/* Copyright (c) 2024 Freya Murphy */

#ifndef __LINK_H__
#define __LINK_H__

#include <linux/limits.h>
#include <mlimits.h>
#include <mips.h>
#include <merror.h>
#include <stdint.h>
#include <elf.h>
#include <stdio.h>


// when mapping porinters, we need to bounds check to
// make sure its in the mapped object file
//
// this checks that
// 1. the end is in the file
// 2. the off and len doesnt integer overflow
#define BOUND_CHK(obj, len, off) \
	(off > UINT32_MAX - len || off + len > obj->mapped_size)


// pre define
struct linker;
struct object;
struct segment;

///
/// relocation table
///

struct relocation_table {
	uint32_t type;
	union {
		void *raw;
		Elf32_Rel  *rel;
		Elf32_Rela *rela;
	};
	size_t len;
	struct symbol_table *symtab;
};

///
/// string table
///

struct string_table {
	char *data;
	size_t len;
};

///
/// symbol table
///

struct symbol_table {
	struct string_table *strtab;
	Elf32_Sym *syms;
	size_t len;
};

///
/// segment
///

/* a loadable program segment */
struct segment {
	// phdr
	Elf32_Phdr *phdr;
	uint32_t phdr_idx;

	// shdr
	Elf32_Shdr *shdr;
	uint32_t shdr_idx;

	// segment data
	char *name;
	unsigned char *bytes;

	// relocation table
	struct relocation_table reltab;
};

int segment_load(struct object *object, struct segment *segment, size_t index);

///
/// object file
///

struct object {
	// file
	int fd;
	char *mapped;
	size_t mapped_size;

	// ehdr
	Elf32_Ehdr *ehdr;

	// section header table
	Elf32_Shdr *shdr;
	size_t shdr_len;

	// program table
	Elf32_Phdr *phdr;
	size_t phdr_len;

	// object meta
	const char *name;
	size_t index;

	// segments
	size_t segment_len;
	struct segment *segments;

	// section header strtab
	struct string_table *shstrtab;

	// strtabs
	struct string_table *strtabs;
	// symtabs
	struct symbol_table *symtabs;
};

int object_load(struct object *object, char *path);

void object_free(struct object *object);

///
/// linker
///

struct linker {
	size_t obj_len;
	struct object *objects;

	struct linker_arguments *args;
};

/* defines arguments to the linker */
struct linker_arguments {
	char **in_files;
	int in_count;
	char *out_file;
};

/* link object files */
int link_files(struct linker_arguments args);

#endif /* __LINK_H__ */