1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
4  * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
5  */
6 
7 #include <stdlib.h>
8 #include <stdbool.h>
9 #include <unistd.h>
10 #include <sched.h>
11 #include <errno.h>
12 #include <string.h>
13 #include <sys/mman.h>
14 #include <sys/wait.h>
15 #include <asm/unistd.h>
16 #include <as-layout.h>
17 #include <init.h>
18 #include <kern_util.h>
19 #include <mem.h>
20 #include <os.h>
21 #include <ptrace_user.h>
22 #include <registers.h>
23 #include <skas.h>
24 #include <sysdep/stub.h>
25 #include <linux/threads.h>
26 
is_skas_winch(int pid,int fd,void * data)27 int is_skas_winch(int pid, int fd, void *data)
28 {
29 	return pid == getpgrp();
30 }
31 
ptrace_reg_name(int idx)32 static const char *ptrace_reg_name(int idx)
33 {
34 #define R(n) case HOST_##n: return #n
35 
36 	switch (idx) {
37 #ifdef __x86_64__
38 	R(BX);
39 	R(CX);
40 	R(DI);
41 	R(SI);
42 	R(DX);
43 	R(BP);
44 	R(AX);
45 	R(R8);
46 	R(R9);
47 	R(R10);
48 	R(R11);
49 	R(R12);
50 	R(R13);
51 	R(R14);
52 	R(R15);
53 	R(ORIG_AX);
54 	R(CS);
55 	R(SS);
56 	R(EFLAGS);
57 #elif defined(__i386__)
58 	R(IP);
59 	R(SP);
60 	R(EFLAGS);
61 	R(AX);
62 	R(BX);
63 	R(CX);
64 	R(DX);
65 	R(SI);
66 	R(DI);
67 	R(BP);
68 	R(CS);
69 	R(SS);
70 	R(DS);
71 	R(FS);
72 	R(ES);
73 	R(GS);
74 	R(ORIG_AX);
75 #endif
76 	}
77 	return "";
78 }
79 
ptrace_dump_regs(int pid)80 static int ptrace_dump_regs(int pid)
81 {
82 	unsigned long regs[MAX_REG_NR];
83 	int i;
84 
85 	if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
86 		return -errno;
87 
88 	printk(UM_KERN_ERR "Stub registers -\n");
89 	for (i = 0; i < ARRAY_SIZE(regs); i++) {
90 		const char *regname = ptrace_reg_name(i);
91 
92 		printk(UM_KERN_ERR "\t%s\t(%2d): %lx\n", regname, i, regs[i]);
93 	}
94 
95 	return 0;
96 }
97 
98 /*
99  * Signals that are OK to receive in the stub - we'll just continue it.
100  * SIGWINCH will happen when UML is inside a detached screen.
101  */
102 #define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
103 
104 /* Signals that the stub will finish with - anything else is an error */
105 #define STUB_DONE_MASK (1 << SIGTRAP)
106 
wait_stub_done(int pid)107 void wait_stub_done(int pid)
108 {
109 	int n, status, err;
110 
111 	while (1) {
112 		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
113 		if ((n < 0) || !WIFSTOPPED(status))
114 			goto bad_wait;
115 
116 		if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
117 			break;
118 
119 		err = ptrace(PTRACE_CONT, pid, 0, 0);
120 		if (err) {
121 			printk(UM_KERN_ERR "wait_stub_done : continue failed, "
122 			       "errno = %d\n", errno);
123 			fatal_sigsegv();
124 		}
125 	}
126 
127 	if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
128 		return;
129 
130 bad_wait:
131 	err = ptrace_dump_regs(pid);
132 	if (err)
133 		printk(UM_KERN_ERR "Failed to get registers from stub, "
134 		       "errno = %d\n", -err);
135 	printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
136 	       "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
137 	       status);
138 	fatal_sigsegv();
139 }
140 
141 extern unsigned long current_stub_stack(void);
142 
get_skas_faultinfo(int pid,struct faultinfo * fi,unsigned long * aux_fp_regs)143 static void get_skas_faultinfo(int pid, struct faultinfo *fi, unsigned long *aux_fp_regs)
144 {
145 	int err;
146 
147 	err = get_fp_registers(pid, aux_fp_regs);
148 	if (err < 0) {
149 		printk(UM_KERN_ERR "save_fp_registers returned %d\n",
150 		       err);
151 		fatal_sigsegv();
152 	}
153 	err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
154 	if (err) {
155 		printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
156 		       "errno = %d\n", pid, errno);
157 		fatal_sigsegv();
158 	}
159 	wait_stub_done(pid);
160 
161 	/*
162 	 * faultinfo is prepared by the stub_segv_handler at start of
163 	 * the stub stack page. We just have to copy it.
