xref: /openbmc/linux/arch/arm64/kernel/signal32.c (revision e2f1cf25)
1 /*
2  * Based on arch/arm/kernel/signal.c
3  *
4  * Copyright (C) 1995-2009 Russell King
5  * Copyright (C) 2012 ARM Ltd.
6  * Modified by Will Deacon <will.deacon@arm.com>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
19  */
20 
21 #include <linux/compat.h>
22 #include <linux/signal.h>
23 #include <linux/syscalls.h>
24 #include <linux/ratelimit.h>
25 
26 #include <asm/esr.h>
27 #include <asm/fpsimd.h>
28 #include <asm/signal32.h>
29 #include <asm/uaccess.h>
30 #include <asm/unistd.h>
31 
32 struct compat_sigcontext {
33 	/* We always set these two fields to 0 */
34 	compat_ulong_t			trap_no;
35 	compat_ulong_t			error_code;
36 
37 	compat_ulong_t			oldmask;
38 	compat_ulong_t			arm_r0;
39 	compat_ulong_t			arm_r1;
40 	compat_ulong_t			arm_r2;
41 	compat_ulong_t			arm_r3;
42 	compat_ulong_t			arm_r4;
43 	compat_ulong_t			arm_r5;
44 	compat_ulong_t			arm_r6;
45 	compat_ulong_t			arm_r7;
46 	compat_ulong_t			arm_r8;
47 	compat_ulong_t			arm_r9;
48 	compat_ulong_t			arm_r10;
49 	compat_ulong_t			arm_fp;
50 	compat_ulong_t			arm_ip;
51 	compat_ulong_t			arm_sp;
52 	compat_ulong_t			arm_lr;
53 	compat_ulong_t			arm_pc;
54 	compat_ulong_t			arm_cpsr;
55 	compat_ulong_t			fault_address;
56 };
57 
58 struct compat_ucontext {
59 	compat_ulong_t			uc_flags;
60 	compat_uptr_t			uc_link;
61 	compat_stack_t			uc_stack;
62 	struct compat_sigcontext	uc_mcontext;
63 	compat_sigset_t			uc_sigmask;
64 	int		__unused[32 - (sizeof (compat_sigset_t) / sizeof (int))];
65 	compat_ulong_t	uc_regspace[128] __attribute__((__aligned__(8)));
66 };
67 
68 struct compat_vfp_sigframe {
69 	compat_ulong_t	magic;
70 	compat_ulong_t	size;
71 	struct compat_user_vfp {
72 		compat_u64	fpregs[32];
73 		compat_ulong_t	fpscr;
74 	} ufp;
75 	struct compat_user_vfp_exc {
76 		compat_ulong_t	fpexc;
77 		compat_ulong_t	fpinst;
78 		compat_ulong_t	fpinst2;
79 	} ufp_exc;
80 } __attribute__((__aligned__(8)));
81 
82 #define VFP_MAGIC		0x56465001
83 #define VFP_STORAGE_SIZE	sizeof(struct compat_vfp_sigframe)
84 
85 #define FSR_WRITE_SHIFT		(11)
86 
87 struct compat_aux_sigframe {
88 	struct compat_vfp_sigframe	vfp;
89 
90 	/* Something that isn't a valid magic number for any coprocessor.  */
91 	unsigned long			end_magic;
92 } __attribute__((__aligned__(8)));
93 
94 struct compat_sigframe {
95 	struct compat_ucontext	uc;
96 	compat_ulong_t		retcode[2];
97 };
98 
99 struct compat_rt_sigframe {
100 	struct compat_siginfo info;
101 	struct compat_sigframe sig;
102 };
103 
104 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
105 
106 static inline int put_sigset_t(compat_sigset_t __user *uset, sigset_t *set)
107 {
108 	compat_sigset_t	cset;
109 
110 	cset.sig[0] = set->sig[0] & 0xffffffffull;
111 	cset.sig[1] = set->sig[0] >> 32;
112 
113 	return copy_to_user(uset, &cset, sizeof(*uset));
114 }
115 
116 static inline int get_sigset_t(sigset_t *set,
117 			       const compat_sigset_t __user *uset)
118 {
119 	compat_sigset_t s32;
120 
121 	if (copy_from_user(&s32, uset, sizeof(*uset)))
122 		return -EFAULT;
123 
124 	set->sig[0] = s32.sig[0] | (((long)s32.sig[1]) << 32);
125 	return 0;
126 }
127 
128 int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
129 {
130 	int err;
131 
132 	if (!access_ok(VERIFY_WRITE, to, sizeof(*to)))
133 		return -EFAULT;
134 
135 	/* If you change siginfo_t structure, please be sure
136 	 * this code is fixed accordingly.
