPORTED;
>> + const u32 required_attributes = EFI_VARIABLE_NON_VOLATILE |
>> + EFI_VARIABLE_BOOTSERVICE_ACCESS |
>> + EFI_VARIABLE_RUNTIME_ACCESS;
>> +
>
> Why not support APPEND_WRITE?

This is the list of attributes that have to be set as a *minimum* in a
valid call to SetVariable. APPEND_WRITE is not required but optional.

>
>
>> + if (attributes &&
>> + (attributes & required_attributes) != required_attributes)
>> + return EFI_INVALID_PARAMETER;
>
> UEFI specification says,
> ===8<====
> Variables that have runtime access but that are not nonvolatile are read-
> only data variables once ExitBootServices() is performed.
> [snip]
> EFI_WRITE_PROTECTED The variable in question is read-only.
> ===>8===
>
> So in this case, we should return WRITE_PROTECTED instead of
> INVALID_PARAMETER.

Here I check the parameters of the call which may create a new variable.

We should later in the code check if the variable already exists and if
it is volatile return EFI_WRITE_PROTECTED.

Best regards

Heinrich

>
>> + if ((attributes & ~(u32)EFI_VARIABLE_MASK))
>> + return EFI_INVALID_PARAMETER;
>> +
>> + return efi_set_variable_rt_int(variable_name, vendor, attributes,
>> + data_size, data);
>
> I didn't follow detailed logic of this function, but
> does it really return UNSUPPORTED if !FAT_WRITE?
>
> -Takahiro Akashi
>
>> }
>>
>> /**
>> --
>> 2.25.1
>>