164 	 */
165 	memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
166 
167 	err = put_fp_registers(pid, aux_fp_regs);
168 	if (err < 0) {
169 		printk(UM_KERN_ERR "put_fp_registers returned %d\n",
170 		       err);
171 		fatal_sigsegv();
172 	}
173 }
174 
handle_segv(int pid,struct uml_pt_regs * regs,unsigned long * aux_fp_regs)175 static void handle_segv(int pid, struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
176 {
177 	get_skas_faultinfo(pid, &regs->faultinfo, aux_fp_regs);
178 	segv(regs->faultinfo, 0, 1, NULL);
179 }
180 
181 /*
182  * To use the same value of using_sysemu as the caller, ask it that value
183  * (in local_using_sysemu
184  */
handle_trap(int pid,struct uml_pt_regs * regs,int local_using_sysemu)185 static void handle_trap(int pid, struct uml_pt_regs *regs,
186 			int local_using_sysemu)
187 {
188 	int err, status;
189 
190 	if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
191 		fatal_sigsegv();
192 
193 	if (!local_using_sysemu)
194 	{
195 		err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
196 			     __NR_getpid);
197 		if (err < 0) {
198 			printk(UM_KERN_ERR "handle_trap - nullifying syscall "
199 			       "failed, errno = %d\n", errno);
200 			fatal_sigsegv();
201 		}
202 
203 		err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
204 		if (err < 0) {
205 			printk(UM_KERN_ERR "handle_trap - continuing to end of "
206 			       "syscall failed, errno = %d\n", errno);
207 			fatal_sigsegv();
208 		}
209 
210 		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
211 		if ((err < 0) || !WIFSTOPPED(status) ||
212 		    (WSTOPSIG(status) != SIGTRAP + 0x80)) {
213 			err = ptrace_dump_regs(pid);
214 			if (err)
215 				printk(UM_KERN_ERR "Failed to get registers "
216 				       "from process, errno = %d\n", -err);
217 			printk(UM_KERN_ERR "handle_trap - failed to wait at "
218 			       "end of syscall, errno = %d, status = %d\n",
219 			       errno, status);
220 			fatal_sigsegv();
221 		}
222 	}
223 
224 	handle_syscall(regs);
225 }
226 
227 extern char __syscall_stub_start[];
228 
229 /**
230  * userspace_tramp() - userspace trampoline
231  * @stack:	pointer to the new userspace stack page, can be NULL, if? FIXME:
232  *
233  * The userspace trampoline is used to setup a new userspace process in start_userspace() after it was clone()'ed.
234  * This function will run on a temporary stack page.
235  * It ptrace()'es itself, then
236  * Two pages are mapped into the userspace address space:
237  * - STUB_CODE (with EXEC), which contains the skas stub code
238  * - STUB_DATA (with R/W), which contains a data page that is used to transfer certain data between the UML userspace process and the UML kernel.
239  * Also for the userspace process a SIGSEGV handler is installed to catch pagefaults in the userspace process.
240  * And last the process stops itself to give control to the UML kernel for this userspace process.