137 	 * It should never copy any pad contained in the structure
138 	 * to avoid security leaks, but must copy the generic
139 	 * 3 ints plus the relevant union member.
140 	 * This routine must convert siginfo from 64bit to 32bit as well
141 	 * at the same time.
142 	 */
143 	err = __put_user(from->si_signo, &to->si_signo);
144 	err |= __put_user(from->si_errno, &to->si_errno);
145 	err |= __put_user((short)from->si_code, &to->si_code);
146 	if (from->si_code < 0)
147 		err |= __copy_to_user(&to->_sifields._pad, &from->_sifields._pad,
148 				      SI_PAD_SIZE);
149 	else switch (from->si_code & __SI_MASK) {
150 	case __SI_KILL:
151 		err |= __put_user(from->si_pid, &to->si_pid);
152 		err |= __put_user(from->si_uid, &to->si_uid);
153 		break;
154 	case __SI_TIMER:
155 		 err |= __put_user(from->si_tid, &to->si_tid);
156 		 err |= __put_user(from->si_overrun, &to->si_overrun);
157 		 err |= __put_user(from->si_int, &to->si_int);
158 		break;
159 	case __SI_POLL:
160 		err |= __put_user(from->si_band, &to->si_band);
161 		err |= __put_user(from->si_fd, &to->si_fd);
162 		break;
163 	case __SI_FAULT:
164 		err |= __put_user((compat_uptr_t)(unsigned long)from->si_addr,
165 				  &to->si_addr);
166 #ifdef BUS_MCEERR_AO
167 		/*
168 		 * Other callers might not initialize the si_lsb field,
169 		 * so check explicitely for the right codes here.
170 		 */
171 		if (from->si_signo == SIGBUS &&
172 		    (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO))
173 			err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb);
174 #endif
175 		break;
176 	case __SI_CHLD:
177 		err |= __put_user(from->si_pid, &to->si_pid);
178 		err |= __put_user(from->si_uid, &to->si_uid);
179 		err |= __put_user(from->si_status, &to->si_status);
180 		err |= __put_user(from->si_utime, &to->si_utime);
181 		err |= __put_user(from->si_stime, &to->si_stime);
182 		break;
183 	case __SI_RT: /* This is not generated by the kernel as of now. */
184 	case __SI_MESGQ: /* But this is */
185 		err |= __put_user(from->si_pid, &to->si_pid);
186 		err |= __put_user(from->si_uid, &to->si_uid);
187 		err |= __put_user(from->si_int, &to->si_int);
188 		break;
189 	case __SI_SYS:
190 		err |= __put_user((compat_uptr_t)(unsigned long)
191 				from->si_call_addr, &to->si_call_addr);
192 		err |= __put_user(from->si_syscall, &to->si_syscall);
193 		err |= __put_user(from->si_arch, &to->si_arch);
194 		break;
195 	default: /* this is just in case for now ... */
196 		err |= __put_user(from->si_pid, &to->si_pid);
197 		err |= __put_user(from->si_uid, &to->si_uid);
198 		break;
199 	}
200 	return err;
201 }
202 
203 int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
204 {
205 	if (copy_from_user(to, from, __ARCH_SI_PREAMBLE_SIZE) ||
206 	    copy_from_user(to->_sifields._pad,
207 			   from->_sifields._pad, SI_PAD_SIZE))
208 		return -EFAULT;
209 
210 	return 0;
211 }
212 
213 /*
214  * VFP save/restore code.
