xref: /openbmc/linux/arch/um/os-Linux/skas/process.c (revision d7a3d85e)
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 <ptrace_user.h>
20 #include <registers.h>
21 #include <skas.h>
22 #include <sysdep/stub.h>
23 
24 int is_skas_winch(int pid, int fd, void *data)
25 {
26 	return pid == getpgrp();
27 }
28 
29 static int ptrace_dump_regs(int pid)
30 {
31 	unsigned long regs[MAX_REG_NR];
32 	int i;
33 
34 	if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
35 		return -errno;
36 
37 	printk(UM_KERN_ERR "Stub registers -\n");
38 	for (i = 0; i < ARRAY_SIZE(regs); i++)
39 		printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]);
40 
41 	return 0;
42 }
43 
44 /*
45  * Signals that are OK to receive in the stub - we'll just continue it.
46  * SIGWINCH will happen when UML is inside a detached screen.
47  */
48 #define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
49 
50 /* Signals that the stub will finish with - anything else is an error */
51 #define STUB_DONE_MASK (1 << SIGTRAP)
52 
53 void wait_stub_done(int pid)
54 {
55 	int n, status, err;
56 
57 	while (1) {
58 		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
59 		if ((n < 0) || !WIFSTOPPED(status))
60 			goto bad_wait;
61 
62 		if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
63 			break;
64 
65 		err = ptrace(PTRACE_CONT, pid, 0, 0);
66 		if (err) {
67 			printk(UM_KERN_ERR "wait_stub_done : continue failed, "
68 			       "errno = %d\n", errno);
69 			fatal_sigsegv();
70 		}
71 	}
72 
73 	if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
74 		return;
75 
76 bad_wait:
77 	err = ptrace_dump_regs(pid);
78 	if (err)
79 		printk(UM_KERN_ERR "Failed to get registers from stub, "
80 		       "errno = %d\n", -err);
81 	printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
82 	       "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
83 	       status);
84 	fatal_sigsegv();
85 }
86 
87 extern unsigned long current_stub_stack(void);
88 
89 static void get_skas_faultinfo(int pid, struct faultinfo *fi)
90 {
91 	int err;
92 	unsigned long fpregs[FP_SIZE];
93 
94 	err = get_fp_registers(pid, fpregs);
95 	if (err < 0) {
96 		printk(UM_KERN_ERR "save_fp_registers returned %d\n",
97 		       err);
98 		fatal_sigsegv();
99 	}
100 	err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
101 	if (err) {
102 		printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
103 		       "errno = %d\n", pid, errno);
104 		fatal_sigsegv();
105 	}
106 	wait_stub_done(pid);
107 
108 	/*
109 	 * faultinfo is prepared by the stub-segv-handler at start of
110 	 * the stub stack page. We just have to copy it.
111 	 */
112 	memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
113 
114 	err = put_fp_registers(pid, fpregs);
115 	if (err < 0) {
116 		printk(UM_KERN_ERR "put_fp_registers returned %d\n",
117 		       err);
118 		fatal_sigsegv();
119 	}
120 }
121 
122 static void handle_segv(int pid, struct uml_pt_regs * regs)
123 {
124 	get_skas_faultinfo(pid, &regs->faultinfo);
125 	segv(regs->faultinfo, 0, 1, NULL);
126 }
127 
128 /*
129  * To use the same value of using_sysemu as the caller, ask it that value
130  * (in local_using_sysemu
131  */
132 static void handle_trap(int pid, struct uml_pt_regs *regs,
133 			int local_using_sysemu)
134 {
135 	int err, status;
136 
137 	if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
138 		fatal_sigsegv();
139 
140 	/* Mark this as a syscall */
141 	UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
142 
143 	if (!local_using_sysemu)
144 	{
145 		err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
146 			     __NR_getpid);
147 		if (err < 0) {
148 			printk(UM_KERN_ERR "handle_trap - nullifying syscall "
149 			       "failed, errno = %d\n", errno);
150 			fatal_sigsegv();
151 		}
152 
