1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Copyright IBM Corp. 1999, 2006 |
4 | * Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com) |
5 | * |
6 | * Based on Intel version |
7 | * |
8 | * Copyright (C) 1991, 1992 Linus Torvalds |
9 | * |
10 | * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson |
11 | */ |
12 | |
13 | #include <linux/sched.h> |
14 | #include <linux/sched/task_stack.h> |
15 | #include <linux/rseq.h> |
16 | #include <linux/mm.h> |
17 | #include <linux/smp.h> |
18 | #include <linux/kernel.h> |
19 | #include <linux/signal.h> |
20 | #include <linux/entry-common.h> |
21 | #include <linux/errno.h> |
22 | #include <linux/wait.h> |
23 | #include <linux/ptrace.h> |
24 | #include <linux/unistd.h> |
25 | #include <linux/stddef.h> |
26 | #include <linux/tty.h> |
27 | #include <linux/personality.h> |
28 | #include <linux/binfmts.h> |
29 | #include <linux/syscalls.h> |
30 | #include <linux/compat.h> |
31 | #include <asm/ucontext.h> |
32 | #include <linux/uaccess.h> |
33 | #include <asm/access-regs.h> |
34 | #include <asm/lowcore.h> |
35 | #include <asm/vdso.h> |
36 | #include "entry.h" |
37 | |
38 | /* |
39 | * Layout of an old-style signal-frame: |
40 | * ----------------------------------------- |
41 | * | save area (_SIGNAL_FRAMESIZE) | |
42 | * ----------------------------------------- |
43 | * | struct sigcontext | |
44 | * | oldmask | |
45 | * | _sigregs * | |
46 | * ----------------------------------------- |
47 | * | _sigregs with | |
48 | * | _s390_regs_common | |
49 | * | _s390_fp_regs | |
50 | * ----------------------------------------- |
51 | * | int signo | |
52 | * ----------------------------------------- |
53 | * | _sigregs_ext with | |
54 | * | gprs_high 64 byte (opt) | |
55 | * | vxrs_low 128 byte (opt) | |
56 | * | vxrs_high 256 byte (opt) | |
57 | * | reserved 128 byte (opt) | |
58 | * ----------------------------------------- |
59 | * | __u16 svc_insn | |
60 | * ----------------------------------------- |
61 | * The svc_insn entry with the sigreturn system call opcode does not |
62 | * have a fixed position and moves if gprs_high or vxrs exist. |
63 | * Future extensions will be added to _sigregs_ext. |
64 | */ |
65 | struct sigframe |
66 | { |
67 | __u8 callee_used_stack[__SIGNAL_FRAMESIZE]; |
68 | struct sigcontext sc; |
69 | _sigregs sregs; |
70 | int signo; |
71 | _sigregs_ext sregs_ext; |
72 | __u16 svc_insn; /* Offset of svc_insn is NOT fixed! */ |
73 | }; |
74 | |
75 | /* |
76 | * Layout of an rt signal-frame: |
77 | * ----------------------------------------- |
78 | * | save area (_SIGNAL_FRAMESIZE) | |
79 | * ----------------------------------------- |
80 | * | svc __NR_rt_sigreturn 2 byte | |
81 | * ----------------------------------------- |
82 | * | struct siginfo | |
83 | * ----------------------------------------- |
84 | * | struct ucontext_extended with | |
85 | * | unsigned long uc_flags | |
86 | * | struct ucontext *uc_link | |
87 | * | stack_t uc_stack | |
88 | * | _sigregs uc_mcontext with | |
89 | * | _s390_regs_common | |
90 | * | _s390_fp_regs | |
91 | * | sigset_t uc_sigmask | |
92 | * | _sigregs_ext uc_mcontext_ext | |
93 | * | gprs_high 64 byte (opt) | |
