kern

annotate src/proc.c @ 96:07fe6a614185

find changesets by author, revision, files, or words in the commit message
filesystem
author John Tsiombikas <nuclear@member.fsf.org>
date Thu, 15 Dec 2011 04:39:00 +0200
parents 7ff2b4971216
children
rev   line source
nuclear@52 1 #include <stdio.h>
nuclear@47 2 #include <string.h>
nuclear@52 3 #include <assert.h>
nuclear@57 4 #include <errno.h>
nuclear@55 5 #include "config.h"
nuclear@42 6 #include "proc.h"
nuclear@42 7 #include "tss.h"
nuclear@45 8 #include "vm.h"
nuclear@47 9 #include "segm.h"
nuclear@47 10 #include "intr.h"
nuclear@47 11 #include "panic.h"
nuclear@51 12 #include "syscall.h"
nuclear@51 13 #include "sched.h"
nuclear@54 14 #include "tss.h"
nuclear@72 15 #include "kdef.h"
nuclear@47 16
nuclear@55 17 #define FLAGS_INTR_BIT (1 << 9)
nuclear@47 18
nuclear@54 19 static void start_first_proc(void);
nuclear@54 20
nuclear@55 21 /* defined in proc-asm.S */
nuclear@57 22 uint32_t switch_stack(uint32_t new_stack, uint32_t *old_stack);
nuclear@57 23 void just_forked(void);
nuclear@54 24
nuclear@47 25 /* defined in test_proc.S */
nuclear@47 26 void test_proc(void);
nuclear@47 27 void test_proc_end(void);
nuclear@42 28
nuclear@42 29 static struct process proc[MAX_PROC];
nuclear@56 30
nuclear@56 31 /* cur_pid: pid of the currently executing process.
nuclear@56 32 * when we're in the idle process cur_pid will be 0.
nuclear@56 33 * last_pid: pid of the last real process that was running, this should
nuclear@56 34 * never become 0. Essentially this defines the active kernel stack.
nuclear@56 35 */
nuclear@56 36 static int cur_pid, last_pid;
nuclear@42 37
nuclear@54 38 static struct task_state *tss;
nuclear@54 39
nuclear@54 40
nuclear@42 41 void init_proc(void)
nuclear@42 42 {
nuclear@54 43 int tss_page;
nuclear@51 44
nuclear@54 45 /* allocate a page for the task state segment, to make sure
nuclear@54 46 * it doesn't cross page boundaries
nuclear@54 47 */
nuclear@54 48 if((tss_page = pgalloc(1, MEM_KERNEL)) == -1) {
nuclear@54 49 panic("failed to allocate memory for the task state segment\n");
nuclear@54 50 }
nuclear@55 51 tss = (struct task_state*)PAGE_TO_ADDR(tss_page);
nuclear@54 52
nuclear@54 53 /* the kernel stack segment never changes so we might as well set it now
nuclear@54 54 * the only other thing that we use in the tss is the kernel stack pointer
nuclear@54 55 * which is different for each process, and thus managed by context_switch
nuclear@54 56 */
nuclear@54 57 memset(tss, 0, sizeof *tss);
nuclear@54 58 tss->ss0 = selector(SEGM_KDATA, 0);
nuclear@54 59
nuclear@55 60 set_tss((uint32_t)tss);
nuclear@54 61
nuclear@54 62 /* initialize system call handler (see syscall.c) */
nuclear@51 63 init_syscall();
nuclear@42 64
nuclear@54 65 start_first_proc(); /* XXX never returns */
nuclear@54 66 }
nuclear@54 67
nuclear@54 68 static void start_first_proc(void)
nuclear@54 69 {
nuclear@54 70 struct process *p;
nuclear@54 71 int proc_size_pg, img_start_pg, stack_pg;
nuclear@55 72 uint32_t img_start_addr;
nuclear@54 73 struct intr_frame ifrm;
nuclear@54 74
nuclear@42 75 /* prepare the first process */
nuclear@54 76 p = proc + 1;
nuclear@54 77 p->id = 1;
nuclear@54 78 p->parent = 0; /* no parent for init */
nuclear@42 79
nuclear@96 80 p->umask = 022;
nuclear@96 81
nuclear@55 82 p->ticks_left = TIMESLICE_TICKS;
nuclear@55 83 p->next = p->prev = 0;
nuclear@55 84
nuclear@55 85 /* the first process may keep this existing page table */
nuclear@55 86 p->ctx.pgtbl_paddr = get_pgdir_addr();
nuclear@55 87
nuclear@42 88 /* allocate a chunk of memory for the process image
nuclear@42 89 * and copy the code of test_proc there.
