Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland...
[linux-2.6] / arch / um / os-Linux / skas / process.c
1 /*
2  * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3  * Licensed under the GPL
4  */
5
6 #include <stdlib.h>
7 #include <unistd.h>
8 #include <sched.h>
9 #include <errno.h>
10 #include <string.h>
11 #include <sys/mman.h>
12 #include <sys/ptrace.h>
13 #include <sys/wait.h>
14 #include <asm/unistd.h>
15 #include "as-layout.h"
16 #include "chan_user.h"
17 #include "kern_constants.h"
18 #include "kern_util.h"
19 #include "mem.h"
20 #include "os.h"
21 #include "process.h"
22 #include "proc_mm.h"
23 #include "ptrace_user.h"
24 #include "registers.h"
25 #include "skas.h"
26 #include "skas_ptrace.h"
27 #include "user.h"
28 #include "sysdep/stub.h"
29
30 int is_skas_winch(int pid, int fd, void *data)
31 {
32         if (pid != getpgrp())
33                 return 0;
34
35         register_winch_irq(-1, fd, -1, data, 0);
36         return 1;
37 }
38
39 static int ptrace_dump_regs(int pid)
40 {
41         unsigned long regs[MAX_REG_NR];
42         int i;
43
44         if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
45                 return -errno;
46
47         printk(UM_KERN_ERR "Stub registers -\n");
48         for (i = 0; i < ARRAY_SIZE(regs); i++)
49                 printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]);
50
51         return 0;
52 }
53
54 /*
55  * Signals that are OK to receive in the stub - we'll just continue it.
56  * SIGWINCH will happen when UML is inside a detached screen.
57  */
58 #define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
59
60 /* Signals that the stub will finish with - anything else is an error */
61 #define STUB_DONE_MASK (1 << SIGTRAP)
62
63 void wait_stub_done(int pid)
64 {
65         int n, status, err;
66
67         while (1) {
68                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
69                 if ((n < 0) || !WIFSTOPPED(status))
70                         goto bad_wait;
71
72                 if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
73                         break;
74
75                 err = ptrace(PTRACE_CONT, pid, 0, 0);
76                 if (err) {
77                         printk(UM_KERN_ERR "wait_stub_done : continue failed, "
78                                "errno = %d\n", errno);
79                         fatal_sigsegv();
80                 }
81         }
82
83         if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
84                 return;
85
86 bad_wait:
87         err = ptrace_dump_regs(pid);
88         if (err)
89                 printk(UM_KERN_ERR "Failed to get registers from stub, "
90                        "errno = %d\n", -err);
91         printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
92                "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
93                status);
94         fatal_sigsegv();
95 }
96
97 extern unsigned long current_stub_stack(void);
98
99 void get_skas_faultinfo(int pid, struct faultinfo * fi)
100 {
101         int err;
102
103         if (ptrace_faultinfo) {
104                 err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
105                 if (err) {
106                         printk(UM_KERN_ERR "get_skas_faultinfo - "
107                                "PTRACE_FAULTINFO failed, errno = %d\n", errno);
108                         fatal_sigsegv();
109                 }
110
111                 /* Special handling for i386, which has different structs */
112                 if (sizeof(struct ptrace_faultinfo) < sizeof(struct faultinfo))
113                         memset((char *)fi + sizeof(struct ptrace_faultinfo), 0,
114                                sizeof(struct faultinfo) -
115                                sizeof(struct ptrace_faultinfo));
116         }
117         else {
118                 unsigned long fpregs[FP_SIZE];
119
120                 err = get_fp_registers(pid, fpregs);
121                 if (err < 0) {
122                         printk(UM_KERN_ERR "save_fp_registers returned %d\n",
123                                err);
124                         fatal_sigsegv();
125                 }
126                 err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
127                 if (err) {
128                         printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
129                                "errno = %d\n", pid, errno);
130                         fatal_sigsegv();
131                 }
132                 wait_stub_done(pid);
133
134                 /*
135                  * faultinfo is prepared by the stub-segv-handler at start of
136                  * the stub stack page. We just have to copy it.
