xlat: Introduce API to get memory attributes of a region

This patch introduces a new API in the translation tables library
(v2), that allows to query the memory attributes of a memory block
or a memory page.

Change-Id: I45a8b39a53da39e7617cbac4bff5658dc1b20a11
Co-authored-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Co-authored-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

include/lib/xlat_tables/xlat_tables_defs.h

@@ -24,9 +24,19 @@
 #define FOUR_KB_INDEX(x)	((x) >> FOUR_KB_SHIFT)
 
 #define INVALID_DESC		U(0x0)
+/*
+ * A block descriptor points to a region of memory bigger than the granule size
+ * (e.g. a 2MB region when the granule size is 4KB).
+ */
 #define BLOCK_DESC		U(0x1) /* Table levels 0-2 */
+/* A table descriptor points to the next level of translation table. */
 #define TABLE_DESC		U(0x3) /* Table levels 0-2 */
+/*
+ * A page descriptor points to a page, i.e. a memory region whose size is the
+ * translation granule size (e.g. 4KB).
+ */
 #define PAGE_DESC		U(0x3) /* Table level 3 */
+
 #define DESC_MASK		U(0x3)
 
 #define FIRST_LEVEL_DESC_N	ONE_GB_SHIFT
@@ -84,10 +94,22 @@
 #define XLAT_BLOCK_MASK(level)	(XLAT_BLOCK_SIZE(level) - 1)
 /* Mask to get the address bits common to a block of a certain table level*/
 #define XLAT_ADDR_MASK(level)	(~XLAT_BLOCK_MASK(level))
+/*
+ * Extract from the given virtual address the index into the given lookup level.
+ * This macro assumes the system is using the 4KB translation granule.
+ */
+#define XLAT_TABLE_IDX(virtual_addr, level)	\
+	(((virtual_addr) >> XLAT_ADDR_SHIFT(level)) & ULL(0x1FF))
 
 /*
- * AP[1] bit is ignored by hardware and is
- * treated as if it is One in EL2/EL3
+ * The ARMv8 translation table descriptor format defines AP[2:1] as the Access
+ * Permissions bits, and does not define an AP[0] bit.
+ *
+ * AP[1] is valid only for a stage 1 translation that supports two VA ranges
+ * (i.e. in the ARMv8A.0 architecture, that is the S-EL1&0 regime).
+ *
+ * AP[1] is RES0 for stage 1 translations that support only one VA range
+ * (e.g. EL3).
  */
 #define AP2_SHIFT			U(0x7)
 #define AP2_RO				U(0x1)
@@ -121,6 +143,28 @@
 #define ATTR_INDEX_MASK			U(0x3)
 #define ATTR_INDEX_GET(attr)		(((attr) >> 2) & ATTR_INDEX_MASK)
 
+/*
+ * Shift values for the attributes fields in a block or page descriptor.
+ * See section D4.3.3 in the ARMv8-A ARM (issue B.a).
+ */
+
+/* Memory attributes index field, AttrIndx[2:0]. */
+#define ATTR_INDEX_SHIFT		2
+/* Non-secure bit, NS. */
+#define NS_SHIFT			5
+/* Shareability field, SH[1:0] */
+#define SHAREABILITY_SHIFT		8
+/* The Access Flag, AF. */
+#define ACCESS_FLAG_SHIFT		10
+/* The not global bit, nG. */
+#define NOT_GLOBAL_SHIFT		11
+/* Contiguous hint bit. */
+#define CONT_HINT_SHIFT			52
+/* Execute-never bits, XN. */
+#define PXN_SHIFT			53
+#define XN_SHIFT			54
+#define UXN_SHIFT			XN_SHIFT
+
 /*
  * Flags to override default values used to program system registers while
  * enabling the MMU.

