summaryrefslogtreecommitdiffstats
path: root/arch/riscv/kernel/signal.c
blob: 5a2edd7f027e5d12e682349c3f1b54b51cd3b735 (plain)
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
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
 *  Chen Liqin <liqin.chen@sunplusct.com>
 *  Lennox Wu <lennox.wu@sunplusct.com>
 * Copyright (C) 2012 Regents of the University of California
 */

#include <linux/compat.h>
#include <linux/signal.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/resume_user_mode.h>
#include <linux/linkage.h>
#include <linux/entry-common.h>

#include <asm/ucontext.h>
#include <asm/vdso.h>
#include <asm/signal.h>
#include <asm/signal32.h>
#include <asm/switch_to.h>
#include <asm/vector.h>
#include <asm/csr.h>
#include <asm/cacheflush.h>

unsigned long signal_minsigstksz __ro_after_init;

extern u32 __user_rt_sigreturn[2];
static size_t riscv_v_sc_size __ro_after_init;

#define DEBUG_SIG 0

struct rt_sigframe {
	struct siginfo info;
	struct ucontext uc;
#ifndef CONFIG_MMU
	u32 sigreturn_code[2];
#endif
};

#ifdef CONFIG_FPU
static long restore_fp_state(struct pt_regs *regs,
			     union __riscv_fp_state __user *sc_fpregs)
{
	long err;
	struct __riscv_d_ext_state __user *state = &sc_fpregs->d;

	err = __copy_from_user(&current->thread.fstate, state, sizeof(*state));
	if (unlikely(err))
		return err;

	fstate_restore(current, regs);
	return 0;
}

static long save_fp_state(struct pt_regs *regs,
			  union __riscv_fp_state __user *sc_fpregs)
{
	long err;
	struct __riscv_d_ext_state __user *state = &sc_fpregs->d;

	fstate_save(current, regs);
	err = __copy_to_user(state, &current->thread.fstate, sizeof(*state));
	return err;
}
#else
#define save_fp_state(task, regs) (0)
#define restore_fp_state(task, regs) (0)
#endif

#ifdef CONFIG_RISCV_ISA_V

static long save_v_state(struct pt_regs *regs, void __user **sc_vec)
{
	struct __riscv_ctx_hdr __user *hdr;
	struct __sc_riscv_v_state __user *state;
	void __user *datap;
	long err;

	hdr = *sc_vec;
	/* Place state to the user's signal context space after the hdr */
	state = (struct __sc_riscv_v_state __user *)(hdr + 1);
	/* Point datap right after the end of __sc_riscv_v_state */
	datap = state + 1;

	/* datap is designed to be 16 byte aligned for better performance */
	WARN_ON(unlikely(!IS_ALIGNED((unsigned long)datap, 16)));

	get_cpu_vector_context();
	riscv_v_vstate_save(&current->thread.vstate, regs);
	put_cpu_vector_context();

	/* Copy everything of vstate but datap. */
	err = __copy_to_user(&state->v_state, &current->thread.vstate,
			     offsetof(struct __riscv_v_ext_state, datap));
	/* Copy the pointer datap itself. */
	err |= __put_user((__force void *)datap, &state->v_state.datap);
	/* Copy the whole vector content to user space datap. */
	err |= __copy_to_user(datap, current->thread.vstate.datap, riscv_v_vsize);
	/* Copy magic to the user space after saving  all vector conetext */
	err |= __put_user(RISCV_V_MAGIC, &hdr->magic);
	err |= __put_user(riscv_v_sc_size, &hdr->size);
	if (unlikely(err))
		return err;

	/* Only progress the sv_vec if everything has done successfully  */
	*sc_vec += riscv_v_sc_size;
	return 0;
}

/*
 * Restore Vector extension context from the user's signal frame. This function
 * assumes a valid extension header. So magic and size checking must be done by
 * the caller.
 */
static long __restore_v_state(struct pt_regs *regs, void __user *sc_vec)
{
	long err;
	struct __sc_riscv_v_state __user *state = sc_vec;
	void __user *datap;