241  *
242  * Return: Always zero, otherwise the current userspace process is ended with non null exit() call
243  */
userspace_tramp(void * stack)244 static int userspace_tramp(void *stack)
245 {
246 	void *addr;
247 	int fd;
248 	unsigned long long offset;
249 
250 	ptrace(PTRACE_TRACEME, 0, 0, 0);
251 
252 	signal(SIGTERM, SIG_DFL);
253 	signal(SIGWINCH, SIG_IGN);
254 
255 	fd = phys_mapping(uml_to_phys(__syscall_stub_start), &offset);
256 	addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
257 		      PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
258 	if (addr == MAP_FAILED) {
259 		printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
260 		       "errno = %d\n", STUB_CODE, errno);
261 		exit(1);
262 	}
263 
264 	if (stack != NULL) {
265 		fd = phys_mapping(uml_to_phys(stack), &offset);
266 		addr = mmap((void *) STUB_DATA,
267 			    UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
268 			    MAP_FIXED | MAP_SHARED, fd, offset);
269 		if (addr == MAP_FAILED) {
270 			printk(UM_KERN_ERR "mapping segfault stack "
271 			       "at 0x%lx failed, errno = %d\n",
272 			       STUB_DATA, errno);
273 			exit(1);
274 		}
275 	}
276 	if (stack != NULL) {
277 		struct sigaction sa;
278 
279 		unsigned long v = STUB_CODE +
280 				  (unsigned long) stub_segv_handler -
281 				  (unsigned long) __syscall_stub_start;
282 
283 		set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
284 		sigemptyset(&sa.sa_mask);
285 		sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
286 		sa.sa_sigaction = (void *) v;
287 		sa.sa_restorer = NULL;
288 		if (sigaction(SIGSEGV, &sa, NULL) < 0) {
289 			printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
290 			       "handler failed - errno = %d\n", errno);
291 			exit(1);
292 		}
293 	}
294 
295 	kill(os_getpid(), SIGSTOP);
296 	return 0;
297 }
298 
299 int userspace_pid[NR_CPUS];
300 int kill_userspace_mm[NR_CPUS];
301 
302 /**
303  * start_userspace() - prepare a new userspace process
304  * @stub_stack:	pointer to the stub stack. Can be NULL, if? FIXME:
305  *
306  * Setups a new temporary stack page that is used while userspace_tramp() runs
307  * Clones the kernel process into a new userspace process, with FDs only.
308  *
309  * Return: When positive: the process id of the new userspace process,
310  *         when negative: an error number.
311  * FIXME: can PIDs become negative?!
312  */
start_userspace(unsigned long stub_stack)313 int start_userspace(unsigned long stub_stack)
314 {
315 	void *stack;
316 	unsigned long sp;
317 	int pid, status, n, flags, err;
318 
319 	/* setup a temporary stack page */
320 	stack = mmap(NULL, UM_KERN_PAGE_SIZE,
321 		     PROT_READ | PROT_WRITE | PROT_EXEC,
322 		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
323 	if (stack == MAP_FAILED) {
324 		err = -errno;
325 		printk(UM_KERN_ERR "start_userspace : mmap failed, "
326 		       "errno = %d\n", errno);
327 		return err;
328 	}
329 
330 	/* set stack pointer to the end of the stack page, so it can grow downwards */
331 	sp = (unsigned long)stack + UM_KERN_PAGE_SIZE;
332 
333 	flags = CLONE_FILES | SIGCHLD;
334 
335 	/* clone into new userspace process */
336 	pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
337 	if (pid < 0) {
338 		err = -errno;
339 		printk(UM_KERN_ERR "start_userspace : clone failed, "
340 		       "errno = %d\n", errno);
341 		return err;
342 	}
343 
344 	do {
345 		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
346 		if (n < 0) {
347 			err = -errno;
