1/*
2 *  linux/arch/x86_64/kernel/signal.c
3 *
4 *  Copyright (C) 1991, 1992  Linus Torvalds
5 *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
6 *
7 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
8 *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
9 *  2000-2002   x86-64 support by Andi Kleen
10 */
11
12#include <linux/sched.h>
13#include <linux/mm.h>
14#include <linux/smp.h>
15#include <linux/kernel.h>
16#include <linux/signal.h>
17#include <linux/errno.h>
18#include <linux/wait.h>
19#include <linux/ptrace.h>
20#include <linux/unistd.h>
21#include <linux/stddef.h>
22#include <linux/personality.h>
23#include <linux/compiler.h>
24#include <asm/ucontext.h>
25#include <asm/uaccess.h>
26#include <asm/i387.h>
27#include <asm/proto.h>
28#include <asm/ia32_unistd.h>
29
30/* #define DEBUG_SIG 1 */
31
32#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
33
34int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
35               sigset_t *set, struct pt_regs * regs);
36int ia32_setup_frame(int sig, struct k_sigaction *ka,
37            sigset_t *set, struct pt_regs * regs);
38
39asmlinkage long
40sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
41		struct pt_regs *regs)
42{
43	return do_sigaltstack(uss, uoss, regs->rsp);
44}
45
46
47/*
48 * Do a signal return; undo the signal stack.
49 */
50
51struct rt_sigframe
52{
53	char __user *pretcode;
54	struct ucontext uc;
55	struct siginfo info;
56};
57
58static int
59restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, unsigned long *prax)
60{
61	unsigned int err = 0;
62
63	/* Always make any pending restarted system calls return -EINTR */
64	current_thread_info()->restart_block.fn = do_no_restart_syscall;
65
66#define COPY(x)		err |= __get_user(regs->x, &sc->x)
67
68	COPY(rdi); COPY(rsi); COPY(rbp); COPY(rsp); COPY(rbx);
69	COPY(rdx); COPY(rcx); COPY(rip);
70	COPY(r8);
71	COPY(r9);
72	COPY(r10);
73	COPY(r11);
74	COPY(r12);
75	COPY(r13);
76	COPY(r14);
77	COPY(r15);
78
79	/* Kernel saves and restores only the CS segment register on signals,
80	 * which is the bare minimum needed to allow mixed 32/64-bit code.
81	 * App's signal handler can save/restore other segments if needed. */
82	{
83		unsigned cs;
84		err |= __get_user(cs, &sc->cs);
85		regs->cs = cs | 3;	/* Force into user mode */
86	}
87
88	{
89		unsigned int tmpflags;
90		err |= __get_user(tmpflags, &sc->eflags);
91		regs->eflags = (regs->eflags & ~0x40DD5) | (tmpflags & 0x40DD5);
92		regs->orig_rax = -1;		/* disable syscall checks */
93	}
94
95	{
96		struct _fpstate __user * buf;
97		err |= __get_user(buf, &sc->fpstate);
98
99		if (buf) {
100			if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
101				goto badframe;
102			err |= restore_i387(buf);
103		} else {
104			struct task_struct *me = current;
105			if (used_math()) {
106				clear_fpu(me);
107				clear_used_math();
108			}
109		}
110	}
111
112	err |= __get_user(*prax, &sc->rax);
113	return err;
114
115badframe:
116	return 1;
117}
118
119asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
120{
121	struct rt_sigframe __user *frame;
122	sigset_t set;
123	unsigned long eax;
124
125	frame = (struct rt_sigframe __user *)(regs->rsp - 8);
126	if (!access_ok(VERIFY_READ, frame, sizeof(*frame))) {
127		goto badframe;
128	}
129	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set))) {
130		goto badframe;
131	}
132
133	sigdelsetmask(&set, ~_BLOCKABLE);
134	spin_lock_irq(&current->sighand->siglock);
135	current->blocked = set;
136	recalc_sigpending();
137	spin_unlock_irq(&current->sighand->siglock);
138
139	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &eax))
140		goto badframe;
141
142#ifdef DEBUG_SIG
143	printk("%d sigreturn rip:%lx rsp:%lx frame:%p rax:%lx\n",current->pid,regs->rip,regs->rsp,frame,eax);
144#endif
145
146	if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->rsp) == -EFAULT)
147		goto badframe;
148
149	return eax;
150
151badframe:
152	signal_fault(regs,frame,"sigreturn");
153	return 0;
154}
155
156/*
157 * Set up a signal frame.
