should be right?

include/config.h

@@ -63,4 +63,8 @@
 /* ssp */
 #define STACK_CHK_GUARD 0x7ABA5C007ABA5C00
 
+/* fs */
+#define FDT_MAX 8 // Maximum amount of file descriptors per process
+
+
 #endif

include/fs/initfs.h

@@ -11,5 +11,7 @@
 
 int initfs_init(struct limine_file* tar_file);
 int tar_lookup(unsigned char* archive, char* filename, char** out);
+int tar_read(char* filename, char** buf);
+int tar_exists(const char* filename);
 
 #endif

include/kernel.h

@@ -8,10 +8,13 @@
 #define KERNEL_H
 
 #include "limine.h"
+
 enum ErrorCodes {
-	ENOMEM,
+	ENOMEM, // No memory
-	EIO,
+	EIO,    // Input/output error
-	ENOENT
+	ENOENT, // No entry
+	EBADFD,  // Bad file descriptor
+	EMFILE  // Too many open files
 };
 
 #define CLEAR_INTERRUPTS __asm__ volatile("cli")

include/sched/process.h

@@ -11,6 +11,7 @@
 #include <config.h>
 #include <stdint.h>
 #include <limine.h>
+#include <stdbool.h>
 
 typedef enum {
     READY,
@@ -18,6 +19,13 @@ typedef enum {
     DEAD
 } status_t;
 
+struct fd {
+    int fd;
+    char filename[PROCESS_NAME_MAX];  // File opened
+    uint64_t cursor; // Cursor position in file
+    bool open;
+};
+
 struct process {
     size_t pid;
     char name[PROCESS_NAME_MAX];
@@ -26,6 +34,10 @@ struct process {
     struct cpu_status* context;
 	void* root_page_table; // Process PML4 (should contain kernel PML4 in higher half [256-511]
     void* kernel_stack; // Used for interrupts (syscall: int 0x80), defines the TSS RSP0
+    
+    struct fd fdt[FDT_MAX]; // File Descriptor Table
+    size_t next_free_fd;
+    
     struct process* next;
 };
 
@@ -38,7 +50,7 @@ void process_exit(void);
 
 void process_display_list(struct process* processes_list);
 
-void process_create_user(struct limine_file* file, char* name);
+
 void process_create_user_raw(char* file, int size, char* name);
 
 #endif

src/arch/x86/syscall.c

@@ -4,15 +4,84 @@
  * @license GPL-3.0-only
  */
 
+#include "config.h"
 #include "sched/scheduler.h"
 #include <arch/x86.h>
 #include <kernel.h>
 #include <stddef.h>
 #include <io/term/term.h>
 #include <sched/process.h>
+#include <io/kbd/ps2.h>
+#include <fs/initfs.h>
+#include <string/string.h>
 
 extern struct process* current_process;
 
