arch/um/kernel/tt/process_kern.c

   1 /*
   2  * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include "linux/sched.h"
   7 #include "linux/signal.h"
   8 #include "linux/kernel.h"
   9 #include "linux/interrupt.h"
  10 #include "linux/ptrace.h"
  11 #include "asm/system.h"
  12 #include "asm/pgalloc.h"
  13 #include "asm/ptrace.h"
  14 #include "asm/tlbflush.h"
  15 #include "irq_user.h"
  16 #include "kern_util.h"
  17 #include "user_util.h"
  18 #include "os.h"
  19 #include "kern.h"
  20 #include "sigcontext.h"
  21 #include "mem_user.h"
  22 #include "tlb.h"
  23 #include "mode.h"
  24 #include "mode_kern.h"
  25 #include "init.h"
  26 #include "tt.h"
  27
  28 void switch_to_tt(void *prev, void *next)
  29 {
  30         struct task_struct *from, *to, *prev_sched;
  31         unsigned long flags;
  32         int err, vtalrm, alrm, prof, cpu;
  33         char c;
  34
  35         from = prev;
  36         to = next;
  37
  38         cpu = task_thread_info(from)->cpu;
  39         if(cpu == 0)
  40                 forward_interrupts(to->thread.mode.tt.extern_pid);
  41 #ifdef CONFIG_SMP
  42         forward_ipi(cpu_data[cpu].ipi_pipe[0], to->thread.mode.tt.extern_pid);
  43 #endif
  44         local_irq_save(flags);
  45
  46         vtalrm = change_sig(SIGVTALRM, 0);
  47         alrm = change_sig(SIGALRM, 0);
  48         prof = change_sig(SIGPROF, 0);
  49
  50         forward_pending_sigio(to->thread.mode.tt.extern_pid);
  51
  52         c = 0;
  53
  54         /* Notice that here we "up" the semaphore on which "to" is waiting, and
  55          * below (the read) we wait on this semaphore (which is implemented by
  56          * switch_pipe) and go sleeping. Thus, after that, we have resumed in
  57          * "to", and can't use any more the value of "from" (which is outdated),
  58          * nor the value in "to" (since it was the task which stole us the CPU,
  59          * which we don't care about). */
  60
  61         err = os_write_file(to->thread.mode.tt.switch_pipe[1], &c, sizeof(c));
  62         if(err != sizeof(c))
  63                 panic("write of switch_pipe failed, err = %d", -err);
  64
  65         if(from->thread.mode.tt.switch_pipe[0] == -1)
  66                 os_kill_process(os_getpid(), 0);
  67
  68         err = os_read_file(from->thread.mode.tt.switch_pipe[0], &c, sizeof(c));
  69         if(err != sizeof(c))
  70                 panic("read of switch_pipe failed, errno = %d", -err);
  71
  72         /* If the process that we have just scheduled away from has exited,
  73          * then it needs to be killed here.  The reason is that, even though
  74          * it will kill itself when it next runs, that may be too late.  Its
  75          * stack will be freed, possibly before then, and if that happens,
  76          * we have a use-after-free situation.  So, it gets killed here
  77          * in case it has not already killed itself.
  78          */
  79         prev_sched = current->thread.prev_sched;
  80         if(prev_sched->thread.mode.tt.switch_pipe[0] == -1)
  81                 os_kill_process(prev_sched->thread.mode.tt.extern_pid, 1);
  82
  83         change_sig(SIGVTALRM, vtalrm);
  84         change_sig(SIGALRM, alrm);
  85         change_sig(SIGPROF, prof);
  86
  87         arch_switch_to_tt(prev_sched, current);
  88
  89         flush_tlb_all();
  90         local_irq_restore(flags);
  91 }
  92
  93 void release_thread_tt(struct task_struct *task)
  94 {
  95         int pid = task->thread.mode.tt.extern_pid;
  96
  97         /*
  98          * We first have to kill the other process, before
  99          * closing its switch_pipe. Else it might wake up
 100          * and receive "EOF" before we could kill it.