nuclear@42 90 */
nuclear@51 91 proc_size_pg = (test_proc_end - test_proc) / PGSIZE + 1;
nuclear@45 92 if((img_start_pg = pgalloc(proc_size_pg, MEM_USER)) == -1) {
nuclear@45 93 panic("failed to allocate space for the init process image\n");
nuclear@45 94 }
nuclear@54 95 img_start_addr = PAGE_TO_ADDR(img_start_pg);
nuclear@54 96 memcpy((void*)img_start_addr, test_proc, proc_size_pg * PGSIZE);
nuclear@54 97 printf("copied init process at: %x\n", img_start_addr);
nuclear@47 98
nuclear@69 99 /* allocate the first page of the user stack */
nuclear@47 100 stack_pg = ADDR_TO_PAGE(KMEM_START) - 1;
nuclear@47 101 if(pgalloc_vrange(stack_pg, 1) == -1) {
nuclear@47 102 panic("failed to allocate user stack page\n");
nuclear@47 103 }
nuclear@54 104 p->user_stack_pg = stack_pg;
nuclear@52 105
nuclear@54 106 /* allocate a kernel stack for this process */
nuclear@54 107 if((p->kern_stack_pg = pgalloc(KERN_STACK_SIZE / PGSIZE, MEM_KERNEL)) == -1) {
nuclear@54 108 panic("failed to allocate kernel stack for the init process\n");
nuclear@54 109 }
nuclear@54 110 /* when switching from user space to kernel space, the ss0:esp0 from TSS
nuclear@54 111 * will be used to switch to the per-process kernel stack, so we need to
nuclear@54 112 * set it correctly before switching to user space.
nuclear@54 113 * tss->ss0 is already set in init_proc above.
nuclear@54 114 */
nuclear@54 115 tss->esp0 = PAGE_TO_ADDR(p->kern_stack_pg) + KERN_STACK_SIZE;
nuclear@45 116
nuclear@45 117
nuclear@54 118 /* now we need to fill in the fake interrupt stack frame */
nuclear@54 119 memset(&ifrm, 0, sizeof ifrm);
nuclear@54 120 /* after the priviledge switch, this ss:esp will be used in userspace */
nuclear@54 121 ifrm.esp = PAGE_TO_ADDR(stack_pg) + PGSIZE;
nuclear@54 122 ifrm.ss = selector(SEGM_UDATA, 3);
nuclear@54 123 /* instruction pointer at the beginning of the process image */
nuclear@55 124 ifrm.eip = img_start_addr;
nuclear@54 125 ifrm.cs = selector(SEGM_UCODE, 3);
nuclear@54 126 /* make sure the user will run with interrupts enabled */
nuclear@54 127 ifrm.eflags = FLAGS_INTR_BIT;
nuclear@54 128 /* user data selectors should all be the same */
nuclear@54 129 ifrm.ds = ifrm.es = ifrm.fs = ifrm.gs = ifrm.ss;
nuclear@42 130
nuclear@51 131 /* add it to the scheduler queues */
nuclear@55 132 add_proc(p->id);
nuclear@55 133
nuclear@56 134 /* make it current */
