um: pull interrupt_end() into userspace()
[linux-3.10.git] / 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/wait.h>
13 #include <asm/unistd.h>
14 #include "as-layout.h"
15 #include "init.h"
16 #include "kern_util.h"
17 #include "mem.h"
18 #include "os.h"
19 #include "proc_mm.h"
20 #include "ptrace_user.h"
21 #include "registers.h"
22 #include "skas.h"
23 #include "skas_ptrace.h"
24 #include "sysdep/stub.h"
25
26 int is_skas_winch(int pid, int fd, void *data)
27 {
28         return pid == getpgrp();
29 }
30
31 static int ptrace_dump_regs(int pid)
32 {
33         unsigned long regs[MAX_REG_NR];
34         int i;
35
36         if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
37                 return -errno;
38
39         printk(UM_KERN_ERR "Stub registers -\n");
40         for (i = 0; i < ARRAY_SIZE(regs); i++)
41                 printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]);
42
43         return 0;
44 }
45
46 /*
47  * Signals that are OK to receive in the stub - we'll just continue it.
48  * SIGWINCH will happen when UML is inside a detached screen.
49  */
50 #define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
51
52 /* Signals that the stub will finish with - anything else is an error */
53 #define STUB_DONE_MASK (1 << SIGTRAP)
54
55 void wait_stub_done(int pid)
56 {
57         int n, status, err;
58
59         while (1) {
60                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
61                 if ((n < 0) || !WIFSTOPPED(status))
62                         goto bad_wait;
63
64                 if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
65                         break;
66
67                 err = ptrace(PTRACE_CONT, pid, 0, 0);
68                 if (err) {
69                         printk(UM_KERN_ERR "wait_stub_done : continue failed, "
70                                "errno = %d\n", errno);
71                         fatal_sigsegv();
72                 }
73         }
74
75         if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
76                 return;
77
78 bad_wait:
79         err = ptrace_dump_regs(pid);
80         if (err)
81                 printk(UM_KERN_ERR "Failed to get registers from stub, "
82                        "errno = %d\n", -err);
83         printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
84                "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
85                status);
86         fatal_sigsegv();
87 }
88
89 extern unsigned long current_stub_stack(void);
90
91 static void get_skas_faultinfo(int pid, struct faultinfo *fi)
92 {
93         int err;
94
95         if (ptrace_faultinfo) {
96                 err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
97                 if (err) {
98                         printk(UM_KERN_ERR "get_skas_faultinfo - "
99                                "PTRACE_FAULTINFO failed, errno = %d\n", errno);
100                         fatal_sigsegv();
101                 }
102
103                 /* Special handling for i386, which has different structs */
104                 if (sizeof(struct ptrace_faultinfo) < sizeof(struct faultinfo))
105                         memset((char *)fi + sizeof(struct ptrace_faultinfo), 0,
106                                sizeof(struct faultinfo) -
107                                sizeof(struct ptrace_faultinfo));
108         }
109         else {
110                 unsigned long fpregs[FP_SIZE];
111
112                 err = get_fp_registers(pid, fpregs);
113                 if (err < 0) {
114                         printk(UM_KERN_ERR "save_fp_registers returned %d\n",
115                                err);
116                         fatal_sigsegv();
117                 }
118                 err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
119                 if (err) {
120                         printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
121                                "errno = %d\n", pid, errno);
122                         fatal_sigsegv();
123                 }
124                 wait_stub_done(pid);
125
126                 /*
127                  * faultinfo is prepared by the stub-segv-handler at start of
128                  * the stub stack page. We just have to copy it.
