hv: cpu: fix 'Pointer arithmetic is not on array'

Use the array for lapic_id directly to avoid the unnecessary pointer
arithmetic.

With current implementation,
  lapic_id_base is always a byte array with CPU_PAGE_SIZE elements

What this patch does:
 - replace 'uint8_t *lapic_id_base' with 'uint8_t
   lapic_id_array[CPU_PAGE_SIZE]' to make the boundary explicit
 - add a range check to ensure that there is no overflow

 v2 -> v3:
 * update the array size of lapic_id_array per discussion with Fengwei

 v1 -> v2:
 * remove the unnecessary range check in parse_madt in cpu.c

Signed-off-by: Shiqing Gao <shiqing.gao@intel.com>
Reviewed-by: Junjie Mao <junjie.mao@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

Author: shiqingg

hypervisor/arch/x86/cpu.c

@@ -28,7 +28,7 @@ volatile uint16_t up_count = 0U;
 uint64_t pcpu_active_bitmap = 0UL;
 
 /* TODO: add more capability per requirement */
-/*APICv features*/
+/* APICv features */
 #define VAPIC_FEATURE_VIRT_ACCESS		(1U << 0)
 #define VAPIC_FEATURE_VIRT_REG			(1U << 1)
 #define VAPIC_FEATURE_INTR_DELIVERY		(1U << 2)
@@ -251,45 +251,39 @@ static void alloc_phy_cpu_data(uint16_t pcpu_num)
 	ASSERT(per_cpu_data_base_ptr != NULL, "");
 }
 
-uint16_t __attribute__((weak)) parse_madt(uint8_t *lapic_id_base)
+uint16_t __attribute__((weak)) parse_madt(uint8_t lapic_id_array[MAX_PCPU_NUM])
 {
 	static const uint8_t lapic_id[] = {0U, 2U, 4U, 6U};
 	uint32_t i;
 
 	for (i = 0U; i < ARRAY_SIZE(lapic_id); i++) {
-		*lapic_id_base = lapic_id[i];
-		lapic_id_base++;
+		lapic_id_array[i] = lapic_id[i];
 	}
 
 	return ((uint16_t)ARRAY_SIZE(lapic_id));
 }
 
-static void init_phy_cpu_storage(void)
+static void init_percpu_data_area(void)
 {
 	uint16_t i;
-	uint16_t pcpu_num=0U;
+	uint16_t pcpu_num = 0U;
 	uint16_t bsp_cpu_id;
 	uint8_t bsp_lapic_id = 0U;
-	uint8_t *lapic_id_base;
+	uint8_t lapic_id_array[MAX_PCPU_NUM];
 
-	/*
-	 * allocate memory to save all lapic_id detected in parse_mdt.
-	 * We allocate 4K size which could save 4K CPUs lapic_id info.
-	 */
-	lapic_id_base = alloc_page();
-	ASSERT(lapic_id_base != NULL, "fail to alloc page");
+	/* Save all lapic_id detected via parse_mdt in lapic_id_array */
+	pcpu_num = parse_madt(lapic_id_array);
+	if (pcpu_num == 0U) {
+		/* failed to get the physcial cpu number */
+		ASSERT(false);
+	}
 
-	pcpu_num = parse_madt(lapic_id_base);
 	alloc_phy_cpu_data(pcpu_num);
 
 	for (i = 0U; i < pcpu_num; i++) {
-		per_cpu(lapic_id, i) = *lapic_id_base;
-		lapic_id_base++;
+		per_cpu(lapic_id, i) = lapic_id_array[i];
 	}
 
-	/* free memory after lapic_id are saved in per_cpu data */
-	free((void *)lapic_id_base);
-
 	bsp_lapic_id = get_cur_lapic_id();
 
 	bsp_cpu_id = get_cpu_id_from_lapic_id(bsp_lapic_id);
@@ -458,7 +452,7 @@ void bsp_boot_init(void)
 
 	early_init_lapic();
 
-	init_phy_cpu_storage();
+	init_percpu_data_area();
 
 	load_gdtr_and_tr();
 

hypervisor/boot/acpi.c

@@ -221,7 +221,7 @@ void *get_acpi_tbl(const char *sig)
 	return HPA2HVA(addr);
 }
 
-static uint16_t _parse_madt(void *madt, uint8_t *lapic_id_base)
+static uint16_t _parse_madt(void *madt, uint8_t lapic_id_array[MAX_PCPU_NUM])
 {
 	uint16_t pcpu_id = 0;
 	struct acpi_madt_local_apic *processor;
@@ -243,9 +243,16 @@ static uint16_t _parse_madt(void *madt, uint8_t *lapic_id_base)
 		if (entry->type == ACPI_MADT_TYPE_LOCAL_APIC) {
 			processor = (struct acpi_madt_local_apic *)entry;
 			if ((processor->lapic_flags & ACPI_MADT_ENABLED) != 0U) {
-				*lapic_id_base = processor->id;
-				lapic_id_base++;
+				lapic_id_array[pcpu_id] = processor->id;
 				pcpu_id++;
+				/*
+				 * set the pcpu_num as 0U to indicate the
+				 * potential overflow
+				 */
+				if (pcpu_id >= MAX_PCPU_NUM) {
+					pcpu_id = 0U;
+					break;
+				}
 			}
 		}
 
@@ -256,8 +263,8 @@ static uint16_t _parse_madt(void *madt, uint8_t *lapic_id_base)
 	return pcpu_id;
 }
 
-/* The lapic_id info gotten from madt will be returned in lapic_id_base */
-uint16_t parse_madt(uint8_t *lapic_id_base)
+/* The lapic_id info gotten from madt will be returned in lapic_id_array */
+uint16_t parse_madt(uint8_t lapic_id_array[MAX_PCPU_NUM])
 {
 	void *madt;
 
@@ -267,7 +274,7 @@ uint16_t parse_madt(uint8_t *lapic_id_base)
 	madt = get_acpi_tbl(ACPI_SIG_MADT);
 	ASSERT(madt != NULL, "fail to get madt");
 
-	return _parse_madt(madt, lapic_id_base);
+	return _parse_madt(madt, lapic_id_array);
 }
 
 void *get_dmar_table(void)

hypervisor/include/arch/x86/cpu.h

@@ -43,6 +43,9 @@
 #define CPU_PAGE_SIZE           0x1000U
 #define CPU_PAGE_MASK           0xFFFFFFFFFFFFF000UL
 
+/* Assume the max physcial cpu number is 128 */
+#define MAX_PCPU_NUM	128U
+
 #define MMU_PTE_PAGE_SHIFT	CPU_PAGE_SHIFT
 #define MMU_PDE_PAGE_SHIFT	21