94 | * | vxrs_low 128 byte (opt) | |
95 | * | vxrs_high 256 byte (opt)| |
96 | * | reserved 128 byte (opt) | |
97 | * ----------------------------------------- |
98 | * Future extensions will be added to _sigregs_ext. |
99 | */ |
100 | struct rt_sigframe |
101 | { |
102 | __u8 callee_used_stack[__SIGNAL_FRAMESIZE]; |
103 | __u16 svc_insn; |
104 | struct siginfo info; |
105 | struct ucontext_extended uc; |
106 | }; |
107 | |
108 | /* Store registers needed to create the signal frame */ |
109 | static void store_sigregs(void) |
110 | { |
111 | save_access_regs(current->thread.acrs); |
112 | save_user_fpu_regs(); |
113 | } |
114 | |
115 | /* Load registers after signal return */ |
116 | static void load_sigregs(void) |
117 | { |
118 | restore_access_regs(current->thread.acrs); |
119 | } |
120 | |
121 | /* Returns non-zero on fault. */ |
122 | static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs) |
123 | { |
124 | _sigregs user_sregs; |
125 | |
126 | /* Copy a 'clean' PSW mask to the user to avoid leaking |
127 | information about whether PER is currently on. */ |
128 | user_sregs.regs.psw.mask = PSW_USER_BITS | |
129 | (regs->psw.mask & (PSW_MASK_USER | PSW_MASK_RI)); |
130 | user_sregs.regs.psw.addr = regs->psw.addr; |
131 | memcpy(&user_sregs.regs.gprs, ®s->gprs, sizeof(sregs->regs.gprs)); |
132 | memcpy(&user_sregs.regs.acrs, current->thread.acrs, |
133 | sizeof(user_sregs.regs.acrs)); |
134 | fpregs_store(&user_sregs.fpregs, ¤t->thread.ufpu); |
135 | if (__copy_to_user(sregs, &user_sregs, sizeof(_sigregs))) |
136 | return -EFAULT; |
137 | return 0; |
138 | } |
139 | |
140 | static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs) |
141 | { |
142 | _sigregs user_sregs; |
143 | |
144 | /* Always make any pending restarted system call return -EINTR */ |
145 | current->restart_block.fn = do_no_restart_syscall; |
146 | |
147 | if (__copy_from_user(to: &user_sregs, from: sregs, n: sizeof(user_sregs))) |
148 | return -EFAULT; |
149 | |
150 | if (!is_ri_task(current) && (user_sregs.regs.psw.mask & PSW_MASK_RI)) |
151 | return -EINVAL; |
152 | |
153 | /* Use regs->psw.mask instead of PSW_USER_BITS to preserve PER bit. */ |
154 | regs->psw.mask = (regs->psw.mask & ~(PSW_MASK_USER | PSW_MASK_RI)) | |
155 | (user_sregs.regs.psw.mask & (PSW_MASK_USER | PSW_MASK_RI)); |
156 | /* Check for invalid user address space control. */ |
157 | if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_HOME) |
158 | regs->psw.mask = PSW_ASC_PRIMARY | |
159 | (regs->psw.mask & ~PSW_MASK_ASC); |
160 | /* Check for invalid amode */ |
161 | if (regs->psw.mask & PSW_MASK_EA) |
162 | regs->psw.mask |= PSW_MASK_BA; |
163 | regs->psw.addr = user_sregs.regs.psw.addr; |
164 | memcpy(®s->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs)); |
165 | memcpy(¤t->thread.acrs, &user_sregs.regs.acrs, |
166 | sizeof(current->thread.acrs)); |
167 | |
168 | fpregs_load(&user_sregs.fpregs, ¤t->thread.ufpu); |
169 | |
170 | clear_pt_regs_flag(regs, PIF_SYSCALL); /* No longer in a system call */ |
171 | return 0; |
172 | } |
173 | |
174 | /* Returns non-zero on fault. */ |
175 | static int save_sigregs_ext(struct pt_regs *regs, |
176 | _sigregs_ext __user *sregs_ext) |
