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1 /*
2  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
3  * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
4  * Licensed under the GPL
5  */
6 
7 #include <stdlib.h>
8 #include <unistd.h>
9 #include <sched.h>
10 #include <errno.h>
11 #include <string.h>
12 #include <sys/mman.h>
13 #include <sys/wait.h>
14 #include <asm/unistd.h>
15 #include <as-layout.h>
16 #include <init.h>
17 #include <kern_util.h>
18 #include <mem.h>
19 #include <os.h>
20 #include <ptrace_user.h>
21 #include <registers.h>
22 #include <skas.h>
23 #include <sysdep/stub.h>
24 
is_skas_winch(int pid,int fd,void * data)25 int is_skas_winch(int pid, int fd, void *data)
26 {
27 	return pid == getpgrp();
28 }
29 
ptrace_dump_regs(int pid)30 static int ptrace_dump_regs(int pid)
31 {
32 	unsigned long regs[MAX_REG_NR];
33 	int i;
34 
35 	if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
36 		return -errno;
37 
38 	printk(UM_KERN_ERR "Stub registers -\n");
39 	for (i = 0; i < ARRAY_SIZE(regs); i++)
40 		printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]);
41 
42 	return 0;
43 }
44 
45 /*
46  * Signals that are OK to receive in the stub - we'll just continue it.
47  * SIGWINCH will happen when UML is inside a detached screen.
48  */
49 #define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
50 
51 /* Signals that the stub will finish with - anything else is an error */
52 #define STUB_DONE_MASK (1 << SIGTRAP)
53 
wait_stub_done(int pid)54 void wait_stub_done(int pid)
55 {
56 	int n, status, err;
57 
58 	while (1) {
59 		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
60 		if ((n < 0) || !WIFSTOPPED(status))
61 			goto bad_wait;
62 
63 		if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
64 			break;
65 
66 		err = ptrace(PTRACE_CONT, pid, 0, 0);
67 		if (err) {
68 			printk(UM_KERN_ERR "wait_stub_done : continue failed, "
69 			       "errno = %d\n", errno);
70 			fatal_sigsegv();
71 		}
72 	}
73 
74 	if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
75 		return;
76 
77 bad_wait:
78 	err = ptrace_dump_regs(pid);
79 	if (err)
80 		printk(UM_KERN_ERR "Failed to get registers from stub, "
81 		       "errno = %d\n", -err);
82 	printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
83 	       "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
84 	       status);
85 	fatal_sigsegv();
86 }
87 
88 extern unsigned long current_stub_stack(void);
89 
get_skas_faultinfo(int pid,struct faultinfo * fi)90 static void get_skas_faultinfo(int pid, struct faultinfo *fi)
91 {
92 	int err;
93 	unsigned long fpregs[FP_SIZE];
94 
95 	err = get_fp_registers(pid, fpregs);
96 	if (err < 0) {
97 		printk(UM_KERN_ERR "save_fp_registers returned %d\n",
98 		       err);
99 		fatal_sigsegv();
100 	}
101 	err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
102 	if (err) {
103 		printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
104 		       "errno = %d\n", pid, errno);
105 		fatal_sigsegv();
106 	}
107 	wait_stub_done(pid);
108 
109 	/*
110 	 * faultinfo is prepared by the stub-segv-handler at start of
111 	 * the stub stack page. We just have to copy it.
