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 "signal_user.h"
  17 #include "kern_util.h"
  18 #include "user_util.h"
  19 #include "os.h"
  20 #include "kern.h"
  21 #include "sigcontext.h"
  22 #include "time_user.h"
  23 #include "mem_user.h"
  24 #include "tlb.h"
  25 #include "mode.h"
  26 #include "init.h"
  27 #include "tt.h"
  28
  29 void *switch_to_tt(void *prev, void *next, void *last)
  30 {
  31         struct task_struct *from, *to, *prev_sched;
  32         unsigned long flags;
  33         int err, vtalrm, alrm, prof, cpu;
  34         char c;
  35         /* jailing and SMP are incompatible, so this doesn't need to be
  36          * made per-cpu
  37          */
  38         static int reading;
  39
  40         from = prev;
  41         to = next;
  42
  43         to->thread.prev_sched = from;
  44
  45         cpu = from->thread_info->cpu;
  46         if(cpu == 0)
  47                 forward_interrupts(to->thread.mode.tt.extern_pid);
  48 #ifdef CONFIG_SMP
  49         forward_ipi(cpu_data[cpu].ipi_pipe[0], to->thread.mode.tt.extern_pid);
  50 #endif
  51         local_irq_save(flags);
  52
  53         vtalrm = change_sig(SIGVTALRM, 0);
  54         alrm = change_sig(SIGALRM, 0);
  55         prof = change_sig(SIGPROF, 0);
  56
  57         forward_pending_sigio(to->thread.mode.tt.extern_pid);
  58
  59         c = 0;
  60         set_current(to);
  61
  62         reading = 0;
  63         err = os_write_file(to->thread.mode.tt.switch_pipe[1], &c, sizeof(c));
  64         if(err != sizeof(c))
  65                 panic("write of switch_pipe failed, err = %d", -err);
  66
  67         reading = 1;
  68         if((from->exit_state == EXIT_ZOMBIE) ||
  69            (from->exit_state == EXIT_DEAD))
  70                 os_kill_process(os_getpid(), 0);
  71
  72         err = os_read_file(from->thread.mode.tt.switch_pipe[0], &c, sizeof(c));
  73         if(err != sizeof(c))
  74                 panic("read of switch_pipe failed, errno = %d", -err);
  75
  76         /* If the process that we have just scheduled away from has exited,
  77          * then it needs to be killed here.  The reason is that, even though
  78          * it will kill itself when it next runs, that may be too late.  Its
  79          * stack will be freed, possibly before then, and if that happens,
  80          * we have a use-after-free situation.  So, it gets killed here
  81          * in case it has not already killed itself.
  82          */
  83         prev_sched = current->thread.prev_sched;
  84         if((prev_sched->exit_state == EXIT_ZOMBIE) ||
  85            (prev_sched->exit_state == EXIT_DEAD))
  86                 os_kill_process(prev_sched->thread.mode.tt.extern_pid, 1);
  87
  88         change_sig(SIGVTALRM, vtalrm);
  89         change_sig(SIGALRM, alrm);
  90         change_sig(SIGPROF, prof);
  91
  92         arch_switch();
  93
  94         flush_tlb_all();
  95         local_irq_restore(flags);
  96
  97         return(current->thread.prev_sched);
  98 }
  99
 100 void release_thread_tt(struct task_struct *task)
 101 {
 102         int pid = task->thread.mode.tt.extern_pid;
 103
 104         if(os_getpid() != pid)
 105                 os_kill_process(pid, 0);
 106 }
 107
 108 void exit_thread_tt(void)
 109 {
 110         os_close_file(current->thread.mode.tt.switch_pipe[0]);
 111         os_close_file(current->thread.mode.tt.switch_pipe[1]);
 112 }
 113
 114 void suspend_new_thread(int fd)
 115 {
 116         int err;
 117         char c;
 118
 119         os_stop_process(os_getpid());
