aboutsummaryrefslogtreecommitdiffstats
path: root/arch/powerpc/kernel/signal_64.c
blob: 59b9c9cdd6a938457a5f3107aa091ef62b85b6fd (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
/*
 *  PowerPC version 
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  Derived from "arch/i386/kernel/signal.c"
 *    Copyright (C) 1991, 1992 Linus Torvalds
 *    1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/config.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/elf.h>
#include <linux/ptrace.h>
#include <linux/module.h>

#include <asm/sigcontext.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/unistd.h>
#include <asm/cacheflush.h>
#include <asm/vdso.h>

#define DEBUG_SIG 0

#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))

#define GP_REGS_SIZE	min(sizeof(elf_gregset_t), sizeof(struct pt_regs))
#define FP_REGS_SIZE	sizeof(elf_fpregset_t)

#define TRAMP_TRACEBACK	3
#define TRAMP_SIZE	6

/*
 * When we have signals to deliver, we set up on the user stack,
 * going down from the original stack pointer:
 *	1) a rt_sigframe struct which contains the ucontext	
 *	2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller
 *	   frame for the signal handler.
 */

struct rt_sigframe {
	/* sys_rt_sigreturn requires the ucontext be the first field */
	struct ucontext uc;
	unsigned long _unused[2];
	unsigned int tramp[TRAMP_SIZE];
	struct siginfo __user *pinfo;
	void __user *puc;
	struct siginfo info;
	/* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
	char abigap[288];
} __attribute__ ((aligned (16)));

long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss, unsigned long r5,
		     unsigned long r6, unsigned long r7, unsigned long r8,
		     struct pt_regs *regs)
{
	return do_sigaltstack(uss, uoss, regs->gpr[1]);
}


/*
 * Set up the sigcontext for the signal frame.
 */

static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
		 int signr, sigset_t *set, unsigned long handler)
{
	/* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
	 * process never used altivec yet (MSR_VEC is zero in pt_regs of
	 * the context). This is very important because we must ensure we
	 * don't lose the VRSAVE content that may have been set prior to
	 * the process doing its first vector operation
	 * Userland shall check AT_HWCAP to know wether it can rely on the
	 * v_regs pointer or not
	 */
#ifdef CONFIG_ALTIVEC
	elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
#endif
	long err = 0;

	flush_fp_to_thread(current);

#ifdef CONFIG_ALTIVEC
	err |= __put_user(v_regs, &sc->v_regs);

	/* save altivec registers */
	if (current->thread.used_vr) {
		flush_altivec_to_thread(current);
		/* Copy 33 vec registers (vr0..31 and vscr) to the stack */
		err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
		/* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
		 * contains valid data.
		 */
		regs->msr |= MSR_VEC;
	}
	/* We always copy to/from vrsave, it's 0 if we don't have or don't
	 * use altivec.
	 */
	err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
#else /* CONFIG_ALTIVEC */
	err |= __put_user(0, &sc->v_regs);
#endif /* CONFIG_ALTIVEC */
	err |= __put_user(&sc->gp_regs, &sc->regs);
	if (!FULL_REGS(regs)) {
		/* Zero out the unsaved GPRs to avoid information
		   leak, and set TIF_SAVE_NVGPRS to ensure that the
		   registers do actually get saved later. */
		memset(&regs->gpr[14], 0, 18 * sizeof(unsigned long));
		set_thread_flag(TIF_SAVE_NVGPRS);
		current_thread_info()->nvgprs_frame = &sc->gp_regs;
	}
	err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
	err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
	err |= __put_user(signr, &sc->signal);
	err |= __put_user(handler, &sc->handler);
	if (set != NULL)
		err |=  __put_user(set->sig[0], &sc->oldmask);

	return err;
}

/*
 * Restore the sigcontext from the signal frame.
 */

static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
			      struct sigcontext __user *sc)
{
#ifdef CONFIG_ALTIVEC
	elf_vrreg_t __user *v_regs;
#endif
	unsigned long err = 0;
	unsigned long save_r13 = 0;
	elf_greg_t *gregs = (elf_greg_t *)regs;
#ifdef CONFIG_ALTIVEC
	unsigned long msr;
#endif
	int i;

