1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2021 Benjamin Berg <benjamin@sipsolutions.net>
4 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
5 * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
6 */
7
8 #include <stdlib.h>
9 #include <stdbool.h>
10 #include <unistd.h>
11 #include <sched.h>
12 #include <errno.h>
13 #include <string.h>
14 #include <fcntl.h>
15 #include <mem_user.h>
16 #include <sys/mman.h>
17 #include <sys/wait.h>
18 #include <sys/stat.h>
19 #include <sys/socket.h>
20 #include <asm/unistd.h>
21 #include <as-layout.h>
22 #include <init.h>
23 #include <kern_util.h>
24 #include <mem.h>
25 #include <os.h>
26 #include <ptrace_user.h>
27 #include <registers.h>
28 #include <skas.h>
29 #include <sysdep/stub.h>
30 #include <sysdep/mcontext.h>
31 #include <linux/futex.h>
32 #include <linux/threads.h>
33 #include <timetravel.h>
34 #include <asm-generic/rwonce.h>
35 #include "../internal.h"
36
is_skas_winch(int pid,int fd,void * data)37 int is_skas_winch(int pid, int fd, void *data)
38 {
39 return pid == getpgrp();
40 }
41
ptrace_reg_name(int idx)42 static const char *ptrace_reg_name(int idx)
43 {
44 #define R(n) case HOST_##n: return #n
45
46 switch (idx) {
47 #ifdef __x86_64__
48 R(BX);
49 R(CX);
50 R(DI);
51 R(SI);
52 R(DX);
53 R(BP);
54 R(AX);
55 R(R8);
56 R(R9);
57 R(R10);
58 R(R11);
59 R(R12);
60 R(R13);
61 R(R14);
62 R(R15);
63 R(ORIG_AX);
64 R(CS);
65 R(SS);
66 R(EFLAGS);
67 #elif defined(__i386__)
68 R(IP);
69 R(SP);
70 R(EFLAGS);
71 R(AX);
72 R(BX);
73 R(CX);
74 R(DX);
75 R(SI);
76 R(DI);
77 R(BP);
78 R(CS);
79 R(SS);
80 R(DS);
81 R(FS);
82 R(ES);
83 R(GS);
84 R(ORIG_AX);
85 #endif
86 }
87 return "";
88 }
89
ptrace_dump_regs(int pid)90 static int ptrace_dump_regs(int pid)
91 {
92 unsigned long regs[MAX_REG_NR];
93 int i;
94
95 if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
96 return -errno;
97
98 printk(UM_KERN_ERR "Stub registers -\n");
99 for (i = 0; i < ARRAY_SIZE(regs); i++) {
100 const char *regname = ptrace_reg_name(i);
101
102 printk(UM_KERN_ERR "\t%s\t(%2d): %lx\n", regname, i, regs[i]);
103 }
104
105 return 0;
106 }
107
108 /*
109 * Signals that are OK to receive in the stub - we'll just continue it.
110 * SIGWINCH will happen when UML is inside a detached screen.
111 */
112 #define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
113
114 /* Signals that the stub will finish with - anything else is an error */
115 #define STUB_DONE_MASK (1 << SIGTRAP)
116
wait_stub_done(int pid)117 void wait_stub_done(int pid)
118 {
119 int n, status, err;
120
121 while (1) {
122 CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
123 if ((n < 0) || !WIFSTOPPED(status))
124 goto bad_wait;
125
126 if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
127 break;
128
129 err = ptrace(PTRACE_CONT, pid, 0, 0);
130 if (err) {
131 printk(UM_KERN_ERR "%s : continue failed, errno = %d\n",
132 __func__, errno);
133 fatal_sigsegv();
134 }
135 }
136
137 if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
138 return;
139
140 bad_wait:
141 err = ptrace_dump_regs(pid);
142 if (err)
143 printk(UM_KERN_ERR "Failed to get registers from stub, errno = %d\n",
144 -err);
145 printk(UM_KERN_ERR "%s : failed to wait for SIGTRAP, pid = %d, n = %d, errno = %d, status = 0x%x\n",
146 __func__, pid, n, errno, status);
147 fatal_sigsegv();
148 }
149
