xref: /openbmc/linux/arch/x86/kernel/signal_32.c (revision a1e58bbd)
1 /*
2  *  Copyright (C) 1991, 1992  Linus Torvalds
3  *
4  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
5  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
6  */
7 
8 #include <linux/sched.h>
9 #include <linux/mm.h>
10 #include <linux/smp.h>
11 #include <linux/kernel.h>
12 #include <linux/signal.h>
13 #include <linux/errno.h>
14 #include <linux/wait.h>
15 #include <linux/unistd.h>
16 #include <linux/stddef.h>
17 #include <linux/personality.h>
18 #include <linux/suspend.h>
19 #include <linux/ptrace.h>
20 #include <linux/elf.h>
21 #include <linux/binfmts.h>
22 #include <asm/processor.h>
23 #include <asm/ucontext.h>
24 #include <asm/uaccess.h>
25 #include <asm/i387.h>
26 #include <asm/vdso.h>
27 #include "sigframe_32.h"
28 
29 #define DEBUG_SIG 0
30 
31 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
32 
33 /*
34  * Atomically swap in the new signal mask, and wait for a signal.
35  */
36 asmlinkage int
37 sys_sigsuspend(int history0, int history1, old_sigset_t mask)
38 {
39 	mask &= _BLOCKABLE;
40 	spin_lock_irq(&current->sighand->siglock);
41 	current->saved_sigmask = current->blocked;
42 	siginitset(&current->blocked, mask);
43 	recalc_sigpending();
44 	spin_unlock_irq(&current->sighand->siglock);
45 
46 	current->state = TASK_INTERRUPTIBLE;
47 	schedule();
48 	set_thread_flag(TIF_RESTORE_SIGMASK);
49 	return -ERESTARTNOHAND;
50 }
51 
52 asmlinkage int
53 sys_sigaction(int sig, const struct old_sigaction __user *act,
54 	      struct old_sigaction __user *oact)
55 {
56 	struct k_sigaction new_ka, old_ka;
57 	int ret;
58 
59 	if (act) {
60 		old_sigset_t mask;
61 		if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
62 		    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
63 		    __get_user(new_ka.sa.sa_restorer, &act->sa_restorer))
64 			return -EFAULT;
65 		__get_user(new_ka.sa.sa_flags, &act->sa_flags);
66 		__get_user(mask, &act->sa_mask);
67 		siginitset(&new_ka.sa.sa_mask, mask);
68 	}
69 
70 	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
71 
72 	if (!ret && oact) {
73 		if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
74 		    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
75 		    __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer))
76 			return -EFAULT;
77 		__put_user(old_ka.sa.sa_flags, &oact->sa_flags);
78 		__put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
79 	}
80 
81 	return ret;
82 }
83 
84 asmlinkage int
85 sys_sigaltstack(unsigned long bx)
86 {
87 	/* This is needed to make gcc realize it doesn't own the "struct pt_regs" */
88 	struct pt_regs *regs = (struct pt_regs *)&bx;
89 	const stack_t __user *uss = (const stack_t __user *)bx;
90 	stack_t __user *uoss = (stack_t __user *)regs->cx;
91 
92 	return do_sigaltstack(uss, uoss, regs->sp);
93 }
94 
95 
96 /*
97  * Do a signal return; undo the signal stack.