177 | { |
178 | __u64 vxrs[__NUM_VXRS_LOW]; |
179 | int i; |
180 | |
181 | /* Save vector registers to signal stack */ |
182 | if (cpu_has_vx()) { |
183 | for (i = 0; i < __NUM_VXRS_LOW; i++) |
184 | vxrs[i] = current->thread.ufpu.vxrs[i].low; |
185 | if (__copy_to_user(&sregs_ext->vxrs_low, vxrs, |
186 | sizeof(sregs_ext->vxrs_low)) || |
187 | __copy_to_user(&sregs_ext->vxrs_high, |
188 | current->thread.ufpu.vxrs + __NUM_VXRS_LOW, |
189 | sizeof(sregs_ext->vxrs_high))) |
190 | return -EFAULT; |
191 | } |
192 | return 0; |
193 | } |
194 | |
195 | static int restore_sigregs_ext(struct pt_regs *regs, |
196 | _sigregs_ext __user *sregs_ext) |
197 | { |
198 | __u64 vxrs[__NUM_VXRS_LOW]; |
199 | int i; |
200 | |
201 | /* Restore vector registers from signal stack */ |
202 | if (cpu_has_vx()) { |
203 | if (__copy_from_user(vxrs, &sregs_ext->vxrs_low, |
204 | sizeof(sregs_ext->vxrs_low)) || |
205 | __copy_from_user(current->thread.ufpu.vxrs + __NUM_VXRS_LOW, |
206 | &sregs_ext->vxrs_high, |
207 | sizeof(sregs_ext->vxrs_high))) |
208 | return -EFAULT; |
209 | for (i = 0; i < __NUM_VXRS_LOW; i++) |
210 | current->thread.ufpu.vxrs[i].low = vxrs[i]; |
211 | } |
212 | return 0; |
213 | } |
214 | |
215 | SYSCALL_DEFINE0(sigreturn) |
216 | { |
217 | struct pt_regs *regs = task_pt_regs(current); |
218 | struct sigframe __user *frame = |
219 | (struct sigframe __user *) regs->gprs[15]; |
220 | sigset_t set; |
221 | |
222 | if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE)) |
223 | goto badframe; |
224 | set_current_blocked(&set); |
225 | save_user_fpu_regs(); |
226 | if (restore_sigregs(regs, &frame->sregs)) |
227 | goto badframe; |
228 | if (restore_sigregs_ext(regs, &frame->sregs_ext)) |
229 | goto badframe; |
230 | load_sigregs(); |
231 | return regs->gprs[2]; |
232 | badframe: |
233 | force_sig(SIGSEGV); |
234 | return 0; |
235 | } |
236 | |
237 | SYSCALL_DEFINE0(rt_sigreturn) |
238 | { |
239 | struct pt_regs *regs = task_pt_regs(current); |
240 | struct rt_sigframe __user *frame = |
241 | (struct rt_sigframe __user *)regs->gprs[15]; |
242 | sigset_t set; |
243 | |
244 | if (__copy_from_user(to: &set.sig, from: &frame->uc.uc_sigmask, n: sizeof(set))) |
245 | goto badframe; |
246 | set_current_blocked(&set); |
247 | if (restore_altstack(&frame->uc.uc_stack)) |
248 | goto badframe; |
249 | save_user_fpu_regs(); |
250 | if (restore_sigregs(regs, &frame->uc.uc_mcontext)) |
251 | goto badframe; |
252 | if (restore_sigregs_ext(regs, &frame->uc.uc_mcontext_ext)) |
253 | goto badframe; |
254 | load_sigregs(); |
255 | return regs->gprs[2]; |
256 | badframe: |
257 | force_sig(SIGSEGV); |
258 | return 0; |
259 | } |
260 | |
261 | /* |
262 | * Determine which stack to use.. |
263 | */ |
264 | static inline void __user * |
265 | get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size) |
266 | { |
267 | unsigned long sp; |
268 | |
269 | /* Default to using normal stack */ |
270 | sp = regs->gprs[15]; |
271 | |
272 | /* Overflow on alternate signal stack gives SIGSEGV. */ |
273 | if (on_sig_stack(sp) && !on_sig_stack(sp: (sp - frame_size) & -8UL)) |
274 | return (void __user *) -1UL; |
275 | |
276 | /* This is the X/Open sanctioned signal stack switching. */ |
