xref: /openbmc/linux/arch/sparc/kernel/sys_sparc_64.c (revision b830f94f)
1 // SPDX-License-Identifier: GPL-2.0
2 /* linux/arch/sparc64/kernel/sys_sparc.c
3  *
4  * This file contains various random system calls that
5  * have a non-standard calling sequence on the Linux/sparc
6  * platform.
7  */
8 
9 #include <linux/errno.h>
10 #include <linux/types.h>
11 #include <linux/sched/signal.h>
12 #include <linux/sched/mm.h>
13 #include <linux/sched/debug.h>
14 #include <linux/fs.h>
15 #include <linux/file.h>
16 #include <linux/mm.h>
17 #include <linux/sem.h>
18 #include <linux/msg.h>
19 #include <linux/shm.h>
20 #include <linux/stat.h>
21 #include <linux/mman.h>
22 #include <linux/utsname.h>
23 #include <linux/smp.h>
24 #include <linux/slab.h>
25 #include <linux/syscalls.h>
26 #include <linux/ipc.h>
27 #include <linux/personality.h>
28 #include <linux/random.h>
29 #include <linux/export.h>
30 #include <linux/context_tracking.h>
31 #include <linux/timex.h>
32 #include <linux/uaccess.h>
33 
34 #include <asm/utrap.h>
35 #include <asm/unistd.h>
36 
37 #include "entry.h"
38 #include "kernel.h"
39 #include "systbls.h"
40 
41 /* #define DEBUG_UNIMP_SYSCALL */
42 
43 SYSCALL_DEFINE0(getpagesize)
44 {
45 	return PAGE_SIZE;
46 }
47 
48 /* Does addr --> addr+len fall within 4GB of the VA-space hole or
49  * overflow past the end of the 64-bit address space?
50  */
51 static inline int invalid_64bit_range(unsigned long addr, unsigned long len)
52 {
53 	unsigned long va_exclude_start, va_exclude_end;
54 
55 	va_exclude_start = VA_EXCLUDE_START;
56 	va_exclude_end   = VA_EXCLUDE_END;
57 
58 	if (unlikely(len >= va_exclude_start))
59 		return 1;
60 
61 	if (unlikely((addr + len) < addr))
62 		return 1;
63 
64 	if (unlikely((addr >= va_exclude_start && addr < va_exclude_end) ||
65 		     ((addr + len) >= va_exclude_start &&
66 		      (addr + len) < va_exclude_end)))
67 		return 1;
68 
69 	return 0;
70 }
71 
72 /* These functions differ from the default implementations in
73  * mm/mmap.c in two ways:
74  *
75  * 1) For file backed MAP_SHARED mmap()'s we D-cache color align,
76  *    for fixed such mappings we just validate what the user gave us.
77  * 2) For 64-bit tasks we avoid mapping anything within 4GB of
78  *    the spitfire/niagara VA-hole.
79  */
80 
81 static inline unsigned long COLOR_ALIGN(unsigned long addr,
82 					 unsigned long pgoff)
83 {
84 	unsigned long base = (addr+SHMLBA-1)&~(SHMLBA-1);
85 	unsigned long off = (pgoff<<PAGE_SHIFT) & (SHMLBA-1);
86 
87 	return base + off;
88 }
89 
90 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags)
91 {
92 	struct mm_struct *mm = current->mm;
93 	struct vm_area_struct * vma;
94 	unsigned long task_size = TASK_SIZE;
95 	int do_color_align;
96 	struct vm_unmapped_area_info info;
97 
98 	if (flags & MAP_FIXED) {
99 		/* We do not accept a shared mapping if it would violate
100 		 * cache aliasing constraints.