348 			printk(UM_KERN_ERR "start_userspace : wait failed, "
349 			       "errno = %d\n", errno);
350 			goto out_kill;
351 		}
352 	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
353 
354 	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
355 		err = -EINVAL;
356 		printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
357 		       "status = %d\n", status);
358 		goto out_kill;
359 	}
360 
361 	if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
362 		   (void *) PTRACE_O_TRACESYSGOOD) < 0) {
363 		err = -errno;
364 		printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
365 		       "failed, errno = %d\n", errno);
366 		goto out_kill;
367 	}
368 
369 	if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
370 		err = -errno;
371 		printk(UM_KERN_ERR "start_userspace : munmap failed, "
372 		       "errno = %d\n", errno);
373 		goto out_kill;
374 	}
375 
376 	return pid;
377 
378  out_kill:
379 	os_kill_ptraced_process(pid, 1);
380 	return err;
381 }
382 
userspace(struct uml_pt_regs * regs,unsigned long * aux_fp_regs)383 void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
384 {
385 	int err, status, op, pid = userspace_pid[0];
386 	/* To prevent races if using_sysemu changes under us.*/
387 	int local_using_sysemu;
388 	siginfo_t si;
389 
390 	/* Handle any immediate reschedules or signals */
391 	interrupt_end();
392 
393 	while (1) {
394 		if (kill_userspace_mm[0])
395 			fatal_sigsegv();
396 
397 		/*
398 		 * This can legitimately fail if the process loads a
399 		 * bogus value into a segment register.  It will
400 		 * segfault and PTRACE_GETREGS will read that value
401 		 * out of the process.  However, PTRACE_SETREGS will
402 		 * fail.  In this case, there is nothing to do but
403 		 * just kill the process.
404 		 */
405 		if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp)) {
406 			printk(UM_KERN_ERR "userspace - ptrace set regs "
407 			       "failed, errno = %d\n", errno);
408 			fatal_sigsegv();
409 		}
410 
411 		if (put_fp_registers(pid, regs->fp)) {
412 			printk(UM_KERN_ERR "userspace - ptrace set fp regs "
413 			       "failed, errno = %d\n", errno);
414 			fatal_sigsegv();
415 		}
416 
417 		/* Now we set local_using_sysemu to be used for one loop */
418 		local_using_sysemu = get_using_sysemu();
419 
420 		op = SELECT_PTRACE_OPERATION(local_using_sysemu,
421 					     singlestepping(NULL));
422 
423 		if (ptrace(op, pid, 0, 0)) {
424 			printk(UM_KERN_ERR "userspace - ptrace continue "
425 			       "failed, op = %d, errno = %d\n", op, errno);
426 			fatal_sigsegv();
427 		}
428 
429 		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
430 		if (err < 0) {
431 			printk(UM_KERN_ERR "userspace - wait failed, "
432 			       "errno = %d\n", errno);
433 			fatal_sigsegv();
434 		}
435 
436 		regs->is_user = 1;
437 		if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
438 			printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
439 			       "errno = %d\n", errno);
440 			fatal_sigsegv();
441 		}
442 
443 		if (get_fp_registers(pid, regs->fp)) {
444 			printk(UM_KERN_ERR "userspace -  get_fp_registers failed, "
445 			       "errno = %d\n", errno);
446 			fatal_sigsegv();
447 		}
448 
449 		UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
450 
451 		if (WIFSTOPPED(status)) {
452 			int sig = WSTOPSIG(status);
453 
454 			/* These signal handlers need the si argument.
455 			 * The SIGIO and SIGALARM handlers which constitute the
456 			 * majority of invocations, do not use it.