98  */
99 
100 static int
101 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, int *peax)
102 {
103 	unsigned int err = 0;
104 
105 	/* Always make any pending restarted system calls return -EINTR */
106 	current_thread_info()->restart_block.fn = do_no_restart_syscall;
107 
108 #define COPY(x)		err |= __get_user(regs->x, &sc->x)
109 
110 #define COPY_SEG(seg)							\
111 	{ unsigned short tmp;						\
112 	  err |= __get_user(tmp, &sc->seg);				\
113 	  regs->seg = tmp; }
114 
115 #define COPY_SEG_STRICT(seg)						\
116 	{ unsigned short tmp;						\
117 	  err |= __get_user(tmp, &sc->seg);				\
118 	  regs->seg = tmp|3; }
119 
120 #define GET_SEG(seg)							\
121 	{ unsigned short tmp;						\
122 	  err |= __get_user(tmp, &sc->seg);				\
123 	  loadsegment(seg,tmp); }
124 
125 #define	FIX_EFLAGS	(X86_EFLAGS_AC | X86_EFLAGS_RF |		 \
126 			 X86_EFLAGS_OF | X86_EFLAGS_DF |		 \
127 			 X86_EFLAGS_TF | X86_EFLAGS_SF | X86_EFLAGS_ZF | \
128 			 X86_EFLAGS_AF | X86_EFLAGS_PF | X86_EFLAGS_CF)
129 
130 	GET_SEG(gs);
131 	COPY_SEG(fs);
132 	COPY_SEG(es);
133 	COPY_SEG(ds);
134 	COPY(di);
135 	COPY(si);
136 	COPY(bp);
137 	COPY(sp);
138 	COPY(bx);
139 	COPY(dx);
140 	COPY(cx);
141 	COPY(ip);
142 	COPY_SEG_STRICT(cs);
143 	COPY_SEG_STRICT(ss);
144 
145 	{
146 		unsigned int tmpflags;
147 		err |= __get_user(tmpflags, &sc->flags);
148 		regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
149 		regs->orig_ax = -1;		/* disable syscall checks */
150 	}
151 
152 	{
153 		struct _fpstate __user * buf;
154 		err |= __get_user(buf, &sc->fpstate);
155 		if (buf) {
156 			if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
157 				goto badframe;
158 			err |= restore_i387(buf);
159 		} else {
160 			struct task_struct *me = current;
161 			if (used_math()) {
162 				clear_fpu(me);
163 				clear_used_math();
164 			}
165 		}
166 	}
167 
168 	err |= __get_user(*peax, &sc->ax);
169 	return err;
170 
171 badframe:
172 	return 1;
173 }
174 
175 asmlinkage int sys_sigreturn(unsigned long __unused)
176 {
177 	struct pt_regs *regs = (struct pt_regs *) &__unused;
178 	struct sigframe __user *frame = (struct sigframe __user *)(regs->sp - 8);
179 	sigset_t set;
180 	int ax;
181 
182 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
183 		goto badframe;
184 	if (__get_user(set.sig[0], &frame->sc.oldmask)
185 	    || (_NSIG_WORDS > 1
186 		&& __copy_from_user(&set.sig[1], &frame->extramask,
187 				    sizeof(frame->extramask))))
188 		goto badframe;
189 
190 	sigdelsetmask(&set, ~_BLOCKABLE);
191 	spin_lock_irq(&current->sighand->siglock);
192 	current->blocked = set;
193 	recalc_sigpending();
194 	spin_unlock_irq(&current->sighand->siglock);
195 
196 	if (restore_sigcontext(regs, &frame->sc, &ax))
197 		goto badframe;
198 	return ax;
199 
200 badframe:
201 	if (show_unhandled_signals && printk_ratelimit()) {
202 		printk("%s%s[%d] bad frame in sigreturn frame:%p ip:%lx"
203 		       " sp:%lx oeax:%lx",
204 		    task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
205 		    current->comm, task_pid_nr(current), frame, regs->ip,
206 		    regs->sp, regs->orig_ax);
207 		print_vma_addr(" in ", regs->ip);
208 		printk("\n");
209 	}
210 
211 	force_sig(SIGSEGV, current);
212 	return 0;
213 }
214 
215 asmlinkage int sys_rt_sigreturn(unsigned long __unused)
216 {
217 	struct pt_regs *regs = (struct pt_regs *) &__unused;
218 	struct rt_sigframe __user *frame = (struct rt_sigframe __user *)(regs->sp - 4);
219 	sigset_t set;
220 	int ax;
221 
222 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
223 		goto badframe;
224 	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
225 		goto badframe;
226 
227 	sigdelsetmask(&set, ~_BLOCKABLE);
228 	spin_lock_irq(&current->sighand->siglock);
229 	current->blocked = set;
230 	recalc_sigpending();
231 	spin_unlock_irq(&current->sighand->siglock);
232 
233 	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
234 		goto badframe;
235 
236 	if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
237 		goto badframe;
238 
239 	return ax;
240 
241 badframe:
242 	force_sig(SIGSEGV, current);
243 	return 0;
244 }
245 
246 /*
247  * Set up a signal frame.