101 		 */
102 		if ((flags & MAP_SHARED) &&
103 		    ((addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1)))
104 			return -EINVAL;
105 		return addr;
106 	}
107 
108 	if (test_thread_flag(TIF_32BIT))
109 		task_size = STACK_TOP32;
110 	if (unlikely(len > task_size || len >= VA_EXCLUDE_START))
111 		return -ENOMEM;
112 
113 	do_color_align = 0;
114 	if (filp || (flags & MAP_SHARED))
115 		do_color_align = 1;
116 
117 	if (addr) {
118 		if (do_color_align)
119 			addr = COLOR_ALIGN(addr, pgoff);
120 		else
121 			addr = PAGE_ALIGN(addr);
122 
123 		vma = find_vma(mm, addr);
124 		if (task_size - len >= addr &&
125 		    (!vma || addr + len <= vm_start_gap(vma)))
126 			return addr;
127 	}
128 
129 	info.flags = 0;
130 	info.length = len;
131 	info.low_limit = TASK_UNMAPPED_BASE;
132 	info.high_limit = min(task_size, VA_EXCLUDE_START);
133 	info.align_mask = do_color_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
134 	info.align_offset = pgoff << PAGE_SHIFT;
135 	addr = vm_unmapped_area(&info);
136 
137 	if ((addr & ~PAGE_MASK) && task_size > VA_EXCLUDE_END) {
138 		VM_BUG_ON(addr != -ENOMEM);
139 		info.low_limit = VA_EXCLUDE_END;
140 		info.high_limit = task_size;
141 		addr = vm_unmapped_area(&info);
142 	}
143 
144 	return addr;
145 }
146 
147 unsigned long
148 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
149 			  const unsigned long len, const unsigned long pgoff,
150 			  const unsigned long flags)
151 {
152 	struct vm_area_struct *vma;
153 	struct mm_struct *mm = current->mm;
154 	unsigned long task_size = STACK_TOP32;
155 	unsigned long addr = addr0;
156 	int do_color_align;
157 	struct vm_unmapped_area_info info;
158 
159 	/* This should only ever run for 32-bit processes.  */
160 	BUG_ON(!test_thread_flag(TIF_32BIT));
161 
162 	if (flags & MAP_FIXED) {
163 		/* We do not accept a shared mapping if it would violate
164 		 * cache aliasing constraints.
165 		 */
166 		if ((flags & MAP_SHARED) &&
167 		    ((addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1)))
168 			return -EINVAL;
169 		return addr;
170 	}
171 
172 	if (unlikely(len > task_size))
173 		return -ENOMEM;
174 
175 	do_color_align = 0;
176 	if (filp || (flags & MAP_SHARED))
177 		do_color_align = 1;
178 
179 	/* requesting a specific address */
180 	if (addr) {
181 		if (do_color_align)
182 			addr = COLOR_ALIGN(addr, pgoff);
183 		else
184 			addr = PAGE_ALIGN(addr);
185 
186 		vma = find_vma(mm, addr);
187 		if (task_size - len >= addr &&
188 		    (!vma || addr + len <= vm_start_gap(vma)))
189 			return addr;
190 	}
191 
192 	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
193 	info.length = len;
194 	info.low_limit = PAGE_SIZE;
195 	info.high_limit = mm->mmap_base;
196 	info.align_mask = do_color_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
197 	info.align_offset = pgoff << PAGE_SHIFT;
198 	addr = vm_unmapped_area(&info);
199 
200 	/*
201 	 * A failed mmap() very likely causes application failure,
202 	 * so fall back to the bottom-up function here. This scenario
203 	 * can happen with large stack limits and large mmap()
204 	 * allocations.
205 	 */
206 	if (addr & ~PAGE_MASK) {
207 		VM_BUG_ON(addr != -ENOMEM);
208 		info.flags = 0;
209 		info.low_limit = TASK_UNMAPPED_BASE;
210 		info.high_limit = STACK_TOP32;
211 		addr = vm_unmapped_area(&info);
212 	}
213 
214 	return addr;
215 }
216 
217 /* Try to align mapping such that we align it as much as possible. */
218 unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, unsigned long len, unsigned long pgoff, unsigned long flags)
219 {
220 	unsigned long align_goal, addr = -ENOMEM;
221 	unsigned long (*get_area)(struct file *, unsigned long,
222 				  unsigned long, unsigned long, unsigned long);
223 
224 	get_area = current->mm->get_unmapped_area;
225 
226 	if (flags & MAP_FIXED) {
227 		/* Ok, don't mess with it. */
228 		return get_area(NULL, orig_addr, len, pgoff, flags);
229 	}
230 	flags &= ~MAP_SHARED;
231 
232 	align_goal = PAGE_SIZE;
233 	if (len >= (4UL * 1024 * 1024))
234 		align_goal = (4UL * 1024 * 1024);
235 	else if (len >= (512UL * 1024))
236 		align_goal = (512UL * 1024);
237 	else if (len >= (64UL * 1024))
238 		align_goal = (64UL * 1024);
239 
240 	do {
241 		addr = get_area(NULL, orig_addr, len + (align_goal - PAGE_SIZE), pgoff, flags);
242 		if (!(addr & ~PAGE_MASK)) {
243 			addr = (addr + (align_goal - 1UL)) & ~(align_goal - 1UL);
244 			break;
245 		}
246 
247 		if (align_goal == (4UL * 1024 * 1024))
248 			align_goal = (512UL * 1024);
249 		else if (align_goal == (512UL * 1024))
250 			align_goal = (64UL * 1024);
251 		else
252 			align_goal = PAGE_SIZE;
253 	} while ((addr & ~PAGE_MASK) && align_goal > PAGE_SIZE);
254 
255 	/* Mapping is smaller than 64K or larger areas could not
256 	 * be obtained.