457 			 */
458 			switch (sig) {
459 			case SIGSEGV:
460 			case SIGTRAP:
461 			case SIGILL:
462 			case SIGBUS:
463 			case SIGFPE:
464 			case SIGWINCH:
465 				ptrace(PTRACE_GETSIGINFO, pid, 0, (struct siginfo *)&si);
466 				break;
467 			}
468 
469 			switch (sig) {
470 			case SIGSEGV:
471 				if (PTRACE_FULL_FAULTINFO) {
472 					get_skas_faultinfo(pid,
473 							   &regs->faultinfo, aux_fp_regs);
474 					(*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
475 							     regs);
476 				}
477 				else handle_segv(pid, regs, aux_fp_regs);
478 				break;
479 			case SIGTRAP + 0x80:
480 			        handle_trap(pid, regs, local_using_sysemu);
481 				break;
482 			case SIGTRAP:
483 				relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
484 				break;
485 			case SIGALRM:
486 				break;
487 			case SIGIO:
488 			case SIGILL:
489 			case SIGBUS:
490 			case SIGFPE:
491 			case SIGWINCH:
492 				block_signals_trace();
493 				(*sig_info[sig])(sig, (struct siginfo *)&si, regs);
494 				unblock_signals_trace();
495 				break;
496 			default:
497 				printk(UM_KERN_ERR "userspace - child stopped "
498 				       "with signal %d\n", sig);
499 				fatal_sigsegv();
500 			}
501 			pid = userspace_pid[0];
502 			interrupt_end();
503 
504 			/* Avoid -ERESTARTSYS handling in host */
505 			if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
506 				PT_SYSCALL_NR(regs->gp) = -1;
507 		}
508 	}
509 }
510 
511 static unsigned long thread_regs[MAX_REG_NR];
512 static unsigned long thread_fp_regs[FP_SIZE];
513 
init_thread_regs(void)514 static int __init init_thread_regs(void)
515 {
516 	get_safe_registers(thread_regs, thread_fp_regs);
517 	/* Set parent's instruction pointer to start of clone-stub */
518 	thread_regs[REGS_IP_INDEX] = STUB_CODE +
519 				(unsigned long) stub_clone_handler -
520 				(unsigned long) __syscall_stub_start;
521 	thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
522 		sizeof(void *);
523 #ifdef __SIGNAL_FRAMESIZE
524 	thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
525 #endif
526 	return 0;
527 }
528 
529 __initcall(init_thread_regs);
530 
copy_context_skas0(unsigned long new_stack,int pid)531 int copy_context_skas0(unsigned long new_stack, int pid)
532 {
533 	int err;
534 	unsigned long current_stack = current_stub_stack();
535 	struct stub_data *data = (struct stub_data *) current_stack;
536 	struct stub_data *child_data = (struct stub_data *) new_stack;
537 	unsigned long long new_offset;
538 	int new_fd = phys_mapping(uml_to_phys((void *)new_stack), &new_offset);
539 
540 	/*
541 	 * prepare offset and fd of child's stack as argument for parent's
542 	 * and child's mmap2 calls
543 	 */
544 	*data = ((struct stub_data) {
545 		.offset	= MMAP_OFFSET(new_offset),
546 		.fd     = new_fd,
547 		.parent_err = -ESRCH,
548 		.child_err = 0,
549 	});
550 
551 	*child_data = ((struct stub_data) {
552 		.child_err = -ESRCH,
553 	});
554 
555 	err = ptrace_setregs(pid, thread_regs);
556 	if (err < 0) {
557 		err = -errno;
558 		printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
559 		       "failed, pid = %d, errno = %d\n", pid, -err);
560 		return err;
561 	}
562 
563 	err = put_fp_registers(pid, thread_fp_regs);
564 	if (err < 0) {
565 		printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
566 		       "failed, pid = %d, err = %d\n", pid, err);
567 		return err;
568 	}
569 
570 	/*
571 	 * Wait, until parent has finished its work: read child's pid from
572 	 * parent's stack, and check, if bad result.
573 	 */
574 	err = ptrace(PTRACE_CONT, pid, 0, 0);
575 	if (err) {
576 		err = -errno;
577 		printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
578 		       "errno = %d\n", pid, errno);
579 		return err;
580 	}
581 
582 	wait_stub_done(pid);
583 
584 	pid = data->parent_err;
585 	if (pid < 0) {
586 		printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
587 		       "error %d\n", -pid);
588 		return pid;
589 	}
590 
591 	/*
592 	 * Wait, until child has finished too: read child's result from
593 	 * child's stack and check it.
