diff options
Diffstat (limited to 'hw/mips/cputimer.c')
| -rw-r--r-- | hw/mips/cputimer.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/hw/mips/cputimer.c b/hw/mips/cputimer.c index 577c9aeab8..ba9264b415 100644 --- a/hw/mips/cputimer.c +++ b/hw/mips/cputimer.c @@ -30,13 +30,21 @@ /* XXX: do not use a global */ uint32_t cpu_mips_get_random (CPUMIPSState *env) { - static uint32_t lfsr = 1; + static uint32_t seed = 1; static uint32_t prev_idx = 0; uint32_t idx; + uint32_t nb_rand_tlb = env->tlb->nb_tlb - env->CP0_Wired; + + if (nb_rand_tlb == 1) { + return env->tlb->nb_tlb - 1; + } + /* Don't return same value twice, so get another value */ do { - lfsr = (lfsr >> 1) ^ (-(lfsr & 1u) & 0xd0000001u); - idx = lfsr % (env->tlb->nb_tlb - env->CP0_Wired) + env->CP0_Wired; + /* Use a simple algorithm of Linear Congruential Generator + * from ISO/IEC 9899 standard. */ + seed = 1103515245 * seed + 12345; + idx = (seed >> 16) % nb_rand_tlb + env->CP0_Wired; } while (idx == prev_idx); prev_idx = idx; return idx; |