	/* If this is not a signal return, we preserve the TLS in r13 */
	if (!sig)
		save_r13 = regs->gpr[13];

	/* copy everything before MSR */
	err |= __copy_from_user(regs, &sc->gp_regs,
				PT_MSR*sizeof(unsigned long));

	/* skip MSR and SOFTE */
	for (i = PT_MSR+1; i <= PT_RESULT; i++) {
		if (i == PT_SOFTE)
			continue;
		err |= __get_user(gregs[i], &sc->gp_regs[i]);
	}

	if (!sig)
		regs->gpr[13] = save_r13;
	if (set != NULL)
		err |=  __get_user(set->sig[0], &sc->oldmask);

	/*
	 * Do this before updating the thread state in
	 * current->thread.fpr/vr.  That way, if we get preempted
	 * and another task grabs the FPU/Altivec, it won't be
	 * tempted to save the current CPU state into the thread_struct
	 * and corrupt what we are writing there.
	 */
	discard_lazy_cpu_state();

	err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);

#ifdef CONFIG_ALTIVEC
	err |= __get_user(v_regs, &sc->v_regs);
	err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
	if (err)
		return err;
	/* Copy 33 vec registers (vr0..31 and vscr) from the stack */
	if (v_regs != 0 && (msr & MSR_VEC) != 0)
		err |= __copy_from_user(current->thread.vr, v_regs,
					33 * sizeof(vector128));
	else if (current->thread.used_vr)
		memset(current->thread.vr, 0, 33 * sizeof(vector128));
	/* Always get VRSAVE back */
	if (v_regs != 0)
		err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
	else
		current->thread.vrsave = 0;
#endif /* CONFIG_ALTIVEC */

	/* Force reload of FP/VEC */
	regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);

	return err;
}

/*
 * Allocate space for the signal frame
 */
static inline void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
				  size_t frame_size)
{
        unsigned long newsp;

        /* Default to using normal stack */
        newsp = regs->gpr[1];

	if (ka->sa.sa_flags & SA_ONSTACK) {
		if (! on_sig_stack(regs->gpr[1]))
			newsp = (current->sas_ss_sp + current->sas_ss_size);
	}

        return (void __user *)((newsp - frame_size) & -16ul);
}

/*
 * Setup the trampoline code on the stack
 */
static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
{
	int i;
	long err = 0;

	/* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
	err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
	/* li r0, __NR_[rt_]sigreturn| */
	err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
	/* sc */
	err |= __put_user(0x44000002UL, &tramp[2]);

	/* Minimal traceback info */
	for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
		err |= __put_user(0, &tramp[i]);

	if (!err)
		flush_icache_range((unsigned long) &tramp[0],
			   (unsigned long) &tramp[TRAMP_SIZE]);

	return err;
}

/*
 * Restore the user process's signal mask (also used by signal32.c)
 */
void restore_sigmask(sigset_t *set)
{
	sigdelsetmask(set, ~_BLOCKABLE);
	spin_lock_irq(&current->sighand->siglock);
	current->blocked = *set;
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);
}


/*
 * Handle {get,set,swap}_context operations
 */
int sys_swapcontext(struct ucontext __user *old_ctx,
		    struct ucontext __user *new_ctx,
		    long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
{
	unsigned char tmp;
	sigset_t set;

	/* Context size is for future use. Right now, we only make sure
	 * we are passed something we understand
	 */
	if (ctx_size < sizeof(struct ucontext))
		return -EINVAL;

	if (old_ctx != NULL) {
		if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
		    || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
		    || __copy_to_user(&old_ctx->uc_sigmask,
				      &current->blocked, sizeof(sigset_t)))
			return -EFAULT;
	}
	if (new_ctx == NULL)
		return 0;
	if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
	    || __get_user(tmp, (u8 __user *) new_ctx)
	    || __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
		return -EFAULT;