248  */
249 
250 static int
251 setup_sigcontext(struct sigcontext __user *sc, struct _fpstate __user *fpstate,
252 		 struct pt_regs *regs, unsigned long mask)
253 {
254 	int tmp, err = 0;
255 
256 	err |= __put_user(regs->fs, (unsigned int __user *)&sc->fs);
257 	savesegment(gs, tmp);
258 	err |= __put_user(tmp, (unsigned int __user *)&sc->gs);
259 
260 	err |= __put_user(regs->es, (unsigned int __user *)&sc->es);
261 	err |= __put_user(regs->ds, (unsigned int __user *)&sc->ds);
262 	err |= __put_user(regs->di, &sc->di);
263 	err |= __put_user(regs->si, &sc->si);
264 	err |= __put_user(regs->bp, &sc->bp);
265 	err |= __put_user(regs->sp, &sc->sp);
266 	err |= __put_user(regs->bx, &sc->bx);
267 	err |= __put_user(regs->dx, &sc->dx);
268 	err |= __put_user(regs->cx, &sc->cx);
269 	err |= __put_user(regs->ax, &sc->ax);
270 	err |= __put_user(current->thread.trap_no, &sc->trapno);
271 	err |= __put_user(current->thread.error_code, &sc->err);
272 	err |= __put_user(regs->ip, &sc->ip);
273 	err |= __put_user(regs->cs, (unsigned int __user *)&sc->cs);
274 	err |= __put_user(regs->flags, &sc->flags);
275 	err |= __put_user(regs->sp, &sc->sp_at_signal);
276 	err |= __put_user(regs->ss, (unsigned int __user *)&sc->ss);
277 
278 	tmp = save_i387(fpstate);
279 	if (tmp < 0)
280 	  err = 1;
281 	else
282 	  err |= __put_user(tmp ? fpstate : NULL, &sc->fpstate);
283 
284 	/* non-iBCS2 extensions.. */
285 	err |= __put_user(mask, &sc->oldmask);
286 	err |= __put_user(current->thread.cr2, &sc->cr2);
287 
288 	return err;
289 }
290 
291 /*
292  * Determine which stack to use..
293  */
294 static inline void __user *
295 get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
296 {
297 	unsigned long sp;
298 
299 	/* Default to using normal stack */
300 	sp = regs->sp;
301 
302 	/*
303 	 * If we are on the alternate signal stack and would overflow it, don't.
304 	 * Return an always-bogus address instead so we will die with SIGSEGV.
305 	 */
306 	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
307 		return (void __user *) -1L;
308 
309 	/* This is the X/Open sanctioned signal stack switching.  */
310 	if (ka->sa.sa_flags & SA_ONSTACK) {
311 		if (sas_ss_flags(sp) == 0)
312 			sp = current->sas_ss_sp + current->sas_ss_size;
313 	}
314 
315 	/* This is the legacy signal stack switching. */
316 	else if ((regs->ss & 0xffff) != __USER_DS &&
317 		 !(ka->sa.sa_flags & SA_RESTORER) &&
318 		 ka->sa.sa_restorer) {
319 		sp = (unsigned long) ka->sa.sa_restorer;
320 	}
321 
322 	sp -= frame_size;
323 	/* Align the stack pointer according to the i386 ABI,
324 	 * i.e. so that on function entry ((sp + 4) & 15) == 0. */
325 	sp = ((sp + 4) & -16ul) - 4;
326 	return (void __user *) sp;
327 }
328 
329 /* These symbols are defined with the addresses in the vsyscall page.