112 	 */
113 	memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
114 
115 	err = put_fp_registers(pid, fpregs);
116 	if (err < 0) {
117 		printk(UM_KERN_ERR "put_fp_registers returned %d\n",
118 		       err);
119 		fatal_sigsegv();
120 	}
121 }
122 
handle_segv(int pid,struct uml_pt_regs * regs)123 static void handle_segv(int pid, struct uml_pt_regs * regs)
124 {
125 	get_skas_faultinfo(pid, &regs->faultinfo);
126 	segv(regs->faultinfo, 0, 1, NULL);
127 }
128 
129 /*
130  * To use the same value of using_sysemu as the caller, ask it that value
131  * (in local_using_sysemu
132  */
handle_trap(int pid,struct uml_pt_regs * regs,int local_using_sysemu)133 static void handle_trap(int pid, struct uml_pt_regs *regs,
134 			int local_using_sysemu)
135 {
136 	int err, status;
137 
138 	if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
139 		fatal_sigsegv();
140 
141 	if (!local_using_sysemu)
142 	{
143 		err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
144 			     __NR_getpid);
145 		if (err < 0) {
146 			printk(UM_KERN_ERR "handle_trap - nullifying syscall "
147 			       "failed, errno = %d\n", errno);
148 			fatal_sigsegv();
149 		}
150 
151 		err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
152 		if (err < 0) {
153 			printk(UM_KERN_ERR "handle_trap - continuing to end of "
154 			       "syscall failed, errno = %d\n", errno);
155 			fatal_sigsegv();
156 		}
157 
158 		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
159 		if ((err < 0) || !WIFSTOPPED(status) ||
160 		    (WSTOPSIG(status) != SIGTRAP + 0x80)) {
161 			err = ptrace_dump_regs(pid);
162 			if (err)
163 				printk(UM_KERN_ERR "Failed to get registers "
164 				       "from process, errno = %d\n", -err);
165 			printk(UM_KERN_ERR "handle_trap - failed to wait at "
166 			       "end of syscall, errno = %d, status = %d\n",
167 			       errno, status);
168 			fatal_sigsegv();
169 		}
170 	}
171 
172 	handle_syscall(regs);
173 }
174 
get_syscall(struct uml_pt_regs * regs)175 int get_syscall(struct uml_pt_regs *regs)
176 {
177 	UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
178 
179 	return UPT_SYSCALL_NR(regs);
180 }
181 
182 extern char __syscall_stub_start[];
183 
userspace_tramp(void * stack)184 static int userspace_tramp(void *stack)
185 {
186 	void *addr;
187 	int fd;
188 	unsigned long long offset;
189 
190 	ptrace(PTRACE_TRACEME, 0, 0, 0);
191 
192 	signal(SIGTERM, SIG_DFL);
193 	signal(SIGWINCH, SIG_IGN);
194 
195 	/*
196 	 * This has a pte, but it can't be mapped in with the usual
197 	 * tlb_flush mechanism because this is part of that mechanism
198 	 */
199 	fd = phys_mapping(to_phys(__syscall_stub_start), &offset);
200 	addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
201 		      PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
202 	if (addr == MAP_FAILED) {
203 		printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
204 		       "errno = %d\n", STUB_CODE, errno);
205 		exit(1);
206 	}
207 
208 	if (stack != NULL) {
209 		fd = phys_mapping(to_phys(stack), &offset);
210 		addr = mmap((void *) STUB_DATA,
211 			    UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
212 			    MAP_FIXED | MAP_SHARED, fd, offset);
213 		if (addr == MAP_FAILED) {
214 			printk(UM_KERN_ERR "mapping segfault stack "
215 			       "at 0x%lx failed, errno = %d\n",
216 			       STUB_DATA, errno);
217 			exit(1);
218 		}
219 	}
220 	if (stack != NULL) {
221 		struct sigaction sa;
222 
223 		unsigned long v = STUB_CODE +
224 				  (unsigned long) stub_segv_handler -
225 				  (unsigned long) __syscall_stub_start;
226 
227 		set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
228 		sigemptyset(&sa.sa_mask);
229 		sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
230 		sa.sa_sigaction = (void *) v;
231 		sa.sa_restorer = NULL;
232 		if (sigaction(SIGSEGV, &sa, NULL) < 0) {
233 			printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
234 			       "handler failed - errno = %d\n", errno);
235 			exit(1);
236 		}