	/*
	 * If we get a fault copying the context into the kernel's
	 * image of the user's registers, we can't just return -EFAULT
	 * because the user's registers will be corrupted.  For instance
	 * the NIP value may have been updated but not some of the
	 * other registers.  Given that we have done the access_ok
	 * and successfully read the first and last bytes of the region
	 * above, this should only happen in an out-of-memory situation
	 * or if another thread unmaps the region containing the context.
	 * We kill the task with a SIGSEGV in this situation.
	 */

	if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
		do_exit(SIGSEGV);
	restore_sigmask(&set);
	if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
		do_exit(SIGSEGV);

	/* This returns like rt_sigreturn */
	set_thread_flag(TIF_RESTOREALL);
	return 0;
}


/*
 * Do a signal return; undo the signal stack.
 */

int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
		     unsigned long r6, unsigned long r7, unsigned long r8,
		     struct pt_regs *regs)
{
	struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
	sigset_t set;

	/* Always make any pending restarted system calls return -EINTR */
	current_thread_info()->restart_block.fn = do_no_restart_syscall;

	if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
		goto badframe;

	if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
		goto badframe;
	restore_sigmask(&set);
	if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
		goto badframe;

	/* do_sigaltstack expects a __user pointer and won't modify
	 * what's in there anyway
	 */
	do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);

	set_thread_flag(TIF_RESTOREALL);
	return 0;

badframe:
#if DEBUG_SIG
	printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
	       regs, uc, &uc->uc_mcontext);
#endif
	force_sig(SIGSEGV, current);
	return 0;
}

static int setup_rt_frame(int signr, struct k_sigaction *ka, siginfo_t *info,
		sigset_t *set, struct pt_regs *regs)
{
	/* Handler is *really* a pointer to the function descriptor for
	 * the signal routine.  The first entry in the function
	 * descriptor is the entry address of signal and the second
	 * entry is the TOC value we need to use.
	 */
	func_descr_t __user *funct_desc_ptr;
	struct rt_sigframe __user *frame;
	unsigned long newsp = 0;
	long err = 0;

	frame = get_sigframe(ka, regs, sizeof(*frame));

	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
		goto badframe;

	err |= __put_user(&frame->info, &frame->pinfo);
	err |= __put_user(&frame->uc, &frame->puc);
	err |= copy_siginfo_to_user(&frame->info, info);
	if (err)
		goto badframe;

	/* Create the ucontext.  */
	err |= __put_user(0, &frame->uc.uc_flags);
	err |= __put_user(0, &frame->uc.uc_link);
	err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
	err |= __put_user(sas_ss_flags(regs->gpr[1]),
			  &frame->uc.uc_stack.ss_flags);
	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
				(unsigned long)ka->sa.sa_handler);
	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
	if (err)
		goto badframe;

	/* Make sure signal handler doesn't get spurious FP exceptions */
	current->thread.fpscr.val = 0;

	/* Set up to return from userspace. */
	if (vdso64_rt_sigtramp && current->thread.vdso_base) {
		regs->link = current->thread.vdso_base + vdso64_rt_sigtramp;
	} else {
		err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
		if (err)
			goto badframe;
		regs->link = (unsigned long) &frame->tramp[0];
	}
	funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;

	/* Allocate a dummy caller frame for the signal handler. */
	newsp = (unsigned long)frame - __SIGNAL_FRAMESIZE;
	err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);

	/* Set up "regs" so we "return" to the signal handler. */
	err |= get_user(regs->nip, &funct_desc_ptr->entry);
	regs->gpr[1] = newsp;
	err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
	regs->gpr[3] = signr;
	regs->result = 0;
	if (ka->sa.sa_flags & SA_SIGINFO) {
		err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
		err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
		regs->gpr[6] = (unsigned long) frame;
	} else {
		regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
	}
	if (err)
		goto badframe;

	return 1;

badframe:
#if DEBUG_SIG
	printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
	       regs, frame, newsp);
#endif
	force_sigsegv(signr, current);
	return 0;
}