wait_stub_done_seccomp(struct mm_id * mm_idp,int running,int wait_sigsys)150 void wait_stub_done_seccomp(struct mm_id *mm_idp, int running, int wait_sigsys)
151 {
152 struct stub_data *data = (void *)mm_idp->stack;
153 int ret;
154
155 do {
156 const char byte = 0;
157 struct iovec iov = {
158 .iov_base = (void *)&byte,
159 .iov_len = sizeof(byte),
160 };
161 union {
162 char data[CMSG_SPACE(sizeof(mm_idp->syscall_fd_map))];
163 struct cmsghdr align;
164 } ctrl;
165 struct msghdr msgh = {
166 .msg_iov = &iov,
167 .msg_iovlen = 1,
168 };
169
170 if (!running) {
171 if (mm_idp->syscall_fd_num) {
172 unsigned int fds_size =
173 sizeof(int) * mm_idp->syscall_fd_num;
174 struct cmsghdr *cmsg;
175
176 msgh.msg_control = ctrl.data;
177 msgh.msg_controllen = CMSG_SPACE(fds_size);
178 cmsg = CMSG_FIRSTHDR(&msgh);
179 cmsg->cmsg_level = SOL_SOCKET;
180 cmsg->cmsg_type = SCM_RIGHTS;
181 cmsg->cmsg_len = CMSG_LEN(fds_size);
182 memcpy(CMSG_DATA(cmsg), mm_idp->syscall_fd_map,
183 fds_size);
184
185 CATCH_EINTR(syscall(__NR_sendmsg, mm_idp->sock,
186 &msgh, 0));
187 }
188
189 data->signal = 0;
190 data->futex = FUTEX_IN_CHILD;
191 CATCH_EINTR(syscall(__NR_futex, &data->futex,
192 FUTEX_WAKE, 1, NULL, NULL, 0));
193 }
194
195 do {
196 /*
197 * We need to check whether the child is still alive
198 * before and after the FUTEX_WAIT call. Before, in
199 * case it just died but we still updated data->futex
200 * to FUTEX_IN_CHILD. And after, in case it died while
201 * we were waiting (and SIGCHLD woke us up, see the
202 * IRQ handler in mmu.c).
203 *
204 * Either way, if PID is negative, then we have no
205 * choice but to kill the task.
206 */
207 if (__READ_ONCE(mm_idp->pid) < 0)
208 goto out_kill;
209
210 ret = syscall(__NR_futex, &data->futex,
211 FUTEX_WAIT, FUTEX_IN_CHILD,
212 NULL, NULL, 0);
213 if (ret < 0 && errno != EINTR && errno != EAGAIN) {
214 printk(UM_KERN_ERR "%s : FUTEX_WAIT failed, errno = %d\n",
215 __func__, errno);
216 goto out_kill;
217 }
218 } while (data->futex == FUTEX_IN_CHILD);
219
220 if (__READ_ONCE(mm_idp->pid) < 0)
221 goto out_kill;
222
223 running = 0;
224
225 /* We may receive a SIGALRM before SIGSYS, iterate again. */
226 } while (wait_sigsys && data->signal == SIGALRM);
227
228 if (data->mctx_offset > sizeof(data->sigstack) - sizeof(mcontext_t)) {
229 printk(UM_KERN_ERR "%s : invalid mcontext offset", __func__);
230 goto out_kill;
231 }
232
233 if (wait_sigsys && data->signal != SIGSYS) {
234 printk(UM_KERN_ERR "%s : expected SIGSYS but got %d",
235 __func__, data->signal);
236 goto out_kill;
237 }
238
239 return;
240
241 out_kill:
242 printk(UM_KERN_ERR "%s : failed to wait for stub, pid = %d, errno = %d\n",
243 __func__, mm_idp->pid, errno);
244 /* This is not true inside start_userspace */
245 if (current_mm_id() == mm_idp)
246 fatal_sigsegv();
247 }
248
249 extern unsigned long current_stub_stack(void);
250
get_skas_faultinfo(int pid,struct faultinfo * fi)251 static void get_skas_faultinfo(int pid, struct faultinfo *fi)
252 {
253 int err;
254
255 err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
256 if (err) {
257 printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
258 "errno = %d\n", pid, errno);
259 fatal_sigsegv();
260 }
261 wait_stub_done(pid);
262
263 /*
264 * faultinfo is prepared by the stub_segv_handler at start of
265 * the stub stack page. We just have to copy it.