137                  */
138                 memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
139
140                 err = put_fp_registers(pid, fpregs);
141                 if (err < 0) {
142                         printk(UM_KERN_ERR "put_fp_registers returned %d\n",
143                                err);
144                         fatal_sigsegv();
145                 }
146         }
147 }
148
149 static void handle_segv(int pid, struct uml_pt_regs * regs)
150 {
151         get_skas_faultinfo(pid, &regs->faultinfo);
152         segv(regs->faultinfo, 0, 1, NULL);
153 }
154
155 /*
156  * To use the same value of using_sysemu as the caller, ask it that value
157  * (in local_using_sysemu
158  */
159 static void handle_trap(int pid, struct uml_pt_regs *regs,
160                         int local_using_sysemu)
161 {
162         int err, status;
163
164         if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
165                 fatal_sigsegv();
166
167         /* Mark this as a syscall */
168         UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
169
170         if (!local_using_sysemu)
171         {
172                 err = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
173                              __NR_getpid);
174                 if (err < 0) {
175                         printk(UM_KERN_ERR "handle_trap - nullifying syscall "
176                                "failed, errno = %d\n", errno);
177                         fatal_sigsegv();
178                 }
179
180                 err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
181                 if (err < 0) {
182                         printk(UM_KERN_ERR "handle_trap - continuing to end of "
183                                "syscall failed, errno = %d\n", errno);
184                         fatal_sigsegv();
185                 }
186
187                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
188                 if ((err < 0) || !WIFSTOPPED(status) ||
189                     (WSTOPSIG(status) != SIGTRAP + 0x80)) {
190                         err = ptrace_dump_regs(pid);
191                         if (err)
192                                 printk(UM_KERN_ERR "Failed to get registers "
193                                        "from process, errno = %d\n", -err);
194                         printk(UM_KERN_ERR "handle_trap - failed to wait at "
195                                "end of syscall, errno = %d, status = %d\n",
196                                errno, status);
197                         fatal_sigsegv();
198                 }
199         }
200
201         handle_syscall(regs);
202 }
203
204 extern int __syscall_stub_start;
205
206 static int userspace_tramp(void *stack)
207 {
208         void *addr;
209         int err;
210
211         ptrace(PTRACE_TRACEME, 0, 0, 0);
212
213         signal(SIGTERM, SIG_DFL);
214         signal(SIGWINCH, SIG_IGN);
215         err = set_interval();
216         if (err) {
217                 printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
218                        "errno = %d\n", err);
219                 exit(1);
220         }
221
222         if (!proc_mm) {
223                 /*
224                  * This has a pte, but it can't be mapped in with the usual
225                  * tlb_flush mechanism because this is part of that mechanism
226                  */
227                 int fd;
228                 unsigned long long offset;
229                 fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
230                 addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
231                               PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
232                 if (addr == MAP_FAILED) {
233                         printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
234                                "errno = %d\n", STUB_CODE, errno);
235                         exit(1);
236                 }
237
238                 if (stack != NULL) {
239                         fd = phys_mapping(to_phys(stack), &offset);
240                         addr = mmap((void *) STUB_DATA,
241                                     UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
242                                     MAP_FIXED | MAP_SHARED, fd, offset);
243                         if (addr == MAP_FAILED) {
244                                 printk(UM_KERN_ERR "mapping segfault stack "
245                                        "at 0x%lx failed, errno = %d\n",
246                                        STUB_DATA, errno);
247                                 exit(1);
248                         }
249                 }
250         }
251         if (!ptrace_faultinfo && (stack != NULL)) {
252                 struct sigaction sa;
253
254                 unsigned long v = STUB_CODE +
255                                   (unsigned long) stub_segv_handler -
256                                   (unsigned long) &__syscall_stub_start;
257
258                 set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
259                 sigemptyset(&sa.sa_mask);
260                 sa.sa_flags = SA_ONSTACK | SA_NODEFER;
261                 sa.sa_handler = (void *) v;
262                 sa.sa_restorer = NULL;
263                 if (sigaction(SIGSEGV, &sa, NULL) < 0) {
264                         printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
265                                "handler failed - errno = %d\n", errno);
266                         exit(1);
267                 }
268         }
269
270         kill(os_getpid(), SIGSTOP);
271         return 0;
272 }
273
274 /* Each element set once, and only accessed by a single processor anyway */
275 #undef NR_CPUS
276 #define NR_CPUS 1
277 int userspace_pid[NR_CPUS];
278
279 int start_userspace(unsigned long stub_stack)
280 {
281         void *stack;
282         unsigned long sp;
283         int pid, status, n, flags, err;
284
285         stack = mmap(NULL, UM_KERN_PAGE_SIZE,
