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target/arm: Fix assert on BRA.

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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 64678fc45d 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: 64678fc45d ("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 64678fc45d to commit message]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Harald van Dijk 2025-11-28 04:38:11 +00:00 • committed by Peter Maydell
parent 9ef49528b5
commit 7248dab3c9
1 changed files with 1 additions and 1 deletions
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2
target/arm/tcg/translate-a64.c
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@ -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;
}