129                  */
130                 memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
131
132                 err = put_fp_registers(pid, fpregs);
133                 if (err < 0) {
134                         printk(UM_KERN_ERR "put_fp_registers returned %d\n",
135                                err);
136                         fatal_sigsegv();
137                 }
138         }
139 }
140
141 static void handle_segv(int pid, struct uml_pt_regs * regs)
142 {
143         get_skas_faultinfo(pid, &regs->faultinfo);
144         segv(regs->faultinfo, 0, 1, NULL);
145 }
146
147 /*
148  * To use the same value of using_sysemu as the caller, ask it that value
149  * (in local_using_sysemu
150  */
151 static void handle_trap(int pid, struct uml_pt_regs *regs,
152                         int local_using_sysemu)
153 {
154         int err, status;
155
156         if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
157                 fatal_sigsegv();
158
159         /* Mark this as a syscall */
160         UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
161
162         if (!local_using_sysemu)
163         {
164                 err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
165                              __NR_getpid);
166                 if (err < 0) {
167                         printk(UM_KERN_ERR "handle_trap - nullifying syscall "
168                                "failed, errno = %d\n", errno);
169                         fatal_sigsegv();
170                 }
171
172                 err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
173                 if (err < 0) {
174                         printk(UM_KERN_ERR "handle_trap - continuing to end of "
175                                "syscall failed, errno = %d\n", errno);
176                         fatal_sigsegv();
177                 }
178
179                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
180                 if ((err < 0) || !WIFSTOPPED(status) ||
181                     (WSTOPSIG(status) != SIGTRAP + 0x80)) {
182                         err = ptrace_dump_regs(pid);
183                         if (err)
184                                 printk(UM_KERN_ERR "Failed to get registers "
185                                        "from process, errno = %d\n", -err);
186                         printk(UM_KERN_ERR "handle_trap - failed to wait at "
187                                "end of syscall, errno = %d, status = %d\n",
188                                errno, status);
189                         fatal_sigsegv();
190                 }
191         }
192
193         handle_syscall(regs);
194 }
195
196 extern int __syscall_stub_start;
197
198 static int userspace_tramp(void *stack)
199 {
200         void *addr;
201         int err;
202
203         ptrace(PTRACE_TRACEME, 0, 0, 0);
204
205         signal(SIGTERM, SIG_DFL);
206         signal(SIGWINCH, SIG_IGN);
207         err = set_interval();
208         if (err) {
209                 printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
210                        "errno = %d\n", err);
211                 exit(1);
212         }
213
214         if (!proc_mm) {
215                 /*
216                  * This has a pte, but it can't be mapped in with the usual
217                  * tlb_flush mechanism because this is part of that mechanism
218                  */
219                 int fd;
220                 unsigned long long offset;
221                 fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
222                 addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
223                               PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
224                 if (addr == MAP_FAILED) {
225                         printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
226                                "errno = %d\n", STUB_CODE, errno);
227                         exit(1);
228                 }
229
230                 if (stack != NULL) {
231                         fd = phys_mapping(to_phys(stack), &offset);
232                         addr = mmap((void *) STUB_DATA,
233                                     UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
234                                     MAP_FIXED | MAP_SHARED, fd, offset);
235                         if (addr == MAP_FAILED) {
236                                 printk(UM_KERN_ERR "mapping segfault stack "
237                                        "at 0x%lx failed, errno = %d\n",
238                                        STUB_DATA, errno);
239                                 exit(1);
240                         }
241                 }
242         }
243         if (!ptrace_faultinfo && (stack != NULL)) {
244                 struct sigaction sa;
245
246                 unsigned long v = STUB_CODE +
247                                   (unsigned long) stub_segv_handler -
248                                   (unsigned long) &__syscall_stub_start;
249
250                 set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
251                 sigemptyset(&sa.sa_mask);
252                 sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
253                 sa.sa_sigaction = (void *) v;
254                 sa.sa_restorer = NULL;
255                 if (sigaction(SIGSEGV, &sa, NULL) < 0) {
256                         printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
257                                "handler failed - errno = %d\n", errno);
258                         exit(1);
259                 }
260         }
261
262         kill(os_getpid(), SIGSTOP);
263         return 0;
264 }
265
266 /* Each element set once, and only accessed by a single processor anyway */
267 #undef NR_CPUS
268 #define NR_CPUS 1
269 int userspace_pid[NR_CPUS];
270
271 int start_userspace(unsigned long stub_stack)
272 {
273         void *stack;
274         unsigned long sp;
275         int pid, status, n, flags, err;
276
277         stack = mmap(NULL, UM_KERN_PAGE_SIZE,
278                      PROT_READ | PROT_WRITE | PROT_EXEC,
279                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
280         if (stack == MAP_FAILED) {
