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