From 3adafef2f35d9061b56a09071b2589b9e0b36f76 Mon Sep 17 00:00:00 2001 From: Leon Alrae Date: Thu, 10 Sep 2015 10:15:28 +0100 Subject: [PATCH] target-mips: fix corner case in TLBWR causing QEMU to hang cpu_mips_get_random() function is used to generate a random index from CP0.Wired to TLBSize-1 range. Current implementation avoids generating the same as before value, hence the while loop. If the guest sets CP0.Wired to TLBSize-1 (which actually does not sound to be very practical) QEMU will get stuck in the loop infinitely as we always generate the same index. Signed-off-by: Leon Alrae Reviewed-by: Aurelien Jarno --- hw/mips/cputimer.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/hw/mips/cputimer.c b/hw/mips/cputimer.c index 1603600..ba9264b 100644 --- a/hw/mips/cputimer.c +++ b/hw/mips/cputimer.c @@ -33,13 +33,18 @@ uint32_t cpu_mips_get_random (CPUMIPSState *env) 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 { /* Use a simple algorithm of Linear Congruential Generator * from ISO/IEC 9899 standard. */ seed = 1103515245 * seed + 12345; - idx = (seed >> 16) % (env->tlb->nb_tlb - env->CP0_Wired) + - env->CP0_Wired; + idx = (seed >> 16) % nb_rand_tlb + env->CP0_Wired; } while (idx == prev_idx); prev_idx = idx; return idx; -- 2.7.4