215  */
216 static int compat_preserve_vfp_context(struct compat_vfp_sigframe __user *frame)
217 {
218 	struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
219 	compat_ulong_t magic = VFP_MAGIC;
220 	compat_ulong_t size = VFP_STORAGE_SIZE;
221 	compat_ulong_t fpscr, fpexc;
222 	int err = 0;
223 
224 	/*
225 	 * Save the hardware registers to the fpsimd_state structure.
226 	 * Note that this also saves V16-31, which aren't visible
227 	 * in AArch32.
228 	 */
229 	fpsimd_preserve_current_state();
230 
231 	/* Place structure header on the stack */
232 	__put_user_error(magic, &frame->magic, err);
233 	__put_user_error(size, &frame->size, err);
234 
235 	/*
236 	 * Now copy the FP registers. Since the registers are packed,
237 	 * we can copy the prefix we want (V0-V15) as it is.
238 	 * FIXME: Won't work if big endian.
239 	 */
240 	err |= __copy_to_user(&frame->ufp.fpregs, fpsimd->vregs,
241 			      sizeof(frame->ufp.fpregs));
242 
243 	/* Create an AArch32 fpscr from the fpsr and the fpcr. */
244 	fpscr = (fpsimd->fpsr & VFP_FPSCR_STAT_MASK) |
245 		(fpsimd->fpcr & VFP_FPSCR_CTRL_MASK);
246 	__put_user_error(fpscr, &frame->ufp.fpscr, err);
247 
248 	/*
249 	 * The exception register aren't available so we fake up a
250 	 * basic FPEXC and zero everything else.
251 	 */
252 	fpexc = (1 << 30);
253 	__put_user_error(fpexc, &frame->ufp_exc.fpexc, err);
254 	__put_user_error(0, &frame->ufp_exc.fpinst, err);
255 	__put_user_error(0, &frame->ufp_exc.fpinst2, err);
256 
257 	return err ? -EFAULT : 0;
258 }
259 
260 static int compat_restore_vfp_context(struct compat_vfp_sigframe __user *frame)
261 {
262 	struct fpsimd_state fpsimd;
263 	compat_ulong_t magic = VFP_MAGIC;
264 	compat_ulong_t size = VFP_STORAGE_SIZE;
265 	compat_ulong_t fpscr;
266 	int err = 0;
267 
268 	__get_user_error(magic, &frame->magic, err);
269 	__get_user_error(size, &frame->size, err);
270 
271 	if (err)
272 		return -EFAULT;
273 	if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE)
274 		return -EINVAL;
275 
276 	/*
277 	 * Copy the FP registers into the start of the fpsimd_state.
278 	 * FIXME: Won't work if big endian.
279 	 */
280 	err |= __copy_from_user(fpsimd.vregs, frame->ufp.fpregs,
281 				sizeof(frame->ufp.fpregs));
282 
283 	/* Extract the fpsr and the fpcr from the fpscr */
284 	__get_user_error(fpscr, &frame->ufp.fpscr, err);
285 	fpsimd.fpsr = fpscr & VFP_FPSCR_STAT_MASK;
286 	fpsimd.fpcr = fpscr & VFP_FPSCR_CTRL_MASK;
287 
288 	/*
289 	 * We don't need to touch the exception register, so
290 	 * reload the hardware state.