/*
 * OK, we're invoking a handler
 */
static int handle_signal(unsigned long sig, struct k_sigaction *ka,
			 siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
{
	int ret;

	/* Set up Signal Frame */
	ret = setup_rt_frame(sig, ka, info, oldset, regs);

	if (ret) {
		spin_lock_irq(&current->sighand->siglock);
		sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);
		if (!(ka->sa.sa_flags & SA_NODEFER))
			sigaddset(&current->blocked,sig);
		recalc_sigpending();
		spin_unlock_irq(&current->sighand->siglock);
	}

	return ret;
}

static inline void syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
{
	switch ((int)regs->result) {
	case -ERESTART_RESTARTBLOCK:
	case -ERESTARTNOHAND:
		/* ERESTARTNOHAND means that the syscall should only be
		 * restarted if there was no handler for the signal, and since
		 * we only get here if there is a handler, we dont restart.
		 */
		regs->result = -EINTR;
		regs->gpr[3] = EINTR;
		regs->ccr |= 0x10000000;
		break;
	case -ERESTARTSYS:
		/* ERESTARTSYS means to restart the syscall if there is no
		 * handler or the handler was registered with SA_RESTART
		 */
		if (!(ka->sa.sa_flags & SA_RESTART)) {
			regs->result = -EINTR;
			regs->gpr[3] = EINTR;
			regs->ccr |= 0x10000000;
			break;
		}
		/* fallthrough */
	case -ERESTARTNOINTR:
		/* ERESTARTNOINTR means that the syscall should be
		 * called again after the signal handler returns.
		 */
		regs->gpr[3] = regs->orig_gpr3;
		regs->nip -= 4;
		regs->result = 0;
		break;
	}
}

/*
 * Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 */
int do_signal(sigset_t *oldset, struct pt_regs *regs)
{
	siginfo_t info;
	int signr;
	struct k_sigaction ka;

	/*
	 * If the current thread is 32 bit - invoke the
	 * 32 bit signal handling code
	 */
	if (test_thread_flag(TIF_32BIT))
		return do_signal32(oldset, regs);

	if (test_thread_flag(TIF_RESTORE_SIGMASK))
		oldset = &current->saved_sigmask;
	else if (!oldset)
		oldset = &current->blocked;

	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
	if (signr > 0) {
		int ret;

		/* Whee!  Actually deliver the signal.  */
		if (TRAP(regs) == 0x0C00)
			syscall_restart(regs, &ka);

		/*
		 * Reenable the DABR before delivering the signal to
		 * user space. The DABR will have been cleared if it
		 * triggered inside the kernel.
		 */
		if (current->thread.dabr)
			set_dabr(current->thread.dabr);

		ret = handle_signal(signr, &ka, &info, oldset, regs);

		/* If a signal was successfully delivered, the saved sigmask is in
		   its frame, and we can clear the TIF_RESTORE_SIGMASK flag */
		if (ret && test_thread_flag(TIF_RESTORE_SIGMASK))
			clear_thread_flag(TIF_RESTORE_SIGMASK);

		return ret;
	}

	if (TRAP(regs) == 0x0C00) {	/* System Call! */
		if ((int)regs->result == -ERESTARTNOHAND ||
		    (int)regs->result == -ERESTARTSYS ||
		    (int)regs->result == -ERESTARTNOINTR) {
			regs->gpr[3] = regs->orig_gpr3;
			regs->nip -= 4; /* Back up & retry system call */
			regs->result = 0;
		} else if ((int)regs->result == -ERESTART_RESTARTBLOCK) {
			regs->gpr[0] = __NR_restart_syscall;
			regs->nip -= 4;
			regs->result = 0;
		}
	}
	/* No signal to deliver -- put the saved sigmask back */
	if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
		clear_thread_flag(TIF_RESTORE_SIGMASK);
		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
	}

	return 0;
}
EXPORT_SYMBOL(do_signal);