286                      PROT_READ | PROT_WRITE | PROT_EXEC,
287                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
288         if (stack == MAP_FAILED) {
289                 err = -errno;
290                 printk(UM_KERN_ERR "start_userspace : mmap failed, "
291                        "errno = %d\n", errno);
292                 return err;
293         }
294
295         sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
296
297         flags = CLONE_FILES;
298         if (proc_mm)
299                 flags |= CLONE_VM;
300         else
301                 flags |= SIGCHLD;
302
303         pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
304         if (pid < 0) {
305                 err = -errno;
306                 printk(UM_KERN_ERR "start_userspace : clone failed, "
307                        "errno = %d\n", errno);
308                 return err;
309         }
310
311         do {
312                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
313                 if (n < 0) {
314                         err = -errno;
315                         printk(UM_KERN_ERR "start_userspace : wait failed, "
316                                "errno = %d\n", errno);
317                         goto out_kill;
318                 }
319         } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
320
321         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
322                 err = -EINVAL;
323                 printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
324                        "status = %d\n", status);
325                 goto out_kill;
326         }
327
328         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
329                    (void *) PTRACE_O_TRACESYSGOOD) < 0) {
330                 err = -errno;
331                 printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
332                        "failed, errno = %d\n", errno);
333                 goto out_kill;
334         }
335
336         if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
337                 err = -errno;
338                 printk(UM_KERN_ERR "start_userspace : munmap failed, "
339                        "errno = %d\n", errno);
340                 goto out_kill;
341         }
342
343         return pid;
344
345  out_kill:
346         os_kill_ptraced_process(pid, 1);
347         return err;
348 }
349
350 void userspace(struct uml_pt_regs *regs)
351 {
352         struct itimerval timer;
353         unsigned long long nsecs, now;
354         int err, status, op, pid = userspace_pid[0];
355         /* To prevent races if using_sysemu changes under us.*/
356         int local_using_sysemu;
357
358         if (getitimer(ITIMER_VIRTUAL, &timer))
359                 printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
360         nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
361                 timer.it_value.tv_usec * UM_NSEC_PER_USEC;
362         nsecs += os_nsecs();
363
364         while (1) {
365                 /*
366                  * This can legitimately fail if the process loads a
367                  * bogus value into a segment register.  It will
368                  * segfault and PTRACE_GETREGS will read that value
369                  * out of the process.  However, PTRACE_SETREGS will
370                  * fail.  In this case, there is nothing to do but
371                  * just kill the process.
372                  */
373                 if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
374                         fatal_sigsegv();
375
376                 /* Now we set local_using_sysemu to be used for one loop */
377                 local_using_sysemu = get_using_sysemu();
378
379                 op = SELECT_PTRACE_OPERATION(local_using_sysemu,
380                                              singlestepping(NULL));
381
382                 if (ptrace(op, pid, 0, 0)) {
383                         printk(UM_KERN_ERR "userspace - ptrace continue "
384                                "failed, op = %d, errno = %d\n", op, errno);
385                         fatal_sigsegv();
386                 }
387
388                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
389                 if (err < 0) {
390                         printk(UM_KERN_ERR "userspace - wait failed, "
391                                "errno = %d\n", errno);
392                         fatal_sigsegv();
393                 }
394
395                 regs->is_user = 1;
396                 if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
397                         printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
398                                "errno = %d\n", errno);
399                         fatal_sigsegv();
400                 }
401
402                 UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
403
404                 if (WIFSTOPPED(status)) {
405                         int sig = WSTOPSIG(status);
406                         switch (sig) {
407                         case SIGSEGV:
408                                 if (PTRACE_FULL_FAULTINFO ||
409                                     !ptrace_faultinfo) {
410                                         get_skas_faultinfo(pid,
411                                                            &regs->faultinfo);
412                                         (*sig_info[SIGSEGV])(SIGSEGV, regs);
413                                 }
414                                 else handle_segv(pid, regs);
415                                 break;
416                         case SIGTRAP + 0x80:
417                                 handle_trap(pid, regs, local_using_sysemu);
418                                 break;
419                         case SIGTRAP:
420                                 relay_signal(SIGTRAP, regs);
421                                 break;
422                         case SIGVTALRM:
423                                 now = os_nsecs();
