diff options
Diffstat (limited to 'src/interface/efi/efi_entropy.c')
| -rw-r--r-- | src/interface/efi/efi_entropy.c | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/src/interface/efi/efi_entropy.c b/src/interface/efi/efi_entropy.c index cda1c3640..8e55c77b1 100644 --- a/src/interface/efi/efi_entropy.c +++ b/src/interface/efi/efi_entropy.c @@ -28,6 +28,11 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); #include <ipxe/profile.h> #include <ipxe/efi/efi.h> +#if defined(__i386) || defined(__x86_64) +#include <ipxe/cpuid.h> +static char have_hwrnd = 0; +#endif + /** @file * * EFI entropy source @@ -128,6 +133,44 @@ static int efi_entropy_tick ( void ) { } /** + * Get noise sample from rdrand + * + * @ret noise Noise sample + * @ret rc Return status code + */ +static int efi_get_noise_rdrand ( noise_sample_t *noise ) { +#if defined(__i386) || defined(__x86_64) + if ( have_hwrnd == 0 ) { + struct x86_features features; + x86_features( &features ); + if ( features.intel.ecx & ( 1 << 30 ) ) { + have_hwrnd = 1; + } else { + have_hwrnd = 2; + } + DBGC( &tick, "Have RDRAND: %s\n", ( have_hwrnd == 1 ? "YES!" : "NO :-(" ) ); + } + if ( have_hwrnd == 1 ) { + int ret, retries = 10; + char ok; + while ( --retries > 0 ) { + __asm__ volatile ( "rdrand %0; setc %1" : "=r" ( ret ), "=qm" ( ok ) ); + if ( ok ) { + if ( ret == -1 ) { + /* Assume this is a broken AMD CPU, fall back to TSC */ + ret = profile_timestamp(); + } + *noise = ret; + return 0; + } + } + return -EBUSY; + } +#endif + return -ENOTSUP; +} + +/** * Get noise sample from timer ticks * * @ret noise Noise sample @@ -138,6 +181,10 @@ static int efi_get_noise ( noise_sample_t *noise ) { int after; int rc; + rc = efi_get_noise_rdrand ( noise ); + if ( rc == 0 ) + return 0; + /* Wait for a timer tick */ before = efi_entropy_tick(); if ( before < 0 ) { |