[Qemu-devel] [PATCH 17/18] armv7m: implement CCR

[Michael Davidsaver <mdavidsaver@gmail.com>]

Implement Configuration and Control register.
Handle STACKALIGN and USERSETMPEND bits.

Signed-off-by: Michael Davidsaver <mdavidsaver@gmail.com>
---
 hw/intc/armv7m_nvic.c | 15 +++++++++++----
 target-arm/cpu.h      |  1 +
 target-arm/helper.c   |  8 +++-----
 target-arm/machine.c  |  1 +
 4 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index a75dd3c..ca8c93c 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -474,8 +474,7 @@ static uint32_t nvic_readl(nvic_state *s, uint32_t offset)
         /* TODO: Implement SLEEPONEXIT.  */
         return 0;
     case 0xd14: /* Configuration Control.  */
-        /* TODO: Implement Configuration Control bits.  */
-        return 0;
+        return cpu->env.v7m.ccr;
     case 0xd24: /* System Handler Status.  */
         val = 0;
         if (s->vectors[ARMV7M_EXCP_MEM].active) val |= (1 << 0);
@@ -619,9 +618,17 @@ static void nvic_writel(nvic_state *s, uint32_t offset, uint32_t value)
         }
         break;
     case 0xd10: /* System Control.  */
-    case 0xd14: /* Configuration Control.  */
         /* TODO: Implement control registers.  */
-        qemu_log_mask(LOG_UNIMP, "NVIC: SCR and CCR unimplemented\n");
+        qemu_log_mask(LOG_UNIMP, "NVIC: SCR unimplemented\n");
+        break;
+    case 0xd14: /* Configuration Control.  */
+        value &= 0x31b;
+        if (value&0x118) {
+            qemu_log_mask(LOG_UNIMP, "CCR unimplemented bits"
+                                     " BFHFNMIGN, DIV_0_TRP, UNALIGN_TRP");
+            value &= ~0x118;
+        }
+        cpu->env.v7m.ccr = value;
         break;
     case 0xd24: /* System Handler Control.  */
         /* TODO: Real hardware allows you to set/clear the active bits
diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 72b0b32..90ccdcd 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -396,6 +396,7 @@ typedef struct CPUARMState {
         uint32_t vecbase;
         uint32_t basepri;
         uint32_t control;
+        uint32_t ccr; /* Configuration and Control */
         uint32_t cfsr; /* Configurable Fault Status */
         uint32_t hfsr; /* HardFault Status */
         int current_sp;
diff --git a/target-arm/helper.c b/target-arm/helper.c
index 3993f77..402bfc5 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -5412,7 +5412,7 @@ static void do_v7m_exception_exit(CPUARMState *env)
         break;
     case 0x9: /* Return to Thread mode w/ Main stack */
     case 0xd: /* Return to Thread mode w/ Process stack */
-        if (env->v7m.exception != 0) {
+        if ((env->v7m.exception != 0) && !(env->v7m.ccr&1)) {
             /* Attempt to return to Thread mode
              * from nested handler while NONBASETHRDENA not set.
              */
@@ -5564,10 +5564,8 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
 
     qemu_log_mask(CPU_LOG_INT, "... as %d\n", env->v7m.exception);
 
-    /* Align stack pointer.  */
-    /* ??? Should only do this if Configuration Control Register
-       STACKALIGN bit is set.  */
-    if (env->regs[13] & 4) {
+    /* Align stack pointer (STACKALIGN)  */
+    if (env->v7m.ccr&(1<<9)) {
         env->regs[13] -= 4;
         xpsr |= 0x200;
     }
diff --git a/target-arm/machine.c b/target-arm/machine.c
index d7c2034..e8b710d 100644
--- a/target-arm/machine.c
+++ b/target-arm/machine.c
@@ -100,6 +100,7 @@ static const VMStateDescription vmstate_m = {
         VMSTATE_UINT32(env.v7m.vecbase, ARMCPU),
         VMSTATE_UINT32(env.v7m.basepri, ARMCPU),
         VMSTATE_UINT32(env.v7m.control, ARMCPU),
+        VMSTATE_UINT32(env.v7m.ccr, ARMCPU),
         VMSTATE_UINT32(env.v7m.cfsr, ARMCPU),
         VMSTATE_UINT32(env.v7m.hfsr, ARMCPU),
         VMSTATE_INT32(env.v7m.current_sp, ARMCPU),
-- 
2.1.4