153 		err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
154 		if (err < 0) {
155 			printk(UM_KERN_ERR "handle_trap - continuing to end of "
156 			       "syscall failed, errno = %d\n", errno);
157 			fatal_sigsegv();
158 		}
159 
160 		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
161 		if ((err < 0) || !WIFSTOPPED(status) ||
162 		    (WSTOPSIG(status) != SIGTRAP + 0x80)) {
163 			err = ptrace_dump_regs(pid);
164 			if (err)
165 				printk(UM_KERN_ERR "Failed to get registers "
166 				       "from process, errno = %d\n", -err);
167 			printk(UM_KERN_ERR "handle_trap - failed to wait at "
168 			       "end of syscall, errno = %d, status = %d\n",
169 			       errno, status);
170 			fatal_sigsegv();
171 		}
172 	}
173 
174 	handle_syscall(regs);
175 }
176 
177 extern int __syscall_stub_start;
178 
179 static int userspace_tramp(void *stack)
180 {
181 	void *addr;
182 	int err, fd;
183 	unsigned long long offset;
184 
185 	ptrace(PTRACE_TRACEME, 0, 0, 0);
186 
187 	signal(SIGTERM, SIG_DFL);
188 	signal(SIGWINCH, SIG_IGN);
189 	err = set_interval();
190 	if (err) {
191 		printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
192 		       "errno = %d\n", err);
193 		exit(1);
194 	}
195 
196 	/*
197 	 * This has a pte, but it can't be mapped in with the usual
198 	 * tlb_flush mechanism because this is part of that mechanism
199 	 */
200 	fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
201 	addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
202 		      PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
203 	if (addr == MAP_FAILED) {
204 		printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
205 		       "errno = %d\n", STUB_CODE, errno);
206 		exit(1);
207 	}
208 
209 	if (stack != NULL) {
210 		fd = phys_mapping(to_phys(stack), &offset);
211 		addr = mmap((void *) STUB_DATA,
212 			    UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
213 			    MAP_FIXED | MAP_SHARED, fd, offset);
214 		if (addr == MAP_FAILED) {
215 			printk(UM_KERN_ERR "mapping segfault stack "
216 			       "at 0x%lx failed, errno = %d\n",
217 			       STUB_DATA, errno);
218 			exit(1);
219 		}
220 	}
221 	if (stack != NULL) {
222 		struct sigaction sa;
223 
224 		unsigned long v = STUB_CODE +
225 				  (unsigned long) stub_segv_handler -
226 				  (unsigned long) &__syscall_stub_start;
227 
228 		set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
229 		sigemptyset(&sa.sa_mask);
230 		sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
231 		sa.sa_sigaction = (void *) v;
232 		sa.sa_restorer = NULL;
233 		if (sigaction(SIGSEGV, &sa, NULL) < 0) {
234 			printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
235 			       "handler failed - errno = %d\n", errno);
236 			exit(1);
237 		}
238 	}
239 
240 	kill(os_getpid(), SIGSTOP);
241 	return 0;
242 }
243 
244 /* Each element set once, and only accessed by a single processor anyway */
245 #undef NR_CPUS
246 #define NR_CPUS 1
247 int userspace_pid[NR_CPUS];
248 
249 int start_userspace(unsigned long stub_stack)
250 {
251 	void *stack;
252 	unsigned long sp;
253 	int pid, status, n, flags, err;
254 
255 	stack = mmap(NULL, UM_KERN_PAGE_SIZE,
256 		     PROT_READ | PROT_WRITE | PROT_EXEC,
257 		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
258 	if (stack == MAP_FAILED) {
259 		err = -errno;
260 		printk(UM_KERN_ERR "start_userspace : mmap failed, "
261 		       "errno = %d\n", errno);
262 		return err;
263 	}
264 
265 	sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
266 
267 	flags = CLONE_FILES | SIGCHLD;
268 
269 	pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
270 	if (pid < 0) {
271 		err = -errno;
272 		printk(UM_KERN_ERR "start_userspace : clone failed, "
273 		       "errno = %d\n", errno);
274 		return err;
275 	}
276 
277 	do {
