arch/armv8-m: Supports interrupt nesting between TEE and REE

The first time interrupt nesting occurs between REE and TEE,
CURRENT_REGS needs to be set.

If TEE nesting REE breaks, then EXC_RETURN.S=0,EXC_RETURN.ES=1;
Conversely, EXC_RETURN.S=1,EXC_RETURN.ES=0;
Interrupt nesting between TEE and REE can be determined based
on the S and ES bits of EXC_RETURN.
Only once nesting between TEE and REE is supported, and cyclic
nesting between TEE and REE is not supported.

Signed-off-by: wangming9 <[email protected]>

arch/arm/src/armv8-m/arm_doirq.c

@@ -36,6 +36,55 @@
 #include "arm_internal.h"
 #include "exc_return.h"
 
+/****************************************************************************
+ * Inline Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: arm_from_thread
+ *
+ * Description:
+ * If not defined CONFIG_ARCH_HAVE_TRUSTZONE
+ * Return true if interrupt return to thread mode, false otherwise.
+ *
+ * If defined CONFIG_ARCH_HAVE_TRUSTZONE
+ * Return true if interrupt return to thread mode, or if it is the first
+ * interrupt from TEE to REE, or REE to TEE, false otherwise.
+ *
+ * Interrupt nesting between TEE and REE can be determined based
+ * on the S and ES bits of EXC_RETURN
+ * If TEE interrupts REE, then EXC_RETURN.S=0, EXC_RETURN.ES=1;
+ * Conversely, EXC_RETURN.S=1, EXC_RETURN.ES=0.
+ *
+ * But only one level nesting between TEE and REE is supported, and
+ * recursive nesting between TEE and REE is not supported.
+ *
+ ****************************************************************************/
+
+static inline bool arm_from_thread(uint32_t excret)
+{
+ if (excret & EXC_RETURN_THREAD_MODE)
+ {
+ return true;
+ }
+
+#ifdef CONFIG_ARCH_HAVE_TRUSTZONE
+ if (!(excret & EXC_RETURN_SECURE_STACK) &&
+ (excret & EXC_RETURN_EXC_SECURE))
+ {
+ return true;
+ }
+
+ if (!(excret & EXC_RETURN_EXC_SECURE) &&
+ (excret & EXC_RETURN_SECURE_STACK))
+ {
+ return true;
+ }
+#endif
+
+ return false;
+}
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -47,7 +96,7 @@ uint32_t *arm_doirq(int irq, uint32_t *regs)
  PANIC();
 #else
 
- if (regs[REG_EXC_RETURN] & EXC_RETURN_THREAD_MODE)
+ if (arm_from_thread(regs[REG_EXC_RETURN]))
  {
  CURRENT_REGS = regs;
  }
@@ -66,7 +115,7 @@ uint32_t *arm_doirq(int irq, uint32_t *regs)
  * switch occurred during interrupt processing.
  */
 
- if (regs[REG_EXC_RETURN] & EXC_RETURN_THREAD_MODE)
+ if (arm_from_thread(regs[REG_EXC_RETURN]))
  {
  /* Restore the cpu lock */