nuclear@56 135 set_current_pid(p->id);
nuclear@42 136
nuclear@68 137 /* build the current vm map */
nuclear@68 138 cons_vmmap(&p->vmmap);
nuclear@68 139
nuclear@54 140 /* execute a fake return from interrupt with the fake stack frame */
nuclear@54 141 intr_ret(ifrm);
nuclear@42 142 }
nuclear@42 143
nuclear@72 144 int sys_fork(void)
nuclear@57 145 {
nuclear@57 146 int i, pid;
nuclear@57 147 struct process *p, *parent;
nuclear@57 148
nuclear@57 149 disable_intr();
nuclear@57 150
nuclear@57 151 /* find a free process slot */
nuclear@57 152 /* TODO don't search up to MAX_PROC if uid != 0 */
nuclear@57 153 pid = -1;
nuclear@57 154 for(i=1; i<MAX_PROC; i++) {
nuclear@57 155 if(proc[i].id == 0) {
nuclear@57 156 pid = i;
nuclear@57 157 break;
nuclear@57 158 }
nuclear@57 159 }
nuclear@57 160
nuclear@57 161 if(pid == -1) {
nuclear@57 162 /* process table full */
nuclear@57 163 return -EAGAIN;
nuclear@57 164 }
nuclear@57 165
nuclear@57 166
nuclear@57 167 p = proc + pid;
nuclear@57 168 parent = get_current_proc();
nuclear@57 169
nuclear@90 170 /* copy file table */
nuclear@90 171 memcpy(p->files, parent->files, sizeof p->files);
nuclear@90 172
nuclear@96 173 p->umask = parent->umask;
nuclear@96 174
nuclear@57 175 /* allocate a kernel stack for the new process */
nuclear@57 176 if((p->kern_stack_pg = pgalloc(KERN_STACK_SIZE / PGSIZE, MEM_KERNEL)) == -1) {
nuclear@57 177 return -EAGAIN;
nuclear@57 178 }
nuclear@57 179 p->ctx.stack_ptr = PAGE_TO_ADDR(p->kern_stack_pg) + KERN_STACK_SIZE;
nuclear@57 180 /* we need to copy the current interrupt frame to the new kernel stack so
nuclear@57 181 * that the new process will return to the same point as the parent, just
nuclear@57 182 * after the fork syscall.
nuclear@57 183 */
nuclear@57 184 p->ctx.stack_ptr -= sizeof(struct intr_frame);
nuclear@57 185 memcpy((void*)p->ctx.stack_ptr, get_intr_frame(), sizeof(struct intr_frame));
nuclear@57 186 /* child's return from fork returns 0 */
nuclear@57 187 ((struct intr_frame*)p->ctx.stack_ptr)->regs.eax = 0;
nuclear@57 188
nuclear@59 189 /* we also need the address of just_forked in the stack, so that switch_stacks
nuclear@59 190 * called from context_switch, will return to just_forked when we first switch
nuclear@59 191 * to a newly forked process. just_forked then just calls intr_ret to return to
nuclear@59 192 * userspace with the already constructed interrupt frame (see above).
