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Re: [Qemu-devel] [PATCH] target/arm: Forbid unprivileged mode for M Base


From: Julia Suvorova
Subject: Re: [Qemu-devel] [PATCH] target/arm: Forbid unprivileged mode for M Baseline
Date: Thu, 5 Jul 2018 13:48:15 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0

On 05.07.2018 13:33, Peter Maydell wrote:
On 4 July 2018 at 21:36, Julia Suvorova <address@hidden> wrote:
MSR handling is the only place where CONTROL.nPRIV is modified.

Signed-off-by: Julia Suvorova <address@hidden>
---
  target/arm/helper.c | 6 ++++--
  1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 5ee229eb35..83cca554ad 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -10781,8 +10781,10 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t 
maskreg, uint32_t val)
              !arm_v7m_is_handler_mode(env)) {
              write_v7m_control_spsel(env, (val & R_V7M_CONTROL_SPSEL_MASK) != 
0);
          }
-        env->v7m.control[env->v7m.secure] &= ~R_V7M_CONTROL_NPRIV_MASK;
-        env->v7m.control[env->v7m.secure] |= val & R_V7M_CONTROL_NPRIV_MASK;
+        if (arm_feature(env, ARM_FEATURE_M_MAIN)) {
+            env->v7m.control[env->v7m.secure] &= ~R_V7M_CONTROL_NPRIV_MASK;
+            env->v7m.control[env->v7m.secure] |= val & 
R_V7M_CONTROL_NPRIV_MASK;
+        }
          break;
      default:
      bad_reg:
--

Could you also guard the similar code in the CONTROL_NS case a
little earlier, in the function, please?

             env->v7m.control[M_REG_NS] &= ~R_V7M_CONTROL_NPRIV_MASK;
             env->v7m.control[M_REG_NS] |= val & R_V7M_CONTROL_NPRIV_MASK;

That won't be executed for v6M but for v8M it matters.

Sure, I'll send v2.

Best regards, Julia Suvorova.



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