target/arm: Fix assert on BRA.

trans_BRA does

    gen_a64_set_pc(s, dst);
    set_btype_for_br(s, a->rn);

gen_a64_set_pc does

    s->pc_save = -1;

set_btype_for_br (if aa64_bti is enabled and the register is not x16 or
x17) does

    gen_pc_plus_diff(s, pc, 0);

gen_pc_plus_diff does

    assert(s->pc_save != -1);

Hence, this assert is getting hit. We need to call set_btype_for_br
before gen_a64_set_pc, and there is nothing in set_btype_for_br that
depends on gen_a64_set_pc having already been called, so this commit
simply swaps the calls.

(The commit message for 64678fc45d8f6 says that set_brtype_for_br()
must be "moved after" get_a64_set_pc(), but this is a mistake in
the commit message -- the actual changes in that commit move
set_brtype_for_br() *before* get_a64_set_pc() and this is necessary
to avoid the assert.)

Cc: qemu-stable@nongnu.org
Fixes: 64678fc45d8f6 ("target/arm: Fix BTI versus CF_PCREL")
Signed-off-by: Harald van Dijk <hdijk@accesssoftek.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: d2265ebb-84bc-41b7-a2d7-05dc9a5a2055@accesssoftek.com
[PMM: added note about 64678fc45d8f6 to commit message]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/target/arm/tcg/translate-a64.c b/target/arm/tcg/translate-a64.c
index 08b21d7dbfa65fb1b887dd7499faf8cabd355c64..cde22a5cca739e325e2e3be2abab1402c9b94052 100644 (file)
--- a/target/arm/tcg/translate-a64.c
+++ b/target/arm/tcg/translate-a64.c
@@ -1916,8 +1916,8 @@ static bool trans_BRA(DisasContext *s, arg_bra *a)
         return false;
     }
     dst = auth_branch_target(s, cpu_reg(s,a->rn), cpu_reg_sp(s, a->rm), !a->m);
-    gen_a64_set_pc(s, dst);
     set_btype_for_br(s, a->rn);
+    gen_a64_set_pc(s, dst);
     s->base.is_jmp = DISAS_JUMP;
     return true;
 }