	/*
	 * Mark the vstate as clean prior performing the actual copy,
	 * to avoid getting the vstate incorrectly clobbered by the
	 *  discarded vector state.
	 */
	riscv_v_vstate_set_restore(current, regs);

	/* Copy everything of __sc_riscv_v_state except datap. */
	err = __copy_from_user(&current->thread.vstate, &state->v_state,
			       offsetof(struct __riscv_v_ext_state, datap));
	if (unlikely(err))
		return err;

	/* Copy the pointer datap itself. */
	err = __get_user(datap, &state->v_state.datap);
	if (unlikely(err))
		return err;
	/*
	 * Copy the whole vector content from user space datap. Use
	 * copy_from_user to prevent information leak.
	 */
	return copy_from_user(current->thread.vstate.datap, datap, riscv_v_vsize);
}
#else
#define save_v_state(task, regs) (0)
#define __restore_v_state(task, regs) (0)
#endif

static long restore_sigcontext(struct pt_regs *regs,
	struct sigcontext __user *sc)
{
	void __user *sc_ext_ptr = &sc->sc_extdesc.hdr;
	__u32 rsvd;
	long err;
	/* sc_regs is structured the same as the start of pt_regs */
	err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs));
	if (unlikely(err))
		return err;

	/* Restore the floating-point state. */
	if (has_fpu()) {
		err = restore_fp_state(regs, &sc->sc_fpregs);
		if (unlikely(err))
			return err;
	}

	/* Check the reserved word before extensions parsing */
	err = __get_user(rsvd, &sc->sc_extdesc.reserved);
	if (unlikely(err))
		return err;
	if (unlikely(rsvd))
		return -EINVAL;

	while (!err) {
		__u32 magic, size;
		struct __riscv_ctx_hdr __user *head = sc_ext_ptr;

		err |= __get_user(magic, &head->magic);
		err |= __get_user(size, &head->size);
		if (unlikely(err))
			return err;

		sc_ext_ptr += sizeof(*head);
		switch (magic) {
		case END_MAGIC:
			if (size != END_HDR_SIZE)
				return -EINVAL;

			return 0;
		case RISCV_V_MAGIC:
			if (!has_vector() || !riscv_v_vstate_query(regs) ||
			    size != riscv_v_sc_size)
				return -EINVAL;

			err = __restore_v_state(regs, sc_ext_ptr);
			break;
		default:
			return -EINVAL;
		}
		sc_ext_ptr = (void __user *)head + size;
	}
	return err;
}

static size_t get_rt_frame_size(bool cal_all)
{
	struct rt_sigframe __user *frame;
	size_t frame_size;
	size_t total_context_size = 0;

	frame_size = sizeof(*frame);

	if (has_vector()) {
		if (cal_all || riscv_v_vstate_query(task_pt_regs(current)))
			total_context_size += riscv_v_sc_size;
	}
	/*
	 * Preserved a __riscv_ctx_hdr for END signal context header if an
	 * extension uses __riscv_extra_ext_header
	 */
	if (total_context_size)
		total_context_size += sizeof(struct __riscv_ctx_hdr);

	frame_size += total_context_size;

	frame_size = round_up(frame_size, 16);
	return frame_size;
}

SYSCALL_DEFINE0(rt_sigreturn)
{
	struct pt_regs *regs = current_pt_regs();
	struct rt_sigframe __user *frame;
	struct task_struct *task;
	sigset_t set;
	size_t frame_size = get_rt_frame_size(false);

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

	frame = (struct rt_sigframe __user *)regs->sp;

	if (!access_ok(frame, frame_size))
		goto badframe;

	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
		goto badframe;

	set_current_blocked(&set);