257 	 */
258 	if (addr & ~PAGE_MASK)
259 		addr = get_area(NULL, orig_addr, len, pgoff, flags);
260 
261 	return addr;
262 }
263 EXPORT_SYMBOL(get_fb_unmapped_area);
264 
265 /* Essentially the same as PowerPC.  */
266 static unsigned long mmap_rnd(void)
267 {
268 	unsigned long rnd = 0UL;
269 
270 	if (current->flags & PF_RANDOMIZE) {
271 		unsigned long val = get_random_long();
272 		if (test_thread_flag(TIF_32BIT))
273 			rnd = (val % (1UL << (23UL-PAGE_SHIFT)));
274 		else
275 			rnd = (val % (1UL << (30UL-PAGE_SHIFT)));
276 	}
277 	return rnd << PAGE_SHIFT;
278 }
279 
280 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
281 {
282 	unsigned long random_factor = mmap_rnd();
283 	unsigned long gap;
284 
285 	/*
286 	 * Fall back to the standard layout if the personality
287 	 * bit is set, or if the expected stack growth is unlimited:
288 	 */
289 	gap = rlim_stack->rlim_cur;
290 	if (!test_thread_flag(TIF_32BIT) ||
291 	    (current->personality & ADDR_COMPAT_LAYOUT) ||
292 	    gap == RLIM_INFINITY ||
293 	    sysctl_legacy_va_layout) {
294 		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
295 		mm->get_unmapped_area = arch_get_unmapped_area;
296 	} else {
297 		/* We know it's 32-bit */
298 		unsigned long task_size = STACK_TOP32;
299 
300 		if (gap < 128 * 1024 * 1024)
301 			gap = 128 * 1024 * 1024;
302 		if (gap > (task_size / 6 * 5))
303 			gap = (task_size / 6 * 5);
304 
305 		mm->mmap_base = PAGE_ALIGN(task_size - gap - random_factor);
306 		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
307 	}
308 }
309 
310 /*
311  * sys_pipe() is the normal C calling standard for creating
312  * a pipe. It's not the way unix traditionally does this, though.
313  */
314 SYSCALL_DEFINE0(sparc_pipe)
315 {
316 	int fd[2];
317 	int error;
318 
319 	error = do_pipe_flags(fd, 0);
320 	if (error)
321 		goto out;
322 	current_pt_regs()->u_regs[UREG_I1] = fd[1];
323 	error = fd[0];
324 out:
325 	return error;
326 }
327 
328 /*
329  * sys_ipc() is the de-multiplexer for the SysV IPC calls..
330  *
331  * This is really horribly ugly.