291 	 */
292 	if (!err)
293 		fpsimd_update_current_state(&fpsimd);
294 
295 	return err ? -EFAULT : 0;
296 }
297 
298 static int compat_restore_sigframe(struct pt_regs *regs,
299 				   struct compat_sigframe __user *sf)
300 {
301 	int err;
302 	sigset_t set;
303 	struct compat_aux_sigframe __user *aux;
304 
305 	err = get_sigset_t(&set, &sf->uc.uc_sigmask);
306 	if (err == 0) {
307 		sigdelsetmask(&set, ~_BLOCKABLE);
308 		set_current_blocked(&set);
309 	}
310 
311 	__get_user_error(regs->regs[0], &sf->uc.uc_mcontext.arm_r0, err);
312 	__get_user_error(regs->regs[1], &sf->uc.uc_mcontext.arm_r1, err);
313 	__get_user_error(regs->regs[2], &sf->uc.uc_mcontext.arm_r2, err);
314 	__get_user_error(regs->regs[3], &sf->uc.uc_mcontext.arm_r3, err);
315 	__get_user_error(regs->regs[4], &sf->uc.uc_mcontext.arm_r4, err);
316 	__get_user_error(regs->regs[5], &sf->uc.uc_mcontext.arm_r5, err);
317 	__get_user_error(regs->regs[6], &sf->uc.uc_mcontext.arm_r6, err);
318 	__get_user_error(regs->regs[7], &sf->uc.uc_mcontext.arm_r7, err);
319 	__get_user_error(regs->regs[8], &sf->uc.uc_mcontext.arm_r8, err);
320 	__get_user_error(regs->regs[9], &sf->uc.uc_mcontext.arm_r9, err);
321 	__get_user_error(regs->regs[10], &sf->uc.uc_mcontext.arm_r10, err);
322 	__get_user_error(regs->regs[11], &sf->uc.uc_mcontext.arm_fp, err);
323 	__get_user_error(regs->regs[12], &sf->uc.uc_mcontext.arm_ip, err);
324 	__get_user_error(regs->compat_sp, &sf->uc.uc_mcontext.arm_sp, err);
325 	__get_user_error(regs->compat_lr, &sf->uc.uc_mcontext.arm_lr, err);
326 	__get_user_error(regs->pc, &sf->uc.uc_mcontext.arm_pc, err);
327 	__get_user_error(regs->pstate, &sf->uc.uc_mcontext.arm_cpsr, err);
328 
329 	/*
330 	 * Avoid compat_sys_sigreturn() restarting.
331 	 */
332 	regs->syscallno = ~0UL;
333 
334 	err |= !valid_user_regs(&regs->user_regs);
335 
336 	aux = (struct compat_aux_sigframe __user *) sf->uc.uc_regspace;
337 	if (err == 0)
338 		err |= compat_restore_vfp_context(&aux->vfp);
339 
340 	return err;
341 }
342 
343 asmlinkage int compat_sys_sigreturn(struct pt_regs *regs)
344 {
345 	struct compat_sigframe __user *frame;
346 
347 	/* Always make any pending restarted system calls return -EINTR */
348 	current->restart_block.fn = do_no_restart_syscall;
349 
350 	/*
351 	 * Since we stacked the signal on a 64-bit boundary,
352 	 * then 'sp' should be word aligned here.  If it's
353 	 * not, then the user is trying to mess with us.
354 	 */
355 	if (regs->compat_sp & 7)
356 		goto badframe;
357 
358 	frame = (struct compat_sigframe __user *)regs->compat_sp;
359 
360 	if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
361 		goto badframe;
362 
363 	if (compat_restore_sigframe(regs, frame))
364 		goto badframe;
365 
366 	return regs->regs[0];
367 
368 badframe:
369 	if (show_unhandled_signals)
370 		pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
371 				    current->comm, task_pid_nr(current), __func__,
372 				    regs->pc, regs->compat_sp);
373 	force_sig(SIGSEGV, current);
374 	return 0;
375 }
376 
377 asmlinkage int compat_sys_rt_sigreturn(struct pt_regs *regs)
378 {
379 	struct compat_rt_sigframe __user *frame;
380 
381 	/* Always make any pending restarted system calls return -EINTR */
382 	current->restart_block.fn = do_no_restart_syscall;
383 
384 	/*
385 	 * Since we stacked the signal on a 64-bit boundary,
386 	 * then 'sp' should be word aligned here.  If it's
387 	 * not, then the user is trying to mess with us.