include/lib/xlat_tables/xlat_tables_v2.h

@@ -251,5 +251,23 @@ int mmap_remove_dynamic_region_ctx(xlat_ctx_t *ctx,
 
 #endif /* PLAT_XLAT_TABLES_DYNAMIC */
 
+/*
+ * Query the memory attributes of a memory page in a set of translation tables.
+ *
+ * Return 0 on success, a negative error code on error.
+ * On success, the attributes are stored into *attributes.
+ *
+ * ctx
+ *   Translation context to work on.
+ * base_va
+ *   Virtual address of the page to get the attributes of.
+ *   There are no alignment restrictions on this address. The attributes of the
+ *   memory page it lies within are returned.
+ * attributes
+ *   Output parameter where to store the attributes of the targeted memory page.
+ */
+int get_mem_attributes(const xlat_ctx_t *ctx, uintptr_t base_va,
+		mmap_attr_t *attributes);
+
 #endif /*__ASSEMBLY__*/
 #endif /* __XLAT_TABLES_V2_H__ */

lib/xlat_tables_v2/xlat_tables_internal.c

@@ -1022,7 +1022,7 @@ int mmap_remove_dynamic_region(uintptr_t base_va, size_t size)
 #if LOG_LEVEL >= LOG_LEVEL_VERBOSE
 
 /* Print the attributes of the specified block descriptor. */
-static void xlat_desc_print(xlat_ctx_t *ctx, uint64_t desc)
+static void xlat_desc_print(const xlat_ctx_t *ctx, uint64_t desc)
 {
 	int mem_type_index = ATTR_INDEX_GET(desc);
 	xlat_regime_t xlat_regime = ctx->xlat_regime;
@@ -1315,3 +1315,195 @@ void enable_mmu_el3(unsigned int flags)
 }
 
