On Thu, 2015-07-16 at 22:25 +0800, Lee, Chun-Yi wrote:
> To grab random numbers through EFI protocol as one of the entropies
> source of swsusp key, this patch adds the logic for accessing EFI RNG
> (random number generator) protocol that's introduced since UEFI 2.4.
>
> Signed-off-by: Lee, Chun-Yi <j...@suse.com>
> ---
> arch/x86/boot/compressed/efi_random.c | 193
> ++++++++++++++++++++++++++++++++++
> include/linux/efi.h | 46 ++++++++
> 2 files changed, 239 insertions(+)
[...]
> @@ -2,6 +2,191 @@
>
> #include <linux/efi.h>
> #include <asm/archrandom.h>
> +#include <asm/efi.h>
> +
> +static efi_status_t efi_locate_rng(efi_system_table_t *sys_table,
> + void ***rng_handle)
> +{
> + efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
> + unsigned long size = 0;
> + efi_status_t status;
> +
> + status = efi_call_early(locate_handle,
> + EFI_LOCATE_BY_PROTOCOL,
> + &rng_proto, NULL, &size, *rng_handle);
> +
> + if (status == EFI_BUFFER_TOO_SMALL) {
> + status = efi_call_early(allocate_pool,
> + EFI_LOADER_DATA,
> + size, (void **)rng_handle);
> +
> + if (status != EFI_SUCCESS) {
> + efi_printk(sys_table, " Failed to alloc mem for
> rng_handle");
> + return status;
> + }
> +
> + status = efi_call_early(locate_handle,
> + EFI_LOCATE_BY_PROTOCOL, &rng_proto,
> + NULL, &size, *rng_handle);
> + }
> +
> + if (status != EFI_SUCCESS) {
> + efi_printk(sys_table, " Failed to locate EFI_RNG_PROTOCOL");
> + goto free_handle;
> + }
> +
> + return EFI_SUCCESS;
> +
> +free_handle:
> + efi_call_early(free_pool, *rng_handle);
> +
> + return status;
> +}
I would suggest setting *rng_handle = NULL at the beginning of this
function just because if we ever forget to set it that way in the caller
this free_pool call might do screwy things.
> +static bool efi_rng_supported(efi_system_table_t *sys_table)
> +{
> + const struct efi_config *efi_early = __efi_early();
> + u32 random = 0;
> + efi_status_t status;
> + void **rng_handle = NULL;
> +
> + status = efi_locate_rng(sys_table, &rng_handle);
> + if (status != EFI_SUCCESS)
> + return false;
> +
> + if (efi_early->is64)
> + random = efi_rng_supported64(sys_table, rng_handle);
> + else
> + random = efi_rng_supported32(sys_table, rng_handle);
> +
> + efi_call_early(free_pool, rng_handle);
> +
> + return random;
Oops, 'random' isn't a bool but it should be.
> @@ -51,6 +236,14 @@ static unsigned long get_random_long(unsigned long
> entropy,
> use_i8254 = false;
> }
>
> + if (efi_rng_supported(sys_table)) {
> + efi_printk(sys_table, " EFI_RNG");
> + raw = efi_get_rng(sys_table);
> + if (raw)
> + random ^= raw;
> + use_i8254 = false;
> + }
> +
> if (use_i8254) {
> efi_printk(sys_table, " i8254");
> random ^= i8254();
Have you looked at the tradeoff in terms of boot time for building a key
array in 'unsigned long' chunks as opposed to passing the array and size
directly for the RNG protocol?
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