summaryrefslogtreecommitdiffstats
path: root/arch/riscv/kernel/signal.c
blob: dee66c9290ccee95e20f93517e47d16a133b02bb (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
// 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 <asm/ucontext.h>
#include <asm/vdso.h>
#include <asm/signal.h>
#include <asm/signal32.h>
#include <asm/switch_to.h>
#include <asm/csr.h>
#include <asm/cacheflush.h>

extern u32 __user_rt_sigreturn[2];

#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;
	size_t i;

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

	fstate_restore(current, regs);

	/* We support no other extension state at this time. */
	for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
		u32 value;

		err = __get_user(value, &sc_fpregs->q.reserved[i]);
		if (unlikely(err))
			break;
		if (value != 0)
			return -EINVAL;
	}

	return err;
}

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;
	size_t i;

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

	/* We support no other extension state at this time. */
	for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
		err = __put_user(0, &sc_fpregs->q.reserved[i]);
		if (unlikely(err))
			break;
	}

	return err;
}
#else
#define save_fp_state(task, regs) (0)
#define restore_fp_state(task, regs) (0)
#endif

static long restore_sigcontext(struct pt_regs *regs,
	struct sigcontext __user *sc)
{
	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));
	/* Restore the floating-point state. */
	if (has_fpu())
		err |= restore_fp_state(regs, &sc->sc_fpregs);
	return err;
}

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

	/* 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, sizeof(*frame)))
		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;
	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);
	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;

	frame = get_sigframe(ksig, regs, sizeof(*frame));
	if (!access_ok(frame, sizeof(*frame)))
		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;

	/* Are we from a system call? */
	if (regs->cause == EXC_SYSCALL) {
		/* Avoid additional syscall restarting via ret_from_exception */
		regs->cause = -1UL;
		/* If so, check system call restarting.. */
		switch (regs->a0) {
		case -ERESTART_RESTARTBLOCK:
		case -ERESTARTNOHAND:
			regs->a0 = -EINTR;
			break;

		case -ERESTARTSYS:
			if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
				regs->a0 = -EINTR;
				break;
			}
			fallthrough;
		case -ERESTARTNOINTR:
                        regs->a0 = regs->orig_a0;
			regs->epc -= 0x4;
			break;
		}
	}

	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);
}

static void do_signal(struct pt_regs *regs)
{
	struct ksignal ksig;

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

	/* Did we come from a system call? */
	if (regs->cause == EXC_SYSCALL) {
		/* Avoid additional syscall restarting via ret_from_exception */
		regs->cause = -1UL;

		/* Restart the system call - no handlers present */
		switch (regs->a0) {
		case -ERESTARTNOHAND:
		case -ERESTARTSYS:
		case -ERESTARTNOINTR:
                        regs->a0 = regs->orig_a0;
			regs->epc -= 0x4;
			break;
		case -ERESTART_RESTARTBLOCK:
                        regs->a0 = regs->orig_a0;
			regs->a7 = __NR_restart_syscall;
			regs->epc -= 0x4;
			break;
		}
	}

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

/*
 * Handle any pending work on the resume-to-userspace path, as indicated by
 * _TIF_WORK_MASK. Entered from assembly with IRQs off.
 */
asmlinkage __visible void do_work_pending(struct pt_regs *regs,
					  unsigned long thread_info_flags)
{
	do {
		if (thread_info_flags & _TIF_NEED_RESCHED) {
			schedule();
		} else {
			local_irq_enable();
			if (thread_info_flags & _TIF_UPROBE)
				uprobe_notify_resume(regs);
			/* Handle pending signal delivery */
			if (thread_info_flags & (_TIF_SIGPENDING |
						 _TIF_NOTIFY_SIGNAL))
				do_signal(regs);
			if (thread_info_flags & _TIF_NOTIFY_RESUME)
				resume_user_mode_work(regs);
		}
		local_irq_disable();
		thread_info_flags = read_thread_flags();
	} while (thread_info_flags & _TIF_WORK_MASK);
}