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         /* This works around a nasty race with 'jail'.  If we are switching
  89          * between two threads of a threaded app and the incoming process
  90          * runs before the outgoing process reaches the read, and it makes
  91          * it all the way out to userspace, then it will have write-protected
  92          * the outgoing process stack.  Then, when the outgoing process
  93          * returns from the write, it will segfault because it can no longer
  94          * write its own stack.  So, in order to avoid that, the incoming
  95          * thread sits in a loop yielding until 'reading' is set.  This
  96          * isn't entirely safe, since there may be a reschedule from a timer
  97          * happening between setting 'reading' and sleeping in read.  But,
  98          * it should get a whole quantum in which to reach the read and sleep,
  99          * which should be enough.
 100          */
 101
 102         if(jail){
 103                 while(!reading) sched_yield();
 104         }
 105
 106         change_sig(SIGVTALRM, vtalrm);
 107         change_sig(SIGALRM, alrm);
 108         change_sig(SIGPROF, prof);
 109
 110         arch_switch();
 111
 112         flush_tlb_all();
 113         local_irq_restore(flags);
 114
 115         return(current->thread.prev_sched);
 116 }
 117
 118 void release_thread_tt(struct task_struct *task)
 119 {
 120         int pid = task->thread.mode.tt.extern_pid;
 121
 122         if(os_getpid() != pid)
 123                 os_kill_process(pid, 0);
 124 }
 125
 126 void exit_thread_tt(void)
 127 {
 128         os_close_file(current->thread.mode.tt.switch_pipe[0]);
 129         os_close_file(current->thread.mode.tt.switch_pipe[1]);
 130 }
 131
 132 void suspend_new_thread(int fd)
 133 {
 134         int err;
 135         char c;
 136
 137         os_stop_process(os_getpid());
 138         err = os_read_file(fd, &c, sizeof(c));
 139         if(err != sizeof(c))
 140                 panic("read failed in suspend_new_thread, err = %d", -err);
 141 }
 142
 143 void schedule_tail(task_t *prev);
 144
 145 static void new_thread_handler(int sig)
 146 {
 147         unsigned long disable;
 148         int (*fn)(void *);
 149         void *arg;
 150
 151         fn = current->thread.request.u.thread.proc;
 152         arg = current->thread.request.u.thread.arg;
 153
 154         UPT_SC(&current->thread.regs.regs) = (void *) (&sig + 1);
 155         disable = (1 << (SIGVTALRM - 1)) | (1 << (SIGALRM - 1)) |
 156                 (1 << (SIGIO - 1)) | (1 << (SIGPROF - 1));
 157         SC_SIGMASK(UPT_SC(&current->thread.regs.regs)) &= ~disable;
 158
 159         suspend_new_thread(current->thread.mode.tt.switch_pipe[0]);
 160
 161         force_flush_all();
 162         if(current->thread.prev_sched != NULL)
 163                 schedule_tail(current->thread.prev_sched);
 164         current->thread.prev_sched = NULL;
 165
 166         init_new_thread_signals(1);
 167         enable_timer();
 168         free_page(current->thread.temp_stack);
 169         set_cmdline("(kernel thread)");
 170
 171         change_sig(SIGUSR1, 1);
 172         change_sig(SIGVTALRM, 1);
 173         change_sig(SIGPROF, 1);
 174         local_irq_enable();
 175         if(!run_kernel_thread(fn, arg, &current->thread.exec_buf))
 176                 do_exit(0);
 177
 178         /* XXX No set_user_mode here because a newly execed process will
 179          * immediately segfault on its non-existent IP, coming straight back
 180          * to the signal handler, which will call set_user_mode on its way
 181          * out.  This should probably change since it's confusing.
 182          */
 183 }
 184
 185 static int new_thread_proc(void *stack)
 186 {
 187         /* local_irq_disable is needed to block out signals until this thread is
 188          * properly scheduled.  Otherwise, the tracing thread will get mighty
 189          * upset about any signals that arrive before that.
 190          * This has the complication that it sets the saved signal mask in
 191          * the sigcontext to block signals.  This gets restored when this
 192          * thread (or a descendant, since they get a copy of this sigcontext)
 193          * returns to userspace.
 194          * So, this is compensated for elsewhere.
 195          * XXX There is still a small window until local_irq_disable() actually
 196          * finishes where signals are possible - shouldn't be a problem in
 197          * practice since SIGIO hasn't been forwarded here yet, and the
 198          * local_irq_disable should finish before a SIGVTALRM has time to be
 199          * delivered.