 120         err = os_read_file(fd, &c, sizeof(c));
 121         if(err != sizeof(c))
 122                 panic("read failed in suspend_new_thread, err = %d", -err);
 123 }
 124
 125 void schedule_tail(task_t *prev);
 126
 127 static void new_thread_handler(int sig)
 128 {
 129         unsigned long disable;
 130         int (*fn)(void *);
 131         void *arg;
 132
 133         fn = current->thread.request.u.thread.proc;
 134         arg = current->thread.request.u.thread.arg;
 135
 136         UPT_SC(&current->thread.regs.regs) = (void *) (&sig + 1);
 137         disable = (1 << (SIGVTALRM - 1)) | (1 << (SIGALRM - 1)) |
 138                 (1 << (SIGIO - 1)) | (1 << (SIGPROF - 1));
 139         SC_SIGMASK(UPT_SC(&current->thread.regs.regs)) &= ~disable;
 140
 141         suspend_new_thread(current->thread.mode.tt.switch_pipe[0]);
 142
 143         force_flush_all();
 144         if(current->thread.prev_sched != NULL)
 145                 schedule_tail(current->thread.prev_sched);
 146         current->thread.prev_sched = NULL;
 147
 148         init_new_thread_signals(1);
 149         enable_timer();
 150         free_page(current->thread.temp_stack);
 151         set_cmdline("(kernel thread)");
 152
 153         change_sig(SIGUSR1, 1);
 154         change_sig(SIGVTALRM, 1);
 155         change_sig(SIGPROF, 1);
 156         local_irq_enable();
 157         if(!run_kernel_thread(fn, arg, &current->thread.exec_buf))
 158                 do_exit(0);
 159
 160         /* XXX No set_user_mode here because a newly execed process will
 161          * immediately segfault on its non-existent IP, coming straight back
 162          * to the signal handler, which will call set_user_mode on its way
 163          * out.  This should probably change since it's confusing.
 164          */
 165 }
 166
 167 static int new_thread_proc(void *stack)
 168 {
 169         /* local_irq_disable is needed to block out signals until this thread is
 170          * properly scheduled.  Otherwise, the tracing thread will get mighty
 171          * upset about any signals that arrive before that.
 172          * This has the complication that it sets the saved signal mask in
 173          * the sigcontext to block signals.  This gets restored when this
 174          * thread (or a descendant, since they get a copy of this sigcontext)
 175          * returns to userspace.
 176          * So, this is compensated for elsewhere.
 177          * XXX There is still a small window until local_irq_disable() actually
 178          * finishes where signals are possible - shouldn't be a problem in
 179          * practice since SIGIO hasn't been forwarded here yet, and the
 180          * local_irq_disable should finish before a SIGVTALRM has time to be
 181          * delivered.
 182          */
 183
 184         local_irq_disable();
 185         init_new_thread_stack(stack, new_thread_handler);
 186         os_usr1_process(os_getpid());
 187         change_sig(SIGUSR1, 1);
 188         return(0);
 189 }
 190
 191 /* Signal masking - signals are blocked at the start of fork_tramp.  They
 192  * are re-enabled when finish_fork_handler is entered by fork_tramp hitting
 193  * itself with a SIGUSR1.  set_user_mode has to be run with SIGUSR1 off,
 194  * so it is blocked before it's called.  They are re-enabled on sigreturn
 195  * despite the fact that they were blocked when the SIGUSR1 was issued because
 196  * copy_thread copies the parent's sigcontext, including the signal mask
 197  * onto the signal frame.