266 */
267 memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
268 }
269
handle_trap(struct uml_pt_regs * regs)270 static void handle_trap(struct uml_pt_regs *regs)
271 {
272 if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
273 fatal_sigsegv();
274
275 handle_syscall(regs);
276 }
277
278 extern char __syscall_stub_start[];
279
280 static int stub_exe_fd;
281
282 struct tramp_data {
283 struct stub_data *stub_data;
284 /* 0 is inherited, 1 is the kernel side */
285 int sockpair[2];
286 };
287
288 #ifndef CLOSE_RANGE_CLOEXEC
289 #define CLOSE_RANGE_CLOEXEC (1U << 2)
290 #endif
291
userspace_tramp(void * data)292 static int userspace_tramp(void *data)
293 {
294 struct tramp_data *tramp_data = data;
295 char *const argv[] = { "uml-userspace", NULL };
296 unsigned long long offset;
297 struct stub_init_data init_data = {
298 .seccomp = using_seccomp,
299 .stub_start = STUB_START,
300 };
301 int ret;
302
303 if (using_seccomp) {
304 init_data.signal_handler = STUB_CODE +
305 (unsigned long) stub_signal_interrupt -
306 (unsigned long) __syscall_stub_start;
307 init_data.signal_restorer = STUB_CODE +
308 (unsigned long) stub_signal_restorer -
309 (unsigned long) __syscall_stub_start;
310 } else {
311 init_data.signal_handler = STUB_CODE +
312 (unsigned long) stub_segv_handler -
313 (unsigned long) __syscall_stub_start;
314 init_data.signal_restorer = 0;
315 }
316
317 init_data.stub_code_fd = phys_mapping(uml_to_phys(__syscall_stub_start),
318 &offset);
319 init_data.stub_code_offset = MMAP_OFFSET(offset);
320
321 init_data.stub_data_fd = phys_mapping(uml_to_phys(tramp_data->stub_data),
322 &offset);
323 init_data.stub_data_offset = MMAP_OFFSET(offset);
324
325 /*
326 * Avoid leaking unneeded FDs to the stub by setting CLOEXEC on all FDs
327 * and then unsetting it on all memory related FDs.
328 * This is not strictly necessary from a safety perspective.
329 */
330 syscall(__NR_close_range, 0, ~0U, CLOSE_RANGE_CLOEXEC);
331
332 fcntl(init_data.stub_data_fd, F_SETFD, 0);
333
334 /* dup2 signaling FD/socket to STDIN */
335 if (dup2(tramp_data->sockpair[0], 0) < 0)
336 exit(3);
337 close(tramp_data->sockpair[0]);
338
339 /* Write init_data and close write side */
340 ret = write(tramp_data->sockpair[1], &init_data, sizeof(init_data));
341 close(tramp_data->sockpair[1]);
342
343 if (ret != sizeof(init_data))
344 exit(4);
345
346 /* Raw execveat for compatibility with older libc versions */
347 syscall(__NR_execveat, stub_exe_fd, (unsigned long)"",
348 (unsigned long)argv, NULL, AT_EMPTY_PATH);
349
350 exit(5);
351 }
352
353 extern char stub_exe_start[];
354 extern char stub_exe_end[];
355
356 extern char *tempdir;
357
358 #define STUB_EXE_NAME_TEMPLATE "/uml-userspace-XXXXXX"
359
360 #ifndef MFD_EXEC
361 #define MFD_EXEC 0x0010U
362 #endif
363
init_stub_exe_fd(void)364 static int __init init_stub_exe_fd(void)
365 {
366 size_t written = 0;
367 char *tmpfile = NULL;
368
369 stub_exe_fd = memfd_create("uml-userspace",
370 MFD_EXEC | MFD_CLOEXEC | MFD_ALLOW_SEALING);
371
372 if (stub_exe_fd < 0) {
373 printk(UM_KERN_INFO "Could not create executable memfd, using temporary file!");
374
375 tmpfile = malloc(strlen(tempdir) +
376 strlen(STUB_EXE_NAME_TEMPLATE) + 1);
377 if (tmpfile == NULL)
378 panic("Failed to allocate memory for stub binary name");
379
380 strcpy(tmpfile, tempdir);
381 strcat(tmpfile, STUB_EXE_NAME_TEMPLATE);
382
383 stub_exe_fd = mkstemp(tmpfile);
384 if (stub_exe_fd < 0)
385 panic("Could not create temporary file for stub binary: %d",
386 -errno);
387 }
388
389 while (written < stub_exe_end - stub_exe_start) {
390 ssize_t res = write(stub_exe_fd, stub_exe_start + written,
391 stub_exe_end - stub_exe_start - written);
392 if (res < 0) {
393 if (errno == EINTR)
394 continue;
395
396 if (tmpfile)
397 unlink(tmpfile);
398 panic("Failed write stub binary: %d", -errno);