 101          */
 102         if(os_getpid() != pid)
 103                 os_kill_process(pid, 0);
 104
 105         os_close_file(task->thread.mode.tt.switch_pipe[0]);
 106         os_close_file(task->thread.mode.tt.switch_pipe[1]);
 107         /* use switch_pipe as flag: thread is released */
 108         task->thread.mode.tt.switch_pipe[0] = -1;
 109 }
 110
 111 void suspend_new_thread(int fd)
 112 {
 113         int err;
 114         char c;
 115
 116         os_stop_process(os_getpid());
 117         err = os_read_file(fd, &c, sizeof(c));
 118         if(err != sizeof(c))
 119                 panic("read failed in suspend_new_thread, err = %d", -err);
 120 }
 121
 122 void schedule_tail(task_t *prev);
 123
 124 static void new_thread_handler(int sig)
 125 {
 126         unsigned long disable;
 127         int (*fn)(void *);
 128         void *arg;
 129
 130         fn = current->thread.request.u.thread.proc;
 131         arg = current->thread.request.u.thread.arg;
 132
 133         UPT_SC(&current->thread.regs.regs) = (void *) (&sig + 1);
 134         disable = (1 << (SIGVTALRM - 1)) | (1 << (SIGALRM - 1)) |
 135                 (1 << (SIGIO - 1)) | (1 << (SIGPROF - 1));
 136         SC_SIGMASK(UPT_SC(&current->thread.regs.regs)) &= ~disable;
 137
 138         suspend_new_thread(current->thread.mode.tt.switch_pipe[0]);
 139
 140         force_flush_all();
 141         if(current->thread.prev_sched != NULL)
 142                 schedule_tail(current->thread.prev_sched);
 143         current->thread.prev_sched = NULL;
 144
 145         init_new_thread_signals(1);
 146         enable_timer();
 147         free_page(current->thread.temp_stack);
 148         set_cmdline("(kernel thread)");
 149
 150         change_sig(SIGUSR1, 1);
 151         change_sig(SIGPROF, 1);
 152         local_irq_enable();
 153         if(!run_kernel_thread(fn, arg, &current->thread.exec_buf))
 154                 do_exit(0);
 155
 156         /* XXX No set_user_mode here because a newly execed process will
 157          * immediately segfault on its non-existent IP, coming straight back
 158          * to the signal handler, which will call set_user_mode on its way
 159          * out.  This should probably change since it's confusing.
 160          */
 161 }
 162
 163 static int new_thread_proc(void *stack)
 164 {
 165         /* local_irq_disable is needed to block out signals until this thread is
 166          * properly scheduled.  Otherwise, the tracing thread will get mighty
 167          * upset about any signals that arrive before that.
 168          * This has the complication that it sets the saved signal mask in
 169          * the sigcontext to block signals.  This gets restored when this
 170          * thread (or a descendant, since they get a copy of this sigcontext)
 171          * returns to userspace.
 172          * So, this is compensated for elsewhere.
 173          * XXX There is still a small window until local_irq_disable() actually
 174          * finishes where signals are possible - shouldn't be a problem in
 175          * practice since SIGIO hasn't been forwarded here yet, and the
 176          * local_irq_disable should finish before a SIGVTALRM has time to be
 177          * delivered.
 178          */
 179
 180         local_irq_disable();
 181         init_new_thread_stack(stack, new_thread_handler);
 182         os_usr1_process(os_getpid());
 183         change_sig(SIGUSR1, 1);
 184         return(0);
 185 }
 186
 187 /* Signal masking - signals are blocked at the start of fork_tramp.  They
 188  * are re-enabled when finish_fork_handler is entered by fork_tramp hitting
 189  * itself with a SIGUSR1.  set_user_mode has to be run with SIGUSR1 off,
 190  * so it is blocked before it's called.  They are re-enabled on sigreturn
 191  * despite the fact that they were blocked when the SIGUSR1 was issued because
 192  * copy_thread copies the parent's sigcontext, including the signal mask
 193  * onto the signal frame.
