/**
 * @file elf.h
 * Functionality to execute ELF files
 *
 * Copyright (C) 2018 Clyne Sullivan
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#ifndef ELF_H_
#define ELF_H_

#include <stdint.h>

/**
 * Attempts to open the given ELF file.
 * @param file Path of the ELF file
 * @param argv argv to be passed to the program
 * @param envp envp to be passed to the program
 * @return -1 on fail, otherwise returns address of ELF entry
 */
uint32_t elf_execve(const char *file, char * const argv[], char * const envp[]);

//
// ELF Standard macros and structures below

#define EI_NIDENT 16

#define PT_NULL     0
#define PT_LOAD     1
#define PT_DYNAMIC  2
#define PT_INTERP   3
#define PT_NOTE     4
#define PT_SHLIB    5
#define PT_PHDR     6
#define PT_RESERVED 0x70000000

#define ELF32_ST_BIND(i)    ((i) >> 4)
#define ELF32_ST_TYPE(i)    ((i) & 0xF)
#define ELF32_ST_INFO(b, t) (((b) << 4) + ((t) & 0xF))

#define ELF32_R_SYM(i)     ((i) >> 8)
#define ELF32_R_TYPE(i)    ((i) & 0xFF)
#define ELF32_R_INFO(s, t) (((s) << 8) + ((t) & 0xFF))

typedef uint32_t Elf32_Addr;
typedef uint16_t Elf32_Half;
typedef uint32_t Elf32_Off;
typedef uint32_t Elf32_Sword;
typedef uint32_t Elf32_Word;

typedef struct {
	unsigned char e_ident[EI_NIDENT];
	Elf32_Half    e_type;
	Elf32_Half    e_machine;
	Elf32_Word    e_version;
	Elf32_Addr    e_entry;
	Elf32_Off     e_phoff;
	Elf32_Off     e_shoff;
	Elf32_Word    e_flags;
	Elf32_Half    e_ehsize;
	Elf32_Half    e_phentsize;
	Elf32_Half    e_phnum;
	Elf32_Half    e_shentsize;
	Elf32_Half    e_shnum;
	Elf32_Half    e_shstrndx;
} __attribute__((packed)) Elf32_Ehdr;

typedef struct {
	Elf32_Word sh_name;
	Elf32_Word sh_type;
	Elf32_Word sh_flags;
	Elf32_Addr sh_addr;
	Elf32_Off  sh_offset;
	Elf32_Word sh_size;
	Elf32_Word sh_link;
	Elf32_Word sh_info;
	Elf32_Word sh_addralign;
	Elf32_Word sh_entsize;
} __attribute__((packed)) Elf32_Shdr;

typedef struct {
	Elf32_Word    st_name;
	Elf32_Addr    st_value;
	Elf32_Word    st_size;
	unsigned char st_info;
	unsigned char st_other;
	Elf32_Half    st_shndx;
} __attribute__((packed)) Elf32_Sym;

typedef struct {
	Elf32_Addr r_offset;
	Elf32_Word r_info;
} __attribute__((packed)) Elf32_Rel;

typedef struct {
	Elf32_Addr  r_offset;
	Elf32_Word  r_info;
	Elf32_Sword r_addend;
} __attribute__((packed)) Elf32_Rela;

typedef struct {
	Elf32_Word p_type;
	Elf32_Off  p_offset;
	Elf32_Addr p_vaddr;
	Elf32_Addr p_paddr;
	Elf32_Word p_filesz;
	Elf32_Word p_memsz;
	Elf32_Word p_flags;
	Elf32_Word p_align;
} __attribute__((packed)) Elf32_Phdr;

#endif // ELF_H_