330    See vsyscall-sigreturn.S.  */
331 extern void __user __kernel_sigreturn;
332 extern void __user __kernel_rt_sigreturn;
333 
334 static int setup_frame(int sig, struct k_sigaction *ka,
335 		       sigset_t *set, struct pt_regs * regs)
336 {
337 	void __user *restorer;
338 	struct sigframe __user *frame;
339 	int err = 0;
340 	int usig;
341 
342 	frame = get_sigframe(ka, regs, sizeof(*frame));
343 
344 	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
345 		goto give_sigsegv;
346 
347 	usig = current_thread_info()->exec_domain
348 		&& current_thread_info()->exec_domain->signal_invmap
349 		&& sig < 32
350 		? current_thread_info()->exec_domain->signal_invmap[sig]
351 		: sig;
352 
353 	err = __put_user(usig, &frame->sig);
354 	if (err)
355 		goto give_sigsegv;
356 
357 	err = setup_sigcontext(&frame->sc, &frame->fpstate, regs, set->sig[0]);
358 	if (err)
359 		goto give_sigsegv;
360 
361 	if (_NSIG_WORDS > 1) {
362 		err = __copy_to_user(&frame->extramask, &set->sig[1],
363 				      sizeof(frame->extramask));
364 		if (err)
365 			goto give_sigsegv;
366 	}
367 
368 	if (current->binfmt->hasvdso)
369 		restorer = VDSO32_SYMBOL(current->mm->context.vdso, sigreturn);
370 	else
371 		restorer = &frame->retcode;
372 	if (ka->sa.sa_flags & SA_RESTORER)
373 		restorer = ka->sa.sa_restorer;
374 
375 	/* Set up to return from userspace.  */
376 	err |= __put_user(restorer, &frame->pretcode);
377 
378 	/*
379 	 * This is popl %eax ; movl $,%eax ; int $0x80
380 	 *
381 	 * WE DO NOT USE IT ANY MORE! It's only left here for historical
382 	 * reasons and because gdb uses it as a signature to notice
383 	 * signal handler stack frames.
384 	 */
385 	err |= __put_user(0xb858, (short __user *)(frame->retcode+0));
386 	err |= __put_user(__NR_sigreturn, (int __user *)(frame->retcode+2));
387 	err |= __put_user(0x80cd, (short __user *)(frame->retcode+6));
388 
389 	if (err)
390 		goto give_sigsegv;
391 
392 	/* Set up registers for signal handler */
393 	regs->sp = (unsigned long) frame;
394 	regs->ip = (unsigned long) ka->sa.sa_handler;
395 	regs->ax = (unsigned long) sig;
396 	regs->dx = (unsigned long) 0;
397 	regs->cx = (unsigned long) 0;
398 
399 	regs->ds = __USER_DS;
400 	regs->es = __USER_DS;
401 	regs->ss = __USER_DS;
402 	regs->cs = __USER_CS;
403 
404 	/*
405 	 * Clear TF when entering the signal handler, but
406 	 * notify any tracer that was single-stepping it.
407 	 * The tracer may want to single-step inside the
408 	 * handler too.
409 	 */
410 	regs->flags &= ~(TF_MASK | X86_EFLAGS_DF);
411 	if (test_thread_flag(TIF_SINGLESTEP))
412 		ptrace_notify(SIGTRAP);
413 
414 #if DEBUG_SIG
415 	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
416 		current->comm, current->pid, frame, regs->ip, frame->pretcode);
417 #endif
418 
419 	return 0;
420 
421 give_sigsegv:
422 	force_sigsegv(sig, current);
423 	return -EFAULT;
424 }
425 
426 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
427 			   sigset_t *set, struct pt_regs * regs)
428 {
429 	void __user *restorer;
430 	struct rt_sigframe __user *frame;
431 	int err = 0;
432 	int usig;
433 
434 	frame = get_sigframe(ka, regs, sizeof(*frame));
435 
436 	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
437 		goto give_sigsegv;
438 
439 	usig = current_thread_info()->exec_domain
440 		&& current_thread_info()->exec_domain->signal_invmap
441 		&& sig < 32
442 		? current_thread_info()->exec_domain->signal_invmap[sig]