399 }
400
401 written += res;
402 }
403
404 if (!tmpfile) {
405 fcntl(stub_exe_fd, F_ADD_SEALS,
406 F_SEAL_WRITE | F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_SEAL);
407 } else {
408 if (fchmod(stub_exe_fd, 00500) < 0) {
409 unlink(tmpfile);
410 panic("Could not make stub binary executable: %d",
411 -errno);
412 }
413
414 close(stub_exe_fd);
415 stub_exe_fd = open(tmpfile, O_RDONLY | O_CLOEXEC | O_NOFOLLOW);
416 if (stub_exe_fd < 0) {
417 unlink(tmpfile);
418 panic("Could not reopen stub binary: %d", -errno);
419 }
420
421 unlink(tmpfile);
422 free(tmpfile);
423 }
424
425 return 0;
426 }
427 __initcall(init_stub_exe_fd);
428
429 int using_seccomp;
430
431 /**
432 * start_userspace() - prepare a new userspace process
433 * @mm_id: The corresponding struct mm_id
434 *
435 * Setups a new temporary stack page that is used while userspace_tramp() runs
436 * Clones the kernel process into a new userspace process, with FDs only.
437 *
438 * Return: When positive: the process id of the new userspace process,
439 * when negative: an error number.
440 * FIXME: can PIDs become negative?!
441 */
start_userspace(struct mm_id * mm_id)442 int start_userspace(struct mm_id *mm_id)
443 {
444 struct stub_data *proc_data = (void *)mm_id->stack;
445 struct tramp_data tramp_data = {
446 .stub_data = proc_data,
447 };
448 void *stack;
449 unsigned long sp;
450 int status, n, err;
451
452 /* setup a temporary stack page */
453 stack = mmap(NULL, UM_KERN_PAGE_SIZE,
454 PROT_READ | PROT_WRITE | PROT_EXEC,
455 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
456 if (stack == MAP_FAILED) {
457 err = -errno;
458 printk(UM_KERN_ERR "%s : mmap failed, errno = %d\n",
459 __func__, errno);
460 return err;
461 }
462
463 /* set stack pointer to the end of the stack page, so it can grow downwards */
464 sp = (unsigned long)stack + UM_KERN_PAGE_SIZE;
465
466 /* socket pair for init data and SECCOMP FD passing (no CLOEXEC here) */
467 if (socketpair(AF_UNIX, SOCK_STREAM, 0, tramp_data.sockpair)) {
468 err = -errno;
469 printk(UM_KERN_ERR "%s : socketpair failed, errno = %d\n",
470 __func__, errno);
471 return err;
472 }
473
474 if (using_seccomp)
475 proc_data->futex = FUTEX_IN_CHILD;
476
477 mm_id->pid = clone(userspace_tramp, (void *) sp,
478 CLONE_VFORK | CLONE_VM | SIGCHLD,
479 (void *)&tramp_data);
480 if (mm_id->pid < 0) {
481 err = -errno;
482 printk(UM_KERN_ERR "%s : clone failed, errno = %d\n",
483 __func__, errno);
484 goto out_close;
485 }
486
487 if (using_seccomp) {
488 wait_stub_done_seccomp(mm_id, 1, 1);
489 } else {
490 do {
491 CATCH_EINTR(n = waitpid(mm_id->pid, &status,
492 WUNTRACED | __WALL));
493 if (n < 0) {
494 err = -errno;
495 printk(UM_KERN_ERR "%s : wait failed, errno = %d\n",
496 __func__, errno);
497 goto out_kill;
498 }
499 } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
500
501 if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
502 err = -EINVAL;
503 printk(UM_KERN_ERR "%s : expected SIGSTOP, got status = %d\n",
504 __func__, status);
505 goto out_kill;
506 }
507
508 if (ptrace(PTRACE_SETOPTIONS, mm_id->pid, NULL,
509 (void *) PTRACE_O_TRACESYSGOOD) < 0) {
510 err = -errno;
511 printk(UM_KERN_ERR "%s : PTRACE_SETOPTIONS failed, errno = %d\n",
512 __func__, errno);
513 goto out_kill;
514 }
515 }
516
517 if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
518 err = -errno;
519 printk(UM_KERN_ERR "%s : munmap failed, errno = %d\n",
520 __func__, errno);
521 goto out_kill;
522 }
523
524 close(tramp_data.sockpair[0]);
525 if (using_seccomp)
526 mm_id->sock = tramp_data.sockpair[1];
527 else
528 close(tramp_data.sockpair[1]);
529
530 return 0;
531
532 out_kill:
533 os_kill_ptraced_process(mm_id->pid, 1);
534 out_close:
535 close(tramp_data.sockpair[0]);
536 close(tramp_data.sockpair[1]);
537
538 mm_id->pid = -1;
539
