target/s390x: Use address generation for register branch targets

Indirect branches to addresses taken from registers go through address
generation, e.g., for BRANCH ON CONDITION Principles of Operation says:

    In the RR format, the contents of general register R2 are used to
    generate the branch address

QEMU uses r2_nz handler for the respective register operands. Currently
it does not zero out extra bits in 24- and 31-bit addressing modes as
required by address generation. The very frequently used
s390x_tr_init_disas_context() function has a workaround for this,
but the code for saving an old PSW during an interrupt does not.

Add the missing masking to r2_nz. Enforce PSW validity by replacing the
workaround with an assertion.

Reported-by: Thomas Weißschuh <linux@weissschuh.net>
Reported-by: Heiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/lkml/ab3131a2-c42a-47ff-bf03-e9f68ac053c0@t-8ch.de/
Cc: qemu-stable@nongnu.org
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Tested-by: Thomas Weißschuh <linux@weissschuh.net>
Message-ID: <20251016175954.41153-4-iii@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

diff --git a/target/s390x/tcg/translate.c b/target/s390x/tcg/translate.c
index ec9e5a07516af3dd275481d8ab3d3c358d823af9..4d2b8c5e2be7f720c9c2113daec7e66dcef744b8 100644 (file)
--- a/target/s390x/tcg/translate.c
+++ b/target/s390x/tcg/translate.c
@@ -5613,6 +5613,7 @@ static void in2_r2_nz(DisasContext *s, DisasOps *o)
     int r2 = get_field(s, r2);
     if (r2 != 0) {
         o->in2 = load_reg(r2);
+        gen_addi_and_wrap_i64(s, o->in2, o->in2, 0);
     }
 }
 #define SPEC_in2_r2_nz 0
@@ -6379,10 +6380,12 @@ static void s390x_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
 {
     DisasContext *dc = container_of(dcbase, DisasContext, base);
 
-    /* 31-bit mode */
-    if (!(dc->base.tb->flags & FLAG_MASK_64)) {
-        dc->base.pc_first &= 0x7fffffff;
-        dc->base.pc_next = dc->base.pc_first;
+    if (dc->base.tb->flags & FLAG_MASK_32) {
+        if (!(dc->base.tb->flags & FLAG_MASK_64)) {
+            assert(!(dc->base.pc_first & ~((1ULL << 31) - 1)));
+        }
+    } else {
+        assert(!(dc->base.pc_first & ~((1ULL << 24) - 1)));
     }
 
     dc->cc_op = CC_OP_DYNAMIC;