+// Return fd on success, -errno on error
+int sys_open(const char* filename, int flags)
+{
+    if (tar_exists(filename) < 0) {
+        return -ENOENT; // file doesn't exist..
+    }
+    // file exists here!
+    if (current_process->next_free_fd >= FDT_MAX) {
+        return -EMFILE;
+    }
+    int fd = current_process->next_free_fd++;
+    current_process->fdt[fd].fd = fd;
+    current_process->fdt[fd].open = true;
+    current_process->fdt[fd].cursor = 0;
+    strncpy(current_process->fdt[fd].filename, filename, PROCESS_NAME_MAX - 1);
+    return fd;
+}
+
+// Return 0 on success, -EBADFD if invalid FD
+int sys_close(int fd)
+{
+    if (fd < 0 || fd >= FDT_MAX) {
+        return -EBADFD;
+    }
+
+    if (!current_process->fdt[fd].open) {
+        return -EBADFD; // FD not opened in the first place
+    }
+
+    current_process->fdt[fd].open = false;
+    current_process->fdt[fd].filename[0] = '\0';
+    current_process->fdt[fd].cursor = 0;
+    return 0;
+}
+
+// Should return the number of bytes read
+int sys_read(unsigned int fd, char* buf, size_t count)
+{
+    size_t i;
+    switch (fd) {
+        case 0: //read from stdin (keyboard)
+            for (i=0; i<count; i++) {
+                buf[i] = keyboard_getchar();
+            }
+            return i;
+        case 1: // from stdout
+        case 2: // from stderr
+            return -EBADFD;
+        default: // from an open file?
+            if (current_process->fdt[fd].open == false) {
+                return -EBADFD; // File descriptor wasn't open
+            }
+            // Here fd refers to a valid opened file..
+            int sz = tar_read(current_process->fdt[fd].filename,&buf);
+            if (sz == 0) {
+                return -ENOENT;
+            } else {
+                return sz;
+            }
+    }
+
+    return -EBADFD;
+}
+
+// TODO: Should have a return value: number of bytes written on success, -1 on error (errno set) 
 void sys_write(unsigned int fd, const char* buf, size_t count)
 {
     switch (fd) {
@@ -61,14 +130,21 @@ struct cpu_status* syscall_handler(struct cpu_status* regs)
     switch (regs->rax)
     {
         case 0: //sys_read
+            regs->rax = sys_read(regs->rdi, (char*)regs->rsi, regs->rdx);
             break;
         case 1: //sys_write
             sys_write(regs->rdi, (char*)regs->rsi, regs->rdx);
             break;
+        case 2:
+            regs->rax = sys_open((const char*)regs->rdi, regs->rsi);
+            break;
+        case 3:
+            regs->rax = sys_close(regs->rdi);
+            break;
         case 60: //sys_exit
             sys_exit(regs->rdi);
             break;
-        default:
+        default: // bad syscall
             regs->rax = 0xbad515ca11;
             break;
     }

src/fs/initfs.c

@@ -59,6 +59,43 @@ int tar_lookup(unsigned char* archive, char* filename, char** out)
     return 0;
 }
 
+/*
+ * tar_read - read a file in the TAR file
+ * @filename: file to read (absolute path)
+ * @out:      out buffer (if file is found)
+ *
+ * Return:
+ * $filesize - size of the file, if found 
+ * $0        - file not found
+ */
+int tar_read(char* filename, char** buf)
+{
+    return tar_lookup(archive_start_addr, filename, buf);
+}
+
+/*
+ * tar_exists - check if a file exists in the TAR archive
+ * @filename: file to check (absolute path)
+ *
+ * Return:
+ * $filesize - size of the file, if found 
+ * $-ENOENT  - file not found
+ */
+int tar_exists(const char* filename)
+{
+    unsigned char* ptr = archive_start_addr;
+
+    while (!memcmp(ptr + 257, "ustar", 5)) {
+        int filesize = tar_oct2bin(ptr + 0x7c, 11);
+        if (!memcmp(ptr, filename, strlen(filename) + 1)) {
+            return filesize;
+        }
+        ptr += (((filesize + 511) / 512) + 1) * 512;
+    }
+    return -ENOENT;
+}
+
+
 /*
  * initfs_init - initialize the TAR initial filesystem
  * @tar_file: pointer to the Limine-loaded archive

src/kmain.c

@@ -78,14 +78,6 @@ void idle_main(void* arg)
 	}
 }
 
-void thing_main(void* arg)
-{
-	printf("What's your name, pal? ");
-	char name[10];
-	keyboard_getline(name, 10);
-	printf("\r\n{%s} is such a nice name!\r\n", name);
-}
-
 extern uintptr_t kheap_start;
 
 /*

src/sched/process.c

@@ -225,59 +225,15 @@ void process_jump_to_user(uintptr_t stack_top, uintptr_t user_code)
 extern struct tss tss;
 
