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  56          * "to", and can't use any more the value of "from" (which is outdated),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