388 	 */
389 	if (regs->compat_sp & 7)
390 		goto badframe;
391 
392 	frame = (struct compat_rt_sigframe __user *)regs->compat_sp;
393 
394 	if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
395 		goto badframe;
396 
397 	if (compat_restore_sigframe(regs, &frame->sig))
398 		goto badframe;
399 
400 	if (compat_restore_altstack(&frame->sig.uc.uc_stack))
401 		goto badframe;
402 
403 	return regs->regs[0];
404 
405 badframe:
406 	if (show_unhandled_signals)
407 		pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
408 				    current->comm, task_pid_nr(current), __func__,
409 				    regs->pc, regs->compat_sp);
410 	force_sig(SIGSEGV, current);
411 	return 0;
412 }
413 
414 static void __user *compat_get_sigframe(struct ksignal *ksig,
415 					struct pt_regs *regs,
416 					int framesize)
417 {
418 	compat_ulong_t sp = sigsp(regs->compat_sp, ksig);
419 	void __user *frame;
420 
421 	/*
422 	 * ATPCS B01 mandates 8-byte alignment
423 	 */
424 	frame = compat_ptr((compat_uptr_t)((sp - framesize) & ~7));
425 
426 	/*
427 	 * Check that we can actually write to the signal frame.
428 	 */
429 	if (!access_ok(VERIFY_WRITE, frame, framesize))
430 		frame = NULL;
431 
432 	return frame;
433 }
434 
435 static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
436 				compat_ulong_t __user *rc, void __user *frame,
437 				int usig)
438 {
439 	compat_ulong_t handler = ptr_to_compat(ka->sa.sa_handler);
440 	compat_ulong_t retcode;
441 	compat_ulong_t spsr = regs->pstate & ~(PSR_f | COMPAT_PSR_E_BIT);
442 	int thumb;
443 
444 	/* Check if the handler is written for ARM or Thumb */
445 	thumb = handler & 1;
446 
447 	if (thumb)
448 		spsr |= COMPAT_PSR_T_BIT;
449 	else
450 		spsr &= ~COMPAT_PSR_T_BIT;
451 
452 	/* The IT state must be cleared for both ARM and Thumb-2 */
453 	spsr &= ~COMPAT_PSR_IT_MASK;
454 
455 	/* Restore the original endianness */
456 	spsr |= COMPAT_PSR_ENDSTATE;
457 
458 	if (ka->sa.sa_flags & SA_RESTORER) {
459 		retcode = ptr_to_compat(ka->sa.sa_restorer);
460 	} else {
461 		/* Set up sigreturn pointer */
462 		unsigned int idx = thumb << 1;
463 
464 		if (ka->sa.sa_flags & SA_SIGINFO)
465 			idx += 3;
466 
467 		retcode = AARCH32_VECTORS_BASE +
468 			  AARCH32_KERN_SIGRET_CODE_OFFSET +
469 			  (idx << 2) + thumb;
470 	}
471 
472 	regs->regs[0]	= usig;
473 	regs->compat_sp	= ptr_to_compat(frame);
474 	regs->compat_lr	= retcode;
475 	regs->pc	= handler;
476 	regs->pstate	= spsr;
477 }
478 
479 static int compat_setup_sigframe(struct compat_sigframe __user *sf,
480 				 struct pt_regs *regs, sigset_t *set)
481 {
482 	struct compat_aux_sigframe __user *aux;
483 	int err = 0;
484 
485 	__put_user_error(regs->regs[0], &sf->uc.uc_mcontext.arm_r0, err);
486 	__put_user_error(regs->regs[1], &sf->uc.uc_mcontext.arm_r1, err);
487 	__put_user_error(regs->regs[2], &sf->uc.uc_mcontext.arm_r2, err);
488 	__put_user_error(regs->regs[3], &sf->uc.uc_mcontext.arm_r3, err);
489 	__put_user_error(regs->regs[4], &sf->uc.uc_mcontext.arm_r4, err);
490 	__put_user_error(regs->regs[5], &sf->uc.uc_mcontext.arm_r5, err);