	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
		goto badframe;

	if (restore_altstack(&frame->uc.uc_stack))
		goto badframe;

	regs->cause = -1UL;

	return regs->a0;

badframe:
	task = current;
	if (show_unhandled_signals) {
		pr_info_ratelimited(
			"%s[%d]: bad frame in %s: frame=%p pc=%p sp=%p\n",
			task->comm, task_pid_nr(task), __func__,
			frame, (void *)regs->epc, (void *)regs->sp);
	}
	force_sig(SIGSEGV);
	return 0;
}

static long setup_sigcontext(struct rt_sigframe __user *frame,
	struct pt_regs *regs)
{
	struct sigcontext __user *sc = &frame->uc.uc_mcontext;
	struct __riscv_ctx_hdr __user *sc_ext_ptr = &sc->sc_extdesc.hdr;
	long err;

	/* sc_regs is structured the same as the start of pt_regs */
	err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs));
	/* Save the floating-point state. */
	if (has_fpu())
		err |= save_fp_state(regs, &sc->sc_fpregs);
	/* Save the vector state. */
	if (has_vector() && riscv_v_vstate_query(regs))
		err |= save_v_state(regs, (void __user **)&sc_ext_ptr);
	/* Write zero to fp-reserved space and check it on restore_sigcontext */
	err |= __put_user(0, &sc->sc_extdesc.reserved);
	/* And put END __riscv_ctx_hdr at the end. */
	err |= __put_user(END_MAGIC, &sc_ext_ptr->magic);
	err |= __put_user(END_HDR_SIZE, &sc_ext_ptr->size);

	return err;
}

static inline void __user *get_sigframe(struct ksignal *ksig,
	struct pt_regs *regs, size_t framesize)
{
	unsigned long sp;
	/* Default to using normal stack */
	sp = regs->sp;

	/*
	 * If we are on the alternate signal stack and would overflow it, don't.
	 * Return an always-bogus address instead so we will die with SIGSEGV.
	 */
	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
		return (void __user __force *)(-1UL);

	/* This is the X/Open sanctioned signal stack switching. */
	sp = sigsp(sp, ksig) - framesize;

	/* Align the stack frame. */
	sp &= ~0xfUL;

	return (void __user *)sp;
}

static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
	struct pt_regs *regs)
{
	struct rt_sigframe __user *frame;
	long err = 0;
	unsigned long __maybe_unused addr;
	size_t frame_size = get_rt_frame_size(false);

	frame = get_sigframe(ksig, regs, frame_size);
	if (!access_ok(frame, frame_size))
		return -EFAULT;

	err |= copy_siginfo_to_user(&frame->info, &ksig->info);

	/* Create the ucontext. */
	err |= __put_user(0, &frame->uc.uc_flags);
	err |= __put_user(NULL, &frame->uc.uc_link);
	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
	err |= setup_sigcontext(frame, regs);
	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
	if (err)
		return -EFAULT;

	/* Set up to return from userspace. */
#ifdef CONFIG_MMU
	regs->ra = (unsigned long)VDSO_SYMBOL(
		current->mm->context.vdso, rt_sigreturn);
#else
	/*
	 * For the nommu case we don't have a VDSO.  Instead we push two
	 * instructions to call the rt_sigreturn syscall onto the user stack.
	 */
	if (copy_to_user(&frame->sigreturn_code, __user_rt_sigreturn,
			 sizeof(frame->sigreturn_code)))
		return -EFAULT;

	addr = (unsigned long)&frame->sigreturn_code;
	/* Make sure the two instructions are pushed to icache. */
	flush_icache_range(addr, addr + sizeof(frame->sigreturn_code));

	regs->ra = addr;
#endif /* CONFIG_MMU */

	/*
	 * Set up registers for signal handler.
	 * Registers that we don't modify keep the value they had from
	 * user-space at the time we took the signal.
	 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
	 * since some things rely on this (e.g. glibc's debug/segfault.c).
	 */
	regs->epc = (unsigned long)ksig->ka.sa.sa_handler;
	regs->sp = (unsigned long)frame;
	regs->a0 = ksig->sig;                     /* a0: signal number */
	regs->a1 = (unsigned long)(&frame->info); /* a1: siginfo pointer */
	regs->a2 = (unsigned long)(&frame->uc);   /* a2: ucontext pointer */