 194  */
 195
 196 void finish_fork_handler(int sig)
 197 {
 198         UPT_SC(&current->thread.regs.regs) = (void *) (&sig + 1);
 199         suspend_new_thread(current->thread.mode.tt.switch_pipe[0]);
 200
 201         force_flush_all();
 202         if(current->thread.prev_sched != NULL)
 203                 schedule_tail(current->thread.prev_sched);
 204         current->thread.prev_sched = NULL;
 205
 206         enable_timer();
 207         change_sig(SIGVTALRM, 1);
 208         local_irq_enable();
 209         if(current->mm != current->parent->mm)
 210                 protect_memory(uml_reserved, high_physmem - uml_reserved, 1,
 211                                1, 0, 1);
 212         task_protections((unsigned long) current_thread);
 213
 214         free_page(current->thread.temp_stack);
 215         local_irq_disable();
 216         change_sig(SIGUSR1, 0);
 217         set_user_mode(current);
 218 }
 219
 220 int fork_tramp(void *stack)
 221 {
 222         local_irq_disable();
 223         arch_init_thread();
 224         init_new_thread_stack(stack, finish_fork_handler);
 225
 226         os_usr1_process(os_getpid());
 227         change_sig(SIGUSR1, 1);
 228         return(0);
 229 }
 230
 231 int copy_thread_tt(int nr, unsigned long clone_flags, unsigned long sp,
 232                    unsigned long stack_top, struct task_struct * p,
 233                    struct pt_regs *regs)
 234 {
 235         int (*tramp)(void *);
 236         int new_pid, err;
 237         unsigned long stack;
 238
 239         if(current->thread.forking)
 240                 tramp = fork_tramp;
 241         else {
 242                 tramp = new_thread_proc;
 243                 p->thread.request.u.thread = current->thread.request.u.thread;
 244         }
 245
 246         err = os_pipe(p->thread.mode.tt.switch_pipe, 1, 1);
 247         if(err < 0){
 248                 printk("copy_thread : pipe failed, err = %d\n", -err);
 249                 return(err);
 250         }
 251
 252         stack = alloc_stack(0, 0);
 253         if(stack == 0){
 254                 printk(KERN_ERR "copy_thread : failed to allocate "
 255                        "temporary stack\n");
 256                 return(-ENOMEM);
 257         }
 258
 259         clone_flags &= CLONE_VM;
 260         p->thread.temp_stack = stack;
 261         new_pid = start_fork_tramp(task_stack_page(p), stack, clone_flags, tramp);
 262         if(new_pid < 0){
 263                 printk(KERN_ERR "copy_thread : clone failed - errno = %d\n",
 264                        -new_pid);
 265                 return(new_pid);
 266         }
 267
 268         if(current->thread.forking){
 269                 sc_to_sc(UPT_SC(&p->thread.regs.regs), UPT_SC(&regs->regs));
 270                 SC_SET_SYSCALL_RETURN(UPT_SC(&p->thread.regs.regs), 0);
 271                 if(sp != 0)
 272                         SC_SP(UPT_SC(&p->thread.regs.regs)) = sp;
 273         }
 274         p->thread.mode.tt.extern_pid = new_pid;
 275
 276         current->thread.request.op = OP_FORK;
 277         current->thread.request.u.fork.pid = new_pid;
 278         os_usr1_process(os_getpid());
 279
 280         /* Enable the signal and then disable it to ensure that it is handled
 281          * here, and nowhere else.
 282          */
 283         change_sig(SIGUSR1, 1);
 284
 285         change_sig(SIGUSR1, 0);
 286         err = 0;
 287         return(err);
 288 }
 289
 290 void reboot_tt(void)
 291 {
 292         current->thread.request.op = OP_REBOOT;
 293         os_usr1_process(os_getpid());
 294         change_sig(SIGUSR1, 1);
 295 }
 296
 297 void halt_tt(void)
 298 {
 299         current->thread.request.op = OP_HALT;
 300         os_usr1_process(os_getpid());
 301         change_sig(SIGUSR1, 1);
 302 }
 303
 304 void kill_off_processes_tt(void)
 305 {
 306         struct task_struct *p;
 307         int me;
 308
 309         me = os_getpid();
 310         for_each_process(p){
 311                 if(p->thread.mode.tt.extern_pid != me)
 312                         os_kill_process(p->thread.mode.tt.extern_pid, 0);
 313         }
 314         if(init_task.thread.mode.tt.extern_pid != me)
 315                 os_kill_process(init_task.thread.mode.tt.extern_pid, 0);