332  */
333 
334 SYSCALL_DEFINE6(sparc_ipc, unsigned int, call, int, first, unsigned long, second,
335 		unsigned long, third, void __user *, ptr, long, fifth)
336 {
337 	long err;
338 
339 	/* No need for backward compatibility. We can start fresh... */
340 	if (call <= SEMTIMEDOP) {
341 		switch (call) {
342 		case SEMOP:
343 			err = sys_semtimedop(first, ptr,
344 					     (unsigned int)second, NULL);
345 			goto out;
346 		case SEMTIMEDOP:
347 			err = sys_semtimedop(first, ptr, (unsigned int)second,
348 				(const struct __kernel_timespec __user *)
349 					     (unsigned long) fifth);
350 			goto out;
351 		case SEMGET:
352 			err = sys_semget(first, (int)second, (int)third);
353 			goto out;
354 		case SEMCTL: {
355 			err = sys_semctl(first, second,
356 					 (int)third | IPC_64,
357 					 (unsigned long) ptr);
358 			goto out;
359 		}
360 		default:
361 			err = -ENOSYS;
362 			goto out;
363 		}
364 	}
365 	if (call <= MSGCTL) {
366 		switch (call) {
367 		case MSGSND:
368 			err = sys_msgsnd(first, ptr, (size_t)second,
369 					 (int)third);
370 			goto out;
371 		case MSGRCV:
372 			err = sys_msgrcv(first, ptr, (size_t)second, fifth,
373 					 (int)third);
374 			goto out;
375 		case MSGGET:
376 			err = sys_msgget((key_t)first, (int)second);
377 			goto out;
378 		case MSGCTL:
379 			err = sys_msgctl(first, (int)second | IPC_64, ptr);
380 			goto out;
381 		default:
382 			err = -ENOSYS;
383 			goto out;
384 		}
385 	}
386 	if (call <= SHMCTL) {
387 		switch (call) {
388 		case SHMAT: {
389 			ulong raddr;
390 			err = do_shmat(first, ptr, (int)second, &raddr, SHMLBA);
391 			if (!err) {
392 				if (put_user(raddr,
393 					     (ulong __user *) third))
394 					err = -EFAULT;
395 			}
396 			goto out;
397 		}
398 		case SHMDT:
399 			err = sys_shmdt(ptr);
400 			goto out;
401 		case SHMGET:
402 			err = sys_shmget(first, (size_t)second, (int)third);
403 			goto out;
404 		case SHMCTL:
405 			err = sys_shmctl(first, (int)second | IPC_64, ptr);
406 			goto out;
407 		default:
408 			err = -ENOSYS;
409 			goto out;
410 		}
411 	} else {
412 		err = -ENOSYS;
413 	}
414 out:
415 	return err;
416 }
417 
418 SYSCALL_DEFINE1(sparc64_personality, unsigned long, personality)
419 {
420 	long ret;
421 
422 	if (personality(current->personality) == PER_LINUX32 &&
423 	    personality(personality) == PER_LINUX)
424 		personality |= PER_LINUX32;
425 	ret = sys_personality(personality);
426 	if (personality(ret) == PER_LINUX32)
427 		ret &= ~PER_LINUX32;
428 
429 	return ret;
430 }
431 
432 int sparc_mmap_check(unsigned long addr, unsigned long len)
433 {
434 	if (test_thread_flag(TIF_32BIT)) {
435 		if (len >= STACK_TOP32)
436 			return -EINVAL;
437 
438 		if (addr > STACK_TOP32 - len)
439 			return -EINVAL;
440 	} else {
441 		if (len >= VA_EXCLUDE_START)
442 			return -EINVAL;
443 
444 		if (invalid_64bit_range(addr, len))
445 			return -EINVAL;
446 	}
447 
448 	return 0;
449 }
450 
451 /* Linux version of mmap */
452 SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
453 		unsigned long, prot, unsigned long, flags, unsigned long, fd,
454 		unsigned long, off)
455 {
456 	unsigned long retval = -EINVAL;
457 
458 	if ((off + PAGE_ALIGN(len)) < off)
459 		goto out;
460 	if (off & ~PAGE_MASK)
461 		goto out;
462 	retval = ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
463 out:
464 	return retval;
465 }
466 
467 SYSCALL_DEFINE2(64_munmap, unsigned long, addr, size_t, len)
