diff options
Diffstat (limited to 'target/arm/helper.c')
| -rw-r--r-- | target/arm/helper.c | 30 |
1 files changed, 27 insertions, 3 deletions
diff --git a/target/arm/helper.c b/target/arm/helper.c index 1bab86cfd2..bee0f5ddb6 100644 --- a/target/arm/helper.c +++ b/target/arm/helper.c @@ -6436,6 +6436,29 @@ static void do_v7m_exception_exit(ARMCPU *cpu) } xpsr = ldl_phys(cs->as, frameptr + 0x1c); + if (arm_feature(env, ARM_FEATURE_V8)) { + /* For v8M we have to check whether the xPSR exception field + * matches the EXCRET value for return to handler/thread + * before we commit to changing the SP and xPSR. + */ + bool will_be_handler = (xpsr & XPSR_EXCP) != 0; + if (return_to_handler != will_be_handler) { + /* Take an INVPC UsageFault on the current stack. + * By this point we will have switched to the security state + * for the background state, so this UsageFault will target + * that state. + */ + armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, + env->v7m.secure); + env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_INVPC_MASK; + v7m_exception_taken(cpu, excret); + qemu_log_mask(CPU_LOG_INT, "...taking UsageFault on existing " + "stackframe: failed exception return integrity " + "check\n"); + return; + } + } + /* Commit to consuming the stack frame */ frameptr += 0x20; /* Undo stack alignment (the SPREALIGN bit indicates that the original @@ -6455,12 +6478,13 @@ static void do_v7m_exception_exit(ARMCPU *cpu) /* The restored xPSR exception field will be zero if we're * resuming in Thread mode. If that doesn't match what the * exception return excret specified then this is a UsageFault. + * v7M requires we make this check here; v8M did it earlier. */ if (return_to_handler != arm_v7m_is_handler_mode(env)) { - /* Take an INVPC UsageFault by pushing the stack again. - * TODO: the v8M version of this code should target the - * background state for this exception. + /* Take an INVPC UsageFault by pushing the stack again; + * we know we're v7M so this is never a Secure UsageFault. */ + assert(!arm_feature(env, ARM_FEATURE_V8)); armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, false); env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_INVPC_MASK; v7m_push_stack(cpu); |