summaryrefslogtreecommitdiff
path: root/arch/arc/kernel/signal.c
blob: c2031e20c04840de43c6398d662e55a40ea4ed4a (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
/*
 * Signal Handling for ARC
 *
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * vineetg: Jan 2010 (Restarting of timer related syscalls)
 *
 * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK)
 *  -do_signal() supports TIF_RESTORE_SIGMASK
 *  -do_signal() no loner needs oldset, required by OLD sys_sigsuspend
 *  -sys_rt_sigsuspend() now comes from generic code, so discard arch implemen
 *  -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed
 *  -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves
 *   the job to do_signal()
 *
 * vineetg: July 2009
 *  -Modified Code to support the uClibc provided userland sigreturn stub
 *   to avoid kernel synthesing it on user stack at runtime, costing TLB
 *   probes and Cache line flushes.
 *
 * vineetg: July 2009
 *  -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs
 *   in done in block copy rather than one word at a time.
 *   This saves around 2K of code and improves LMBench lat_sig <catch>
 *
 * rajeshwarr: Feb 2009
 *  - Support for Realtime Signals
 *
 * vineetg: Aug 11th 2008: Bug #94183
 *  -ViXS were still seeing crashes when using insmod to load drivers.
 *   It turned out that the code to change Execute permssions for TLB entries
 *   of user was not guarded for interrupts (mod_tlb_permission)
 *   This was cauing TLB entries to be overwritten on unrelated indexes
 *
 * Vineetg: July 15th 2008: Bug #94183
 *  -Exception happens in Delay slot of a JMP, and before user space resumes,
 *   Signal is delivered (Ctrl + C) = >SIGINT.
 *   setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler
 *   to run, but doesn't clear the Delay slot bit from status32. As a result,
 *   on resuming user mode, signal handler branches off to BTA of orig JMP
 *  -FIX: clear the DE bit from status32 in setup_frame( )
 *
 * Rahul Trivedi, Kanika Nema: Codito Technologies 2004
 */

#include <linux/signal.h>
#include <linux/ptrace.h>
#include <linux/personality.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/tracehook.h>
#include <asm/ucontext.h>

struct rt_sigframe {
	struct siginfo info;
	struct ucontext uc;
#define MAGIC_SIGALTSTK		0x07302004
	unsigned int sigret_magic;
};

static int
stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs,
	       sigset_t *set)
{
	int err;
	err = __copy_to_user(&(sf->uc.uc_mcontext.regs), regs,
			     sizeof(sf->uc.uc_mcontext.regs.scratch));
	err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t));

	return err;
}

static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf)
{
	sigset_t set;
	int err;

	err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
	if (!err)
		set_current_blocked(&set);

	err |= __copy_from_user(regs, &(sf->uc.uc_mcontext.regs),
				sizeof(sf->uc.uc_mcontext.regs.scratch));

	return err;
}

static inline int is_do_ss_needed(unsigned int magic)
{
	if (MAGIC_SIGALTSTK == magic)
		return 1;
	else
		return 0;
}

SYSCALL_DEFINE0(rt_sigreturn)
{
	struct rt_sigframe __user *sf;
	unsigned int magic;
	struct pt_regs *regs = current_pt_regs();

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

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

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

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

	if (__get_user(magic, &sf->sigret_magic))
		goto badframe;

	if (unlikely(is_do_ss_needed(magic)))
		if (restore_altstack(&sf->uc.uc_stack))
			goto badframe;

	if (restore_usr_regs(regs, sf))
		goto badframe;

	/* Don't restart from sigreturn */
	syscall_wont_restart(regs);

	return regs->r0;

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

/*
 * Determine which stack to use..
 */
static inline void __user *get_sigframe(struct k_sigaction *ka,
					struct pt_regs *regs,
					unsigned long framesize)
{
	unsigned long sp = regs->sp;
	void __user *frame;

	/* This is the X/Open sanctioned signal stack switching */
	if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
		sp = current->sas_ss_sp + current->sas_ss_size;

	/* No matter what happens, 'sp' must be word
	 * aligned otherwise nasty things could happen
	 */

	/* ATPCS B01 mandates 8-byte alignment */
	frame = (void __user *)((sp - framesize) & ~7);

	/* Check that we can actually write to the signal frame */
	if (!access_ok(VERIFY_WRITE, frame, framesize))
		frame = NULL;

	return frame;
}

/*
 * translate the signal
 */
static inline int map_sig(int sig)
{
	struct thread_info *thread = current_thread_info();
	if (thread->exec_domain && thread->exec_domain->signal_invmap
	    && sig < 32)
		sig = thread->exec_domain->signal_invmap[sig];
	return sig;
}

static int
setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
{
	struct rt_sigframe __user *sf;
	unsigned int magic = 0;
	int err = 0;

	sf = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe));
	if (!sf)
		return 1;