237 	}
238 
239 	kill(os_getpid(), SIGSTOP);
240 	return 0;
241 }
242 
243 /* Each element set once, and only accessed by a single processor anyway */
244 #undef NR_CPUS
245 #define NR_CPUS 1
246 int userspace_pid[NR_CPUS];
247 
start_userspace(unsigned long stub_stack)248 int start_userspace(unsigned long stub_stack)
249 {
250 	void *stack;
251 	unsigned long sp;
252 	int pid, status, n, flags, err;
253 
254 	stack = mmap(NULL, UM_KERN_PAGE_SIZE,
255 		     PROT_READ | PROT_WRITE | PROT_EXEC,
256 		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
257 	if (stack == MAP_FAILED) {
258 		err = -errno;
259 		printk(UM_KERN_ERR "start_userspace : mmap failed, "
260 		       "errno = %d\n", errno);
261 		return err;
262 	}
263 
264 	sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
265 
266 	flags = CLONE_FILES | SIGCHLD;
267 
268 	pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
269 	if (pid < 0) {
270 		err = -errno;
271 		printk(UM_KERN_ERR "start_userspace : clone failed, "
272 		       "errno = %d\n", errno);
273 		return err;
274 	}
275 
276 	do {
277 		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
278 		if (n < 0) {
279 			err = -errno;
280 			printk(UM_KERN_ERR "start_userspace : wait failed, "
281 			       "errno = %d\n", errno);
282 			goto out_kill;
283 		}
284 	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
285 
286 	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
287 		err = -EINVAL;
288 		printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
289 		       "status = %d\n", status);
290 		goto out_kill;
291 	}
292 
293 	if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
294 		   (void *) PTRACE_O_TRACESYSGOOD) < 0) {
295 		err = -errno;
296 		printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
297 		       "failed, errno = %d\n", errno);
298 		goto out_kill;
299 	}
300 
301 	if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
302 		err = -errno;
303 		printk(UM_KERN_ERR "start_userspace : munmap failed, "
304 		       "errno = %d\n", errno);
305 		goto out_kill;
306 	}
307 
308 	return pid;
309 
310  out_kill:
311 	os_kill_ptraced_process(pid, 1);
312 	return err;
313 }
314 
userspace(struct uml_pt_regs * regs)315 void userspace(struct uml_pt_regs *regs)
316 {
317 	int err, status, op, pid = userspace_pid[0];
318 	/* To prevent races if using_sysemu changes under us.*/
319 	int local_using_sysemu;
320 	siginfo_t si;
321 
322 	/* Handle any immediate reschedules or signals */
323 	interrupt_end();
324 
325 	while (1) {
326 
327 		/*
328 		 * This can legitimately fail if the process loads a
329 		 * bogus value into a segment register.  It will
330 		 * segfault and PTRACE_GETREGS will read that value
331 		 * out of the process.  However, PTRACE_SETREGS will
332 		 * fail.  In this case, there is nothing to do but
333 		 * just kill the process.
334 		 */
335 		if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
336 			fatal_sigsegv();
337 
338 		if (put_fp_registers(pid, regs->fp))
339 			fatal_sigsegv();
340 
341 		/* Now we set local_using_sysemu to be used for one loop */
342 		local_using_sysemu = get_using_sysemu();
343 
344 		op = SELECT_PTRACE_OPERATION(local_using_sysemu,
345 					     singlestepping(NULL));
346 
347 		if (ptrace(op, pid, 0, 0)) {
348 			printk(UM_KERN_ERR "userspace - ptrace continue "
349 			       "failed, op = %d, errno = %d\n", op, errno);
350 			fatal_sigsegv();
351 		}
352 
353 		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
354 		if (err < 0) {
355 			printk(UM_KERN_ERR "userspace - wait failed, "
356 			       "errno = %d\n", errno);
357 			fatal_sigsegv();
358 		}
359 
360 		regs->is_user = 1;
361 		if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
362 			printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
363 			       "errno = %d\n", errno);
364 			fatal_sigsegv();
365 		}
366 
367 		if (get_fp_registers(pid, regs->fp)) {
368 			printk(UM_KERN_ERR "userspace -  get_fp_registers failed, "