281                 err = -errno;
282                 printk(UM_KERN_ERR "start_userspace : mmap failed, "
283                        "errno = %d\n", errno);
284                 return err;
285         }
286
287         sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
288
289         flags = CLONE_FILES;
290         if (proc_mm)
291                 flags |= CLONE_VM;
292         else
293                 flags |= SIGCHLD;
294
295         pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
296         if (pid < 0) {
297                 err = -errno;
298                 printk(UM_KERN_ERR "start_userspace : clone failed, "
299                        "errno = %d\n", errno);
300                 return err;
301         }
302
303         do {
304                 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
305                 if (n < 0) {
306                         err = -errno;
307                         printk(UM_KERN_ERR "start_userspace : wait failed, "
308                                "errno = %d\n", errno);
309                         goto out_kill;
310                 }
311         } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
312
313         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
314                 err = -EINVAL;
315                 printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
316                        "status = %d\n", status);
317                 goto out_kill;
318         }
319
320         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
321                    (void *) PTRACE_O_TRACESYSGOOD) < 0) {
322                 err = -errno;
323                 printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
324                        "failed, errno = %d\n", errno);
325                 goto out_kill;
326         }
327
328         if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
329                 err = -errno;
330                 printk(UM_KERN_ERR "start_userspace : munmap failed, "
331                        "errno = %d\n", errno);
332                 goto out_kill;
333         }
334
335         return pid;
336
337  out_kill:
338         os_kill_ptraced_process(pid, 1);
339         return err;
340 }
341
342 void userspace(struct uml_pt_regs *regs)
343 {
344         struct itimerval timer;
345         unsigned long long nsecs, now;
346         int err, status, op, pid = userspace_pid[0];
347         /* To prevent races if using_sysemu changes under us.*/
348         int local_using_sysemu;
349
350         /* Handle any immediate reschedules or signals */
351         interrupt_end();
352
353         if (getitimer(ITIMER_VIRTUAL, &timer))
354                 printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
355         nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
356                 timer.it_value.tv_usec * UM_NSEC_PER_USEC;
357         nsecs += os_nsecs();
358
359         while (1) {
360                 /*
361                  * This can legitimately fail if the process loads a
362                  * bogus value into a segment register.  It will
363                  * segfault and PTRACE_GETREGS will read that value
364                  * out of the process.  However, PTRACE_SETREGS will
365                  * fail.  In this case, there is nothing to do but
366                  * just kill the process.
367                  */
368                 if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
369                         fatal_sigsegv();
370
371                 if (put_fp_registers(pid, regs->fp))
372                         fatal_sigsegv();
373
374                 /* Now we set local_using_sysemu to be used for one loop */
375                 local_using_sysemu = get_using_sysemu();
376
377                 op = SELECT_PTRACE_OPERATION(local_using_sysemu,
378                                              singlestepping(NULL));
379
380                 if (ptrace(op, pid, 0, 0)) {
381                         printk(UM_KERN_ERR "userspace - ptrace continue "
382                                "failed, op = %d, errno = %d\n", op, errno);
383                         fatal_sigsegv();
384                 }
385
386                 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
387                 if (err < 0) {
388                         printk(UM_KERN_ERR "userspace - wait failed, "
389                                "errno = %d\n", errno);
390                         fatal_sigsegv();
391                 }
392
393                 regs->is_user = 1;
394                 if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
395                         printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
396                                "errno = %d\n", errno);
397                         fatal_sigsegv();
398                 }
399
400                 if (get_fp_registers(pid, regs->fp)) {
401                         printk(UM_KERN_ERR "userspace -  get_fp_registers failed, "
402                                "errno = %d\n", errno);
403                         fatal_sigsegv();
404                 }
405
406                 UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
407
408                 if (WIFSTOPPED(status)) {
409                         int sig = WSTOPSIG(status);
410                         switch (sig) {
411                         case SIGSEGV:
412                                 if (PTRACE_FULL_FAULTINFO ||
413                                     !ptrace_faultinfo) {
414                                         get_skas_faultinfo(pid,
415                                                            &regs->faultinfo);
416                                         (*sig_info[SIGSEGV])(SIGSEGV, regs);
417                                 }
418                                 else handle_segv(pid, regs);
419                                 break;
420                         case SIGTRAP + 0x80:
421                                 handle_trap(pid, regs, local_using_sysemu);
422                                 break;
423                         case SIGTRAP:
424                                 relay_signal(SIGTRAP, regs);
425                                 break;
