HV: vuart: MISRA clean in vuart.c

1. remove multiple return
2. remove goto
3. fix potential NULL pointer dereferencing
4. rename struct fifo to struct vuart_fifo to avoid naming conflicts.

Tracked-On: #2987
Signed-off-by: Conghui Chen <conghui.chen@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/dm/vuart.c

@@ -43,14 +43,14 @@ static uint16_t vuart_com_base = CONFIG_COM_BASE;
 #define vuart_lock(vu)		spinlock_obtain(&((vu)->lock))
 #define vuart_unlock(vu)	spinlock_release(&((vu)->lock))
 
-static inline void fifo_reset(struct fifo *fifo)
+static inline void fifo_reset(struct vuart_fifo *fifo)
 {
 	fifo->rindex = 0U;
 	fifo->windex = 0U;
 	fifo->num = 0U;
 }
 
-static inline void fifo_putchar(struct fifo *fifo, char ch)
+static inline void fifo_putchar(struct vuart_fifo *fifo, char ch)
 {
 	fifo->buf[fifo->windex] = ch;
 	if (fifo->num < fifo->size) {
@@ -62,21 +62,19 @@ static inline void fifo_putchar(struct fifo *fifo, char ch)
 	}
 }
 
-static inline char fifo_getchar(struct fifo *fifo)
+static inline char fifo_getchar(struct vuart_fifo *fifo)
 {
-	char c;
+	char c = -1;
 
 	if (fifo->num > 0U) {
 		c = fifo->buf[fifo->rindex];
 		fifo->rindex = (fifo->rindex + 1U) % fifo->size;
 		fifo->num--;
-		return c;
-	} else {
-		return -1;
 	}
+	return c;
 }
 
-static inline uint32_t fifo_numchars(const struct fifo *fifo)
+static inline uint32_t fifo_numchars(const struct vuart_fifo *fifo)
 {
 	return fifo->num;
 }
@@ -117,15 +115,16 @@ static inline void vuart_fifo_init(struct acrn_vuart *vu)
  */
 static uint8_t vuart_intr_reason(const struct acrn_vuart *vu)
 {
+	uint8_t ret = IIR_NOPEND;
+
 	if (((vu->lsr & LSR_OE) != 0U) && ((vu->ier & IER_ELSI) != 0U)) {
-		return IIR_RLS;
+		ret = IIR_RLS;
 	} else if ((fifo_numchars(&vu->rxfifo) > 0U) && ((vu->ier & IER_ERBFI) != 0U)) {
-		return IIR_RXTOUT;
+		ret = IIR_RXTOUT;
 	} else if (vu->thre_int_pending && ((vu->ier & IER_ETBEI) != 0U)) {
-		return IIR_TXRDY;
+		ret = IIR_TXRDY;
-	} else {
-		return IIR_NOPEND;
 	}
+	return ret;
 }
 
 struct acrn_vuart *find_vuart_by_port(struct acrn_vm *vm, uint16_t offset)
@@ -194,29 +193,21 @@ static bool vuart_write(struct acrn_vm *vm, uint16_t offset_arg,
 	uint8_t value_u8 = (uint8_t)value;
 	struct acrn_vuart *target_vu = NULL;
 
+	if (vu) {
 		offset -= vu->port_base;
 		target_vu = vu->target_vu;
 		if ((offset == UART16550_THR) && target_vu) {
 			vuart_write_to_target(target_vu, value_u8);
-		return true;
+		} else {
-	}
-
 			vuart_lock(vu);
 			/*
 			 * Take care of the special case DLAB accesses first
 			 */
-	if ((vu->lcr & LCR_DLAB) != 0U) {
+			if ((vu->lcr & LCR_DLAB) != 0U && offset == UART16550_DLL) {
-		if (offset == UART16550_DLL) {
 				vu->dll = value_u8;
-			goto done;
+			} else if ((vu->lcr & LCR_DLAB) != 0U && offset == UART16550_DLM) {
-		}
-
-		if (offset == UART16550_DLM) {
 				vu->dlh = value_u8;
-			goto done;
+			} else {
-		}
-	}
-
 				switch (offset) {
 				case UART16550_THR:
 					fifo_putchar(&vu->txfifo, (char)value_u8);
@@ -272,11 +263,12 @@ static bool vuart_write(struct acrn_vm *vm, uint16_t offset_arg,
 					 */
 					break;
 				}
+			}
 
-done:
 			vuart_toggle_intr(vu);
 			vuart_unlock(vu);
-
+		}
+	}
 	return true;
 }
 
@@ -288,6 +280,7 @@ static bool vuart_read(struct acrn_vm *vm, struct acrn_vcpu *vcpu, uint16_t offs
 	struct acrn_vuart *vu = find_vuart_by_port(vm, offset);
 	struct pio_request *pio_req = &vcpu->req.reqs.pio;
 
+	if (vu) {
 		offset -= vu->port_base;
 		vuart_lock(vu);
 		/*
@@ -296,14 +289,12 @@ static bool vuart_read(struct acrn_vm *vm, struct acrn_vcpu *vcpu, uint16_t offs
 		if ((vu->lcr & LCR_DLAB) != 0U) {
 			if (offset == UART16550_DLL) {
 				reg = vu->dll;
-			goto done;
+			} else if (offset == UART16550_DLM) {
-		}
-
-		if (offset == UART16550_DLM) {
 				reg = vu->dlh;
-			goto done;
+			} else {
-		}
+				reg = 0U;
 			}
+		} else {
 			switch (offset) {
 			case UART16550_RBR:
 				vu->lsr &= ~LSR_OE;
@@ -354,10 +345,11 @@ static bool vuart_read(struct acrn_vm *vm, struct acrn_vcpu *vcpu, uint16_t offs
 				reg = 0xFFU;
 				break;
 			}
-done:
+		}
 		vuart_toggle_intr(vu);
 		pio_req->value = (uint32_t)reg;
 		vuart_unlock(vu);
+	}
 
 	return true;
 }

hypervisor/include/dm/vuart.h

@@ -48,7 +48,7 @@
 #define COM3_IRQ		6U
 #define COM4_IRQ		7U
 
-struct fifo {
+struct vuart_fifo {
 	char *buf;
 	uint32_t rindex;	/* index to read from */
 	uint32_t windex;	/* index to write to */