 200          */
 201
 202         local_irq_disable();
 203         init_new_thread_stack(stack, new_thread_handler);
 204         os_usr1_process(os_getpid());
 205         change_sig(SIGUSR1, 1);
 206         return(0);
 207 }
 208
 209 /* Signal masking - signals are blocked at the start of fork_tramp.  They
 210  * are re-enabled when finish_fork_handler is entered by fork_tramp hitting
 211  * itself with a SIGUSR1.  set_user_mode has to be run with SIGUSR1 off,
 212  * so it is blocked before it's called.  They are re-enabled on sigreturn
 213  * despite the fact that they were blocked when the SIGUSR1 was issued because
 214  * copy_thread copies the parent's sigcontext, including the signal mask
 215  * onto the signal frame.
 216  */
 217
 218 void finish_fork_handler(int sig)
 219 {
 220         UPT_SC(&current->thread.regs.regs) = (void *) (&sig + 1);
 221         suspend_new_thread(current->thread.mode.tt.switch_pipe[0]);
 222
 223         force_flush_all();
 224         if(current->thread.prev_sched != NULL)
 225                 schedule_tail(current->thread.prev_sched);
 226         current->thread.prev_sched = NULL;
 227
 228         enable_timer();
 229         change_sig(SIGVTALRM, 1);
 230         local_irq_enable();
 231         if(current->mm != current->parent->mm)
 232                 protect_memory(uml_reserved, high_physmem - uml_reserved, 1,
 233                                1, 0, 1);
 234         task_protections((unsigned long) current_thread);
 235
 236         free_page(current->thread.temp_stack);
 237         local_irq_disable();
 238         change_sig(SIGUSR1, 0);
 239         set_user_mode(current);
 240 }
 241
 242 int fork_tramp(void *stack)
 243 {
 244         local_irq_disable();
 245         arch_init_thread();
 246         init_new_thread_stack(stack, finish_fork_handler);
 247
 248         os_usr1_process(os_getpid());
 249         change_sig(SIGUSR1, 1);
 250         return(0);
 251 }
 252
 253 int copy_thread_tt(int nr, unsigned long clone_flags, unsigned long sp,
 254                    unsigned long stack_top, struct task_struct * p,
 255                    struct pt_regs *regs)
 256 {
 257         int (*tramp)(void *);
 258         int new_pid, err;
 259         unsigned long stack;
 260
 261         if(current->thread.forking)
 262                 tramp = fork_tramp;
 263         else {
 264                 tramp = new_thread_proc;
 265                 p->thread.request.u.thread = current->thread.request.u.thread;
 266         }
 267
 268         err = os_pipe(p->thread.mode.tt.switch_pipe, 1, 1);
 269         if(err < 0){
 270                 printk("copy_thread : pipe failed, err = %d\n", -err);
 271                 return(err);
 272         }
 273
 274         stack = alloc_stack(0, 0);
 275         if(stack == 0){
 276                 printk(KERN_ERR "copy_thread : failed to allocate "
 277                        "temporary stack\n");
 278                 return(-ENOMEM);
 279         }
 280
 281         clone_flags &= CLONE_VM;
 282         p->thread.temp_stack = stack;
 283         new_pid = start_fork_tramp(p->thread_info, stack, clone_flags, tramp);
 284         if(new_pid < 0){
 285                 printk(KERN_ERR "copy_thread : clone failed - errno = %d\n",
 286                        -new_pid);
 287                 return(new_pid);
 288         }
 289
 290         if(current->thread.forking){
 291                 sc_to_sc(UPT_SC(&p->thread.regs.regs),
 292                          UPT_SC(&current->thread.regs.regs));
 293                 SC_SET_SYSCALL_RETURN(UPT_SC(&p->thread.regs.regs), 0);
 294                 if(sp != 0) SC_SP(UPT_SC(&p->thread.regs.regs)) = sp;
 295         }
 296         p->thread.mode.tt.extern_pid = new_pid;
 297
 298         current->thread.request.op = OP_FORK;
 299         current->thread.request.u.fork.pid = new_pid;
 300         os_usr1_process(os_getpid());
 301
 302         /* Enable the signal and then disable it to ensure that it is handled
 303          * here, and nowhere else.