594 	 */
595 	wait_stub_done(pid);
596 	if (child_data->child_err != STUB_DATA) {
597 		printk(UM_KERN_ERR "copy_context_skas0 - stub-child %d reports "
598 		       "error %ld\n", pid, data->child_err);
599 		err = data->child_err;
600 		goto out_kill;
601 	}
602 
603 	if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
604 		   (void *)PTRACE_O_TRACESYSGOOD) < 0) {
605 		err = -errno;
606 		printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
607 		       "failed, errno = %d\n", errno);
608 		goto out_kill;
609 	}
610 
611 	return pid;
612 
613  out_kill:
614 	os_kill_ptraced_process(pid, 1);
615 	return err;
616 }
617 
new_thread(void * stack,jmp_buf * buf,void (* handler)(void))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 
switch_threads(jmp_buf * me,jmp_buf * you)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 
start_idle_thread(void * stack,jmp_buf * switch_buf)643 int start_idle_thread(void *stack, jmp_buf *switch_buf)
644 {
645 	int n;
646 
647 	set_handler(SIGWINCH);
648 
649 	/*
650 	 * Can't use UML_SETJMP or UML_LONGJMP here because they save
651 	 * and restore signals, with the possible side-effect of
652 	 * trying to handle any signals which came when they were
653 	 * blocked, which can't be done on this stack.
654 	 * Signals must be blocked when jumping back here and restored
655 	 * after returning to the jumper.
656 	 */
657 	n = setjmp(initial_jmpbuf);
658 	switch (n) {
659 	case INIT_JMP_NEW_THREAD:
660 		(*switch_buf)[0].JB_IP = (unsigned long) uml_finishsetup;
661 		(*switch_buf)[0].JB_SP = (unsigned long) stack +
662 			UM_THREAD_SIZE - sizeof(void *);
663 		break;
664 	case INIT_JMP_CALLBACK:
665 		(*cb_proc)(cb_arg);
666 		longjmp(*cb_back, 1);
667 		break;
668 	case INIT_JMP_HALT:
669 		kmalloc_ok = 0;
670 		return 0;
671 	case INIT_JMP_REBOOT:
672 		kmalloc_ok = 0;
673 		return 1;
674 	default:
675 		printk(UM_KERN_ERR "Bad sigsetjmp return in "
676 		       "start_idle_thread - %d\n", n);
677 		fatal_sigsegv();
678 	}
679 	longjmp(*switch_buf, 1);
680 
681 	/* unreachable */
682 	printk(UM_KERN_ERR "impossible long jump!");
683 	fatal_sigsegv();
684 	return 0;
685 }
686 
initial_thread_cb_skas(void (* proc)(void *),void * arg)687 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
688 {
689 	jmp_buf here;
690 
691 	cb_proc = proc;
692 	cb_arg = arg;
693 	cb_back = &here;
694 
695 	block_signals_trace();
696 	if (UML_SETJMP(&here) == 0)
697 		UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
698 	unblock_signals_trace();
699 
700 	cb_proc = NULL;
701 	cb_arg = NULL;
702 	cb_back = NULL;
703 }
704 
halt_skas(void)705 void halt_skas(void)
706 {
707 	block_signals_trace();
708 	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
709 }
710 
711 static bool noreboot;
712 
noreboot_cmd_param(char * str,int * add)713 static int __init noreboot_cmd_param(char *str, int *add)
714 {
715 	noreboot = true;
716 	return 0;
717 }
718 
719 __uml_setup("noreboot", noreboot_cmd_param,
720 "noreboot\n"
721 "    Rather than rebooting, exit always, akin to QEMU's -no-reboot option.\n"
722 "    This is useful if you're using CONFIG_PANIC_TIMEOUT in order to catch\n"
723 "    crashes in CI\n");
724 
reboot_skas(void)725 void reboot_skas(void)
726 {
727 	block_signals_trace();
728 	UML_LONGJMP(&initial_jmpbuf, noreboot ? INIT_JMP_HALT : INIT_JMP_REBOOT);
729 }
730 
__switch_mm(struct mm_id * mm_idp)731 void __switch_mm(struct mm_id *mm_idp)
732 {
733 	userspace_pid[0] = mm_idp->u.pid;
734 	kill_userspace_mm[0] = mm_idp->kill;
735 }
736