278 		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
279 		if (n < 0) {
280 			err = -errno;
281 			printk(UM_KERN_ERR "start_userspace : wait failed, "
282 			       "errno = %d\n", errno);
283 			goto out_kill;
284 		}
285 	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
286 
287 	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
288 		err = -EINVAL;
289 		printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
290 		       "status = %d\n", status);
291 		goto out_kill;
292 	}
293 
294 	if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
295 		   (void *) PTRACE_O_TRACESYSGOOD) < 0) {
296 		err = -errno;
297 		printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
298 		       "failed, errno = %d\n", errno);
299 		goto out_kill;
300 	}
301 
302 	if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
303 		err = -errno;
304 		printk(UM_KERN_ERR "start_userspace : munmap failed, "
305 		       "errno = %d\n", errno);
306 		goto out_kill;
307 	}
308 
309 	return pid;
310 
311  out_kill:
312 	os_kill_ptraced_process(pid, 1);
313 	return err;
314 }
315 
316 void userspace(struct uml_pt_regs *regs)
317 {
318 	struct itimerval timer;
319 	unsigned long long nsecs, now;
320 	int err, status, op, pid = userspace_pid[0];
321 	/* To prevent races if using_sysemu changes under us.*/
322 	int local_using_sysemu;
323 	siginfo_t si;
324 
325 	/* Handle any immediate reschedules or signals */
326 	interrupt_end();
327 
328 	if (getitimer(ITIMER_VIRTUAL, &timer))
329 		printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
330 	nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
331 		timer.it_value.tv_usec * UM_NSEC_PER_USEC;
332 	nsecs += os_nsecs();
333 
334 	while (1) {
335 		/*
336 		 * This can legitimately fail if the process loads a
337 		 * bogus value into a segment register.  It will
338 		 * segfault and PTRACE_GETREGS will read that value
339 		 * out of the process.  However, PTRACE_SETREGS will
340 		 * fail.  In this case, there is nothing to do but
341 		 * just kill the process.
342 		 */
343 		if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
344 			fatal_sigsegv();
345 
346 		if (put_fp_registers(pid, regs->fp))
347 			fatal_sigsegv();
348 
349 		/* Now we set local_using_sysemu to be used for one loop */
350 		local_using_sysemu = get_using_sysemu();
351 
352 		op = SELECT_PTRACE_OPERATION(local_using_sysemu,
353 					     singlestepping(NULL));
354 
355 		if (ptrace(op, pid, 0, 0)) {
356 			printk(UM_KERN_ERR "userspace - ptrace continue "
357 			       "failed, op = %d, errno = %d\n", op, errno);
358 			fatal_sigsegv();
359 		}
360 
361 		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
362 		if (err < 0) {
363 			printk(UM_KERN_ERR "userspace - wait failed, "
364 			       "errno = %d\n", errno);
365 			fatal_sigsegv();
366 		}
367 
368 		regs->is_user = 1;
369 		if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
370 			printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
371 			       "errno = %d\n", errno);
372 			fatal_sigsegv();
373 		}
374 
375 		if (get_fp_registers(pid, regs->fp)) {
376 			printk(UM_KERN_ERR "userspace -  get_fp_registers failed, "
377 			       "errno = %d\n", errno);
378 			fatal_sigsegv();
379 		}
380 
381 		UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
382 
383 		if (WIFSTOPPED(status)) {
384 			int sig = WSTOPSIG(status);
385 
386 			ptrace(PTRACE_GETSIGINFO, pid, 0, (struct siginfo *)&si);
387 
388 			switch (sig) {
389 			case SIGSEGV:
390 				if (PTRACE_FULL_FAULTINFO) {
391 					get_skas_faultinfo(pid,
392 							   &regs->faultinfo);
393 					(*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
394 							     regs);
395 				}
396 				else handle_segv(pid, regs);
397 				break;
398 			case SIGTRAP + 0x80:
399 			        handle_trap(pid, regs, local_using_sysemu);