#if DEBUG_SIG
	pr_info("SIG deliver (%s:%d): sig=%d pc=%p ra=%p sp=%p\n",
		current->comm, task_pid_nr(current), ksig->sig,
		(void *)regs->epc, (void *)regs->ra, frame);
#endif

	return 0;
}

static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
	sigset_t *oldset = sigmask_to_save();
	int ret;

	rseq_signal_deliver(ksig, regs);

	/* Set up the stack frame */
	if (is_compat_task())
		ret = compat_setup_rt_frame(ksig, oldset, regs);
	else
		ret = setup_rt_frame(ksig, oldset, regs);

	signal_setup_done(ret, ksig, 0);
}

void arch_do_signal_or_restart(struct pt_regs *regs)
{
	unsigned long continue_addr = 0, restart_addr = 0;
	int retval = 0;
	struct ksignal ksig;
	bool syscall = (regs->cause == EXC_SYSCALL);

	/* If we were from a system call, check for system call restarting */
	if (syscall) {
		continue_addr = regs->epc;
		restart_addr = continue_addr - 4;
		retval = regs->a0;

		/* Avoid additional syscall restarting via ret_from_exception */
		regs->cause = -1UL;

		/*
		 * Prepare for system call restart. We do this here so that a
		 * debugger will see the already changed PC.
		 */
		switch (retval) {
		case -ERESTARTNOHAND:
		case -ERESTARTSYS:
		case -ERESTARTNOINTR:
		case -ERESTART_RESTARTBLOCK:
			regs->a0 = regs->orig_a0;
			regs->epc = restart_addr;
			break;
		}
	}

	/*
	 * Get the signal to deliver. When running under ptrace, at this point
	 * the debugger may change all of our registers.
	 */
	if (get_signal(&ksig)) {
		/*
		 * Depending on the signal settings, we may need to revert the
		 * decision to restart the system call, but skip this if a
		 * debugger has chosen to restart at a different PC.
		 */
		if (regs->epc == restart_addr &&
		    (retval == -ERESTARTNOHAND ||
		     retval == -ERESTART_RESTARTBLOCK ||
		     (retval == -ERESTARTSYS &&
		      !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
			regs->a0 = -EINTR;
			regs->epc = continue_addr;
		}

		/* Actually deliver the signal */
		handle_signal(&ksig, regs);
		return;
	}

	/*
	 * Handle restarting a different system call. As above, if a debugger
	 * has chosen to restart at a different PC, ignore the restart.
	 */
	if (syscall && regs->epc == restart_addr && retval == -ERESTART_RESTARTBLOCK)
		regs->a7 = __NR_restart_syscall;

	/*
	 * If there is no signal to deliver, we just put the saved
	 * sigmask back.
	 */
	restore_saved_sigmask();
}

void init_rt_signal_env(void);
void __init init_rt_signal_env(void)
{
	riscv_v_sc_size = sizeof(struct __riscv_ctx_hdr) +
			  sizeof(struct __sc_riscv_v_state) + riscv_v_vsize;
	/*
	 * Determine the stack space required for guaranteed signal delivery.
	 * The signal_minsigstksz will be populated into the AT_MINSIGSTKSZ entry
	 * in the auxiliary array at process startup.
	 */
	signal_minsigstksz = get_rt_frame_size(true);
}

#ifdef CONFIG_DYNAMIC_SIGFRAME
bool sigaltstack_size_valid(size_t ss_size)
{
	return ss_size > get_rt_frame_size(false);
}
#endif /* CONFIG_DYNAMIC_SIGFRAME */