 198  */
 199
 200 void finish_fork_handler(int sig)
 201 {
 202         UPT_SC(&current->thread.regs.regs) = (void *) (&sig + 1);
 203         suspend_new_thread(current->thread.mode.tt.switch_pipe[0]);
 204
 205         force_flush_all();
 206         if(current->thread.prev_sched != NULL)
 207                 schedule_tail(current->thread.prev_sched);
 208         current->thread.prev_sched = NULL;
 209
 210         enable_timer();
 211         change_sig(SIGVTALRM, 1);
 212         local_irq_enable();
 213         if(current->mm != current->parent->mm)
 214                 protect_memory(uml_reserved, high_physmem - uml_reserved, 1,
 215                                1, 0, 1);
 216         task_protections((unsigned long) current_thread);
 217
 218         free_page(current->thread.temp_stack);
 219         local_irq_disable();
 220         change_sig(SIGUSR1, 0);
 221         set_user_mode(current);
 222 }
 223
 224 int fork_tramp(void *stack)
 225 {
 226         local_irq_disable();
 227         arch_init_thread();
 228         init_new_thread_stack(stack, finish_fork_handler);
 229
 230         os_usr1_process(os_getpid());
 231         change_sig(SIGUSR1, 1);
 232         return(0);
 233 }
 234
 235 int copy_thread_tt(int nr, unsigned long clone_flags, unsigned long sp,
 236                    unsigned long stack_top, struct task_struct * p,
 237                    struct pt_regs *regs)
 238 {
 239         int (*tramp)(void *);
 240         int new_pid, err;
 241         unsigned long stack;
 242
 243         if(current->thread.forking)
 244                 tramp = fork_tramp;
 245         else {
 246                 tramp = new_thread_proc;
 247                 p->thread.request.u.thread = current->thread.request.u.thread;
 248         }
 249
 250         err = os_pipe(p->thread.mode.tt.switch_pipe, 1, 1);
 251         if(err < 0){
 252                 printk("copy_thread : pipe failed, err = %d\n", -err);
 253                 return(err);
 254         }
 255
 256         stack = alloc_stack(0, 0);
 257         if(stack == 0){
 258                 printk(KERN_ERR "copy_thread : failed to allocate "
 259                        "temporary stack\n");
 260                 return(-ENOMEM);
 261         }
 262
 263         clone_flags &= CLONE_VM;
 264         p->thread.temp_stack = stack;
 265         new_pid = start_fork_tramp(p->thread_info, stack, clone_flags, tramp);
 266         if(new_pid < 0){
 267                 printk(KERN_ERR "copy_thread : clone failed - errno = %d\n",
 268                        -new_pid);
 269                 return(new_pid);
 270         }
 271
 272         if(current->thread.forking){
 273                 sc_to_sc(UPT_SC(&p->thread.regs.regs),
 274                          UPT_SC(&current->thread.regs.regs));
 275                 SC_SET_SYSCALL_RETURN(UPT_SC(&p->thread.regs.regs), 0);
 276                 if(sp != 0) SC_SP(UPT_SC(&p->thread.regs.regs)) = sp;
 277         }
 278         p->thread.mode.tt.extern_pid = new_pid;
 279
 280         current->thread.request.op = OP_FORK;
 281         current->thread.request.u.fork.pid = new_pid;
 282         os_usr1_process(os_getpid());
 283
 284         /* Enable the signal and then disable it to ensure that it is handled
 285          * here, and nowhere else.
 286          */
 287         change_sig(SIGUSR1, 1);
 288
 289         change_sig(SIGUSR1, 0);
 290         err = 0;
 291         return(err);
 292 }
 293
 294 void reboot_tt(void)
 295 {
 296         current->thread.request.op = OP_REBOOT;
 297         os_usr1_process(os_getpid());
 298         change_sig(SIGUSR1, 1);
 299 }
 300
 301 void halt_tt(void)
 302 {
 303         current->thread.request.op = OP_HALT;
 304         os_usr1_process(os_getpid());
 305         change_sig(SIGUSR1, 1);
 306 }
 307
 308 void kill_off_processes_tt(void)
 309 {
 310         struct task_struct *p;
 311         int me;
 312
 313         me = os_getpid();
 314         for_each_process(p){
 315                 if(p->thread.mode.tt.extern_pid != me)
 316                         os_kill_process(p->thread.mode.tt.extern_pid, 0);
 317         }
 318         if(init_task.thread.mode.tt.extern_pid != me)
 319                 os_kill_process(init_task.thread.mode.tt.extern_pid, 0);
 320 }
 321
 322 void initial_thread_cb_tt(void (*proc)(void *), void *arg)
 323 {
 324         if(os_getpid() == tracing_pid){
 325                 (*proc)(arg);
 326         }
 327         else {