 316 }
 317
 318 void initial_thread_cb_tt(void (*proc)(void *), void *arg)
 319 {
 320         if(os_getpid() == tracing_pid){
 321                 (*proc)(arg);
 322         }
 323         else {
 324                 current->thread.request.op = OP_CB;
 325                 current->thread.request.u.cb.proc = proc;
 326                 current->thread.request.u.cb.arg = arg;
 327                 os_usr1_process(os_getpid());
 328                 change_sig(SIGUSR1, 1);
 329
 330                 change_sig(SIGUSR1, 0);
 331         }
 332 }
 333
 334 int do_proc_op(void *t, int proc_id)
 335 {
 336         struct task_struct *task;
 337         struct thread_struct *thread;
 338         int op, pid;
 339
 340         task = t;
 341         thread = &task->thread;
 342         op = thread->request.op;
 343         switch(op){
 344         case OP_NONE:
 345         case OP_TRACE_ON:
 346                 break;
 347         case OP_EXEC:
 348                 pid = thread->request.u.exec.pid;
 349                 do_exec(thread->mode.tt.extern_pid, pid);
 350                 thread->mode.tt.extern_pid = pid;
 351                 cpu_tasks[task_thread_info(task)->cpu].pid = pid;
 352                 break;
 353         case OP_FORK:
 354                 attach_process(thread->request.u.fork.pid);
 355                 break;
 356         case OP_CB:
 357                 (*thread->request.u.cb.proc)(thread->request.u.cb.arg);
 358                 break;
 359         case OP_REBOOT:
 360         case OP_HALT:
 361                 break;
 362         default:
 363                 tracer_panic("Bad op in do_proc_op");
 364                 break;
 365         }
 366         thread->request.op = OP_NONE;
 367         return(op);
 368 }
 369
 370 void init_idle_tt(void)
 371 {
 372         default_idle();
 373 }
 374
 375 extern void start_kernel(void);
 376
 377 static int start_kernel_proc(void *unused)
 378 {
 379         int pid;
 380
 381         block_signals();
 382         pid = os_getpid();
 383
 384         cpu_tasks[0].pid = pid;
 385         cpu_tasks[0].task = current;
 386 #ifdef CONFIG_SMP
 387         cpu_online_map = cpumask_of_cpu(0);
 388 #endif
 389         if(debug) os_stop_process(pid);
 390         start_kernel();
 391         return(0);
 392 }
 393
 394 void set_tracing(void *task, int tracing)
 395 {
 396         ((struct task_struct *) task)->thread.mode.tt.tracing = tracing;
 397 }
 398
 399 int is_tracing(void *t)
 400 {
 401         return (((struct task_struct *) t)->thread.mode.tt.tracing);
 402 }
 403
 404 int set_user_mode(void *t)
 405 {
 406         struct task_struct *task;
 407
 408         task = t ? t : current;
 409         if(task->thread.mode.tt.tracing)
 410                 return(1);
 411         task->thread.request.op = OP_TRACE_ON;
 412         os_usr1_process(os_getpid());
 413         return(0);
 414 }
 415
 416 void set_init_pid(int pid)
 417 {
 418         int err;
 419
 420         init_task.thread.mode.tt.extern_pid = pid;
 421         err = os_pipe(init_task.thread.mode.tt.switch_pipe, 1, 1);
 422         if(err)
 423                 panic("Can't create switch pipe for init_task, errno = %d",
 424                       -err);
 425 }
 426
 427 int start_uml_tt(void)
 428 {
 429         void *sp;
 430         int pages;
 431
 432         pages = (1 << CONFIG_KERNEL_STACK_ORDER);
 433         sp = task_stack_page(&init_task) +
 434                 pages * PAGE_SIZE - sizeof(unsigned long);
 435         return(tracer(start_kernel_proc, sp));
 436 }
 437
 438 int external_pid_tt(struct task_struct *task)
 439 {
 440         return(task->thread.mode.tt.extern_pid);
 441 }
 442
 443 int thread_pid_tt(struct task_struct *task)
 444 {
 445         return(task->thread.mode.tt.extern_pid);
 446 }
 447
 448 int is_valid_pid(int pid)
 449 {
 450         struct task_struct *task;
 451
 452         read_lock(&tasklist_lock);
 453         for_each_process(task){
 454                 if(task->thread.mode.tt.extern_pid == pid){
 455                         read_unlock(&tasklist_lock);
 456                         return(1);
 457                 }
 458         }
 459         read_unlock(&tasklist_lock);
 460         return(0);
 461 }