added initramfs parsing to hal

Author: frogrammer9

include/stdbigos/error.h

@@ -17,6 +17,8 @@ typedef enum [[nodiscard]] {
 	ERR_NOT_ENOUGH_MEMORY,
 	ERR_REPEATED_INITIALIZATION,
 	ERR_ALLOCATION_FAILED,
+	ERR_DT_NODE_NOT_FOUND,
+	ERR_DT_PROP_NOT_FOUND,
 } error_t;
 
 #endif // !BIGOS_INCLUDE_STDBIGOS_ERROR

src/kernel/hal/include/initramfs.h

@@ -0,0 +1,9 @@
+#ifndef HAL_INITRAMFS
+#define HAL_INITRAMFS
+
+#include "stdbigos/buffer.h"
+#include "stdbigos/error.h"
+
+error_t hal_initramfs_read(const char* filename, buffer_t* buffOUT);
+
+#endif // !HAL_INITRAMFS

src/kernel/hal/initramfs.c

@@ -0,0 +1,108 @@
+#include "hal/include/initramfs.h"
+
+#include "dt/dt.h"
+#include "hal_internal.h"
+#include "stdbigos/buffer.h"
+#include "stdbigos/string.h"
+
+/*
+ * initramfs layout (big endian)
+ *
+ * u32 magic
+ * u32 version
+ * u16 - file_count
+ *
+ *	u32 - offset (from the start of initramfs)
+ *	u32 - size
+ *	u8 - namesize
+ *	char[] - name
+ *	...
+ *
+ * data blob
+ * */
+
+static error_t validate(buffer_t initramfs_buff) {
+	const u32 INITRAMFS_MAGIC = 0xB16B00B5;
+	u32 magic = 0;
+	u32 version = 0;
+	if (!buffer_read_u32_be(initramfs_buff, 0, &magic))
+		return ERR_INVALID_MEMORY_REGION;
+	if (magic != INITRAMFS_MAGIC)
+		return ERR_INVALID_MEMORY_REGION;
+	if (!buffer_read_u32_be(initramfs_buff, 4, &version))
+		return ERR_INVALID_MEMORY_REGION;
+	// TODO: Handle version
+	return ERR_NONE;
+}
+
+static error_t find_initramfs_buffer(buffer_t* buffOUT) {
+	void* dtbptr = nullptr;
+	if (ihal_get_dtb(&dtbptr) != ERR_NONE)
+		return ERR_NOT_INITIALIZED;
+	fdt_t fdt;
+	(void)dt_init(dtbptr, &fdt); // This error is checkd on hal init
+	dt_node_t initramfs_node;
+	error_t err = dt_get_node_by_path(&fdt, "initramfs", &initramfs_node);
+	if (err)
+		return ERR_DT_NODE_NOT_FOUND;
+	dt_prop_t initramfs_reg;
+	err = dt_get_prop_by_name(&fdt, initramfs_node, "reg", &initramfs_reg);
+	if (err)
+		return ERR_DT_PROP_NOT_FOUND;
+	return dt_get_prop_buffer(&fdt, initramfs_reg, buffOUT);
+}
+
+typedef struct {
+	u32 offset;
+	u32 size;
+} file_header_t;
+
+// TODO: Change filename to string_view
+static error_t find_file_by_name(const char* filename, buffer_t initramfs_buff, file_header_t* headerOUT) {
+	u64 cursor = 8;
+	u16 filecount = 0;
+	if (!buffer_read_u16_be(initramfs_buff, cursor, &filecount))
+		return ERR_INVALID_MEMORY_REGION;
+	cursor += sizeof(u16);
+	for (u16 i = 0; i < filecount; ++i) {
+		if (!buffer_read_u32_be(initramfs_buff, cursor, &headerOUT->offset))
+			return ERR_INVALID_MEMORY_REGION;
+		cursor += sizeof(u32);
+		if (!buffer_read_u32_be(initramfs_buff, cursor, &headerOUT->size))
+			return ERR_INVALID_MEMORY_REGION;
+		cursor += sizeof(u32);
+		u64 file_name_size = 0; // This is of type u8 but buffer_t interface wants u64
+		if (!buffer_read_u8(initramfs_buff, cursor, (u8*)&file_name_size))
+			return ERR_INVALID_MEMORY_REGION;
+		cursor += sizeof(u8);
+
+		buffer_t target_filename_buff = make_buffer(filename, strlen(filename));
+		buffer_t filename_buff = make_buffer(initramfs_buff.data + cursor, file_name_size);
+		cursor += file_name_size;
+
+		if (buffer_memcmp(target_filename_buff, filename_buff) == 0) {
+			if (headerOUT->offset + headerOUT->size > initramfs_buff.size)
+				return ERR_OUT_OF_BOUNDS;
+			return ERR_NONE;
+		}
+	}
+	headerOUT->size = 0;
+	headerOUT->offset = 0;
+	return ERR_NOT_FOUND;
+}
+
+error_t hal_initramfs_read(const char* filename, buffer_t* buffOUT) {
+	buffer_t initramfs_buff;
+	error_t err = find_initramfs_buffer(&initramfs_buff);
+	if (err)
+		return err;
+	err = validate(initramfs_buff);
+	if (err)
+		return err;
+	file_header_t file_header;
+	err = find_file_by_name(filename, initramfs_buff, &file_header);
+	if (err)
+		return err;
+	*buffOUT = make_buffer(initramfs_buff.data + file_header.offset, file_header.size);
+	return ERR_NONE;
+}