 304          */
 305         change_sig(SIGUSR1, 1);
 306
 307         change_sig(SIGUSR1, 0);
 308         err = 0;
 309         return(err);
 310 }
 311
 312 void reboot_tt(void)
 313 {
 314         current->thread.request.op = OP_REBOOT;
 315         os_usr1_process(os_getpid());
 316         change_sig(SIGUSR1, 1);
 317 }
 318
 319 void halt_tt(void)
 320 {
 321         current->thread.request.op = OP_HALT;
 322         os_usr1_process(os_getpid());
 323         change_sig(SIGUSR1, 1);
 324 }
 325
 326 void kill_off_processes_tt(void)
 327 {
 328         struct task_struct *p;
 329         int me;
 330
 331         me = os_getpid();
 332         for_each_process(p){
 333                 if(p->thread.mode.tt.extern_pid != me)
 334                         os_kill_process(p->thread.mode.tt.extern_pid, 0);
 335         }
 336         if(init_task.thread.mode.tt.extern_pid != me)
 337                 os_kill_process(init_task.thread.mode.tt.extern_pid, 0);
 338 }
 339
 340 void initial_thread_cb_tt(void (*proc)(void *), void *arg)
 341 {
 342         if(os_getpid() == tracing_pid){
 343                 (*proc)(arg);
 344         }
 345         else {
 346                 current->thread.request.op = OP_CB;
 347                 current->thread.request.u.cb.proc = proc;
 348                 current->thread.request.u.cb.arg = arg;
 349                 os_usr1_process(os_getpid());
 350                 change_sig(SIGUSR1, 1);
 351
 352                 change_sig(SIGUSR1, 0);
 353         }
 354 }
 355
 356 int do_proc_op(void *t, int proc_id)
 357 {
 358         struct task_struct *task;
 359         struct thread_struct *thread;
 360         int op, pid;
 361
 362         task = t;
 363         thread = &task->thread;
 364         op = thread->request.op;
 365         switch(op){
 366         case OP_NONE:
 367         case OP_TRACE_ON:
 368                 break;
 369         case OP_EXEC:
 370                 pid = thread->request.u.exec.pid;
 371                 do_exec(thread->mode.tt.extern_pid, pid);
 372                 thread->mode.tt.extern_pid = pid;
 373                 cpu_tasks[task->thread_info->cpu].pid = pid;
 374                 break;
 375         case OP_FORK:
 376                 attach_process(thread->request.u.fork.pid);
 377                 break;
 378         case OP_CB:
 379                 (*thread->request.u.cb.proc)(thread->request.u.cb.arg);
 380                 break;
 381         case OP_REBOOT:
 382         case OP_HALT:
 383                 break;
 384         default:
 385                 tracer_panic("Bad op in do_proc_op");
 386                 break;
 387         }
 388         thread->request.op = OP_NONE;
 389         return(op);
 390 }
 391
 392 void init_idle_tt(void)
 393 {
 394         default_idle();
 395 }
 396
 397 /* Changed by jail_setup, which is a setup */
 398 int jail = 0;
 399
 400 int __init jail_setup(char *line, int *add)
 401 {
 402         int ok = 1;
 403
 404         if(jail) return(0);
 405 #ifdef CONFIG_SMP
 406         printf("'jail' may not used used in a kernel with CONFIG_SMP "
 407                "enabled\n");
 408         ok = 0;
 409 #endif
 410 #ifdef CONFIG_HOSTFS
 411         printf("'jail' may not used used in a kernel with CONFIG_HOSTFS "
 412                "enabled\n");
 413         ok = 0;
 414 #endif
 415 #ifdef CONFIG_MODULES
 416         printf("'jail' may not used used in a kernel with CONFIG_MODULES "
 417                "enabled\n");
 418         ok = 0;
 419 #endif
 420         if(!ok) exit(1);
 421
 422         /* CAP_SYS_RAWIO controls the ability to open /dev/mem and /dev/kmem.
 423          * Removing it from the bounding set eliminates the ability of anything
 424          * to acquire it, and thus read or write kernel memory.