443 		: sig;
444 
445 	err |= __put_user(usig, &frame->sig);
446 	err |= __put_user(&frame->info, &frame->pinfo);
447 	err |= __put_user(&frame->uc, &frame->puc);
448 	err |= copy_siginfo_to_user(&frame->info, info);
449 	if (err)
450 		goto give_sigsegv;
451 
452 	/* Create the ucontext.  */
453 	err |= __put_user(0, &frame->uc.uc_flags);
454 	err |= __put_user(0, &frame->uc.uc_link);
455 	err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
456 	err |= __put_user(sas_ss_flags(regs->sp),
457 			  &frame->uc.uc_stack.ss_flags);
458 	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
459 	err |= setup_sigcontext(&frame->uc.uc_mcontext, &frame->fpstate,
460 			        regs, set->sig[0]);
461 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
462 	if (err)
463 		goto give_sigsegv;
464 
465 	/* Set up to return from userspace.  */
466 	restorer = VDSO32_SYMBOL(current->mm->context.vdso, rt_sigreturn);
467 	if (ka->sa.sa_flags & SA_RESTORER)
468 		restorer = ka->sa.sa_restorer;
469 	err |= __put_user(restorer, &frame->pretcode);
470 
471 	/*
472 	 * This is movl $,%ax ; int $0x80
473 	 *
474 	 * WE DO NOT USE IT ANY MORE! It's only left here for historical
475 	 * reasons and because gdb uses it as a signature to notice
476 	 * signal handler stack frames.
477 	 */
478 	err |= __put_user(0xb8, (char __user *)(frame->retcode+0));
479 	err |= __put_user(__NR_rt_sigreturn, (int __user *)(frame->retcode+1));
480 	err |= __put_user(0x80cd, (short __user *)(frame->retcode+5));
481 
482 	if (err)
483 		goto give_sigsegv;
484 
485 	/* Set up registers for signal handler */
486 	regs->sp = (unsigned long) frame;
487 	regs->ip = (unsigned long) ka->sa.sa_handler;
488 	regs->ax = (unsigned long) usig;
489 	regs->dx = (unsigned long) &frame->info;
490 	regs->cx = (unsigned long) &frame->uc;
491 
492 	regs->ds = __USER_DS;
493 	regs->es = __USER_DS;
494 	regs->ss = __USER_DS;
495 	regs->cs = __USER_CS;
496 
497 	/*
498 	 * Clear TF when entering the signal handler, but
499 	 * notify any tracer that was single-stepping it.
500 	 * The tracer may want to single-step inside the
501 	 * handler too.
502 	 */
503 	regs->flags &= ~(TF_MASK | X86_EFLAGS_DF);
504 	if (test_thread_flag(TIF_SINGLESTEP))
505 		ptrace_notify(SIGTRAP);
506 
507 #if DEBUG_SIG
508 	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
509 		current->comm, current->pid, frame, regs->ip, frame->pretcode);
510 #endif
511 
512 	return 0;
513 
514 give_sigsegv:
515 	force_sigsegv(sig, current);
516 	return -EFAULT;
517 }
518 
519 /*
520  * OK, we're invoking a handler
521  */
522 
523 static int
524 handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
525 	      sigset_t *oldset,	struct pt_regs * regs)
526 {
527 	int ret;
528 
529 	/* Are we from a system call? */
530 	if (regs->orig_ax >= 0) {
531 		/* If so, check system call restarting.. */
532 		switch (regs->ax) {
533 		        case -ERESTART_RESTARTBLOCK:
534 			case -ERESTARTNOHAND:
535 				regs->ax = -EINTR;
536 				break;
537 
538 			case -ERESTARTSYS:
539 				if (!(ka->sa.sa_flags & SA_RESTART)) {
540 					regs->ax = -EINTR;
541 					break;
542 				}
543 			/* fallthrough */
544 			case -ERESTARTNOINTR:
545 				regs->ax = regs->orig_ax;
546 				regs->ip -= 2;
547 		}
548 	}
549 
550 	/*
551 	 * If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
552 	 * flag so that register information in the sigcontext is correct.
