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, ®s->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 ®s->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