540 return err;
541 }
542
543 static int unscheduled_userspace_iterations;
544 extern unsigned long tt_extra_sched_jiffies;
545
userspace(struct uml_pt_regs * regs)546 void userspace(struct uml_pt_regs *regs)
547 {
548 int err, status, op;
549 siginfo_t si_local;
550 siginfo_t *si;
551 int sig;
552
553 /* Handle any immediate reschedules or signals */
554 interrupt_end();
555
556 while (1) {
557 struct mm_id *mm_id = current_mm_id();
558
559 /*
560 * At any given time, only one CPU thread can enter the
561 * turnstile to operate on the same stub process, including
562 * executing stub system calls (mmap and munmap).
563 */
564 enter_turnstile(mm_id);
565
566 /*
567 * When we are in time-travel mode, userspace can theoretically
568 * do a *lot* of work without being scheduled. The problem with
569 * this is that it will prevent kernel bookkeeping (primarily
570 * the RCU) from running and this can for example cause OOM
571 * situations.
572 *
573 * This code accounts a jiffie against the scheduling clock
574 * after the defined userspace iterations in the same thread.
575 * By doing so the situation is effectively prevented.
576 */
577 if (time_travel_mode == TT_MODE_INFCPU ||
578 time_travel_mode == TT_MODE_EXTERNAL) {
579 #ifdef CONFIG_UML_MAX_USERSPACE_ITERATIONS
580 if (CONFIG_UML_MAX_USERSPACE_ITERATIONS &&
581 unscheduled_userspace_iterations++ >
582 CONFIG_UML_MAX_USERSPACE_ITERATIONS) {
583 tt_extra_sched_jiffies += 1;
584 unscheduled_userspace_iterations = 0;
585 }
586 #endif
587 }
588
589 time_travel_print_bc_msg();
590
591 current_mm_sync();
592
593 if (using_seccomp) {
594 struct stub_data *proc_data = (void *) mm_id->stack;
595
596 err = set_stub_state(regs, proc_data, singlestepping());
597 if (err) {
598 printk(UM_KERN_ERR "%s - failed to set regs: %d",
599 __func__, err);
600 fatal_sigsegv();
601 }
602
603 /* Must have been reset by the syscall caller */
604 if (proc_data->restart_wait != 0)
605 panic("Programming error: Flag to only run syscalls in child was not cleared!");
606
607 /* Mark pending syscalls for flushing */
608 proc_data->syscall_data_len = mm_id->syscall_data_len;
609
610 wait_stub_done_seccomp(mm_id, 0, 0);
611
612 sig = proc_data->signal;
613
614 if (sig == SIGTRAP && proc_data->err != 0) {
615 printk(UM_KERN_ERR "%s - Error flushing stub syscalls",
616 __func__);
617 syscall_stub_dump_error(mm_id);
618 mm_id->syscall_data_len = proc_data->err;
619 fatal_sigsegv();
620 }
621
622 mm_id->syscall_data_len = 0;
623 mm_id->syscall_fd_num = 0;
624
625 err = get_stub_state(regs, proc_data, NULL);
626 if (err) {
627 printk(UM_KERN_ERR "%s - failed to get regs: %d",
628 __func__, err);
629 fatal_sigsegv();
630 }
631
632 if (proc_data->si_offset > sizeof(proc_data->sigstack) - sizeof(*si))
633 panic("%s - Invalid siginfo offset from child", __func__);
634
635 si = &si_local;
636 memcpy(si, &proc_data->sigstack[proc_data->si_offset], sizeof(*si));
637
638 regs->is_user = 1;
639
640 /* Fill in ORIG_RAX and extract fault information */
641 PT_SYSCALL_NR(regs->gp) = si->si_syscall;
642 if (sig == SIGSEGV) {
643 mcontext_t *mcontext = (void *)&proc_data->sigstack[proc_data->mctx_offset];
644
645 GET_FAULTINFO_FROM_MC(regs->faultinfo, mcontext);
646 }
647 } else {
648 int pid = mm_id->pid;
649
650 /* Flush out any pending syscalls */
651 err = syscall_stub_flush(mm_id);
652 if (err) {
653 if (err == -ENOMEM)
654 report_enomem();
655
656 printk(UM_KERN_ERR "%s - Error flushing stub syscalls: %d",
657 __func__, -err);
658 fatal_sigsegv();
659 }
660
661 /*
662 * This can legitimately fail if the process loads a
663 * bogus value into a segment register. It will
664 * segfault and PTRACE_GETREGS will read that value
665 * out of the process. However, PTRACE_SETREGS will
666 * fail. In this case, there is nothing to do but
667 * just kill the process.