369 			       "errno = %d\n", errno);
370 			fatal_sigsegv();
371 		}
372 
373 		UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
374 
375 		if (WIFSTOPPED(status)) {
376 			int sig = WSTOPSIG(status);
377 
378 			ptrace(PTRACE_GETSIGINFO, pid, 0, (struct siginfo *)&si);
379 
380 			switch (sig) {
381 			case SIGSEGV:
382 				if (PTRACE_FULL_FAULTINFO) {
383 					get_skas_faultinfo(pid,
384 							   &regs->faultinfo);
385 					(*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
386 							     regs);
387 				}
388 				else handle_segv(pid, regs);
389 				break;
390 			case SIGTRAP + 0x80:
391 			        handle_trap(pid, regs, local_using_sysemu);
392 				break;
393 			case SIGTRAP:
394 				relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
395 				break;
396 			case SIGALRM:
397 				break;
398 			case SIGIO:
399 			case SIGILL:
400 			case SIGBUS:
401 			case SIGFPE:
402 			case SIGWINCH:
403 				block_signals();
404 				(*sig_info[sig])(sig, (struct siginfo *)&si, regs);
405 				unblock_signals();
406 				break;
407 			default:
408 				printk(UM_KERN_ERR "userspace - child stopped "
409 				       "with signal %d\n", sig);
410 				fatal_sigsegv();
411 			}
412 			pid = userspace_pid[0];
413 			interrupt_end();
414 
415 			/* Avoid -ERESTARTSYS handling in host */
416 			if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
417 				PT_SYSCALL_NR(regs->gp) = -1;
418 		}
419 	}
420 }
421 
422 static unsigned long thread_regs[MAX_REG_NR];
423 static unsigned long thread_fp_regs[FP_SIZE];
424 
init_thread_regs(void)425 static int __init init_thread_regs(void)
426 {
427 	get_safe_registers(thread_regs, thread_fp_regs);
428 	/* Set parent's instruction pointer to start of clone-stub */
429 	thread_regs[REGS_IP_INDEX] = STUB_CODE +
430 				(unsigned long) stub_clone_handler -
431 				(unsigned long) __syscall_stub_start;
432 	thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
433 		sizeof(void *);
434 #ifdef __SIGNAL_FRAMESIZE
435 	thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
436 #endif
437 	return 0;
438 }
439 
440 __initcall(init_thread_regs);
441 
copy_context_skas0(unsigned long new_stack,int pid)442 int copy_context_skas0(unsigned long new_stack, int pid)
443 {
444 	int err;
445 	unsigned long current_stack = current_stub_stack();
446 	struct stub_data *data = (struct stub_data *) current_stack;
447 	struct stub_data *child_data = (struct stub_data *) new_stack;
448 	unsigned long long new_offset;
449 	int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
450 
451 	/*
452 	 * prepare offset and fd of child's stack as argument for parent's
453 	 * and child's mmap2 calls
454 	 */
455 	*data = ((struct stub_data) {
456 			.offset	= MMAP_OFFSET(new_offset),
457 			.fd     = new_fd
458 	});
459 
460 	err = ptrace_setregs(pid, thread_regs);
461 	if (err < 0) {
462 		err = -errno;
463 		printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
464 		       "failed, pid = %d, errno = %d\n", pid, -err);
465 		return err;
466 	}
467 
468 	err = put_fp_registers(pid, thread_fp_regs);
469 	if (err < 0) {
470 		printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
471 		       "failed, pid = %d, err = %d\n", pid, err);
472 		return err;
473 	}
474 
475 	/* set a well known return code for detection of child write failure */
476 	child_data->err = 12345678;
477 
478 	/*
479 	 * Wait, until parent has finished its work: read child's pid from
480 	 * parent's stack, and check, if bad result.
481 	 */
482 	err = ptrace(PTRACE_CONT, pid, 0, 0);
483 	if (err) {
484 		err = -errno;
485 		printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
486 		       "errno = %d\n", pid, errno);
487 		return err;
488 	}
489 
490 	wait_stub_done(pid);
491 
492 	pid = data->err;
493 	if (pid < 0) {
494 		printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
495 		       "error %d\n", -pid);
496 		return pid;
497 	}
498 
499 	/*
500 	 * Wait, until child has finished too: read child's result from
501 	 * child's stack and check it.