 /*
- * process_create_user - Create a new user process
+ * process_create_user_raw - Create a new user process from raw binary
- * @file: pointer to Limine file structure
+ * @file: pointer to beginning of binary
+ * @size: size of the binary
  * @name: name for the new process
  *
- * This function takes a loaded Limine executable
+ * This function takes an executable loaded in memory
- * module, and maps its code, a user stack, sets the
+ * and maps its code, a user stack, sets the TSS RSP0
- * TSS RSP0 for interrupts, and finally jumps to the
+ * for interrupts, and finally jumps to the user code.
- * user code.
  */
-void process_create_user(struct limine_file* file, char* name)
-{
-    CLEAR_INTERRUPTS;
-    struct process* proc = (struct process*)kmalloc(sizeof(struct process));
-    struct cpu_status* ctx = (struct cpu_status*)kmalloc(sizeof(struct cpu_status));
-
-    if (!proc || !ctx) panic(NULL, "out of memory while creating user process");
-
-    strncpy(proc->name, name, PROCESS_NAME_MAX);
-    memset(ctx, 0, sizeof(struct cpu_status)); // set GP registers to zero
-    proc->pid = next_free_pid++;
-    proc->status = READY;
-    proc->next = 0;
-    proc->context = ctx;
-    proc->context->iret_ss = USER_DATA_SEGMENT | 3;
-    proc->context->iret_cs = USER_CODE_SEGMENT | 3;
-    proc->context->iret_flags = 0x202; // Interrupt Flag set
-
-    void* exec_addr = file->address;
-    uint64_t exec_size = file->size;
-
-    uint64_t* user_pml4 = vmm_create_address_space();
-    if (!user_pml4) panic(NULL, "failed to create user address space");
-    proc->root_page_table = user_pml4;
-
-    uintptr_t stack_top = vmm_alloc_user_stack(user_pml4);
-    uint64_t code = vmm_alloc_user_code(user_pml4, exec_addr, exec_size);
-    
-    proc->context->iret_rsp = stack_top;
-    proc->context->iret_rip = code;
-    proc->kernel_stack = kalloc_stack();
-    if (!proc->kernel_stack) panic(NULL, "failed to allocate kernel stack");
-
-    // Copy code into user pages; for that we need to temporarily switch to the user pml4
-    load_cr3(VIRT_TO_PHYS((uint64_t)user_pml4));
-    memcpy((uint64_t*)code, exec_addr, exec_size);
-    load_cr3(VIRT_TO_PHYS((uint64_t)kernel_pml4));
-
-    process_add(&processes_list, proc);
-    DEBUG("user process '%s' (pid=%u) enqueued for scheduling", name, proc->pid);
-    SET_INTERRUPTS;
-}
-
-// Same as above but for a raw data pointer (pointing to raw binary, no ELF)
 void process_create_user_raw(char* file, int size, char* name)
 {
     CLEAR_INTERRUPTS;
@@ -286,8 +242,10 @@ void process_create_user_raw(char* file, int size, char* name)
 
     if (!proc || !ctx) panic(NULL, "out of memory while creating user process");
 
+    memset(proc, 0, sizeof(struct process));
+    memset(ctx, 0, sizeof(struct cpu_status));
+
     strncpy(proc->name, name, PROCESS_NAME_MAX);
-    memset(ctx, 0, sizeof(struct cpu_status)); // set GP registers to zero
     proc->pid = next_free_pid++;
     proc->status = READY;
     proc->next = 0;
@@ -296,6 +254,24 @@ void process_create_user_raw(char* file, int size, char* name)
     proc->context->iret_cs = USER_CODE_SEGMENT | 3;
     proc->context->iret_flags = 0x202; // Interrupt Flag set
 
+        /* Set basic entries for the process's File Descriptor Table */
+    proc->fdt[0].fd = 0;
+    proc->fdt[0].open = true;
+    proc->fdt[0].cursor = 0;
+    strncpy(proc->fdt[0].filename, "stdin", PROCESS_NAME_MAX - 1);
+
+    proc->fdt[1].fd = 1;
+    proc->fdt[1].open = true;
+    proc->fdt[1].cursor = 0;
+    strncpy(proc->fdt[1].filename, "stdout", PROCESS_NAME_MAX - 1);
+
+    proc->fdt[2].fd = 2;
+    proc->fdt[2].open = true;
+    proc->fdt[2].cursor = 0;
+    strncpy(proc->fdt[2].filename, "stderr", PROCESS_NAME_MAX - 1);
+
+    proc->next_free_fd = 3; // file descriptors are also bump-allocated
+
     void* exec_addr = (void*)file;
     uint64_t exec_size = size;