553 	 */
554 	if (unlikely(regs->flags & X86_EFLAGS_TF) &&
555 	    likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
556 		regs->flags &= ~X86_EFLAGS_TF;
557 
558 	/* Set up the stack frame */
559 	if (ka->sa.sa_flags & SA_SIGINFO)
560 		ret = setup_rt_frame(sig, ka, info, oldset, regs);
561 	else
562 		ret = setup_frame(sig, ka, oldset, regs);
563 
564 	if (ret == 0) {
565 		spin_lock_irq(&current->sighand->siglock);
566 		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
567 		if (!(ka->sa.sa_flags & SA_NODEFER))
568 			sigaddset(&current->blocked,sig);
569 		recalc_sigpending();
570 		spin_unlock_irq(&current->sighand->siglock);
571 	}
572 
573 	return ret;
574 }
575 
576 /*
577  * Note that 'init' is a special process: it doesn't get signals it doesn't
578  * want to handle. Thus you cannot kill init even with a SIGKILL even by
579  * mistake.
580  */
581 static void do_signal(struct pt_regs *regs)
582 {
583 	siginfo_t info;
584 	int signr;
585 	struct k_sigaction ka;
586 	sigset_t *oldset;
587 
588 	/*
589 	 * We want the common case to go fast, which
590 	 * is why we may in certain cases get here from
591 	 * kernel mode. Just return without doing anything
592  	 * if so.  vm86 regs switched out by assembly code
593  	 * before reaching here, so testing against kernel
594  	 * CS suffices.
595 	 */
596 	if (!user_mode(regs))
597 		return;
598 
599 	if (test_thread_flag(TIF_RESTORE_SIGMASK))
600 		oldset = &current->saved_sigmask;
601 	else
602 		oldset = &current->blocked;
603 
604 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
605 	if (signr > 0) {
606 		/* Re-enable any watchpoints before delivering the
607 		 * signal to user space. The processor register will
608 		 * have been cleared if the watchpoint triggered
609 		 * inside the kernel.
610 		 */
611 		if (unlikely(current->thread.debugreg7))
612 			set_debugreg(current->thread.debugreg7, 7);
613 
614 		/* Whee!  Actually deliver the signal.  */
615 		if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
616 			/* a signal was successfully delivered; the saved
617 			 * sigmask will have been stored in the signal frame,
618 			 * and will be restored by sigreturn, so we can simply
619 			 * clear the TIF_RESTORE_SIGMASK flag */
620 			if (test_thread_flag(TIF_RESTORE_SIGMASK))
621 				clear_thread_flag(TIF_RESTORE_SIGMASK);
622 		}
623 
624 		return;
625 	}
626 
627 	/* Did we come from a system call? */
628 	if (regs->orig_ax >= 0) {
629 		/* Restart the system call - no handlers present */
630 		switch (regs->ax) {
631 		case -ERESTARTNOHAND:
632 		case -ERESTARTSYS:
633 		case -ERESTARTNOINTR:
634 			regs->ax = regs->orig_ax;
635 			regs->ip -= 2;
636 			break;
637 
638 		case -ERESTART_RESTARTBLOCK:
639 			regs->ax = __NR_restart_syscall;
640 			regs->ip -= 2;
641 			break;
642 		}
643 	}
644 
645 	/* if there's no signal to deliver, we just put the saved sigmask
646 	 * back */
647 	if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
648 		clear_thread_flag(TIF_RESTORE_SIGMASK);
649 		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
650 	}
651 }
652 
653 /*
654  * notification of userspace execution resumption
655  * - triggered by the TIF_WORK_MASK flags
656  */
657 __attribute__((regparm(3)))
658 void do_notify_resume(struct pt_regs *regs, void *_unused,
659 		      __u32 thread_info_flags)
660 {
661 	/* Pending single-step? */
662 	if (thread_info_flags & _TIF_SINGLESTEP) {
663 		regs->flags |= TF_MASK;
664 		clear_thread_flag(TIF_SINGLESTEP);
665 	}
666 
667 	/* deal with pending signal delivery */
668 	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
669 		do_signal(regs);
670 
671 	if (thread_info_flags & _TIF_HRTICK_RESCHED)
672 		hrtick_resched();
673 
674 	clear_thread_flag(TIF_IRET);
675 }
676