diff options
Diffstat (limited to 'src/include/ipxe/entropy.h')
| -rw-r--r-- | src/include/ipxe/entropy.h | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/src/include/ipxe/entropy.h b/src/include/ipxe/entropy.h index beeb3abf..d2e3ce50 100644 --- a/src/include/ipxe/entropy.h +++ b/src/include/ipxe/entropy.h @@ -52,6 +52,25 @@ typedef uint8_t noise_sample_t; /** An entropy sample */ typedef uint8_t entropy_sample_t; +/** An amount of min-entropy + * + * Expressed as a fixed-point quantity in order to avoid floating + * point calculations. + */ +typedef unsigned int min_entropy_t; + +/** Fixed-point scale for min-entropy amounts */ +#define MIN_ENTROPY_SCALE ( 1 << 16 ) + +/** + * Construct a min-entropy fixed-point value + * + * @v bits min-entropy in bits + * @ret min_entropy min-entropy as a fixed-point value + */ +#define MIN_ENTROPY( bits ) \ + ( ( min_entropy_t ) ( (bits) * MIN_ENTROPY_SCALE ) ) + /* Include all architecture-independent entropy API headers */ #include <ipxe/null_entropy.h> #include <ipxe/efi/efi_entropy.h> @@ -87,7 +106,7 @@ void entropy_disable ( void ); * * This must be a compile-time constant. */ -double min_entropy_per_sample ( void ); +min_entropy_t min_entropy_per_sample ( void ); /** * Get noise sample @@ -142,7 +161,7 @@ get_entropy_input ( unsigned int min_entropy_bits, void *data, size_t min_len, /* Sanity checks */ linker_assert ( ( min_entropy_per_sample() <= - ( 8 * sizeof ( noise_sample_t ) ) ), + MIN_ENTROPY ( 8 * sizeof ( noise_sample_t ) ) ), min_entropy_per_sample_is_impossibly_high ); linker_assert ( ( min_entropy_bits <= ( 8 * max_len ) ), entropy_buffer_too_small ); @@ -151,7 +170,8 @@ get_entropy_input ( unsigned int min_entropy_bits, void *data, size_t min_len, min_entropy_bits = ( ( min_entropy_bits + 7 ) & ~7 ); /* Calculate number of samples required to contain sufficient entropy */ - min_samples = ( ( min_entropy_bits * 1.0 ) / min_entropy_per_sample() ); + min_samples = ( MIN_ENTROPY ( min_entropy_bits ) / + min_entropy_per_sample() ); /* Round up to a whole number of samples. We don't have the * ceil() function available, so do the rounding by hand. |