277 | if (ka->sa.sa_flags & SA_ONSTACK) { |
278 | if (! sas_ss_flags(sp)) |
279 | sp = current->sas_ss_sp + current->sas_ss_size; |
280 | } |
281 | |
282 | return (void __user *)((sp - frame_size) & -8ul); |
283 | } |
284 | |
285 | static int setup_frame(int sig, struct k_sigaction *ka, |
286 | sigset_t *set, struct pt_regs * regs) |
287 | { |
288 | struct sigframe __user *frame; |
289 | struct sigcontext sc; |
290 | unsigned long restorer; |
291 | size_t frame_size; |
292 | |
293 | /* |
294 | * gprs_high are only present for a 31-bit task running on |
295 | * a 64-bit kernel (see compat_signal.c) but the space for |
296 | * gprs_high need to be allocated if vector registers are |
297 | * included in the signal frame on a 31-bit system. |
298 | */ |
299 | frame_size = sizeof(*frame) - sizeof(frame->sregs_ext); |
300 | if (cpu_has_vx()) |
301 | frame_size += sizeof(frame->sregs_ext); |
302 | frame = get_sigframe(ka, regs, frame_size); |
303 | if (frame == (void __user *) -1UL) |
304 | return -EFAULT; |
305 | |
306 | /* Set up backchain. */ |
307 | if (__put_user(regs->gprs[15], (addr_t __user *) frame)) |
308 | return -EFAULT; |
309 | |
310 | /* Create struct sigcontext on the signal stack */ |
311 | memcpy(&sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE); |
312 | sc.sregs = (_sigregs __user __force *) &frame->sregs; |
313 | if (__copy_to_user(to: &frame->sc, from: &sc, n: sizeof(frame->sc))) |
314 | return -EFAULT; |
315 | |
316 | /* Store registers needed to create the signal frame */ |
317 | store_sigregs(); |
318 | |
319 | /* Create _sigregs on the signal stack */ |
320 | if (save_sigregs(regs, &frame->sregs)) |
321 | return -EFAULT; |
322 | |
323 | /* Place signal number on stack to allow backtrace from handler. */ |
324 | if (__put_user(regs->gprs[2], (int __user *) &frame->signo)) |
325 | return -EFAULT; |
326 | |
327 | /* Create _sigregs_ext on the signal stack */ |
328 | if (save_sigregs_ext(regs, &frame->sregs_ext)) |
329 | return -EFAULT; |
330 | |
331 | /* Set up to return from userspace. If provided, use a stub |
332 | already in userspace. */ |
333 | if (ka->sa.sa_flags & SA_RESTORER) |
334 | restorer = (unsigned long) ka->sa.sa_restorer; |
335 | else |
336 | restorer = VDSO64_SYMBOL(current, sigreturn); |
337 | |
338 | /* Set up registers for signal handler */ |
339 | regs->gprs[14] = restorer; |
340 | regs->gprs[15] = (unsigned long) frame; |
341 | /* Force default amode and default user address space control. */ |
342 | regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA | |
343 | (PSW_USER_BITS & PSW_MASK_ASC) | |
344 | (regs->psw.mask & ~PSW_MASK_ASC); |
345 | regs->psw.addr = (unsigned long) ka->sa.sa_handler; |
346 | |
347 | regs->gprs[2] = sig; |
348 | regs->gprs[3] = (unsigned long) &frame->sc; |
349 | |
350 | /* We forgot to include these in the sigcontext. |
351 | To avoid breaking binary compatibility, they are passed as args. */ |
352 | if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL || |
353 | sig == SIGTRAP || sig == SIGFPE) { |
354 | /* set extra registers only for synchronous signals */ |
355 | regs->gprs[4] = regs->int_code & 127; |
