Memory reservation map access

include/dt/dt.h

@@ -32,11 +32,20 @@ typedef struct {
 	dt_node_t root_node; /**< Root node offset. */
 	u32 total_size;      /**< Total size of the FDT. */
 	u32 struct_off;      /**< Structure block offset. */
+	u32 rsvmap_off;      /**< Memory reservation map offset. */
 	u32 strings_off;     /**< Strings block offset. */
 	u32 struct_size;     /**< Structure block size. */
 	u32 fdt_version;     /**< FDT version. */
 } fdt_t;
 
+/**
+ * @brief Reserved memory entry structure.
+ */
+typedef struct {
+	u64 address; /**< Entry address. */
+	u64 size;    /**< Entry size. */
+} fdt_rsv_entry;
+
 /**
  * @brief Read the header at fdt and set fields of obj.
  * @param fdt Pointer to the flattened device tree data.
@@ -214,6 +223,19 @@ error_t dt_get_prop_name_ptr(const fdt_t* fdt, dt_prop_t prop, const char** ptrO
 [[gnu::nonnull(3)]]
 error_t dt_get_prop_buffer(const fdt_t* fdt, dt_prop_t prop, buffer_t* bufOUT);
 
+/**
+ * @brief Get a reserved memory entry at index from the Memory Reservation Block.
+ * @param fdt Pointer to the fdt object.
+ * @param index Index of the entry to get.
+ * @param[out] entryOUT Entry at index.
+ * @retval ERR_NONE on success
+ * @retval ERR_BAD_ARG on nullptr args
+ * @retval ERR_NOT_VALID if the FDT is invalid
+ * @retval ERR_OUT_OF_BOUNDS if index is out of bounds or the Memory Reservation Block is malformed
+ */
+[[gnu::nonnull(3)]]
+error_t dt_get_rsv_mem_entry(const fdt_t* fdt, u32 index, fdt_rsv_entry* entryOUT);
+
 /// @}
 
 #endif // !DT_DT

src/example_dtree/entry.c

@@ -54,4 +54,14 @@ void main([[maybe_unused]] u32 hartid, const void* fdt) {
 	DEBUG_PRINTF("First prop: %s\n", prop_name);
 	error = dt_get_prop_name_ptr(&fdt_obj, next_prop, &prop_name);
 	DEBUG_PRINTF("Next prop: %s\n", prop_name);
+
+	fdt_rsv_entry entry;
+	error = dt_get_rsv_mem_entry(&fdt_obj, 0, &entry);
+
+	if (error != ERR_NONE) {
+		// To show that there's only one (terminating) entry in the rsvmap
+		DEBUG_PRINTF("%u %u\n", fdt_obj.rsvmap_off, fdt_obj.struct_off);
+		DEBUG_PRINTF("Failed to get reserved memory entry: %d\n", error);
+		return;
+	}
 }

src/lib/dt/dt_access.c

@@ -363,3 +363,40 @@ error_t dt_get_prop_buffer(const fdt_t* fdt, dt_prop_t prop, buffer_t* bufOUT) {
 
 	return ERR_NONE;
 }
+
+error_t dt_get_rsv_mem_entry(const fdt_t* fdt, u32 index, fdt_rsv_entry* entryOUT) {
+	if (fdt == nullptr)
+		return ERR_BAD_ARG;
+
+	buffer_t fdt_buf = fdt->fdt_buffer;
+
+	u32 curr_index = 0;
+
+	u32 curr_offset = fdt->rsvmap_off;
+
+	u32 max_offset = fdt->struct_off + fdt->struct_size;
+	fdt_rsv_entry entry;
+
+	do {
+		if (!buffer_read_u64_be(fdt_buf, curr_offset, &entry.address) ||
+		    !buffer_read_u64_be(fdt_buf, curr_offset + sizeof(u64), &entry.size)) {
+			return ERR_NOT_VALID;
+		}
+
+		if (entry.address == 0 && entry.size == 0) {
+			return ERR_OUT_OF_BOUNDS;
+		}
+
+		if (curr_index == index) {
+			entryOUT->address = entry.address;
+			entryOUT->size = entry.size;
+			return ERR_NONE;
+		}
+
+		curr_index += 1;
+		curr_offset += 2 * sizeof(u64);
+
+	} while (curr_offset < max_offset);
+
+	return ERR_OUT_OF_BOUNDS;
+}

src/lib/dt/dt_defines.h

@@ -20,7 +20,7 @@
 #define FDT_OFF_TOTAL_SIZE        0x04       /**< Offset to total size. */
 #define FDT_OFF_OFF_DT_STRUCT     0x08       /**< Offset to structure block offset. */
 #define FDT_OFF_OFF_DT_STRINGS    0x0C       /**< Offset to strings block offset. */
-#define FDT_OFF_MEM_RSVMAP        0x10       /**< Offset to memory reservation map. */
+#define FDT_OFF_OFF_MEM_RSVMAP    0x10       /**< Offset to memory reservation map offset. */
 #define FDT_OFF_VERSION           0x14       /**< Offset to version. */
 #define FDT_OFF_LAST_COMP_VERSION 0x18       /**< Offset to last compatible version. */
 #define FDT_OFF_BOOT_CPUID_PHYS   0x1C       /**< Offset to boot CPU physical ID. */

src/lib/dt/dt_utils.c

@@ -31,9 +31,10 @@ error_t dt_init(const void* fdt, fdt_t* obj) {
 	if (!buffer_read_u32_be(fdt_buf, FDT_OFF_TOTAL_SIZE, &obj->total_size) ||
 	    !buffer_read_u32_be(fdt_buf, FDT_OFF_OFF_DT_STRUCT, &obj->struct_off) ||
 	    !buffer_read_u32_be(fdt_buf, FDT_OFF_OFF_DT_STRINGS, &obj->strings_off) ||
+	    !buffer_read_u32_be(fdt_buf, FDT_OFF_OFF_MEM_RSVMAP, &obj->rsvmap_off) ||
 	    !buffer_read_u32_be(fdt_buf, FDT_OFF_SIZE_DT_STRUCT, &obj->struct_size) ||
 	    !buffer_read_u32_be(fdt_buf, FDT_OFF_VERSION, &obj->fdt_version) ||
-	    !buffer_read_u32_be(fdt_buf, FDT_OFF_VERSION, &last_comp_version)) {
+	    !buffer_read_u32_be(fdt_buf, FDT_OFF_LAST_COMP_VERSION, &last_comp_version)) {
 		obj->fdt_buffer = make_buffer(nullptr, 0);
 		return ERR_NOT_VALID;
 	}