toaruos/userspace/ld.c

/*
 * ToAruOS Loader
 * (C) 2011 Kevin Lange
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>

/* The Master ELF Header */
#include "../kernel/include/elf.h"

/**
 * Show usage for the readelf application.
 * @param argc Argument count (unused)
 * @param argv Arguments to binary
 */
void usage(int argc, char ** argv) {
	/* Show usage */
	printf("%s [filename]\n", argv[0]);
	printf("Loads a /static/ binary into memory and executes it.\n");
	exit(1);
}

#define   SOURCE        0x02000000
uintptr_t DESTINATION = 0x03000000;

int _main();
int argc;
char ** argv;
uintptr_t epoint = 0;

/**
 * Application entry point.
 * @returns 0 on sucess, 1 on failure
 */
int main(int argc_, char ** argv_) {
	/* ld stuff */
	uintptr_t END = (uintptr_t)sbrk(0);
	if (END > DESTINATION) {
		return 2;
	}
	sbrk(DESTINATION + (END - SOURCE) - SOURCE);

	argc = argc_;
	argv = argv_;

	memcpy((void *)DESTINATION, (void *)SOURCE, END - SOURCE);
	uintptr_t location = ((uintptr_t)&_main - SOURCE + DESTINATION);
	__asm__ __volatile__ ("jmp *%0" : : "m"(location));

	return -1;
}

int _main() {
here:

	/* Process arguments */
	if (argc < 2) usage(argc,argv);

	FILE * binary;           /**< File pointer for requested executable */
	size_t binary_size;      /**< Size of the file */
	char * binary_buf;       /**< Buffer to store the binary in memory */
	Elf32_Header * header;   /**< ELF header */
	char * string_table;     /**< Room for some string tables */
	uintptr_t __init = 0;

	/* Open the requested binary */
	binary = fopen(argv[1], "r");

	if (!binary) {
		printf("Oh no! This is terrible!\n");
		return 1;
	}

	/* Hack because we don't have seek/tell */
	fseek(binary, 0, SEEK_END);
	binary_size = ftell(binary);
	fseek(binary, 0, SEEK_SET);

	/* Read the binary into a buffer */
	binary_buf = malloc(binary_size);
	fread((void *)binary_buf, binary_size, 1, binary);

	/* Let's start considering this guy an elf, 'eh? */
	header = (Elf32_Header *)binary_buf;

	/* Verify the magic */
	if (	header->e_ident[0] != ELFMAG0 ||
			header->e_ident[1] != ELFMAG1 ||
			header->e_ident[2] != ELFMAG2 ||
			header->e_ident[3] != ELFMAG3) {
		printf("Failed to load binary: bad magic\n");
		return 1;
	}

	uint32_t i = 0;
	for (uint32_t x = 0; x < header->e_shentsize * header->e_shnum; x += header->e_shentsize) {
		Elf32_Shdr * shdr = (Elf32_Shdr *)((uintptr_t)header + (header->e_shoff + x));
		if (i == header->e_shstrndx) {
			string_table = (char *)((uintptr_t)header + shdr->sh_offset);
		}
		++i;
	}

	if (!string_table) {
		printf("No string table?\n");
		return 1;
	}

	/* Read the section headers */
	for (uint32_t x = 0; x < header->e_shentsize * header->e_shnum; x += header->e_shentsize) {
		if (header->e_shoff + x > binary_size) {
			return 1;
		}
		Elf32_Shdr * shdr = (Elf32_Shdr *)((uintptr_t)binary_buf + (header->e_shoff + x));

		if (shdr->sh_addr) {
			if (shdr->sh_type == SHT_NOBITS) {
				/* This is the .bss, zero it */
				memset((void *)(shdr->sh_addr), 0x0, shdr->sh_size);
			} else {
				memcpy((void *)(shdr->sh_addr), (void *)((uintptr_t)header + shdr->sh_offset), shdr->sh_size);
			}
			char * sh_name = (char *)((uintptr_t)string_table + shdr->sh_name);
			printf("%s %p\n", sh_name, shdr->sh_addr);
			if (!strcmp(sh_name,".init")) {
				__init = shdr->sh_addr;
				printf("Found .init\n");
			}
		}
	}

	if (__init) {
		printf("Calling _init()\n");
		__asm__ __volatile__ (
				"call *%0\n"
				: : "m"(__init));
	}


	epoint = header->e_entry;
	__asm__ __volatile__ (
			"pushl $0\n"
			"pushl %2\n"
			"pushl %1\n"
			"pushl $0xDECADE21\n"
			"jmp *%0\n"
			: : "m"(epoint), "r"(argc-1), "r"(argv+1));

	return 0;
}

/*
 * vim:noexpandtab
 * vim:tabstop=4
 * vim:shiftwidth=4
 */