 328                 current->thread.request.op = OP_CB;
 329                 current->thread.request.u.cb.proc = proc;
 330                 current->thread.request.u.cb.arg = arg;
 331                 os_usr1_process(os_getpid());
 332                 change_sig(SIGUSR1, 1);
 333
 334                 change_sig(SIGUSR1, 0);
 335         }
 336 }
 337
 338 int do_proc_op(void *t, int proc_id)
 339 {
 340         struct task_struct *task;
 341         struct thread_struct *thread;
 342         int op, pid;
 343
 344         task = t;
 345         thread = &task->thread;
 346         op = thread->request.op;
 347         switch(op){
 348         case OP_NONE:
 349         case OP_TRACE_ON:
 350                 break;
 351         case OP_EXEC:
 352                 pid = thread->request.u.exec.pid;
 353                 do_exec(thread->mode.tt.extern_pid, pid);
 354                 thread->mode.tt.extern_pid = pid;
 355                 cpu_tasks[task->thread_info->cpu].pid = pid;
 356                 break;
 357         case OP_FORK:
 358                 attach_process(thread->request.u.fork.pid);
 359                 break;
 360         case OP_CB:
 361                 (*thread->request.u.cb.proc)(thread->request.u.cb.arg);
 362                 break;
 363         case OP_REBOOT:
 364         case OP_HALT:
 365                 break;
 366         default:
 367                 tracer_panic("Bad op in do_proc_op");
 368                 break;
 369         }
 370         thread->request.op = OP_NONE;
 371         return(op);
 372 }
 373
 374 void init_idle_tt(void)
 375 {
 376         default_idle();
 377 }
 378
 379 extern void start_kernel(void);
 380
 381 static int start_kernel_proc(void *unused)
 382 {
 383         int pid;
 384
 385         block_signals();
 386         pid = os_getpid();
 387
 388         cpu_tasks[0].pid = pid;
 389         cpu_tasks[0].task = current;
 390 #ifdef CONFIG_SMP
 391         cpu_online_map = cpumask_of_cpu(0);
 392 #endif
 393         if(debug) os_stop_process(pid);
 394         start_kernel();
 395         return(0);
 396 }
 397
 398 void set_tracing(void *task, int tracing)
 399 {
 400         ((struct task_struct *) task)->thread.mode.tt.tracing = tracing;
 401 }
 402
 403 int is_tracing(void *t)
 404 {
 405         return (((struct task_struct *) t)->thread.mode.tt.tracing);
 406 }
 407
 408 int set_user_mode(void *t)
 409 {
 410         struct task_struct *task;
 411
 412         task = t ? t : current;
 413         if(task->thread.mode.tt.tracing)
 414                 return(1);
 415         task->thread.request.op = OP_TRACE_ON;
 416         os_usr1_process(os_getpid());
 417         return(0);
 418 }
 419
 420 void set_init_pid(int pid)
 421 {
 422         int err;
 423
 424         init_task.thread.mode.tt.extern_pid = pid;
 425         err = os_pipe(init_task.thread.mode.tt.switch_pipe, 1, 1);
 426         if(err)
 427                 panic("Can't create switch pipe for init_task, errno = %d",
 428                       -err);
 429 }
 430
 431 int start_uml_tt(void)
 432 {
 433         void *sp;
 434         int pages;
 435
 436         pages = (1 << CONFIG_KERNEL_STACK_ORDER);
 437         sp = (void *) ((unsigned long) init_task.thread_info) +
 438                 pages * PAGE_SIZE - sizeof(unsigned long);
 439         return(tracer(start_kernel_proc, sp));
 440 }
 441
 442 int external_pid_tt(struct task_struct *task)
 443 {
 444         return(task->thread.mode.tt.extern_pid);
 445 }
 446
 447 int thread_pid_tt(struct task_struct *task)
 448 {
 449         return(task->thread.mode.tt.extern_pid);
 450 }
 451
 452 int is_valid_pid(int pid)
 453 {
 454         struct task_struct *task;
 455
 456         read_lock(&tasklist_lock);
 457         for_each_process(task){
 458                 if(task->thread.mode.tt.extern_pid == pid){
 459                         read_unlock(&tasklist_lock);
 460                         return(1);
 461                 }
 462         }
 463         read_unlock(&tasklist_lock);
 464         return(0);
 465 }
 466
 467 /*
 468  * Overrides for Emacs so that we follow Linus's tabbing style.
 469  * Emacs will notice this stuff at the end of the file and automatically
 470  * adjust the settings for this buffer only.  This must remain at the end
 471  * of the file.
 472  * ---------------------------------------------------------------------------
 473  * Local variables:
 474  * c-file-style: "linux"
 475  * End:
 476  */