356 | regs->gprs[5] = regs->int_parm_long; |
357 | regs->gprs[6] = current->thread.last_break; |
358 | } |
359 | return 0; |
360 | } |
361 | |
362 | static int setup_rt_frame(struct ksignal *ksig, sigset_t *set, |
363 | struct pt_regs *regs) |
364 | { |
365 | struct rt_sigframe __user *frame; |
366 | unsigned long uc_flags, restorer; |
367 | size_t frame_size; |
368 | |
369 | frame_size = sizeof(struct rt_sigframe) - sizeof(_sigregs_ext); |
370 | /* |
371 | * gprs_high are only present for a 31-bit task running on |
372 | * a 64-bit kernel (see compat_signal.c) but the space for |
373 | * gprs_high need to be allocated if vector registers are |
374 | * included in the signal frame on a 31-bit system. |
375 | */ |
376 | uc_flags = 0; |
377 | if (cpu_has_vx()) { |
378 | frame_size += sizeof(_sigregs_ext); |
379 | uc_flags |= UC_VXRS; |
380 | } |
381 | frame = get_sigframe(ka: &ksig->ka, regs, frame_size); |
382 | if (frame == (void __user *) -1UL) |
383 | return -EFAULT; |
384 | |
385 | /* Set up backchain. */ |
386 | if (__put_user(regs->gprs[15], (addr_t __user *) frame)) |
387 | return -EFAULT; |
388 | |
389 | /* Set up to return from userspace. If provided, use a stub |
390 | already in userspace. */ |
391 | if (ksig->ka.sa.sa_flags & SA_RESTORER) |
392 | restorer = (unsigned long) ksig->ka.sa.sa_restorer; |
393 | else |
394 | restorer = VDSO64_SYMBOL(current, rt_sigreturn); |
395 | |
396 | /* Create siginfo on the signal stack */ |
397 | if (copy_siginfo_to_user(to: &frame->info, from: &ksig->info)) |
398 | return -EFAULT; |
399 | |
400 | /* Store registers needed to create the signal frame */ |
401 | store_sigregs(); |
402 | |
403 | /* Create ucontext on the signal stack. */ |
404 | if (__put_user(uc_flags, &frame->uc.uc_flags) || |
405 | __put_user(NULL, &frame->uc.uc_link) || |
406 | __save_altstack(&frame->uc.uc_stack, regs->gprs[15]) || |
407 | save_sigregs(regs, &frame->uc.uc_mcontext) || |
408 | __copy_to_user(to: &frame->uc.uc_sigmask, from: set, n: sizeof(*set)) || |
409 | save_sigregs_ext(regs, &frame->uc.uc_mcontext_ext)) |
410 | return -EFAULT; |
411 | |
412 | /* Set up registers for signal handler */ |
413 | regs->gprs[14] = restorer; |
414 | regs->gprs[15] = (unsigned long) frame; |
415 | /* Force default amode and default user address space control. */ |
416 | regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA | |
417 | (PSW_USER_BITS & PSW_MASK_ASC) | |
418 | (regs->psw.mask & ~PSW_MASK_ASC); |
419 | regs->psw.addr = (unsigned long) ksig->ka.sa.sa_handler; |
420 | |
421 | regs->gprs[2] = ksig->sig; |
422 | regs->gprs[3] = (unsigned long) &frame->info; |
423 | regs->gprs[4] = (unsigned long) &frame->uc; |
424 | regs->gprs[5] = current->thread.last_break; |
425 | return 0; |
426 | } |
427 | |
428 | static void handle_signal(struct ksignal *ksig, sigset_t *oldset, |
429 | struct pt_regs *regs) |
430 | { |
431 | int ret; |
432 | |
433 | /* Set up the stack frame */ |
434 | if (ksig->ka.sa.sa_flags & SA_SIGINFO) |
435 | ret = setup_rt_frame(ksig, set: oldset, regs); |
436 | else |
437 | ret = setup_frame(sig: ksig->sig, ka: &ksig->ka, set: oldset, regs); |
438 | |
439 | signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLE_STEP)); |
