tests: mbox_api: testcase test_mbox_data_get_null has some bugs.

[IRISZZW]

relative pull request: #31012

we can't k_mbox_data_get from a _syncing_thread who didn't send a msg.

sending_thread->base.swap_data not initialized.

zephyr/kernel/mailbox.c

Lines 189 to 191 in 1ce264e

	sending_thread = rx_msg->_syncing_thread;
	rx_msg->_syncing_thread = NULL;
	tx_msg = (struct k_mbox_msg *)sending_thread->base.swap_data;

static void thread_mbox_data_get_null(void *p1, void *p2, void *p3)
{
	struct k_mbox_msg get_msg = {0};
	char str_data[] = "it string for get msg test";

	get_msg.size = 16;
	get_msg.rx_source_thread = K_ANY;
	get_msg.tx_block.data = str_data;
	get_msg._syncing_thread = receiver_tid;

	k_mbox_data_get(&get_msg, NULL);

	get_msg._syncing_thread = NULL;
	k_mbox_data_get(&get_msg, NULL);
	k_sem_give(&end_sema);
}

relative codes

zephyr/tests/kernel/mbox/mbox_api/src/test_mbox_api.c

Lines 466 to 478 in 1ce264e

	void test_mbox_data_get_null(void)
	{
	k_sem_reset(&end_sema);
	receiver_tid = k_thread_create(&tdata, tstack, STACK_SIZE,
	thread_mbox_data_get_null,
	NULL, NULL, NULL,
	K_PRIO_PREEMPT(0), 0,
	K_NO_WAIT);
	k_sem_take(&end_sema, K_FOREVER);
	/*test case teardown*/
	k_thread_abort(receiver_tid);
	}

zephyr/tests/kernel/mbox/mbox_api/src/test_mbox_api.c

Lines 436 to 452 in 1ce264e

	K_MBOX_DEFINE(send_mbox);
	static void thread_mbox_data_get_null(void *p1, void *p2, void *p3)
	{
	struct k_mbox_msg get_msg = {0};
	char str_data[] = "it string for get msg test";
	get_msg.size = 16;
	get_msg.rx_source_thread = K_ANY;
	get_msg.tx_block.data = str_data;
	get_msg._syncing_thread = receiver_tid;
	k_mbox_data_get(&get_msg, NULL);
	get_msg._syncing_thread = NULL;
	k_mbox_data_get(&get_msg, NULL);
	k_sem_give(&end_sema);
	}

zephyr/kernel/mailbox.c

Lines 336 to 350 in 1ce264e

	void k_mbox_data_get(struct k_mbox_msg *rx_msg, void *buffer)
	{
	/* handle case where data is to be discarded */
	if (buffer == NULL) {
	rx_msg->size = 0;
	mbox_message_dispose(rx_msg);
	return;
	}
	/* copy message data to buffer, then dispose of message */
	if ((rx_msg->tx_data != NULL) && (rx_msg->size > 0)) {
	(void)memcpy(buffer, rx_msg->tx_data, rx_msg->size);
	}
	mbox_message_dispose(rx_msg);
	}

zephyr/kernel/mailbox.c

Lines 174 to 194 in 1ce264e

	static void mbox_message_dispose(struct k_mbox_msg *rx_msg)
	{
	struct k_thread *sending_thread;
	struct k_mbox_msg *tx_msg;
	/* do nothing if message was disposed of when it was received */
	if (rx_msg->_syncing_thread == NULL) {
	return;
	}
	if (rx_msg->tx_block.data != NULL) {
	rx_msg->tx_block.data = NULL;
	}
	/* recover sender info */
	sending_thread = rx_msg->_syncing_thread;
	rx_msg->_syncing_thread = NULL;
	tx_msg = (struct k_mbox_msg *)sending_thread->base.swap_data;
	/* update data size field for sender */
	tx_msg->size = rx_msg->size;

[IRISZZW]

this testcase will fail in nsim_em:

START - test_mbox_data_get_null
E: ***** Exception vector: 0x6, cause code: 0x2, parameter 0x2
E: Address 0x80000824
E: EV_ProtV
E: Memory write protection violation (stack checking scheme)
E:  r0: 0x80000168  r1: 0x00000000  r2: 0x80000820  r3: 0x00000000
E:  r4: 0xffffffff  r5: 0x00000000  r6: 0x00000000  r7: 0x00000000
E:  r8: 0x00000000  r9: 0x00000000 r10: 0x00000000 r11: 0x00000000
E: r12: 0x00000000 r13: 0x00000033  pc: 0x0000360e
E:  blink: 0x00000a12 status32: 0x80084406
E: lp_end: 0x00000000 lp_start: 0x00000000 lp_count: 0x00000000
E: >>> ZEPHYR FATAL ERROR 2: Stack overflow on CPU 0
E: Current thread: 0x80000168 (unknown)
E: Halting system

how to reproduce:

1. west build -b nsim_em -d build tests/kernel/mbox/mbox_api/
2. west flash