	/*
	 * w/o SA_SIGINFO, struct ucontext is partially populated (only
	 * uc_mcontext/uc_sigmask) for kernel's normal user state preservation
	 * during signal handler execution. This works for SA_SIGINFO as well
	 * although the semantics are now overloaded (the same reg state can be
	 * inspected by userland: but are they allowed to fiddle with it ?
	 */
	err |= stash_usr_regs(sf, regs, set);

	/*
	 * SA_SIGINFO requires 3 args to signal handler:
	 *  #1: sig-no (common to any handler)
	 *  #2: struct siginfo
	 *  #3: struct ucontext (completely populated)
	 */
	if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) {
		err |= copy_siginfo_to_user(&sf->info, &ksig->info);
		err |= __put_user(0, &sf->uc.uc_flags);
		err |= __put_user(NULL, &sf->uc.uc_link);
		err |= __save_altstack(&sf->uc.uc_stack, regs->sp);

		/* setup args 2 and 3 for user mode handler */
		regs->r1 = (unsigned long)&sf->info;
		regs->r2 = (unsigned long)&sf->uc;

		/*
		 * small optim to avoid unconditonally calling do_sigaltstack
		 * in sigreturn path, now that we only have rt_sigreturn
		 */
		magic = MAGIC_SIGALTSTK;
	}

	err |= __put_user(magic, &sf->sigret_magic);
	if (err)
		return err;

	/* #1 arg to the user Signal handler */
	regs->r0 = map_sig(ksig->sig);

	/* setup PC of user space signal handler */
	regs->ret = (unsigned long)ksig->ka.sa.sa_handler;

	/*
	 * handler returns using sigreturn stub provided already by userpsace
	 */
	BUG_ON(!(ksig->ka.sa.sa_flags & SA_RESTORER));
	regs->blink = (unsigned long)ksig->ka.sa.sa_restorer;

	/* User Stack for signal handler will be above the frame just carved */
	regs->sp = (unsigned long)sf;

	/*
	 * Bug 94183, Clear the DE bit, so that when signal handler
	 * starts to run, it doesn't use BTA
	 */
	regs->status32 &= ~STATUS_DE_MASK;
	regs->status32 |= STATUS_L_MASK;

	return err;
}

static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs)
{
	switch (regs->r0) {
	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 don't restart
		 */
		regs->r0 = -EINTR;   /* ERESTART_xxx is internal */
		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->r0 = -EINTR;
			break;
		}
		/* fallthrough */

	case -ERESTARTNOINTR:
		/*
		 * ERESTARTNOINTR means that the syscall should
		 * be called again after the signal handler returns.
		 * Setup reg state just as it was before doing the trap
		 * r0 has been clobbered with sys call ret code thus it
		 * needs to be reloaded with orig first arg to syscall
		 * in orig_r0. Rest of relevant reg-file:
		 * r8 (syscall num) and (r1 - r7) will be reset to
		 * their orig user space value when we ret from kernel
		 */
		regs->r0 = regs->orig_r0;
		regs->ret -= 4;
		break;
	}
}

/*
 * OK, we're invoking a handler
 */
static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
	sigset_t *oldset = sigmask_to_save();
	int ret;

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

	signal_setup_done(ret, ksig, 0);
}

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

	restart_scall = in_syscall(regs) && syscall_restartable(regs);

	if (get_signal(&ksig)) {
		if (restart_scall) {
			arc_restart_syscall(&ksig.ka, regs);
			syscall_wont_restart(regs);	/* No more restarts */
		}
		handle_signal(&ksig, regs);
		return;
	}

	if (restart_scall) {
		/* No handler for syscall: restart it */
		if (regs->r0 == -ERESTARTNOHAND ||
		    regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) {
			regs->r0 = regs->orig_r0;
			regs->ret -= 4;
		} else if (regs->r0 == -ERESTART_RESTARTBLOCK) {
			regs->r8 = __NR_restart_syscall;
			regs->ret -= 4;
		}
		syscall_wont_restart(regs);	/* No more restarts */
	}

	/* If there's no signal to deliver, restore the saved sigmask back */
	restore_saved_sigmask();
}

void do_notify_resume(struct pt_regs *regs)
{
	/*
	 * ASM glue gaurantees that this is only called when returning to
	 * user mode
	 */
	if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
		tracehook_notify_resume(regs);
}