 425          */
 426         cap_lower(cap_bset, CAP_SYS_RAWIO);
 427         jail = 1;
 428         return(0);
 429 }
 430
 431 __uml_setup("jail", jail_setup,
 432 "jail\n"
 433 "    Enables the protection of kernel memory from processes.\n\n"
 434 );
 435
 436 static void mprotect_kernel_mem(int w)
 437 {
 438         unsigned long start, end;
 439         int pages;
 440
 441         if(!jail || (current == &init_task)) return;
 442
 443         pages = (1 << CONFIG_KERNEL_STACK_ORDER);
 444
 445         start = (unsigned long) current_thread + PAGE_SIZE;
 446         end = (unsigned long) current_thread + PAGE_SIZE * pages;
 447         protect_memory(uml_reserved, start - uml_reserved, 1, w, 1, 1);
 448         protect_memory(end, high_physmem - end, 1, w, 1, 1);
 449
 450         start = (unsigned long) UML_ROUND_DOWN(&_stext);
 451         end = (unsigned long) UML_ROUND_UP(&_etext);
 452         protect_memory(start, end - start, 1, w, 1, 1);
 453
 454         start = (unsigned long) UML_ROUND_DOWN(&_unprotected_end);
 455         end = (unsigned long) UML_ROUND_UP(&_edata);
 456         protect_memory(start, end - start, 1, w, 1, 1);
 457
 458         start = (unsigned long) UML_ROUND_DOWN(&__bss_start);
 459         end = (unsigned long) UML_ROUND_UP(brk_start);
 460         protect_memory(start, end - start, 1, w, 1, 1);
 461
 462         mprotect_kernel_vm(w);
 463 }
 464
 465 void unprotect_kernel_mem(void)
 466 {
 467         mprotect_kernel_mem(1);
 468 }
 469
 470 void protect_kernel_mem(void)
 471 {
 472         mprotect_kernel_mem(0);
 473 }
 474
 475 extern void start_kernel(void);
 476
 477 static int start_kernel_proc(void *unused)
 478 {
 479         int pid;
 480
 481         block_signals();
 482         pid = os_getpid();
 483
 484         cpu_tasks[0].pid = pid;
 485         cpu_tasks[0].task = current;
 486 #ifdef CONFIG_SMP
 487         cpu_online_map = cpumask_of_cpu(0);
 488 #endif
 489         if(debug) os_stop_process(pid);
 490         start_kernel();
 491         return(0);
 492 }
 493
 494 void set_tracing(void *task, int tracing)
 495 {
 496         ((struct task_struct *) task)->thread.mode.tt.tracing = tracing;
 497 }
 498
 499 int is_tracing(void *t)
 500 {
 501         return (((struct task_struct *) t)->thread.mode.tt.tracing);
 502 }
 503
 504 int set_user_mode(void *t)
 505 {
 506         struct task_struct *task;
 507
 508         task = t ? t : current;
 509         if(task->thread.mode.tt.tracing)
 510                 return(1);
 511         task->thread.request.op = OP_TRACE_ON;
 512         os_usr1_process(os_getpid());
 513         return(0);
 514 }
 515
 516 void set_init_pid(int pid)
 517 {
 518         int err;
 519
 520         init_task.thread.mode.tt.extern_pid = pid;
 521         err = os_pipe(init_task.thread.mode.tt.switch_pipe, 1, 1);
 522         if(err)
 523                 panic("Can't create switch pipe for init_task, errno = %d",
 524                       -err);
 525 }
 526
 527 int start_uml_tt(void)
 528 {
 529         void *sp;
 530         int pages;
 531
 532         pages = (1 << CONFIG_KERNEL_STACK_ORDER);
 533         sp = (void *) ((unsigned long) init_task.thread_info) +
 534                 pages * PAGE_SIZE - sizeof(unsigned long);
 535         return(tracer(start_kernel_proc, sp));
 536 }
 537
 538 int external_pid_tt(struct task_struct *task)
 539 {
 540         return(task->thread.mode.tt.extern_pid);
 541 }
 542
 543 int thread_pid_tt(struct task_struct *task)
 544 {
 545         return(task->thread.mode.tt.extern_pid);
 546 }
 547
 548 int is_valid_pid(int pid)
 549 {
 550         struct task_struct *task;
 551
 552         read_lock(&tasklist_lock);
 553         for_each_process(task){
 554                 if(task->thread.mode.tt.extern_pid == pid){
 555                         read_unlock(&tasklist_lock);
 556                         return(1);
 557                 }
 558         }
 559         read_unlock(&tasklist_lock);
 560         return(0);
 561 }
 562
 563 /*
 564  * Overrides for Emacs so that we follow Linus's tabbing style.
 565  * Emacs will notice this stuff at the end of the file and automatically
 566  * adjust the settings for this buffer only.  This must remain at the end
 567  * of the file.
 568  * ---------------------------------------------------------------------------
 569  * Local variables:
 570  * c-file-style: "linux"
 571  * End:
 572  */