nuclear@59 193 */
nuclear@57 194 p->ctx.stack_ptr -= 4;
nuclear@57 195 *(uint32_t*)p->ctx.stack_ptr = (uint32_t)just_forked;
nuclear@57 196
nuclear@57 197 /* initialize the rest of the process structure */
nuclear@57 198 p->id = pid;
nuclear@57 199 p->parent = parent->id;
nuclear@72 200 p->child_list = 0;
nuclear@57 201 p->next = p->prev = 0;
nuclear@57 202
nuclear@72 203 /* add to the child list */
nuclear@72 204 p->sib_next = parent->child_list;
nuclear@72 205 parent->child_list = p;
nuclear@72 206
nuclear@57 207 /* will be copied on write */
nuclear@57 208 p->user_stack_pg = parent->user_stack_pg;
nuclear@57 209
nuclear@69 210 /* clone the parent's virtual memory */
nuclear@69 211 clone_vm(p, parent, CLONE_COW);
nuclear@57 212
nuclear@57 213 /* done, now let's add it to the scheduler runqueue */
nuclear@57 214 add_proc(p->id);
nuclear@57 215
nuclear@57 216 return pid;
nuclear@57 217 }
nuclear@47 218
nuclear@72 219 int sys_exit(int status)
nuclear@72 220 {
nuclear@72 221 struct process *p, *child;
nuclear@72 222
nuclear@72 223 p = get_current_proc();
nuclear@72 224
nuclear@75 225 printf("process %d exit(%d)\n", p->id, status);
nuclear@75 226
nuclear@72 227 /* TODO deliver SIGCHLD to the parent */
nuclear@72 228
nuclear@72 229 /* find any child processes and make init adopt them */
nuclear@72 230 child = p->child_list;
nuclear@72 231 while(child) {
nuclear@72 232 child->parent = 1;
nuclear@72 233 child = child->sib_next;
nuclear@72 234 }
nuclear@72 235
nuclear@72 236 cleanup_vm(p);
nuclear@72 237
nuclear@72 238 /* remove it from the runqueue */
nuclear@72 239 remove_proc(p->id);
nuclear@72 240
nuclear@72 241 /* make it a zombie until its parent reaps it */
nuclear@72 242 p->state = STATE_ZOMBIE;
nuclear@72 243 p->exit_status = (status & _WSTATUS_MASK) | (_WREASON_EXITED << _WREASON_SHIFT);
nuclear@72 244
nuclear@72 245 /* wakeup any processes waiting for it
nuclear@72 246 * we're waking up the parent's address, because waitpid waits
nuclear@72 247 * on it's own process struct, not knowing which child will die
nuclear@72 248 * first.
nuclear@72 249 */
nuclear@72 250 wakeup(get_process(p->parent));
nuclear@72 251 return 0;
nuclear@72 252 }
nuclear@72 253
nuclear@72 254 int sys_waitpid(int pid, int *status, int opt)
nuclear@72 255 {
nuclear@72 256 struct process *p, *child;
nuclear@72 257
nuclear@72 258 p = get_current_proc();
nuclear@72 259
nuclear@72 260 restart:
nuclear@72 261 if(pid <= 0) {
nuclear@72 262 /* search for zombie children */
nuclear@72 263 child = p->child_list;
nuclear@72 264 while(child) {
nuclear@72 265 if(child->state == STATE_ZOMBIE) {
nuclear@72 266 break;
nuclear@72 267 }
nuclear@72 268 child = child->sib_next;
nuclear@72 269 }
nuclear@72 270 } else {
nuclear@72 271 if(!(child = get_process(pid)) || child->parent != p->id) {
nuclear@72 272 return -ECHILD;
nuclear@72 273 }
nuclear@72 274 if(child->state != STATE_ZOMBIE) {
nuclear@72 275 child = 0;
nuclear@72 276 }
nuclear@72 277 }
nuclear@72 278
nuclear@72 279 /* found ? */
nuclear@72 280 if(child) {
nuclear@72 281 int res;
nuclear@72 282 struct process *prev, dummy;
nuclear@72 283
nuclear@72 284 if(status) {
nuclear@72 285 *status = child->exit_status;
nuclear@72 286 }
nuclear@72 287 res = child->id;
nuclear@72 288
nuclear@72 289 /* remove it from our children list */
nuclear@72 290 dummy.sib_next = p->child_list;
nuclear@72 291 prev = &dummy;
nuclear@72 292 while(prev->next) {
nuclear@72 293 if(prev->next == child) {
nuclear@72 294 prev->next = child->next;
nuclear@72 295 break;
nuclear@72 296 }
nuclear@72 297 }
nuclear@72 298 p->child_list = dummy.next;
nuclear@72 299
nuclear@72 300 /* invalidate the id */
nuclear@72 301 child->id = 0;
nuclear@72 302 return res;
nuclear@72 303 }
nuclear@72 304
nuclear@72 305 /* not found, wait or sod off */
nuclear@72 306 if(!(opt & WNOHANG)) {
nuclear@72 307 /* wait on our own process struct because
nuclear@72 308 * we have no way of knowing which child will
nuclear@72 309 * die first.