400 				break;
401 			case SIGTRAP:
402 				relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
403 				break;
404 			case SIGVTALRM:
405 				now = os_nsecs();
406 				if (now < nsecs)
407 					break;
408 				block_signals();
409 				(*sig_info[sig])(sig, (struct siginfo *)&si, regs);
410 				unblock_signals();
411 				nsecs = timer.it_value.tv_sec *
412 					UM_NSEC_PER_SEC +
413 					timer.it_value.tv_usec *
414 					UM_NSEC_PER_USEC;
415 				nsecs += os_nsecs();
416 				break;
417 			case SIGIO:
418 			case SIGILL:
419 			case SIGBUS:
420 			case SIGFPE:
421 			case SIGWINCH:
422 				block_signals();
423 				(*sig_info[sig])(sig, (struct siginfo *)&si, regs);
424 				unblock_signals();
425 				break;
426 			default:
427 				printk(UM_KERN_ERR "userspace - child stopped "
428 				       "with signal %d\n", sig);
429 				fatal_sigsegv();
430 			}
431 			pid = userspace_pid[0];
432 			interrupt_end();
433 
434 			/* Avoid -ERESTARTSYS handling in host */
435 			if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
436 				PT_SYSCALL_NR(regs->gp) = -1;
437 		}
438 	}
439 }
440 
441 static unsigned long thread_regs[MAX_REG_NR];
442 static unsigned long thread_fp_regs[FP_SIZE];
443 
444 static int __init init_thread_regs(void)
445 {
446 	get_safe_registers(thread_regs, thread_fp_regs);
447 	/* Set parent's instruction pointer to start of clone-stub */
448 	thread_regs[REGS_IP_INDEX] = STUB_CODE +
449 				(unsigned long) stub_clone_handler -
450 				(unsigned long) &__syscall_stub_start;
451 	thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
452 		sizeof(void *);
453 #ifdef __SIGNAL_FRAMESIZE
454 	thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
455 #endif
456 	return 0;
457 }
458 
459 __initcall(init_thread_regs);
460 
461 int copy_context_skas0(unsigned long new_stack, int pid)
462 {
463 	struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
464 	int err;
465 	unsigned long current_stack = current_stub_stack();
466 	struct stub_data *data = (struct stub_data *) current_stack;
467 	struct stub_data *child_data = (struct stub_data *) new_stack;
468 	unsigned long long new_offset;
469 	int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
470 
471 	/*
472 	 * prepare offset and fd of child's stack as argument for parent's
473 	 * and child's mmap2 calls
474 	 */
475 	*data = ((struct stub_data) { .offset	= MMAP_OFFSET(new_offset),
476 				      .fd	= new_fd,
477 				      .timer    = ((struct itimerval)
478 					           { .it_value = tv,
479 						     .it_interval = tv }) });
480 
481 	err = ptrace_setregs(pid, thread_regs);
482 	if (err < 0) {
483 		err = -errno;
484 		printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
485 		       "failed, pid = %d, errno = %d\n", pid, -err);
486 		return err;
487 	}
488 
489 	err = put_fp_registers(pid, thread_fp_regs);
490 	if (err < 0) {
491 		printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
492 		       "failed, pid = %d, err = %d\n", pid, err);
493 		return err;
494 	}
495 
496 	/* set a well known return code for detection of child write failure */
497 	child_data->err = 12345678;
498 
499 	/*
500 	 * Wait, until parent has finished its work: read child's pid from
501 	 * parent's stack, and check, if bad result.
502 	 */
503 	err = ptrace(PTRACE_CONT, pid, 0, 0);
504 	if (err) {
505 		err = -errno;
506 		printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
507 		       "errno = %d\n", pid, errno);
508 		return err;
509 	}
510 
511 	wait_stub_done(pid);
512 
513 	pid = data->err;
514 	if (pid < 0) {
515 		printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
516 		       "error %d\n", -pid);
517 		return pid;
518 	}
519 
520 	/*
521 	 * Wait, until child has finished too: read child's result from
522 	 * child's stack and check it.
