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target/arm: Use correct mmu_idx for exception-return unstacking 

For M-profile exception returns, the mmu index to use for exception
return unstacking is supposed to be that of wherever we are returning to:
 * if returning to handler mode, privileged
 * if returning to thread mode, privileged or unprivileged depending on
   CONTROL.nPRIV for the destination security state

We were passing the wrong thing as the 'priv' argument to
arm_v7m_mmu_idx_for_secstate_and_priv(). The effect was that guests
which programmed the MPU to behave differently for privileged and
unprivileged code could get spurious MemManage Unstack exceptions.

Reported-by: Adithya Baglody <adithya.nagaraj.baglody@intel.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180709124535.1116-1-peter.maydell@linaro.org
master
Peter Maydell 2018-07-09 13:45:35 +01:00
parent 3a340e8437
commit 2b83714d4e
1 changed files with 3 additions and 1 deletions
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4
target/arm/helper.c
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@ -7171,9 +7171,11 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
uint32_t frameptr = *frame_sp_p;
bool pop_ok = true;
ARMMMUIdx mmu_idx;
bool return_to_priv = return_to_handler ||
!(env->v7m.control[return_to_secure] & R_V7M_CONTROL_NPRIV_MASK);
mmu_idx = arm_v7m_mmu_idx_for_secstate_and_priv(env, return_to_secure,
!return_to_handler);
return_to_priv);
if (!QEMU_IS_ALIGNED(frameptr, 8) &&
arm_feature(env, ARM_FEATURE_V8)) {