426                         case SIGVTALRM:
427                                 now = os_nsecs();
428                                 if (now < nsecs)
429                                         break;
430                                 block_signals();
431                                 (*sig_info[sig])(sig, regs);
432                                 unblock_signals();
433                                 nsecs = timer.it_value.tv_sec *
434                                         UM_NSEC_PER_SEC +
435                                         timer.it_value.tv_usec *
436                                         UM_NSEC_PER_USEC;
437                                 nsecs += os_nsecs();
438                                 break;
439                         case SIGIO:
440                         case SIGILL:
441                         case SIGBUS:
442                         case SIGFPE:
443                         case SIGWINCH:
444                                 block_signals();
445                                 (*sig_info[sig])(sig, regs);
446                                 unblock_signals();
447                                 break;
448                         default:
449                                 printk(UM_KERN_ERR "userspace - child stopped "
450                                        "with signal %d\n", sig);
451                                 fatal_sigsegv();
452                         }
453                         pid = userspace_pid[0];
454                         interrupt_end();
455
456                         /* Avoid -ERESTARTSYS handling in host */
457                         if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
458                                 PT_SYSCALL_NR(regs->gp) = -1;
459                 }
460         }
461 }
462
463 static unsigned long thread_regs[MAX_REG_NR];
464 static unsigned long thread_fp_regs[FP_SIZE];
465
466 static int __init init_thread_regs(void)
467 {
468         get_safe_registers(thread_regs, thread_fp_regs);
469         /* Set parent's instruction pointer to start of clone-stub */
470         thread_regs[REGS_IP_INDEX] = STUB_CODE +
471                                 (unsigned long) stub_clone_handler -
472                                 (unsigned long) &__syscall_stub_start;
473         thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
474                 sizeof(void *);
475 #ifdef __SIGNAL_FRAMESIZE
476         thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
477 #endif
478         return 0;
479 }
480
481 __initcall(init_thread_regs);
482
483 int copy_context_skas0(unsigned long new_stack, int pid)
484 {
485         struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
486         int err;
487         unsigned long current_stack = current_stub_stack();
488         struct stub_data *data = (struct stub_data *) current_stack;
489         struct stub_data *child_data = (struct stub_data *) new_stack;
490         unsigned long long new_offset;
491         int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
492
493         /*
494          * prepare offset and fd of child's stack as argument for parent's
495          * and child's mmap2 calls
496          */
497         *data = ((struct stub_data) { .offset   = MMAP_OFFSET(new_offset),
498                                       .fd       = new_fd,
499                                       .timer    = ((struct itimerval)
500                                                    { .it_value = tv,
501                                                      .it_interval = tv }) });
502
503         err = ptrace_setregs(pid, thread_regs);
504         if (err < 0) {
505                 err = -errno;
506                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
507                        "failed, pid = %d, errno = %d\n", pid, -err);
508                 return err;
509         }
510
511         err = put_fp_registers(pid, thread_fp_regs);
512         if (err < 0) {
513                 printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
514                        "failed, pid = %d, err = %d\n", pid, err);
515                 return err;
516         }
517
518         /* set a well known return code for detection of child write failure */
519         child_data->err = 12345678;
520
521         /*
522          * Wait, until parent has finished its work: read child's pid from
523          * parent's stack, and check, if bad result.
524          */
525         err = ptrace(PTRACE_CONT, pid, 0, 0);
526         if (err) {
527                 err = -errno;
528                 printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
529                        "errno = %d\n", pid, errno);
530                 return err;
531         }
532
533         wait_stub_done(pid);
534
535         pid = data->err;
536         if (pid < 0) {
537                 printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
538                        "error %d\n", -pid);
539                 return pid;
540         }
541
542         /*
543          * Wait, until child has finished too: read child's result from
544          * child's stack and check it.
545          */
546         wait_stub_done(pid);
547         if (child_data->err != STUB_DATA) {
548                 printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
549                        "error %ld\n", child_data->err);
550                 err = child_data->err;
551                 goto out_kill;
552         }
553
554         if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
555                    (void *)PTRACE_O_TRACESYSGOOD) < 0) {
556                 err = -errno;
557                 printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
558                        "failed, errno = %d\n", errno);
559                 goto out_kill;
560         }
561
562         return pid;
563
564  out_kill:
565         os_kill_ptraced_process(pid, 1);
566         return err;
567 }
568
569 /*
570  * This is used only, if stub pages are needed, while proc_mm is
571  * available. Opening /proc/mm creates a new mm_context, which lacks
572  * the stub-pages. Thus, we map them using /proc/mm-fd
573  */
