unsigned long kaslr_get_random_long(const char *purpose)
{
#ifdef CONFIG_X86_64
const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
#else
const unsigned long mix_const = 0x3f39e593UL;
#endif
unsigned long raw, random = get_boot_seed();
bool use_i8254 = true;
debug_putstr(purpose);
debug_putstr(" KASLR using");
if (has_cpuflag(X86_FEATURE_RDRAND)) {
debug_putstr(" RDRAND");
if (rdrand_long(&raw)) {
random ^= raw;
use_i8254 = false;
}
}
if (has_cpuflag(X86_FEATURE_TSC)) {
debug_putstr(" RDTSC");
raw = rdtsc();
random ^= raw;
use_i8254 = false;
}
if (use_i8254) {
debug_putstr(" i8254");
random ^= i8254();
}
/* Circular multiply for better bit diffusion */
asm("mul %3"
: "=a" (random), "=d" (raw)
: "a" (random), "rm" (mix_const));
random += raw;
debug_putstr("...\n");
return random;
}
void x86_init_rdrand(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_ARCH_RANDOM
unsigned long tmp;
int i, count, ok;
if (!cpu_has(c, X86_FEATURE_RDRAND))
return; /* Nothing to do */
for (count = i = 0; i < RESEED_LOOP; i++) {
ok = rdrand_long(&tmp);
if (ok)
count++;
}
if (count != RESEED_LOOP)
clear_cpu_cap(c, X86_FEATURE_RDRAND);
#endif
}
