Flat memory model, read_file() accepts statbuf.

cpu/gdt.c

@@ -32,10 +32,10 @@ struct seg_desc_t {
 struct seg_desc_t seg_desc[6];
 
 void init_seg_desc() {
-    seg_desc[SEG_KCODE] = SEG(STA_X|STA_R, 0,         0xffffffff, 0);
-    seg_desc[SEG_KDATA] = SEG(STA_W,       0,         0xffffffff, 0);
-    seg_desc[SEG_UCODE] = SEG(STA_X|STA_R, USER_BASE, 0xffffffff - USER_BASE, DPL_USER);
-    seg_desc[SEG_UDATA] = SEG(STA_W,       USER_BASE, 0xffffffff - USER_BASE, DPL_USER);
+    seg_desc[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, 0);
+    seg_desc[SEG_KDATA] = SEG(STA_W,       0, 0xffffffff, 0);
+    seg_desc[SEG_UCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, DPL_USER);
+    seg_desc[SEG_UDATA] = SEG(STA_W,       0, 0xffffffff, DPL_USER);
 }
 
 struct gdt_desc_t {

fs/fs.c

@@ -13,7 +13,7 @@ int stat(const char* name, struct stat *buf) {
         struct dirent *e = &dir.entries[i];
         if (!strncmp(e->name, name, sizeof(e->name))) {
             buf->size = e->size_bytes;
-            buf->reserved[0] = e->offset_sectors;
+            buf->start_sector = e->offset_sectors;
             return 0;
         }
     }
@@ -23,14 +23,10 @@ int stat(const char* name, struct stat *buf) {
 /* Find file by name and read it into buffer with size bufsize.
  * At most (bufsize & -512) bytes will be read.
  * Return number of bytes read or -1 on failure. */
-int read_file(const char* name, void* buf, uint32_t bufsize) {
-    struct stat statbuf;
-    if (stat(name, &statbuf) != 0) {
-        return -1;
-    }
-    uint32_t sector = fs_start + statbuf.reserved[0];
+int read_file(const struct stat *statbuf, void* buf, uint32_t bufsize) {
+    uint32_t sector = fs_start + statbuf->start_sector;
     uint32_t bytes_read = 0;
-    uint32_t file_sectors = (statbuf.size + sector_size - 1) / sector_size;
+    uint32_t file_sectors = (statbuf->size + sector_size - 1) / sector_size;
     while (bufsize >= sector_size && file_sectors > 0) {
         read_sectors_ATA_PIO(buf, sector, 1);
         sector++;
@@ -39,5 +35,5 @@ int read_file(const char* name, void* buf, uint32_t bufsize) {
         buf += sector_size;
         bytes_read += sector_size;
     }
-    return bytes_read < statbuf.size ? bytes_read : statbuf.size;
+    return bytes_read < statbuf->size ? bytes_read : statbuf->size;
 }

fs/fs.h

@@ -38,7 +38,8 @@ struct dir {
 
 struct stat {
 	uint32_t size;
-	uint32_t reserved[3];
+	uint32_t start_sector;
+	uint32_t reserved1, reserved2;
 };
 
 /* Find file by name and fill information in buf.
@@ -48,4 +49,4 @@ int stat(const char* name, struct stat *buf);
 /* Find file by name and read it into buffer with size bufsize.
  * At most (bufsize & ~511) bytes will be read.
  * Return number of bytes read or -1 on failure. */
-int read_file(const char* name, void* buf, uint32_t bufsize);
+int read_file(const struct stat *statbuf, void* buf, uint32_t bufsize);

kernel.c

@@ -26,16 +26,9 @@ void kmain() {
     load_idt();
     sti();
 
-    char *buf = (char*)(16 << 20);
-
     vga_clear_screen();
     printk("YABLOKO\n");
 
-    if (read_file("kernel.bin", buf, 4096 + sector_size) > 0) {
-        printk(buf + 4096);
-    } else {
-        printk("failed to read file\n");
-    }
     printk("\n> ");
     while (1) {
         if (kbd_buf_size > 0 && kbd_buf[kbd_buf_size-1] == '\n') {

proc.c

@@ -23,31 +23,36 @@ struct kstack {
 struct task {
     struct taskstate tss;
     struct kstack stack;
+    pde_t *pgdir;
 };
 
 struct vm {
     void *kernel_thread;
-    void *user_thread;
     struct task *user_task;
-} *vm;
+} vm;
 
 void trapret();
 void swtch(void** oldstack, void* newstack);
 
 void run_elf(const char* name) {
-    if (!vm) {
-        vm = kalloc();
-        vm->user_task = kalloc();
-        switchuvm(&vm->user_task->tss, vm->user_task->stack.bottom);
+    struct stat statbuf;
+    if (stat(name, &statbuf) != 0) {
+        printk(name);
+        printk(": file not found\n");
+        return;
     }
-    if (read_file(name, (void*)USER_BASE, 100 << 20) <= 0) {
+    if (!vm.user_task) {
+        vm.user_task = kalloc();
+        switchuvm(&vm.user_task->tss, vm.user_task->stack.bottom);
+    }
+    if (read_file(&statbuf, (void*)USER_BASE, 100 << 20) <= 0) {
         printk(name);
         printk(": file not found\n");
         return;
     }
     Elf32_Ehdr *hdr = (void*)USER_BASE;
 
-    struct kstack *u = &vm->user_task->stack;
+    struct kstack *u = &vm.user_task->stack;
     memset(u, 0, sizeof(*u));
     u->context.eip = (uint32_t)trapret;
 
@@ -63,13 +68,13 @@ void run_elf(const char* name) {
     tf->useresp = USER_STACK_BASE;
 
     // initialization done, now switch to the process
-    swtch(&vm->kernel_thread, &u->context);
+    swtch(&vm.kernel_thread, &u->context);
 
     // process has finished
 }
 
 _Noreturn void killproc() {
     void* task_stack;
-    swtch(&task_stack, vm->kernel_thread);
+    swtch(&task_stack, vm.kernel_thread);
     __builtin_unreachable();
 }