468 {
469 	if (invalid_64bit_range(addr, len))
470 		return -EINVAL;
471 
472 	return vm_munmap(addr, len);
473 }
474 
475 SYSCALL_DEFINE5(64_mremap, unsigned long, addr,	unsigned long, old_len,
476 		unsigned long, new_len, unsigned long, flags,
477 		unsigned long, new_addr)
478 {
479 	if (test_thread_flag(TIF_32BIT))
480 		return -EINVAL;
481 	return sys_mremap(addr, old_len, new_len, flags, new_addr);
482 }
483 
484 SYSCALL_DEFINE0(nis_syscall)
485 {
486 	static int count;
487 	struct pt_regs *regs = current_pt_regs();
488 
489 	/* Don't make the system unusable, if someone goes stuck */
490 	if (count++ > 5)
491 		return -ENOSYS;
492 
493 	printk ("Unimplemented SPARC system call %ld\n",regs->u_regs[1]);
494 #ifdef DEBUG_UNIMP_SYSCALL
495 	show_regs (regs);
496 #endif
497 
498 	return -ENOSYS;
499 }
500 
501 /* #define DEBUG_SPARC_BREAKPOINT */
502 
503 asmlinkage void sparc_breakpoint(struct pt_regs *regs)
504 {
505 	enum ctx_state prev_state = exception_enter();
506 
507 	if (test_thread_flag(TIF_32BIT)) {
508 		regs->tpc &= 0xffffffff;
509 		regs->tnpc &= 0xffffffff;
510 	}
511 #ifdef DEBUG_SPARC_BREAKPOINT
512         printk ("TRAP: Entering kernel PC=%lx, nPC=%lx\n", regs->tpc, regs->tnpc);
513 #endif
514 	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->tpc, 0);
515 #ifdef DEBUG_SPARC_BREAKPOINT
516 	printk ("TRAP: Returning to space: PC=%lx nPC=%lx\n", regs->tpc, regs->tnpc);
517 #endif
518 	exception_exit(prev_state);
519 }
520 
521 SYSCALL_DEFINE2(getdomainname, char __user *, name, int, len)
522 {
523 	int nlen, err;
524 	char tmp[__NEW_UTS_LEN + 1];
525 
526 	if (len < 0)
527 		return -EINVAL;
528 
529 	down_read(&uts_sem);
530 
531 	nlen = strlen(utsname()->domainname) + 1;
532 	err = -EINVAL;
533 	if (nlen > len)
534 		goto out_unlock;
535 	memcpy(tmp, utsname()->domainname, nlen);
536 
537 	up_read(&uts_sem);
538 
539 	if (copy_to_user(name, tmp, nlen))
540 		return -EFAULT;
541 	return 0;
542 
543 out_unlock:
544 	up_read(&uts_sem);
545 	return err;
546 }
547 
548 SYSCALL_DEFINE1(sparc_adjtimex, struct timex __user *, txc_p)
549 {
550 	struct timex txc;		/* Local copy of parameter */
551 	struct __kernel_timex *kt = (void *)&txc;
552 	int ret;
553 
554 	/* Copy the user data space into the kernel copy
555 	 * structure. But bear in mind that the structures
556 	 * may change
557 	 */
558 	if (copy_from_user(&txc, txc_p, sizeof(struct timex)))
559 		return -EFAULT;
560 
561 	/*
562 	 * override for sparc64 specific timeval type: tv_usec
563 	 * is 32 bit wide instead of 64-bit in __kernel_timex
564 	 */
565 	kt->time.tv_usec = txc.time.tv_usec;
566 	ret = do_adjtimex(kt);
567 	txc.time.tv_usec = kt->time.tv_usec;
568 
569 	return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
570 }
571 
572 SYSCALL_DEFINE2(sparc_clock_adjtime, const clockid_t, which_clock,struct timex __user *, txc_p)
573 {
574 	struct timex txc;		/* Local copy of parameter */
575 	struct __kernel_timex *kt = (void *)&txc;
576 	int ret;
577 
578 	if (!IS_ENABLED(CONFIG_POSIX_TIMERS)) {
579 		pr_err_once("process %d (%s) attempted a POSIX timer syscall "
580 		    "while CONFIG_POSIX_TIMERS is not set\n",
581 		    current->pid, current->comm);
582 
583 		return -ENOSYS;
584 	}
585 
586 	/* Copy the user data space into the kernel copy
587 	 * structure. But bear in mind that the structures
588 	 * may change
589 	 */