491 	__put_user_error(regs->regs[6], &sf->uc.uc_mcontext.arm_r6, err);
492 	__put_user_error(regs->regs[7], &sf->uc.uc_mcontext.arm_r7, err);
493 	__put_user_error(regs->regs[8], &sf->uc.uc_mcontext.arm_r8, err);
494 	__put_user_error(regs->regs[9], &sf->uc.uc_mcontext.arm_r9, err);
495 	__put_user_error(regs->regs[10], &sf->uc.uc_mcontext.arm_r10, err);
496 	__put_user_error(regs->regs[11], &sf->uc.uc_mcontext.arm_fp, err);
497 	__put_user_error(regs->regs[12], &sf->uc.uc_mcontext.arm_ip, err);
498 	__put_user_error(regs->compat_sp, &sf->uc.uc_mcontext.arm_sp, err);
499 	__put_user_error(regs->compat_lr, &sf->uc.uc_mcontext.arm_lr, err);
500 	__put_user_error(regs->pc, &sf->uc.uc_mcontext.arm_pc, err);
501 	__put_user_error(regs->pstate, &sf->uc.uc_mcontext.arm_cpsr, err);
502 
503 	__put_user_error((compat_ulong_t)0, &sf->uc.uc_mcontext.trap_no, err);
504 	/* set the compat FSR WnR */
505 	__put_user_error(!!(current->thread.fault_code & ESR_ELx_WNR) <<
506 			 FSR_WRITE_SHIFT, &sf->uc.uc_mcontext.error_code, err);
507 	__put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
508 	__put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err);
509 
510 	err |= put_sigset_t(&sf->uc.uc_sigmask, set);
511 
512 	aux = (struct compat_aux_sigframe __user *) sf->uc.uc_regspace;
513 
514 	if (err == 0)
515 		err |= compat_preserve_vfp_context(&aux->vfp);
516 	__put_user_error(0, &aux->end_magic, err);
517 
518 	return err;
519 }
520 
521 /*
522  * 32-bit signal handling routines called from signal.c
523  */
524 int compat_setup_rt_frame(int usig, struct ksignal *ksig,
525 			  sigset_t *set, struct pt_regs *regs)
526 {
527 	struct compat_rt_sigframe __user *frame;
528 	int err = 0;
529 
530 	frame = compat_get_sigframe(ksig, regs, sizeof(*frame));
531 
532 	if (!frame)
533 		return 1;
534 
535 	err |= copy_siginfo_to_user32(&frame->info, &ksig->info);
536 
537 	__put_user_error(0, &frame->sig.uc.uc_flags, err);
538 	__put_user_error(0, &frame->sig.uc.uc_link, err);
539 
540 	err |= __compat_save_altstack(&frame->sig.uc.uc_stack, regs->compat_sp);
541 
542 	err |= compat_setup_sigframe(&frame->sig, regs, set);
543 
544 	if (err == 0) {
545 		compat_setup_return(regs, &ksig->ka, frame->sig.retcode, frame, usig);
546 		regs->regs[1] = (compat_ulong_t)(unsigned long)&frame->info;
547 		regs->regs[2] = (compat_ulong_t)(unsigned long)&frame->sig.uc;
548 	}
549 
550 	return err;
551 }
552 
553 int compat_setup_frame(int usig, struct ksignal *ksig, sigset_t *set,
554 		       struct pt_regs *regs)
555 {
556 	struct compat_sigframe __user *frame;
557 	int err = 0;
558 
559 	frame = compat_get_sigframe(ksig, regs, sizeof(*frame));
560 
561 	if (!frame)
562 		return 1;
563 
564 	__put_user_error(0x5ac3c35a, &frame->uc.uc_flags, err);
565 
566 	err |= compat_setup_sigframe(frame, regs, set);
567 	if (err == 0)
568 		compat_setup_return(regs, &ksig->ka, frame->retcode, frame, usig);
569 
570 	return err;
571 }
572 
573 void compat_setup_restart_syscall(struct pt_regs *regs)
574 {
575        regs->regs[7] = __NR_compat_restart_syscall;
576 }
577