424                                 if (now < nsecs)
425                                         break;
426                                 block_signals();
427                                 (*sig_info[sig])(sig, regs);
428                                 unblock_signals();
429                                 nsecs = timer.it_value.tv_sec *
430                                         UM_NSEC_PER_SEC +
431                                         timer.it_value.tv_usec *
432                                         UM_NSEC_PER_USEC;
433                                 nsecs += os_nsecs();
434                                 break;
435                         case SIGIO:
436                         case SIGILL:
437                         case SIGBUS:
438                         case SIGFPE:
439                         case SIGWINCH:
440                                 block_signals();
441                                 (*sig_info[sig])(sig, regs);
442                                 unblock_signals();
443                                 break;
444                         default:
445                                 printk(UM_KERN_ERR "userspace - child stopped "
446                                        "with signal %d\n", sig);
447                                 fatal_sigsegv();
448                         }
449                         pid = userspace_pid[0];
450                         interrupt_end();
451
452                         /* Avoid -ERESTARTSYS handling in host */
453                         if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
454                                 PT_SYSCALL_NR(regs->gp) = -1;
455                 }
456         }
457 }
458
459 static unsigned long thread_regs[MAX_REG_NR];
460
461 static int __init init_thread_regs(void)
462 {
463         get_safe_registers(thread_regs);
464         /* Set parent's instruction pointer to start of clone-stub */
465         thread_regs[REGS_IP_INDEX] = STUB_CODE +
466                                 (unsigned long) stub_clone_handler -
467                                 (unsigned long) &__syscall_stub_start;
468         thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
469                 sizeof(void *);
470 #ifdef __SIGNAL_FRAMESIZE
471         thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
472 #endif
473         return 0;
474 }
475
476 __initcall(init_thread_regs);
477
478 int copy_context_skas0(unsigned long new_stack, int pid)
479 {
480         struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
481         int err;
482         unsigned long current_stack = current_stub_stack();
483         struct stub_data *data = (struct stub_data *) current_stack;
484         struct stub_data *child_data = (struct stub_data *) new_stack;
485         unsigned long long new_offset;
486         int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
487
488         /*
489          * prepare offset and fd of child's stack as argument for parent's
490          * and child's mmap2 calls
491          */
492         *data = ((struct stub_data) { .offset   = MMAP_OFFSET(new_offset),
493                                       .fd       = new_fd,
494                                       .timer    = ((struct itimerval)
495                                                    { .it_value = tv,
496                                                      .it_interval = tv }) });
497
498         err = ptrace_setregs(pid, thread_regs);
499         if (err < 0) {
500                 err = -errno;
501                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
502                        "failed, pid = %d, errno = %d\n", pid, -err);
503                 return err;
504         }
505
506         /* set a well known return code for detection of child write failure */
507         child_data->err = 12345678;
508
509         /*
510          * Wait, until parent has finished its work: read child's pid from
511          * parent's stack, and check, if bad result.
512          */
513         err = ptrace(PTRACE_CONT, pid, 0, 0);
514         if (err) {
515                 err = -errno;
516                 printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
517                        "errno = %d\n", pid, errno);
518                 return err;
519         }
520
521         wait_stub_done(pid);
522
523         pid = data->err;
524         if (pid < 0) {
525                 printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
526                        "error %d\n", -pid);
527                 return pid;
528         }
529
530         /*
531          * Wait, until child has finished too: read child's result from
532          * child's stack and check it.
533          */
534         wait_stub_done(pid);
535         if (child_data->err != STUB_DATA) {
536                 printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
537                        "error %ld\n", child_data->err);
538                 err = child_data->err;
539                 goto out_kill;
540         }
541
542         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
543                    (void *)PTRACE_O_TRACESYSGOOD) < 0) {
544                 err = -errno;
545                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
546                        "failed, errno = %d\n", errno);
547                 goto out_kill;
548         }
549
550         return pid;
551
552  out_kill:
553         os_kill_ptraced_process(pid, 1);
554         return err;
555 }
556
557 /*
558  * This is used only, if stub pages are needed, while proc_mm is
559  * available. Opening /proc/mm creates a new mm_context, which lacks
560  * the stub-pages. Thus, we map them using /proc/mm-fd
561  */
562 int map_stub_pages(int fd, unsigned long code, unsigned long data,
563                    unsigned long stack)
564 {
565         struct proc_mm_op mmop;
566         int n;
567         unsigned long long code_offset;
568         int code_fd = phys_mapping(to_phys((void *) &__syscall_stub_start),