158 */
159
160static inline int
161setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, unsigned long mask, struct task_struct *me)
162{
163	int err = 0;
164
165	err |= __put_user(regs->cs, &sc->cs);
166	err |= __put_user(0, &sc->gs);
167	err |= __put_user(0, &sc->fs);
168
169	err |= __put_user(regs->rdi, &sc->rdi);
170	err |= __put_user(regs->rsi, &sc->rsi);
171	err |= __put_user(regs->rbp, &sc->rbp);
172	err |= __put_user(regs->rsp, &sc->rsp);
173	err |= __put_user(regs->rbx, &sc->rbx);
174	err |= __put_user(regs->rdx, &sc->rdx);
175	err |= __put_user(regs->rcx, &sc->rcx);
176	err |= __put_user(regs->rax, &sc->rax);
177	err |= __put_user(regs->r8, &sc->r8);
178	err |= __put_user(regs->r9, &sc->r9);
179	err |= __put_user(regs->r10, &sc->r10);
180	err |= __put_user(regs->r11, &sc->r11);
181	err |= __put_user(regs->r12, &sc->r12);
182	err |= __put_user(regs->r13, &sc->r13);
183	err |= __put_user(regs->r14, &sc->r14);
184	err |= __put_user(regs->r15, &sc->r15);
185	err |= __put_user(me->thread.trap_no, &sc->trapno);
186	err |= __put_user(me->thread.error_code, &sc->err);
187	err |= __put_user(regs->rip, &sc->rip);
188	err |= __put_user(regs->eflags, &sc->eflags);
189	err |= __put_user(mask, &sc->oldmask);
190	err |= __put_user(me->thread.cr2, &sc->cr2);
191
192	return err;
193}
194
195/*
196 * Determine which stack to use..
197 */
198
199static void __user *
200get_stack(struct k_sigaction *ka, struct pt_regs *regs, unsigned long size)
201{
202	unsigned long rsp;
203
204	/* Default to using normal stack - redzone*/
205	rsp = regs->rsp - 128;
206
207	/* This is the X/Open sanctioned signal stack switching.  */
208	if (ka->sa.sa_flags & SA_ONSTACK) {
209		if (sas_ss_flags(rsp) == 0)
210			rsp = current->sas_ss_sp + current->sas_ss_size;
211	}
212
213	return (void __user *)round_down(rsp - size, 16);
214}
215
216static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
217			   sigset_t *set, struct pt_regs * regs)
218{
219	struct rt_sigframe __user *frame;
220	struct _fpstate __user *fp = NULL;
221	int err = 0;
222	struct task_struct *me = current;
223
224	if (used_math()) {
225		fp = get_stack(ka, regs, sizeof(struct _fpstate));
226		frame = (void __user *)round_down(
227			(unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;
228
229		if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate)))
230			goto give_sigsegv;
231
232		if (save_i387(fp) < 0)
233			err |= -1;
234	} else
235		frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;
236
237	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
238		goto give_sigsegv;
239
240	if (ka->sa.sa_flags & SA_SIGINFO) {
241		err |= copy_siginfo_to_user(&frame->info, info);
242		if (err)
243			goto give_sigsegv;
244	}
245
246	/* Create the ucontext.  */
247	err |= __put_user(0, &frame->uc.uc_flags);
248	err |= __put_user(0, &frame->uc.uc_link);
249	err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
250	err |= __put_user(sas_ss_flags(regs->rsp),
251			  &frame->uc.uc_stack.ss_flags);
252	err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