574 int map_stub_pages(int fd, unsigned long code, unsigned long data,
575                    unsigned long stack)
576 {
577         struct proc_mm_op mmop;
578         int n;
579         unsigned long long code_offset;
580         int code_fd = phys_mapping(to_phys((void *) &__syscall_stub_start),
581                                    &code_offset);
582
583         mmop = ((struct proc_mm_op) { .op        = MM_MMAP,
584                                       .u         =
585                                       { .mmap    =
586                                         { .addr    = code,
587                                           .len     = UM_KERN_PAGE_SIZE,
588                                           .prot    = PROT_EXEC,
589                                           .flags   = MAP_FIXED | MAP_PRIVATE,
590                                           .fd      = code_fd,
591                                           .offset  = code_offset
592         } } });
593         CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
594         if (n != sizeof(mmop)) {
595                 n = errno;
596                 printk(UM_KERN_ERR "mmap args - addr = 0x%lx, fd = %d, "
597                        "offset = %llx\n", code, code_fd,
598                        (unsigned long long) code_offset);
599                 printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for code "
600                        "failed, err = %d\n", n);
601                 return -n;
602         }
603
604         if (stack) {
605                 unsigned long long map_offset;
606                 int map_fd = phys_mapping(to_phys((void *)stack), &map_offset);
607                 mmop = ((struct proc_mm_op)
608                                 { .op        = MM_MMAP,
609                                   .u         =
610                                   { .mmap    =
611                                     { .addr    = data,
612                                       .len     = UM_KERN_PAGE_SIZE,
613                                       .prot    = PROT_READ | PROT_WRITE,
614                                       .flags   = MAP_FIXED | MAP_SHARED,
615                                       .fd      = map_fd,
616                                       .offset  = map_offset
617                 } } });
618                 CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
619                 if (n != sizeof(mmop)) {
620                         n = errno;
621                         printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for "
622                                "data failed, err = %d\n", n);
623                         return -n;
624                 }
625         }
626
627         return 0;
628 }
629
630 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
631 {
632         (*buf)[0].JB_IP = (unsigned long) handler;
633         (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
634                 sizeof(void *);
635 }
636
637 #define INIT_JMP_NEW_THREAD 0
638 #define INIT_JMP_CALLBACK 1
639 #define INIT_JMP_HALT 2
640 #define INIT_JMP_REBOOT 3
641
642 void switch_threads(jmp_buf *me, jmp_buf *you)
643 {
644         if (UML_SETJMP(me) == 0)
645                 UML_LONGJMP(you, 1);
646 }
647
648 static jmp_buf initial_jmpbuf;
649
650 /* XXX Make these percpu */
651 static void (*cb_proc)(void *arg);
652 static void *cb_arg;
653 static jmp_buf *cb_back;
654
655 int start_idle_thread(void *stack, jmp_buf *switch_buf)
656 {
657         int n;
658
659         set_handler(SIGWINCH);
660
661         /*
662          * Can't use UML_SETJMP or UML_LONGJMP here because they save
663          * and restore signals, with the possible side-effect of
664          * trying to handle any signals which came when they were
665          * blocked, which can't be done on this stack.
666          * Signals must be blocked when jumping back here and restored
667          * after returning to the jumper.
668          */
669         n = setjmp(initial_jmpbuf);
670         switch (n) {
671         case INIT_JMP_NEW_THREAD:
672                 (*switch_buf)[0].JB_IP = (unsigned long) new_thread_handler;
673                 (*switch_buf)[0].JB_SP = (unsigned long) stack +
674                         UM_THREAD_SIZE - sizeof(void *);
675                 break;
676         case INIT_JMP_CALLBACK:
677                 (*cb_proc)(cb_arg);
678                 longjmp(*cb_back, 1);
679                 break;
680         case INIT_JMP_HALT:
681                 kmalloc_ok = 0;
682                 return 0;
683         case INIT_JMP_REBOOT:
684                 kmalloc_ok = 0;
685                 return 1;
686         default:
687                 printk(UM_KERN_ERR "Bad sigsetjmp return in "
688                        "start_idle_thread - %d\n", n);
689                 fatal_sigsegv();
690         }
691         longjmp(*switch_buf, 1);
692 }
693
694 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
695 {
696         jmp_buf here;
697
698         cb_proc = proc;
699         cb_arg = arg;
700         cb_back = &here;
701
702         block_signals();
703         if (UML_SETJMP(&here) == 0)
704                 UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
705         unblock_signals();
706
707         cb_proc = NULL;
708         cb_arg = NULL;
709         cb_back = NULL;
710 }
711
712 void halt_skas(void)
713 {
714         block_signals();
715         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
716 }
717
718 void reboot_skas(void)
719 {
720         block_signals();
721         UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
722 }
723
724 void __switch_mm(struct mm_id *mm_idp)
725 {
726         int err;
727
728         /* FIXME: need cpu pid in __switch_mm */
729         if (proc_mm) {
730                 err = ptrace(PTRACE_SWITCH_MM, userspace_pid[0], 0,
731                              mm_idp->u.mm_fd);
732                 if (err) {
733                         printk(UM_KERN_ERR "__switch_mm - PTRACE_SWITCH_MM "
734                                "failed, errno = %d\n", errno);
735                         fatal_sigsegv();
736                 }
737         }
738         else userspace_pid[0] = mm_idp->u.pid;
739 }