569                                    &code_offset);
570
571         mmop = ((struct proc_mm_op) { .op        = MM_MMAP,
572                                       .u         =
573                                       { .mmap    =
574                                         { .addr    = code,
575                                           .len     = UM_KERN_PAGE_SIZE,
576                                           .prot    = PROT_EXEC,
577                                           .flags   = MAP_FIXED | MAP_PRIVATE,
578                                           .fd      = code_fd,
579                                           .offset  = code_offset
580         } } });
581         CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
582         if (n != sizeof(mmop)) {
583                 n = errno;
584                 printk(UM_KERN_ERR "mmap args - addr = 0x%lx, fd = %d, "
585                        "offset = %llx\n", code, code_fd,
586                        (unsigned long long) code_offset);
587                 printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for code "
588                        "failed, err = %d\n", n);
589                 return -n;
590         }
591
592         if (stack) {
593                 unsigned long long map_offset;
594                 int map_fd = phys_mapping(to_phys((void *)stack), &map_offset);
595                 mmop = ((struct proc_mm_op)
596                                 { .op        = MM_MMAP,
597                                   .u         =
598                                   { .mmap    =
599                                     { .addr    = data,
600                                       .len     = UM_KERN_PAGE_SIZE,
601                                       .prot    = PROT_READ | PROT_WRITE,
602                                       .flags   = MAP_FIXED | MAP_SHARED,
603                                       .fd      = map_fd,
604                                       .offset  = map_offset
605                 } } });
606                 CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
607                 if (n != sizeof(mmop)) {
608                         n = errno;
609                         printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for "
610                                "data failed, err = %d\n", n);
611                         return -n;
612                 }
613         }
614
615         return 0;
616 }
617
618 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
619 {
620         (*buf)[0].JB_IP = (unsigned long) handler;
621         (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
622                 sizeof(void *);
623 }
624
625 #define INIT_JMP_NEW_THREAD 0
626 #define INIT_JMP_CALLBACK 1
627 #define INIT_JMP_HALT 2
628 #define INIT_JMP_REBOOT 3
629
630 void switch_threads(jmp_buf *me, jmp_buf *you)
631 {
632         if (UML_SETJMP(me) == 0)
633                 UML_LONGJMP(you, 1);
634 }
635
636 static jmp_buf initial_jmpbuf;
637
638 /* XXX Make these percpu */
639 static void (*cb_proc)(void *arg);
640 static void *cb_arg;
641 static jmp_buf *cb_back;
642
643 int start_idle_thread(void *stack, jmp_buf *switch_buf)
644 {
645         int n;
646
647         set_handler(SIGWINCH, (__sighandler_t) sig_handler,
648                     SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGVTALRM, -1);
649
650         /*
651          * Can't use UML_SETJMP or UML_LONGJMP here because they save
652          * and restore signals, with the possible side-effect of
653          * trying to handle any signals which came when they were
654          * blocked, which can't be done on this stack.
655          * Signals must be blocked when jumping back here and restored
656          * after returning to the jumper.
657          */
658         n = setjmp(initial_jmpbuf);
659         switch (n) {
660         case INIT_JMP_NEW_THREAD:
661                 (*switch_buf)[0].JB_IP = (unsigned long) new_thread_handler;
662                 (*switch_buf)[0].JB_SP = (unsigned long) stack +
663                         UM_THREAD_SIZE - sizeof(void *);
664                 break;
665         case INIT_JMP_CALLBACK:
666                 (*cb_proc)(cb_arg);
667                 longjmp(*cb_back, 1);
668                 break;
669         case INIT_JMP_HALT:
670                 kmalloc_ok = 0;
671                 return 0;
672         case INIT_JMP_REBOOT:
673                 kmalloc_ok = 0;
674                 return 1;
675         default:
676                 printk(UM_KERN_ERR "Bad sigsetjmp return in "
677                        "start_idle_thread - %d\n", n);
678                 fatal_sigsegv();
679         }
680         longjmp(*switch_buf, 1);
681 }
682
683 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
684 {
685         jmp_buf here;
686
687         cb_proc = proc;
688         cb_arg = arg;
689         cb_back = &here;
690
691         block_signals();
692         if (UML_SETJMP(&here) == 0)
693                 UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
694         unblock_signals();
695
696         cb_proc = NULL;
697         cb_arg = NULL;
698         cb_back = NULL;
699 }
700
701 void halt_skas(void)
702 {
703         block_signals();
704         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
705 }
706
707 void reboot_skas(void)
708 {
709         block_signals();
710         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
711 }
712
713 void __switch_mm(struct mm_id *mm_idp)
714 {
715         int err;
716
717         /* FIXME: need cpu pid in __switch_mm */
718         if (proc_mm) {
719                 err = ptrace(PTRACE_SWITCH_MM, userspace_pid[0], 0,
720                              mm_idp->u.mm_fd);
721                 if (err) {
722                         printk(UM_KERN_ERR "__switch_mm - PTRACE_SWITCH_MM "
723                                "failed, errno = %d\n", errno);
724                         fatal_sigsegv();
725                 }
726         }
727         else userspace_pid[0] = mm_idp->u.pid;
728 }