668 */
669 if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp)) {
670 printk(UM_KERN_ERR "%s - ptrace set regs failed, errno = %d\n",
671 __func__, errno);
672 fatal_sigsegv();
673 }
674
675 if (put_fp_registers(pid, regs->fp)) {
676 printk(UM_KERN_ERR "%s - ptrace set fp regs failed, errno = %d\n",
677 __func__, errno);
678 fatal_sigsegv();
679 }
680
681 if (singlestepping())
682 op = PTRACE_SYSEMU_SINGLESTEP;
683 else
684 op = PTRACE_SYSEMU;
685
686 if (ptrace(op, pid, 0, 0)) {
687 printk(UM_KERN_ERR "%s - ptrace continue failed, op = %d, errno = %d\n",
688 __func__, op, errno);
689 fatal_sigsegv();
690 }
691
692 CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
693 if (err < 0) {
694 printk(UM_KERN_ERR "%s - wait failed, errno = %d\n",
695 __func__, errno);
696 fatal_sigsegv();
697 }
698
699 regs->is_user = 1;
700 if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
701 printk(UM_KERN_ERR "%s - PTRACE_GETREGS failed, errno = %d\n",
702 __func__, errno);
703 fatal_sigsegv();
704 }
705
706 if (get_fp_registers(pid, regs->fp)) {
707 printk(UM_KERN_ERR "%s - get_fp_registers failed, errno = %d\n",
708 __func__, errno);
709 fatal_sigsegv();
710 }
711
712 if (WIFSTOPPED(status)) {
713 sig = WSTOPSIG(status);
714
715 /*
716 * These signal handlers need the si argument
717 * and SIGSEGV needs the faultinfo.
718 * The SIGIO and SIGALARM handlers which constitute
719 * the majority of invocations, do not use it.
720 */
721 switch (sig) {
722 case SIGSEGV:
723 get_skas_faultinfo(pid,
724 ®s->faultinfo);
725 fallthrough;
726 case SIGTRAP:
727 case SIGILL:
728 case SIGBUS:
729 case SIGFPE:
730 case SIGWINCH:
731 ptrace(PTRACE_GETSIGINFO, pid, 0,
732 (struct siginfo *)&si_local);
733 si = &si_local;
734 break;
735 default:
736 si = NULL;
737 break;
738 }
739 } else {
740 sig = 0;
741 }
742 }
743
744 exit_turnstile(mm_id);
745
746 UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
747
748 if (sig) {
749 switch (sig) {
750 case SIGSEGV:
751 if (using_seccomp || PTRACE_FULL_FAULTINFO)
752 (*sig_info[SIGSEGV])(SIGSEGV,
753 (struct siginfo *)si,
754 regs, NULL);
755 else
756 segv(regs->faultinfo, 0, 1, NULL, NULL);
757
758 break;
759 case SIGSYS:
760 handle_syscall(regs);
761 break;
762 case SIGTRAP + 0x80:
763 handle_trap(regs);
764 break;
765 case SIGTRAP:
766 relay_signal(SIGTRAP, (struct siginfo *)si, regs, NULL);
767 break;
768 case SIGALRM:
769 break;
770 case SIGIO:
771 case SIGILL:
772 case SIGBUS:
773 case SIGFPE:
774 case SIGWINCH:
775 block_signals_trace();
776 (*sig_info[sig])(sig, (struct siginfo *)si, regs, NULL);
777 unblock_signals_trace();
778 break;
779 default:
780 printk(UM_KERN_ERR "%s - child stopped with signal %d\n",
781 __func__, sig);
782 fatal_sigsegv();
783 }
784 interrupt_end();
785
786 /* Avoid -ERESTARTSYS handling in host */
787 if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
788 PT_SYSCALL_NR(regs->gp) = -1;
789 }
790 }
791 }
792
new_thread(void * stack,jmp_buf * buf,void (* handler)(void))793 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
794 {