 #endif /* AARCH32 */
+
+/*
+ * Do a translation table walk to find the block or page descriptor that maps
+ * virtual_addr.
+ *
+ * On success, return the address of the descriptor within the translation
+ * table. Its lookup level is stored in '*out_level'.
+ * On error, return NULL.
+ *
+ * xlat_table_base
+ *   Base address for the initial lookup level.
+ * xlat_table_base_entries
+ *   Number of entries in the translation table for the initial lookup level.
+ * virt_addr_space_size
+ *   Size in bytes of the virtual address space.
+ */
+static uint64_t *find_xlat_table_entry(uintptr_t virtual_addr,
+				       void *xlat_table_base,
+				       int xlat_table_base_entries,
+				       unsigned long long virt_addr_space_size,
+				       int *out_level)
+{
+	unsigned int start_level;
+	uint64_t *table;
+	int entries;
+
+	VERBOSE("%s(%p)\n", __func__, (void *)virtual_addr);
+
+	start_level = GET_XLAT_TABLE_LEVEL_BASE(virt_addr_space_size);
+	VERBOSE("Starting translation table walk from level %i\n", start_level);
+
+	table = xlat_table_base;
+	entries = xlat_table_base_entries;
+
+	for (unsigned int level = start_level;
+	     level <= XLAT_TABLE_LEVEL_MAX;
+	     ++level) {
+		int idx;
+		uint64_t desc;
+		uint64_t desc_type;
+
+		VERBOSE("Table address: %p\n", (void *)table);
+
+		idx = XLAT_TABLE_IDX(virtual_addr, level);
+		VERBOSE("Index into level %i table: %i\n", level, idx);
+		if (idx >= entries) {
+			VERBOSE("Invalid address\n");
+			return NULL;
+		}
+
+		desc = table[idx];
+		desc_type = desc & DESC_MASK;
+		VERBOSE("Descriptor at level %i: 0x%llx\n", level,
+				(unsigned long long)desc);
+
+		if (desc_type == INVALID_DESC) {
+			VERBOSE("Invalid entry (memory not mapped)\n");
+			return NULL;
+		}
+
+		if (level == XLAT_TABLE_LEVEL_MAX) {
+			/*
+			 * There can't be table entries at the final lookup
+			 * level.
+			 */
+			assert(desc_type == PAGE_DESC);
+			VERBOSE("Descriptor mapping a memory page (size: 0x%llx)\n",
+				(unsigned long long)XLAT_BLOCK_SIZE(XLAT_TABLE_LEVEL_MAX));
+			*out_level = level;
+			return &table[idx];
+		}
+
+		if (desc_type == BLOCK_DESC) {
+			VERBOSE("Descriptor mapping a memory block (size: 0x%llx)\n",
+				(unsigned long long)XLAT_BLOCK_SIZE(level));
+			*out_level = level;
+			return &table[idx];
+		}
+
+		assert(desc_type == TABLE_DESC);
+		VERBOSE("Table descriptor, continuing xlat table walk...\n");
+		table = (uint64_t *)(uintptr_t)(desc & TABLE_ADDR_MASK);
+		entries = XLAT_TABLE_ENTRIES;
+	}
+
+	/*
+	 * This shouldn't be reached, the translation table walk should end at
+	 * most at level XLAT_TABLE_LEVEL_MAX and return from inside the loop.
+	 */
+	assert(0);
+
+	return NULL;
+}
+
+
+static int get_mem_attributes_internal(const xlat_ctx_t *ctx, uintptr_t base_va,
+		mmap_attr_t *attributes, uint64_t **table_entry,
+		unsigned long long *addr_pa, int *table_level)
+{
+	uint64_t *entry;
+	uint64_t desc;
+	int level;
+	unsigned long long virt_addr_space_size;
+
+	/*
+	 * Sanity-check arguments.
+	 */
+	assert(ctx != NULL);
+	assert(ctx->initialized);
+	assert(ctx->xlat_regime == EL1_EL0_REGIME || ctx->xlat_regime == EL3_REGIME);
+
+	virt_addr_space_size = (unsigned long long)ctx->va_max_address + 1;
+	assert(virt_addr_space_size > 0);
+
+	entry = find_xlat_table_entry(base_va,
+				ctx->base_table,
+				ctx->base_table_entries,
+				virt_addr_space_size,
+				&level);
+	if (entry == NULL) {
+		WARN("Address %p is not mapped.\n", (void *)base_va);
+		return -EINVAL;
+	}
+
+	if (addr_pa != NULL) {
+		*addr_pa = *entry & TABLE_ADDR_MASK;
+	}
+
+	if (table_entry != NULL) {
+		*table_entry = entry;
+	}
+
+	if (table_level != NULL) {
+		*table_level = level;
+	}
+
+	desc = *entry;
+
+#if LOG_LEVEL >= LOG_LEVEL_VERBOSE
+	VERBOSE("Attributes: ");
+	xlat_desc_print(ctx, desc);
+	tf_printf("\n");
+#endif /* LOG_LEVEL >= LOG_LEVEL_VERBOSE */
+
+	assert(attributes != NULL);
+	*attributes = 0;
+
+	int attr_index = (desc >> ATTR_INDEX_SHIFT) & ATTR_INDEX_MASK;
+
+	if (attr_index == ATTR_IWBWA_OWBWA_NTR_INDEX) {
+		*attributes |= MT_MEMORY;
+	} else if (attr_index == ATTR_NON_CACHEABLE_INDEX) {
+		*attributes |= MT_NON_CACHEABLE;
+	} else {
+		assert(attr_index == ATTR_DEVICE_INDEX);
+		*attributes |= MT_DEVICE;
+	}
+
+	int ap2_bit = (desc >> AP2_SHIFT) & 1;
+
+	if (ap2_bit == AP2_RW)
+		*attributes |= MT_RW;
+
+	if (ctx->xlat_regime == EL1_EL0_REGIME) {
+		int ap1_bit = (desc >> AP1_SHIFT) & 1;
+		if (ap1_bit == AP1_ACCESS_UNPRIVILEGED)
+			*attributes |= MT_USER;
+	}
+
+	int ns_bit = (desc >> NS_SHIFT) & 1;
+
+	if (ns_bit == 1)
+		*attributes |= MT_NS;
+
+	uint64_t xn_mask = xlat_arch_regime_get_xn_desc(ctx->xlat_regime);
+
+	if ((desc & xn_mask) == xn_mask) {
+		*attributes |= MT_EXECUTE_NEVER;
+	} else {
+		assert((desc & xn_mask) == 0);
+	}
+
+	return 0;
+}
+
+
+int get_mem_attributes(const xlat_ctx_t *ctx, uintptr_t base_va,
+		mmap_attr_t *attributes)
+{
+	return get_mem_attributes_internal(ctx, base_va, attributes,
+					   NULL, NULL, NULL);
+}