arch: arc: put the init context into privileged stack

as the thread is created in privileged mode, the init
context should also be in privileged stack.

Signed-off-by: Wayne Ren <[email protected]>

Author: Wayne Ren

arch/arc/core/swap.S

@@ -164,15 +164,6 @@ _swap_return_from_coop:
 	pop_s blink /* pc into blink */
 #ifdef CONFIG_ARC_HAS_SECURE
 	pop_s r3    /* pop SEC_STAT */
-#endif
-	pop_s r2    /* status32 into r2 */
-/*
- * the above pop may happen in the unprivileged stack, but now it's
- * kernel mode, the write to status32/sec_stat before pop may cause
- * stack check fail.
- */
-	kflag r2    /* write status32 */
-#ifdef CONFIG_ARC_HAS_SECURE
 	/* sflag r3 */
 	/* sflag instruction is not supported in current ARC GNU */
 	.long 0x00ff302f
@@ -182,6 +173,9 @@ _swap_return_from_coop:
 #endif
 return_loc:
 
+	pop_s r3    /* status32 into r3 */
+	kflag r3    /* write status32 */
+
 	j_s.d [blink] /* always execute delay slot */
 	seti r1       /* delay slot */
 

arch/arc/core/thread.c

@@ -88,6 +88,23 @@ void _new_thread(struct k_thread *thread, k_thread_stack_t *stack,
 			(u32_t)(stackEnd + STACK_GUARD_SIZE);
 		thread->arch.priv_stack_size =
 			(u32_t)(CONFIG_PRIVILEGED_STACK_SIZE);
+
+		stackAdjEnd = (char *)STACK_ROUND_DOWN(stackEnd + STACK_GUARD_SIZE +
+					CONFIG_PRIVILEGED_STACK_SIZE);
+
+		/* reserve 4 bytes for the start of user sp */
+		stackAdjEnd -= 4;
+		(*(u32_t *)stackAdjEnd) = (u32_t)stackEnd;
+
+#ifdef CONFIG_THREAD_USERSPACE_LOCAL_DATA
+		/* reserve stack space for the userspace local data struct */
+		thread->userspace_local_data =
+			(struct _thread_userspace_local_data *)
+			STACK_ROUND_DOWN(stackEnd - sizeof(*thread->userspace_local_data));
+		/* update the start of user sp */
+		(*(u32_t *)stackAdjEnd) = (u32_t) thread->userspace_local_data;
+#endif
+
 	} else {
 	/* for kernel thread, the privilege stack is merged into thread stack */
 	/* if MPU_STACK_GUARD is enabled, reserve the the stack area
@@ -105,32 +122,31 @@ void _new_thread(struct k_thread *thread, k_thread_stack_t *stack,
 
 		thread->arch.priv_stack_start = 0;
 		thread->arch.priv_stack_size = 0;
+
+		stackAdjEnd = (char *)STACK_ROUND_DOWN(stackEnd);
+
+#ifdef CONFIG_THREAD_USERSPACE_LOCAL_DATA
+		/* reserve stack space for the userspace local data struct */
+		stackAdjEnd = (char *)STACK_ROUND_DOWN(stackEnd
+			- sizeof(*thread->userspace_local_data));
+		thread->userspace_local_data =
+			(struct _thread_userspace_local_data *)stackAdjEnd;
+#endif
 	}
 
 	_new_thread_init(thread, pStackMem, stackSize, priority, options);
 
-	stackAdjEnd = stackEnd;
 
-#ifdef CONFIG_THREAD_USERSPACE_LOCAL_DATA
-	/* reserve stack space for the userspace local data struct */
-	stackAdjEnd = (char *)STACK_ROUND_DOWN(stackEnd
-		- sizeof(*thread->userspace_local_data));
-	thread->userspace_local_data =
-		(struct _thread_userspace_local_data *)stackAdjEnd;
-#endif
 	/* carve the thread entry struct from the "base" of
-		  the user stack */
+		the privileged stack */
 	pInitCtx = (struct init_stack_frame *)(
-		STACK_ROUND_DOWN(stackAdjEnd) -
-		sizeof(struct init_stack_frame));
+		stackAdjEnd - sizeof(struct init_stack_frame));
 
 	/* fill init context */
+	pInitCtx->status32 = 0;
 	if (options & K_USER) {
-		/* through exception return to user mode */
-		pInitCtx->status32 = _ARC_V2_STATUS32_AE;
 		pInitCtx->pc = ((u32_t)_user_thread_entry_wrapper);
 	} else {
-		pInitCtx->status32 = 0;
 		pInitCtx->pc = ((u32_t)_thread_entry_wrapper);
 	}
 

arch/arc/core/userspace.S

@@ -53,14 +53,24 @@ GTEXT(z_arch_user_string_nlen_fault_end)
 GTEXT(z_arch_user_string_nlen_fixup)
 /*
  * @brief Wrapper for _thread_entry in the case of user thread
+ * The init parameters are in privileged stack
  *
  * @return N/A
  */
 SECTION_FUNC(TEXT, _user_thread_entry_wrapper)
-	/* sp the  user stack pointer,  r0-r4 are in stack */
-	mov r5, sp
-	/* start of privilege stack */
-	add blink, r5, CONFIG_PRIVILEGED_STACK_SIZE+STACK_GUARD_SIZE+16
+	pop_s r3
+	pop_s r2
+	pop_s r1
+	pop_s r0
+/* the start of user sp is in r5 */
+	pop r5
+/* start of privilege stack in blink */
+	mov blink, sp
+
+	st.aw r0, [r5, -4]
+	st.aw r1, [r5, -4]
+	st.aw r2, [r5, -4]
+	st.aw r3, [r5, -4]
 
 /*
  * when CONFIG_INIT_STACKS is enable, stack will be initialized
@@ -140,7 +150,6 @@ _clear_user_stack:
 _arc_go_to_user_space:
 	lr r0, [_ARC_V2_STATUS32]
 	bset r0, r0, _ARC_V2_STATUS32_U_BIT
-	bclr r0, r0, _ARC_V2_STATUS32_AE_BIT
 
 	mov r1, _thread_entry_wrapper