Add ET_DYN support for the ELF loader, which required adding

relocations, add some more functions to libxunil, use include inside of
tests instead of manually defining types and add basic libc header
files. Move libxunil to the user folder, and add helloworld and
doomgeneric as apps

user/apps/helloworld/compile.sh

@@ -0,0 +1,4 @@
+gcc -nostdlib -nostdinc -static -static-pie \
+    -o $1 $1.c \
+    -L../../libxunil/target/release -l:libxunil.a
+mv $1 ../../../assets/$1.elf

user/apps/helloworld/helloworld.c

@@ -0,0 +1,6 @@
+#include "../src/stdio.h"
+
+void _start() {
+   write(0, "Hello, World!", 13);
+   exit(0);
+}

user/libxunil/.gitignore

@@ -0,0 +1 @@
+/target

user/libxunil/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "libxunil"
+version = "0.1.0"

user/libxunil/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "libxunil"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+name = "xunil"
+crate-type = ["staticlib"]
+
+[profile.release]
+panic = "abort"
+opt-level = "s"

user/libxunil/include/inttypes.h

@@ -0,0 +1,2 @@
+#include <stddef.h>
+#include <stdint.h>

user/libxunil/include/stdio.h

@@ -0,0 +1,32 @@
+#pragma once
+#include <stddef.h>
+#include <stdarg.h>
+
+typedef struct FILE FILE;
+
+extern FILE *stdin;
+extern FILE *stdout;
+extern FILE *stderr;
+
+#define EOF (-1)
+
+FILE  *fopen(const char *path, const char *mode);
+int    fclose(FILE *fp);
+size_t fread(void *ptr, size_t size, size_t nmemb, FILE *fp);
+size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *fp);
+int    fseek(FILE *fp, long offset, int whence);
+long   ftell(FILE *fp);
+int    fflush(FILE *fp);
+char  *fgets(char *s, int size, FILE *fp);
+int    fputs(const char *s, FILE *fp);
+int    feof(FILE *fp);
+int    ferror(FILE *fp);
+
+int    printf(const char *fmt, ...);
+int    fprintf(FILE *fp, const char *fmt, ...);
+int    sprintf(char *buf, const char *fmt, ...);
+int    snprintf(char *buf, size_t size, const char *fmt, ...);
+int    vsnprintf(char *buf, size_t size, const char *fmt, va_list ap);
+int    vfprintf(FILE *fp, const char *fmt, va_list ap);
+void write(int fd, const char* buf, unsigned long count);
+void exit(int code);

user/libxunil/include/stdlib.h

@@ -0,0 +1,20 @@
+#pragma once
+#include <stddef.h>
+
+void  *malloc(size_t size);
+void  *calloc(size_t nmemb, size_t size);
+void  *realloc(void *ptr, size_t size);
+void   free(void *ptr);
+
+void   exit(int status);
+void   abort(void);
+
+int    atoi(const char *s);
+long   atol(const char *s);
+double atof(const char *s);
+long   strtol(const char *s, char **endptr, int base);
+double strtod(const char *s, char **endptr);
+
+char  *getenv(const char *name);
+void   qsort(void *base, size_t nmemb, size_t size, int (*cmp)(const void *, const void *));
+int    abs(int x);

user/libxunil/include/string.h

@@ -0,0 +1,22 @@
+#pragma once
+#include <stddef.h>
+
+void *memset(void *s, int c, size_t n);
+void *memcpy(void *dst, const void *src, size_t n);
+void *memmove(void *dst, const void *src, size_t n);
+int   memcmp(const void *s1, const void *s2, size_t n);
+void *memchr(const void *s, int c, size_t n);
+
+size_t strlen(const char *s);
+char  *strcpy(char *dst, const char *src);
+char  *strncpy(char *dst, const char *src, size_t n);
+char  *strcat(char *dst, const char *src);
+char  *strncat(char *dst, const char *src, size_t n);
+int    strcmp(const char *s1, const char *s2);
+int    strncmp(const char *s1, const char *s2, size_t n);
+char  *strchr(const char *s, int c);
+char  *strrchr(const char *s, int c);
+char  *strstr(const char *haystack, const char *needle);
+char  *strtok(char *str, const char *delim);
+char  *strdup(const char *s);
+char  *strerror(int errnum);

user/libxunil/include/strings.h

@@ -0,0 +1,8 @@
+#pragma once
+#include <stddef.h>
+
+int    strcasecmp(const char *s1, const char *s2);
+int    strncasecmp(const char *s1, const char *s2, size_t n);
+void   bzero(void *s, size_t n);
+void   bcopy(const void *src, void *dest, size_t n);
+int    bcmp(const void *s1, const void *s2, size_t n);

user/libxunil/src/lib.rs

@@ -0,0 +1,67 @@
+#![no_std]
+#![no_main]
+
+use crate::syscall::syscall3;
+
+pub mod syscall;
+
+const SYS_EXIT: usize = 1;
+const SYS_WRITE: usize = 60;
+
+#[unsafe(no_mangle)]
+extern "C" fn write(fd: i32, buf: *const u8, count: usize) -> isize {
+    unsafe { syscall3(SYS_WRITE, fd as usize, buf as usize, count) }
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn exit(code: i32) -> ! {
+    unsafe { syscall3(SYS_EXIT, code as usize, 0, 0) };
+    loop {}
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn strlen(s: *const u8) -> usize {
+    let mut len = 0;
+    while unsafe { *s.add(len) } != 0 {
+        len += 1;
+    }
+    len
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn puts(s: *const u8) -> isize {
+    write(1, s, strlen(s));
+
+    0
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn abs(n: i32) -> i32 {
+    n.abs()
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn atoi(mut c: *const u8) -> i32 {
+    let mut value: i32 = 0;
+    let mut sign: i32 = 1;
+    unsafe {
+        if (*c) == b'+' || (*c) == b'-' {
+            if *c == b'-' {
+                sign = -1;
+            }
+            c = c.add(1);
+        }
+        while (*c).is_ascii_digit() {
+            value *= 10;
+            value += ((*c) - b'0') as i32;
+            c = c.add(1);
+        }
+    }
+
+    value * sign
+}
+
+#[panic_handler]
+fn panic(_: &core::panic::PanicInfo) -> ! {
+    loop {}
+}

user/libxunil/src/syscall.rs

@@ -0,0 +1,32 @@
+#[inline(always)]
+pub unsafe fn syscall0(num: usize) -> isize {
+    let ret: isize;
+    unsafe {
+        core::arch::asm!(
+            "int 0x80",
+            in("rax") num,
+            lateout("rax") ret,
+            options(nostack)
+        );
+    }
+
+    ret
+}
+
+#[inline(always)]
+pub unsafe fn syscall3(num: usize, arg0: usize, arg1: usize, arg2: usize) -> isize {
+    let ret: isize;
+    unsafe {
+        core::arch::asm!(
+            "int 0x80",
+            in("rax") num,
+            in("rdi") arg0,
+            in("rsi") arg1,
+            in("rdx") arg2,
+            lateout("rax") ret,
+            options(nostack)
+        );
+    }
+
+    ret
+}

user/libxunil/to_implement.txt

@@ -0,0 +1,22 @@
+abs
+atoi
+calloc
+__ctype_toupper_loc
+fprintf
+free
+malloc
+memcpy
+memset
+printf
+realloc
+__stack_chk_fail
+stderr
+strcasecmp
+strcmp
+strdup
+strlen
+strncasecmp
+strncmp
+strncpy
+strrchr
+toupper