502 	 */
503 	wait_stub_done(pid);
504 	if (child_data->err != STUB_DATA) {
505 		printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
506 		       "error %ld\n", child_data->err);
507 		err = child_data->err;
508 		goto out_kill;
509 	}
510 
511 	if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
512 		   (void *)PTRACE_O_TRACESYSGOOD) < 0) {
513 		err = -errno;
514 		printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
515 		       "failed, errno = %d\n", errno);
516 		goto out_kill;
517 	}
518 
519 	return pid;
520 
521  out_kill:
522 	os_kill_ptraced_process(pid, 1);
523 	return err;
524 }
525 
new_thread(void * stack,jmp_buf * buf,void (* handler)(void))526 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
527 {
528 	(*buf)[0].JB_IP = (unsigned long) handler;
529 	(*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
530 		sizeof(void *);
531 }
532 
533 #define INIT_JMP_NEW_THREAD 0
534 #define INIT_JMP_CALLBACK 1
535 #define INIT_JMP_HALT 2
536 #define INIT_JMP_REBOOT 3
537 
switch_threads(jmp_buf * me,jmp_buf * you)538 void switch_threads(jmp_buf *me, jmp_buf *you)
539 {
540 	if (UML_SETJMP(me) == 0)
541 		UML_LONGJMP(you, 1);
542 }
543 
544 static jmp_buf initial_jmpbuf;
545 
546 /* XXX Make these percpu */
547 static void (*cb_proc)(void *arg);
548 static void *cb_arg;
549 static jmp_buf *cb_back;
550 
start_idle_thread(void * stack,jmp_buf * switch_buf)551 int start_idle_thread(void *stack, jmp_buf *switch_buf)
552 {
553 	int n;
554 
555 	set_handler(SIGWINCH);
556 
557 	/*
558 	 * Can't use UML_SETJMP or UML_LONGJMP here because they save
559 	 * and restore signals, with the possible side-effect of
560 	 * trying to handle any signals which came when they were
561 	 * blocked, which can't be done on this stack.
562 	 * Signals must be blocked when jumping back here and restored
563 	 * after returning to the jumper.
564 	 */
565 	n = setjmp(initial_jmpbuf);
566 	switch (n) {
567 	case INIT_JMP_NEW_THREAD:
568 		(*switch_buf)[0].JB_IP = (unsigned long) uml_finishsetup;
569 		(*switch_buf)[0].JB_SP = (unsigned long) stack +
570 			UM_THREAD_SIZE - sizeof(void *);
571 		break;
572 	case INIT_JMP_CALLBACK:
573 		(*cb_proc)(cb_arg);
574 		longjmp(*cb_back, 1);
575 		break;
576 	case INIT_JMP_HALT:
577 		kmalloc_ok = 0;
578 		return 0;
579 	case INIT_JMP_REBOOT:
580 		kmalloc_ok = 0;
581 		return 1;
582 	default:
583 		printk(UM_KERN_ERR "Bad sigsetjmp return in "
584 		       "start_idle_thread - %d\n", n);
585 		fatal_sigsegv();
586 	}
587 	longjmp(*switch_buf, 1);
588 
589 	/* unreachable */
590 	printk(UM_KERN_ERR "impossible long jump!");
591 	fatal_sigsegv();
592 	return 0;
593 }
594 
initial_thread_cb_skas(void (* proc)(void *),void * arg)595 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
596 {
597 	jmp_buf here;
598 
599 	cb_proc = proc;
600 	cb_arg = arg;
601 	cb_back = &here;
602 
603 	block_signals();
604 	if (UML_SETJMP(&here) == 0)
605 		UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
606 	unblock_signals();
607 
608 	cb_proc = NULL;
609 	cb_arg = NULL;
610 	cb_back = NULL;
611 }
612 
halt_skas(void)613 void halt_skas(void)
614 {
615 	block_signals();
616 	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
617 }
618 
reboot_skas(void)619 void reboot_skas(void)
620 {
621 	block_signals();
622 	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
623 }
624 
__switch_mm(struct mm_id * mm_idp)625 void __switch_mm(struct mm_id *mm_idp)
626 {
627 	userspace_pid[0] = mm_idp->u.pid;
628 }
629