nuclear@72 310 * exit will wakeup the parent structure...
nuclear@72 311 */
nuclear@72 312 wait(p);
nuclear@72 313 /* done waiting, restart waitpid */
nuclear@72 314 goto restart;
nuclear@72 315 }
nuclear@72 316
nuclear@72 317 return 0; /* he's not dead jim */
nuclear@72 318 }
nuclear@72 319
nuclear@47 320 void context_switch(int pid)
nuclear@42 321 {
nuclear@56 322 static struct process *prev, *new;
nuclear@49 323
nuclear@55 324 assert(get_intr_state() == 0);
nuclear@56 325 assert(pid > 0);
nuclear@56 326 assert(last_pid > 0);
nuclear@55 327
nuclear@56 328 prev = proc + last_pid;
nuclear@54 329 new = proc + pid;
nuclear@52 330
nuclear@56 331 if(last_pid != pid) {
nuclear@57 332 set_current_pid(new->id);
nuclear@47 333
nuclear@56 334 /* switch to the new process' address space */
nuclear@56 335 set_pgdir_addr(new->ctx.pgtbl_paddr);
nuclear@47 336
nuclear@56 337 /* make sure we'll return to the correct kernel stack next time
nuclear@56 338 * we enter from userspace
nuclear@56 339 */
nuclear@56 340 tss->esp0 = PAGE_TO_ADDR(new->kern_stack_pg) + KERN_STACK_SIZE;
nuclear@57 341
nuclear@57 342 /* push all registers onto the stack before switching stacks */
nuclear@57 343 push_regs();
nuclear@57 344
nuclear@57 345 /* XXX: when switching to newly forked processes this switch_stack call
nuclear@57 346 * WILL NOT RETURN HERE. It will return to just_forked instead. So the
nuclear@57 347 * rest of this function will not run.
nuclear@57 348 */
nuclear@57 349 switch_stack(new->ctx.stack_ptr, &prev->ctx.stack_ptr);
nuclear@57 350
nuclear@57 351 /* restore registers from the new stack */
nuclear@57 352 pop_regs();
nuclear@57 353 } else {
nuclear@57 354 set_current_pid(new->id);
nuclear@56 355 }
nuclear@56 356 }
nuclear@56 357
nuclear@56 358
nuclear@56 359 void set_current_pid(int pid)
nuclear@56 360 {
nuclear@56 361 cur_pid = pid;
nuclear@56 362 if(pid > 0) {
nuclear@56 363 last_pid = pid;
nuclear@56 364 }
nuclear@47 365 }
nuclear@51 366
nuclear@51 367 int get_current_pid(void)
nuclear@51 368 {
nuclear@51 369 return cur_pid;
nuclear@51 370 }
nuclear@51 371
nuclear@51 372 struct process *get_current_proc(void)
nuclear@51 373 {
nuclear@56 374 return cur_pid > 0 ? &proc[cur_pid] : 0;
nuclear@51 375 }
nuclear@51 376
nuclear@51 377 struct process *get_process(int pid)
nuclear@51 378 {
nuclear@72 379 struct process *p = proc + pid;
nuclear@72 380 if(p->id != pid) {
nuclear@72 381 printf("get_process called with invalid pid: %d\n", pid);
nuclear@72 382 return 0;
nuclear@72 383 }
nuclear@72 384 return p;
nuclear@51 385 }
nuclear@72 386
nuclear@72 387 int sys_getpid(void)
nuclear@72 388 {
nuclear@72 389 return cur_pid;
nuclear@72 390 }
nuclear@72 391
nuclear@72 392 int sys_getppid(void)
nuclear@72 393 {
nuclear@72 394 struct process *p = get_current_proc();
nuclear@72 395
nuclear@72 396 if(!p) {
nuclear@72 397 return 0;
nuclear@72 398 }
nuclear@72 399 return p->parent;
nuclear@72 400 }