253	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0], me);
254	err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
255	if (sizeof(*set) == 16) {
256		__put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
257		__put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]);
258	} else
259		err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
260
261	/* Set up to return from userspace.  If provided, use a stub
262	   already in userspace.  */
263	/* x86-64 should always use SA_RESTORER. */
264	if (ka->sa.sa_flags & SA_RESTORER) {
265		err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
266	} else {
267		/* could use a vstub here */
268		goto give_sigsegv;
269	}
270
271	if (err)
272		goto give_sigsegv;
273
274#ifdef DEBUG_SIG
275	printk("%d old rip %lx old rsp %lx old rax %lx\n", current->pid,regs->rip,regs->rsp,regs->rax);
276#endif
277
278	/* Set up registers for signal handler */
279	regs->rdi = sig;
280	/* In case the signal handler was declared without prototypes */
281	regs->rax = 0;
282
283	/* This also works for non SA_SIGINFO handlers because they expect the
284	   next argument after the signal number on the stack. */
285	regs->rsi = (unsigned long)&frame->info;
286	regs->rdx = (unsigned long)&frame->uc;
287	regs->rip = (unsigned long) ka->sa.sa_handler;
288
289	regs->rsp = (unsigned long)frame;
290
291	/* Set up the CS register to run signal handlers in 64-bit mode,
292	   even if the handler happens to be interrupting 32-bit code. */
293	regs->cs = __USER_CS;
294
295	/* This, by contrast, has nothing to do with segment registers -
296	   see include/asm-x86_64/uaccess.h for details. */
297	set_fs(USER_DS);
298
299	regs->eflags &= ~TF_MASK;
300	if (test_thread_flag(TIF_SINGLESTEP))
301		ptrace_notify(SIGTRAP);
302#ifdef DEBUG_SIG
303	printk("SIG deliver (%s:%d): sp=%p pc=%lx ra=%p\n",
304		current->comm, current->pid, frame, regs->rip, frame->pretcode);
305#endif
306
307	return 0;
308
309give_sigsegv:
310	force_sigsegv(sig, current);
311	return -EFAULT;
312}
313
314/*
315 * OK, we're invoking a handler
316 */
317
318static int
319handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
320		sigset_t *oldset, struct pt_regs *regs)
321{
322	int ret;
323
324#ifdef DEBUG_SIG
325	printk("handle_signal pid:%d sig:%lu rip:%lx rsp:%lx regs=%p\n",
326		current->pid, sig,
327		regs->rip, regs->rsp, regs);
328#endif
329
330	/* Are we from a system call? */
331	if ((long)regs->orig_rax >= 0) {
332		/* If so, check system call restarting.. */
333		switch (regs->rax) {
334		        case -ERESTART_RESTARTBLOCK:
335			case -ERESTARTNOHAND:
336				regs->rax = -EINTR;
337				break;
338
339			case -ERESTARTSYS:
340				if (!(ka->sa.sa_flags & SA_RESTART)) {
341					regs->rax = -EINTR;
342					break;
343				}
344				/* fallthrough */
345			case -ERESTARTNOINTR:
346				regs->rax = regs->orig_rax;
347				regs->rip -= 2;
348				break;
349		}
350	}
351
352	/*
353	 * If TF is set due to a debugger (PT_DTRACE), clear the TF
354	 * flag so that register information in the sigcontext is
355	 * correct.