590 	if (copy_from_user(&txc, txc_p, sizeof(struct timex)))
591 		return -EFAULT;
592 
593 	/*
594 	 * override for sparc64 specific timeval type: tv_usec
595 	 * is 32 bit wide instead of 64-bit in __kernel_timex
596 	 */
597 	kt->time.tv_usec = txc.time.tv_usec;
598 	ret = do_clock_adjtime(which_clock, kt);
599 	txc.time.tv_usec = kt->time.tv_usec;
600 
601 	return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
602 }
603 
604 SYSCALL_DEFINE5(utrap_install, utrap_entry_t, type,
605 		utrap_handler_t, new_p, utrap_handler_t, new_d,
606 		utrap_handler_t __user *, old_p,
607 		utrap_handler_t __user *, old_d)
608 {
609 	if (type < UT_INSTRUCTION_EXCEPTION || type > UT_TRAP_INSTRUCTION_31)
610 		return -EINVAL;
611 	if (new_p == (utrap_handler_t)(long)UTH_NOCHANGE) {
612 		if (old_p) {
613 			if (!current_thread_info()->utraps) {
614 				if (put_user(NULL, old_p))
615 					return -EFAULT;
616 			} else {
617 				if (put_user((utrap_handler_t)(current_thread_info()->utraps[type]), old_p))
618 					return -EFAULT;
619 			}
620 		}
621 		if (old_d) {
622 			if (put_user(NULL, old_d))
623 				return -EFAULT;
624 		}
625 		return 0;
626 	}
627 	if (!current_thread_info()->utraps) {
628 		current_thread_info()->utraps =
629 			kcalloc(UT_TRAP_INSTRUCTION_31 + 1, sizeof(long),
630 				GFP_KERNEL);
631 		if (!current_thread_info()->utraps)
632 			return -ENOMEM;
633 		current_thread_info()->utraps[0] = 1;
634 	} else {
635 		if ((utrap_handler_t)current_thread_info()->utraps[type] != new_p &&
636 		    current_thread_info()->utraps[0] > 1) {
637 			unsigned long *p = current_thread_info()->utraps;
638 
639 			current_thread_info()->utraps =
640 				kmalloc_array(UT_TRAP_INSTRUCTION_31 + 1,
641 					      sizeof(long),
642 					      GFP_KERNEL);
643 			if (!current_thread_info()->utraps) {
644 				current_thread_info()->utraps = p;
645 				return -ENOMEM;
646 			}
647 			p[0]--;
648 			current_thread_info()->utraps[0] = 1;
649 			memcpy(current_thread_info()->utraps+1, p+1,
650 			       UT_TRAP_INSTRUCTION_31*sizeof(long));
651 		}
652 	}
653 	if (old_p) {
654 		if (put_user((utrap_handler_t)(current_thread_info()->utraps[type]), old_p))
655 			return -EFAULT;
656 	}
657 	if (old_d) {
658 		if (put_user(NULL, old_d))
659 			return -EFAULT;
660 	}
661 	current_thread_info()->utraps[type] = (long)new_p;
662 
663 	return 0;
664 }
665 
666 SYSCALL_DEFINE1(memory_ordering, unsigned long, model)
667 {
668 	struct pt_regs *regs = current_pt_regs();
669 	if (model >= 3)
670 		return -EINVAL;
671 	regs->tstate = (regs->tstate & ~TSTATE_MM) | (model << 14);
672 	return 0;
673 }
674 
675 SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
676 		struct sigaction __user *, oact, void __user *, restorer,
677 		size_t, sigsetsize)
678 {
679 	struct k_sigaction new_ka, old_ka;
680 	int ret;
681 
682 	/* XXX: Don't preclude handling different sized sigset_t's.  */
683 	if (sigsetsize != sizeof(sigset_t))
684 		return -EINVAL;
685 
686 	if (act) {
687 		new_ka.ka_restorer = restorer;
688 		if (copy_from_user(&new_ka.sa, act, sizeof(*act)))
689 			return -EFAULT;
690 	}
691 
692 	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
693 
694 	if (!ret && oact) {
695 		if (copy_to_user(oact, &old_ka.sa, sizeof(*oact)))
696 			return -EFAULT;
697 	}
698 
699 	return ret;
700 }
701 
702 SYSCALL_DEFINE0(kern_features)
703 {
704 	return KERN_FEATURE_MIXED_MODE_STACK;
705 }
706