523 	 */
524 	wait_stub_done(pid);
525 	if (child_data->err != STUB_DATA) {
526 		printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
527 		       "error %ld\n", child_data->err);
528 		err = child_data->err;
529 		goto out_kill;
530 	}
531 
532 	if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
533 		   (void *)PTRACE_O_TRACESYSGOOD) < 0) {
534 		err = -errno;
535 		printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
536 		       "failed, errno = %d\n", errno);
537 		goto out_kill;
538 	}
539 
540 	return pid;
541 
542  out_kill:
543 	os_kill_ptraced_process(pid, 1);
544 	return err;
545 }
546 
547 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
548 {
549 	(*buf)[0].JB_IP = (unsigned long) handler;
550 	(*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
551 		sizeof(void *);
552 }
553 
554 #define INIT_JMP_NEW_THREAD 0
555 #define INIT_JMP_CALLBACK 1
556 #define INIT_JMP_HALT 2
557 #define INIT_JMP_REBOOT 3
558 
559 void switch_threads(jmp_buf *me, jmp_buf *you)
560 {
561 	if (UML_SETJMP(me) == 0)
562 		UML_LONGJMP(you, 1);
563 }
564 
565 static jmp_buf initial_jmpbuf;
566 
567 /* XXX Make these percpu */
568 static void (*cb_proc)(void *arg);
569 static void *cb_arg;
570 static jmp_buf *cb_back;
571 
572 int start_idle_thread(void *stack, jmp_buf *switch_buf)
573 {
574 	int n;
575 
576 	set_handler(SIGWINCH);
577 
578 	/*
579 	 * Can't use UML_SETJMP or UML_LONGJMP here because they save
580 	 * and restore signals, with the possible side-effect of
581 	 * trying to handle any signals which came when they were
582 	 * blocked, which can't be done on this stack.
583 	 * Signals must be blocked when jumping back here and restored
584 	 * after returning to the jumper.
585 	 */
586 	n = setjmp(initial_jmpbuf);
587 	switch (n) {
588 	case INIT_JMP_NEW_THREAD:
589 		(*switch_buf)[0].JB_IP = (unsigned long) uml_finishsetup;
590 		(*switch_buf)[0].JB_SP = (unsigned long) stack +
591 			UM_THREAD_SIZE - sizeof(void *);
592 		break;
593 	case INIT_JMP_CALLBACK:
594 		(*cb_proc)(cb_arg);
595 		longjmp(*cb_back, 1);
596 		break;
597 	case INIT_JMP_HALT:
598 		kmalloc_ok = 0;
599 		return 0;
600 	case INIT_JMP_REBOOT:
601 		kmalloc_ok = 0;
602 		return 1;
603 	default:
604 		printk(UM_KERN_ERR "Bad sigsetjmp return in "
605 		       "start_idle_thread - %d\n", n);
606 		fatal_sigsegv();
607 	}
608 	longjmp(*switch_buf, 1);
609 }
610 
611 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
612 {
613 	jmp_buf here;
614 
615 	cb_proc = proc;
616 	cb_arg = arg;
617 	cb_back = &here;
618 
619 	block_signals();
620 	if (UML_SETJMP(&here) == 0)
621 		UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
622 	unblock_signals();
623 
624 	cb_proc = NULL;
625 	cb_arg = NULL;
626 	cb_back = NULL;
627 }
628 
629 void halt_skas(void)
630 {
631 	block_signals();
632 	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
633 }
634 
635 void reboot_skas(void)
636 {
637 	block_signals();
638 	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
639 }
640 
641 void __switch_mm(struct mm_id *mm_idp)
642 {
643 	userspace_pid[0] = mm_idp->u.pid;
644 }
645