356	 */
357	if (unlikely(regs->eflags & TF_MASK)) {
358		if (likely(current->ptrace & PT_DTRACE)) {
359			current->ptrace &= ~PT_DTRACE;
360			regs->eflags &= ~TF_MASK;
361		}
362	}
363
364#ifdef CONFIG_IA32_EMULATION
365	if (test_thread_flag(TIF_IA32)) {
366		if (ka->sa.sa_flags & SA_SIGINFO)
367			ret = ia32_setup_rt_frame(sig, ka, info, oldset, regs);
368		else
369			ret = ia32_setup_frame(sig, ka, oldset, regs);
370	} else
371#endif
372	ret = setup_rt_frame(sig, ka, info, oldset, regs);
373
374	if (ret == 0) {
375		spin_lock_irq(&current->sighand->siglock);
376		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
377		if (!(ka->sa.sa_flags & SA_NODEFER))
378			sigaddset(&current->blocked,sig);
379		recalc_sigpending();
380		spin_unlock_irq(&current->sighand->siglock);
381	}
382
383	return ret;
384}
385
386/*
387 * Note that 'init' is a special process: it doesn't get signals it doesn't
388 * want to handle. Thus you cannot kill init even with a SIGKILL even by
389 * mistake.
390 */
391static void do_signal(struct pt_regs *regs)
392{
393	struct k_sigaction ka;
394	siginfo_t info;
395	int signr;
396	sigset_t *oldset;
397
398	/*
399	 * We want the common case to go fast, which
400	 * is why we may in certain cases get here from
401	 * kernel mode. Just return without doing anything
402	 * if so.
403	 */
404	if (!user_mode(regs))
405		return;
406
407	if (test_thread_flag(TIF_RESTORE_SIGMASK))
408		oldset = &current->saved_sigmask;
409	else
410		oldset = &current->blocked;
411
412	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
413	if (signr > 0) {
414		/* Reenable any watchpoints before delivering the
415		 * signal to user space. The processor register will
416		 * have been cleared if the watchpoint triggered
417		 * inside the kernel.
418		 */
419		if (current->thread.debugreg7)
420			set_debugreg(current->thread.debugreg7, 7);
421
422		/* Whee!  Actually deliver the signal.  */
423		if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
424			/* a signal was successfully delivered; the saved
425			 * sigmask will have been stored in the signal frame,
426			 * and will be restored by sigreturn, so we can simply
427			 * clear the TIF_RESTORE_SIGMASK flag */
428			clear_thread_flag(TIF_RESTORE_SIGMASK);
429		}
430		return;
431	}
432
433	/* Did we come from a system call? */
434	if ((long)regs->orig_rax >= 0) {
435		/* Restart the system call - no handlers present */
436		long res = regs->rax;
437		switch (res) {
438		case -ERESTARTNOHAND:
439		case -ERESTARTSYS:
440		case -ERESTARTNOINTR:
441			regs->rax = regs->orig_rax;
442			regs->rip -= 2;
443			break;
444		case -ERESTART_RESTARTBLOCK:
445			regs->rax = test_thread_flag(TIF_IA32) ?
446					__NR_ia32_restart_syscall :
447					__NR_restart_syscall;
448			regs->rip -= 2;
449			break;
450		}
451	}
452
453	/* if there's no signal to deliver, we just put the saved sigmask
454	   back. */
455	if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
456		clear_thread_flag(TIF_RESTORE_SIGMASK);
457		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
458	}
459}
460
461void
462do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
463{
464#ifdef DEBUG_SIG
465	printk("do_notify_resume flags:%x rip:%lx rsp:%lx caller:%p pending:%x\n",
466	       thread_info_flags, regs->rip, regs->rsp, __builtin_return_address(0),signal_pending(current));
467#endif
468
469	/* Pending single-step? */
470	if (thread_info_flags & _TIF_SINGLESTEP) {
471		regs->eflags |= TF_MASK;
472		clear_thread_flag(TIF_SINGLESTEP);
473	}
474
475	/* deal with pending signal delivery */
476	if (thread_info_flags & (_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK))
477		do_signal(regs);
478}
479
480void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
481{
482	struct task_struct *me = current;
483	if (exception_trace)
484		printk("%s[%d] bad frame in %s frame:%p rip:%lx rsp:%lx orax:%lx\n",
485	       me->comm,me->pid,where,frame,regs->rip,regs->rsp,regs->orig_rax);
486
487	force_sig(SIGSEGV, me);
488}
489