1 files changed, 25 insertions, 0 deletions
diff --git a/target/mips/cp0_helper.c b/target/mips/cp0_helper.c
index de64add038..12143ac55b 100644
--- a/target/mips/cp0_helper.c
+++ b/target/mips/cp0_helper.c
@@ -203,6 +203,31 @@ static void sync_c0_entryhi(CPUMIPSState *cpu, int tc)
     *tcst |= asid;
 }
 
+/* XXX: do not use a global */
+uint32_t cpu_mips_get_random(CPUMIPSState *env)
+{
+    static uint32_t seed = 1;
+    static uint32_t prev_idx;
+    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 {
+        /*
+         * 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;
+}
+
 /* CP0 helpers */
 target_ulong helper_mfc0_mvpcontrol(CPUMIPSState *env)
 {