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Re: [PATCH] target/arm: Get correct MMU index for other-security-state

From: Richard Henderson
Subject: Re: [PATCH] target/arm: Get correct MMU index for other-security-state
Date: Fri, 30 Oct 2020 12:21:37 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0

On 10/22/20 9:44 AM, Peter Maydell wrote:
> In arm_v7m_mmu_idx_for_secstate() we get the 'priv' level to pass to
> armv7m_mmu_idx_for_secstate_and_priv() by calling arm_current_el().
> This is incorrect when the security state being queried is not the
> current one, because arm_current_el() uses the current security state
> to determine which of the banked CONTROL.nPRIV bits to look at.
> The effect was that if (for instance) Secure state was in privileged
> mode but Non-Secure was not then we would return the wrong MMU index.
> The only places where we are using this function in a way that could
> trigger this bug are for the stack loads during a v8M function-return
> and for the instruction fetch of a v8M SG insn.
> Fix the bug by expanding out the M-profile version of the
> arm_current_el() logic inline so it can use the passed in secstate
> rather than env->v7m.secure.
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/m_helper.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


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