summaryrefslogtreecommitdiffstats
path: root/arch/openrisc/kernel/signal.c
blob: 7d1b8235bf90a9b2172654325e2bee576d3a4163 (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
/*
 * OpenRISC signal.c
 *
 * Linux architectural port borrowing liberally from similar works of
 * others.  All original copyrights apply as per the original source
 * declaration.
 *
 * Modifications for the OpenRISC architecture:
 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
 *
 *      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/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/tracehook.h>

#include <asm/processor.h>
#include <asm/syscall.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>

#define DEBUG_SIG 0

struct rt_sigframe {
	struct siginfo info;
	struct ucontext uc;
	unsigned char retcode[16];	/* trampoline code */
};

static int restore_sigcontext(struct pt_regs *regs,
			      struct sigcontext __user *sc)
{
	int err = 0;

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

	/*
	 * Restore the regs from &sc->regs.
	 * (sc is already checked for VERIFY_READ since the sigframe was
	 *  checked in sys_sigreturn previously)
	 */
	err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long));
	err |= __copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long));
	err |= __copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long));

	/* make sure the SM-bit is cleared so user-mode cannot fool us */
	regs->sr &= ~SPR_SR_SM;

	regs->orig_gpr11 = -1;	/* Avoid syscall restart checks */

	/* TODO: the other ports use regs->orig_XX to disable syscall checks
	 * after this completes, but we don't use that mechanism. maybe we can
	 * use it now ?
	 */

	return err;
}

asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
{
	struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
	sigset_t set;

	/*
	 * Since we stacked the signal on a dword boundary,
	 * then frame should be dword aligned here.  If it's
	 * not, then the user is trying to mess with us.
	 */
	if (((long)frame) & 3)
		goto badframe;

	if (!access_ok(VERIFY_READ, 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;

	return regs->gpr[11];

badframe:
	force_sig(SIGSEGV, current);
	return 0;
}

/*
 * Set up a signal frame.
 */

static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
	int err = 0;

	/* copy the regs */
	/* There should be no need to save callee-saved registers here...
	 * ...but we save them anyway.  Revisit this
	 */
	err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
	err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
	err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));

	return err;
}

static inline unsigned long align_sigframe(unsigned long sp)
{
	return sp & ~3UL;
}

/*
 * Work out where the signal frame should go.  It's either on the user stack
 * or the alternate stack.
 */

static inline void __user *get_sigframe(struct ksignal *ksig,
					struct pt_regs *regs, size_t frame_size)
{
	unsigned long sp = regs->sp;

	/* redzone */
	sp -= STACK_FRAME_OVERHEAD;
	sp = sigsp(sp, ksig);
	sp = align_sigframe(sp - frame_size);

	return (void __user *)sp;
}

/* grab and setup a signal frame.
 *
 * basically we stack a lot of state info, and arrange for the
 * user-mode program to return to the kernel using either a
 * trampoline which performs the syscall sigreturn, or a provided
 * user-mode trampoline.
 */
static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
			  struct pt_regs *regs)
{
	struct rt_sigframe *frame;
	unsigned long return_ip;
	int err = 0;

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

	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
		return -EFAULT;

	/* Create siginfo.  */
	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
		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(regs, &frame->uc.uc_mcontext);

	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

	if (err)
		return -EFAULT;

	/* trampoline - the desired return ip is the retcode itself */
	return_ip = (unsigned long)&frame->retcode;
	/* This is:
		l.ori r11,r0,__NR_sigreturn
		l.sys 1
	 */
	err |= __put_user(0xa960,             (short *)(frame->retcode + 0));
	err |= __put_user(__NR_rt_sigreturn,  (short *)(frame->retcode + 2));
	err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
	err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));

	if (err)
		return -EFAULT;

	/* TODO what is the current->exec_domain stuff and invmap ? */

	/* Set up registers for signal handler */
	regs->pc = (unsigned long)ksig->ka.sa.sa_handler; /* what we enter NOW */
	regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
	regs->gpr[3] = (unsigned long)ksig->sig;           /* arg 1: signo */
	regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
	regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */

	/* actually move the usp to reflect the stacked frame */
	regs->sp = (unsigned long)frame;

	return 0;
}

static inline void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
	int ret;

	ret = setup_rt_frame(ksig, sigmask_to_save(), regs);

	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
}

/*
 * 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.
 *
 * Also note that the regs structure given here as an argument, is the latest
 * pushed pt_regs. It may or may not be the same as the first pushed registers
 * when the initial usermode->kernelmode transition took place. Therefore
 * we can use user_mode(regs) to see if we came directly from kernel or user
 * mode below.
 */

int do_signal(struct pt_regs *regs, int syscall)
{
	struct ksignal ksig;
	unsigned long continue_addr = 0;
	unsigned long restart_addr = 0;
	unsigned long retval = 0;
	int restart = 0;

	if (syscall) {
		continue_addr = regs->pc;
		restart_addr = continue_addr - 4;
		retval = regs->gpr[11];

		/*
		 * Setup syscall restart here so that a debugger will
		 * see the already changed PC.
		 */
		switch (retval) {
		case -ERESTART_RESTARTBLOCK:
			restart = -2;
			/* Fall through */
		case -ERESTARTNOHAND:
		case -ERESTARTSYS:
		case -ERESTARTNOINTR:
			restart++;
			regs->gpr[11] = regs->orig_gpr11;
			regs->pc = restart_addr;
			break;
		}
	}

	/*
	 * Get the signal to deliver.  During the call to get_signal the
	 * debugger may change all our registers so we may need to revert
	 * the decision to restart the syscall; specifically, if the PC is
	 * changed, don't restart the syscall.
	 */
	if (get_signal(&ksig)) {
		if (unlikely(restart) && regs->pc == restart_addr) {
			if (retval == -ERESTARTNOHAND ||
			    retval == -ERESTART_RESTARTBLOCK
			    || (retval == -ERESTARTSYS
			        && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
				/* No automatic restart */
				regs->gpr[11] = -EINTR;
				regs->pc = continue_addr;
			}
		}
		handle_signal(&ksig, regs);
	} else {
		/* no handler */
		restore_saved_sigmask();
		/*
		 * Restore pt_regs PC as syscall restart will be handled by
		 * kernel without return to userspace
		 */
		if (unlikely(restart) && regs->pc == restart_addr) {
			regs->pc = continue_addr;
			return restart;
		}
	}

	return 0;
}

asmlinkage int
do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
{
	do {
		if (likely(thread_flags & _TIF_NEED_RESCHED)) {
			schedule();
		} else {
			if (unlikely(!user_mode(regs)))
				return 0;
			local_irq_enable();
			if (thread_flags & _TIF_SIGPENDING) {
				int restart = do_signal(regs, syscall);
				if (unlikely(restart)) {
					/*
					 * Restart without handlers.
					 * Deal with it without leaving
					 * the kernel space.
					 */
					return restart;
				}
				syscall = 0;
			} else {
				clear_thread_flag(TIF_NOTIFY_RESUME);
				tracehook_notify_resume(regs);
			}
		}
		local_irq_disable();
		thread_flags = current_thread_info()->flags;
	} while (thread_flags & _TIF_WORK_MASK);
	return 0;
}