[PATCH 04/12] target/s390x: Fix MVCRL with a large value in R0

[Ilya Leoshkevich]

Using a large R0 causes an assertion error:

    qemu-s390x: target/s390x/tcg/mem_helper.c:183: access_prepare_nf: Assertion 
`size > 0 && size <= 4096' failed.

Even though PoP explicitly advises against using more than 8 bits for the
size, an emulator crash is never a good thing.

Fix by truncating the size to 8 bits.

Fixes: ea0a1053e276 ("s390x/tcg: Implement Miscellaneous-Instruction-Extensions 
Facility 3 for the s390x")
Cc: qemu-sta...@nongnu.org
Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com>
---
 target/s390x/tcg/mem_helper.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/target/s390x/tcg/mem_helper.c b/target/s390x/tcg/mem_helper.c
index d02ec861d8b..84ad85212c9 100644
--- a/target/s390x/tcg/mem_helper.c
+++ b/target/s390x/tcg/mem_helper.c
@@ -514,6 +514,7 @@ void HELPER(mvcrl)(CPUS390XState *env, uint64_t l, uint64_t 
dest, uint64_t src)
     int32_t i;
 
     /* MVCRL always copies one more byte than specified - maximum is 256 */
+    l &= 0xff;
     l++;
 
     access_prepare(&srca, env, src, l, MMU_DATA_LOAD, mmu_idx, ra);
-- 
2.41.0