440 | } |
441 | |
442 | /* |
443 | * Note that 'init' is a special process: it doesn't get signals it doesn't |
444 | * want to handle. Thus you cannot kill init even with a SIGKILL even by |
445 | * mistake. |
446 | * |
447 | * Note that we go through the signals twice: once to check the signals that |
448 | * the kernel can handle, and then we build all the user-level signal handling |
449 | * stack-frames in one go after that. |
450 | */ |
451 | |
452 | void arch_do_signal_or_restart(struct pt_regs *regs) |
453 | { |
454 | struct ksignal ksig; |
455 | sigset_t *oldset = sigmask_to_save(); |
456 | |
457 | /* |
458 | * Get signal to deliver. When running under ptrace, at this point |
459 | * the debugger may change all our registers, including the system |
460 | * call information. |
461 | */ |
462 | current->thread.system_call = |
463 | test_pt_regs_flag(regs, PIF_SYSCALL) ? regs->int_code : 0; |
464 | |
465 | if (get_signal(ksig: &ksig)) { |
466 | /* Whee! Actually deliver the signal. */ |
467 | if (current->thread.system_call) { |
468 | regs->int_code = current->thread.system_call; |
469 | /* Check for system call restarting. */ |
470 | switch (regs->gprs[2]) { |
471 | case -ERESTART_RESTARTBLOCK: |
472 | case -ERESTARTNOHAND: |
473 | regs->gprs[2] = -EINTR; |
474 | break; |
475 | case -ERESTARTSYS: |
476 | if (!(ksig.ka.sa.sa_flags & SA_RESTART)) { |
477 | regs->gprs[2] = -EINTR; |
478 | break; |
479 | } |
480 | fallthrough; |
481 | case -ERESTARTNOINTR: |
482 | regs->gprs[2] = regs->orig_gpr2; |
483 | regs->psw.addr = |
484 | __rewind_psw(regs->psw, |
485 | regs->int_code >> 16); |
486 | break; |
487 | } |
488 | } |
489 | /* No longer in a system call */ |
490 | clear_pt_regs_flag(regs, PIF_SYSCALL); |
491 | |
492 | rseq_signal_deliver(ksig: &ksig, regs); |
493 | if (is_compat_task()) |
494 | handle_signal32(ksig: &ksig, oldset, regs); |
495 | else |
496 | handle_signal(ksig: &ksig, oldset, regs); |
497 | return; |
498 | } |
499 | |
500 | /* No handlers present - check for system call restart */ |
501 | clear_pt_regs_flag(regs, PIF_SYSCALL); |
502 | if (current->thread.system_call) { |
503 | regs->int_code = current->thread.system_call; |
504 | switch (regs->gprs[2]) { |
505 | case -ERESTART_RESTARTBLOCK: |
506 | /* Restart with sys_restart_syscall */ |
507 | regs->gprs[2] = regs->orig_gpr2; |
508 | current->restart_block.arch_data = regs->psw.addr; |
509 | if (is_compat_task()) |
510 | regs->psw.addr = VDSO32_SYMBOL(current, restart_syscall); |
511 | else |
512 | regs->psw.addr = VDSO64_SYMBOL(current, restart_syscall); |
513 | if (test_thread_flag(TIF_SINGLE_STEP)) |
514 | clear_thread_flag(TIF_PER_TRAP); |
515 | break; |
516 | case -ERESTARTNOHAND: |
517 | case -ERESTARTSYS: |
518 | case -ERESTARTNOINTR: |
519 | regs->gprs[2] = regs->orig_gpr2; |
520 | regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); |
521 | if (test_thread_flag(TIF_SINGLE_STEP)) |
522 | clear_thread_flag(TIF_PER_TRAP); |
523 | break; |
524 | } |
525 | } |
526 | |
527 | /* |
528 | * If there's no signal to deliver, we just put the saved sigmask back. |
529 | */ |
530 | restore_saved_sigmask(); |
531 | } |
532 | |