795 (*buf)[0].JB_IP = (unsigned long) handler;
796 (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
797 sizeof(void *);
798 }
799
800 #define INIT_JMP_NEW_THREAD 0
801 #define INIT_JMP_CALLBACK 1
802 #define INIT_JMP_HALT 2
803 #define INIT_JMP_REBOOT 3
804
switch_threads(jmp_buf * me,jmp_buf * you)805 void switch_threads(jmp_buf *me, jmp_buf *you)
806 {
807 unscheduled_userspace_iterations = 0;
808
809 if (UML_SETJMP(me) == 0)
810 UML_LONGJMP(you, 1);
811 }
812
813 static jmp_buf initial_jmpbuf;
814
815 static __thread void (*cb_proc)(void *arg);
816 static __thread void *cb_arg;
817 static __thread jmp_buf *cb_back;
818
start_idle_thread(void * stack,jmp_buf * switch_buf)819 int start_idle_thread(void *stack, jmp_buf *switch_buf)
820 {
821 int n;
822
823 set_handler(SIGWINCH);
824
825 /*
826 * Can't use UML_SETJMP or UML_LONGJMP here because they save
827 * and restore signals, with the possible side-effect of
828 * trying to handle any signals which came when they were
829 * blocked, which can't be done on this stack.
830 * Signals must be blocked when jumping back here and restored
831 * after returning to the jumper.
832 */
833 n = setjmp(initial_jmpbuf);
834 switch (n) {
835 case INIT_JMP_NEW_THREAD:
836 (*switch_buf)[0].JB_IP = (unsigned long) uml_finishsetup;
837 (*switch_buf)[0].JB_SP = (unsigned long) stack +
838 UM_THREAD_SIZE - sizeof(void *);
839 break;
840 case INIT_JMP_CALLBACK:
841 (*cb_proc)(cb_arg);
842 longjmp(*cb_back, 1);
843 break;
844 case INIT_JMP_HALT:
845 kmalloc_ok = 0;
846 return 0;
847 case INIT_JMP_REBOOT:
848 kmalloc_ok = 0;
849 return 1;
850 default:
851 printk(UM_KERN_ERR "Bad sigsetjmp return in %s - %d\n",
852 __func__, n);
853 fatal_sigsegv();
854 }
855 longjmp(*switch_buf, 1);
856
857 /* unreachable */
858 printk(UM_KERN_ERR "impossible long jump!");
859 fatal_sigsegv();
860 return 0;
861 }
862
initial_thread_cb_skas(void (* proc)(void *),void * arg)863 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
864 {
865 jmp_buf here;
866
867 cb_proc = proc;
868 cb_arg = arg;
869 cb_back = &here;
870
871 initial_jmpbuf_lock();
872 if (UML_SETJMP(&here) == 0)
873 UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
874 initial_jmpbuf_unlock();
875
876 cb_proc = NULL;
877 cb_arg = NULL;
878 cb_back = NULL;
879 }
880
halt_skas(void)881 void halt_skas(void)
882 {
883 initial_jmpbuf_lock();
884 UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
885 /* unreachable */
886 }
887
888 static bool noreboot;
889
noreboot_cmd_param(char * str,int * add)890 static int __init noreboot_cmd_param(char *str, int *add)
891 {
892 *add = 0;
893 noreboot = true;
894 return 0;
895 }
896
897 __uml_setup("noreboot", noreboot_cmd_param,
898 "noreboot\n"
899 " Rather than rebooting, exit always, akin to QEMU's -no-reboot option.\n"
900 " This is useful if you're using CONFIG_PANIC_TIMEOUT in order to catch\n"
901 " crashes in CI\n\n");
902
reboot_skas(void)903 void reboot_skas(void)
904 {
905 initial_jmpbuf_lock();
906 UML_LONGJMP(&initial_jmpbuf, noreboot ? INIT_JMP_HALT : INIT_JMP_REBOOT);
907 /* unreachable */
908 }
909