1/*
2 * Copyright (C) 1991, 1992  Linus Torvalds
3 * Copyright 2010 Tilera Corporation. All Rights Reserved.
4 *
5 *   This program is free software; you can redistribute it and/or
6 *   modify it under the terms of the GNU General Public License
7 *   as published by the Free Software Foundation, version 2.
8 *
9 *   This program is distributed in the hope that it will be useful, but
10 *   WITHOUT ANY WARRANTY; without even the implied warranty of
11 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
12 *   NON INFRINGEMENT.  See the GNU General Public License for
13 *   more details.
14 */
15
16#include <linux/sched.h>
17#include <linux/mm.h>
18#include <linux/smp.h>
19#include <linux/kernel.h>
20#include <linux/signal.h>
21#include <linux/errno.h>
22#include <linux/wait.h>
23#include <linux/unistd.h>
24#include <linux/stddef.h>
25#include <linux/personality.h>
26#include <linux/suspend.h>
27#include <linux/ptrace.h>
28#include <linux/elf.h>
29#include <linux/compat.h>
30#include <linux/syscalls.h>
31#include <linux/uaccess.h>
32#include <asm/processor.h>
33#include <asm/ucontext.h>
34#include <asm/sigframe.h>
35#include <asm/syscalls.h>
36#include <asm/vdso.h>
37#include <arch/interrupts.h>
38
39#define DEBUG_SIG 0
40
41/*
42 * Do a signal return; undo the signal stack.
43 */
44
45int restore_sigcontext(struct pt_regs *regs,
46		       struct sigcontext __user *sc)
47{
48	int err;
49
50	/* Always make any pending restarted system calls return -EINTR */
51	current->restart_block.fn = do_no_restart_syscall;
52
53	/*
54	 * Enforce that sigcontext is like pt_regs, and doesn't mess
55	 * up our stack alignment rules.
56	 */
57	BUILD_BUG_ON(sizeof(struct sigcontext) != sizeof(struct pt_regs));
58	BUILD_BUG_ON(sizeof(struct sigcontext) % 8 != 0);
59	err = __copy_from_user(regs, sc, sizeof(*regs));
60
61	/* Ensure that the PL is always set to USER_PL. */
62	regs->ex1 = PL_ICS_EX1(USER_PL, EX1_ICS(regs->ex1));
63
64	regs->faultnum = INT_SWINT_1_SIGRETURN;
65
66	return err;
67}
68
69void signal_fault(const char *type, struct pt_regs *regs,
70		  void __user *frame, int sig)
71{
72	trace_unhandled_signal(type, regs, (unsigned long)frame, SIGSEGV);
73	force_sigsegv(sig, current);
74}
75
76/* The assembly shim for this function arranges to ignore the return value. */
77SYSCALL_DEFINE0(rt_sigreturn)
78{
79	struct pt_regs *regs = current_pt_regs();
80	struct rt_sigframe __user *frame =
81		(struct rt_sigframe __user *)(regs->sp);
82	sigset_t set;
83
84	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
85		goto badframe;
86	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
87		goto badframe;
88
89	set_current_blocked(&set);
90
91	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
92		goto badframe;
93
94	if (restore_altstack(&frame->uc.uc_stack))
95		goto badframe;
96
97	return 0;
98
99badframe:
100	signal_fault("bad sigreturn frame", regs, frame, 0);
101	return 0;
102}
103
104/*
105 * Set up a signal frame.
106 */
107
108int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
109{
110	return  __copy_to_user(sc, regs, sizeof(*regs));
111}
112
113/*
114 * Determine which stack to use..
115 */
116static inline void __user *get_sigframe(struct k_sigaction *ka,
117					struct pt_regs *regs,
118					size_t frame_size)
119{
120	unsigned long sp;
121
122	/* Default to using normal stack */
123	sp = regs->sp;
124
125	/*
126	 * If we are on the alternate signal stack and would overflow
127	 * it, don't.  Return an always-bogus address instead so we
128	 * will die with SIGSEGV.
129	 */
130	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
131		return (void __user __force *)-1UL;
132
133	/* This is the X/Open sanctioned signal stack switching.  */
134	if (ka->sa.sa_flags & SA_ONSTACK) {
135		if (sas_ss_flags(sp) == 0)
136			sp = current->sas_ss_sp + current->sas_ss_size;
137	}
138
139	sp -= frame_size;
140	/*
141	 * Align the stack pointer according to the TILE ABI,
142	 * i.e. so that on function entry (sp & 15) == 0.
143	 */
144	sp &= -16UL;
145	return (void __user *) sp;
146}
147
148static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
149			  struct pt_regs *regs)
150{
151	unsigned long restorer;
152	struct rt_sigframe __user *frame;
153	int err = 0, sig = ksig->sig;
154
155	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame));
156
157	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
158		goto err;
159
160	/* Always write at least the signal number for the stack backtracer. */
161	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
162		/* At sigreturn time, restore the callee-save registers too. */
163		err |= copy_siginfo_to_user(&frame->info, &ksig->info);
164		regs->flags |= PT_FLAGS_RESTORE_REGS;
165	} else {
166		err |= __put_user(ksig->info.si_signo, &frame->info.si_signo);
167	}
168
169	/* Create the ucontext.  */
170	err |= __clear_user(&frame->save_area, sizeof(frame->save_area));
171	err |= __put_user(0, &frame->uc.uc_flags);
172	err |= __put_user(NULL, &frame->uc.uc_link);
173	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
174	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs);
175	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
176	if (err)
177		goto err;
178
179	restorer = VDSO_SYM(&__vdso_rt_sigreturn);
180	if (ksig->ka.sa.sa_flags & SA_RESTORER)
181		restorer = (unsigned long) ksig->ka.sa.sa_restorer;
182
183	/*
184	 * Set up registers for signal handler.
185	 * Registers that we don't modify keep the value they had from
186	 * user-space at the time we took the signal.
187	 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
188	 * since some things rely on this (e.g. glibc's debug/segfault.c).
189	 */
190	regs->pc = (unsigned long) ksig->ka.sa.sa_handler;
191	regs->ex1 = PL_ICS_EX1(USER_PL, 1); /* set crit sec in handler */
192	regs->sp = (unsigned long) frame;
193	regs->lr = restorer;
194	regs->regs[0] = (unsigned long) sig;
195	regs->regs[1] = (unsigned long) &frame->info;
196	regs->regs[2] = (unsigned long) &frame->uc;
197	regs->flags |= PT_FLAGS_CALLER_SAVES;
198	return 0;
199
200err:
201	trace_unhandled_signal("bad sigreturn frame", regs,
202			      (unsigned long)frame, SIGSEGV);
203	return -EFAULT;
204}
205
206/*
207 * OK, we're invoking a handler
208 */
209
210static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
211{
212	sigset_t *oldset = sigmask_to_save();
213	int ret;
214
215	/* Are we from a system call? */
216	if (regs->faultnum == INT_SWINT_1) {
217		/* If so, check system call restarting.. */
218		switch (regs->regs[0]) {
219		case -ERESTART_RESTARTBLOCK:
220		case -ERESTARTNOHAND:
221			regs->regs[0] = -EINTR;
222			break;
223
224		case -ERESTARTSYS:
225			if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
226				regs->regs[0] = -EINTR;
227				break;
228			}
229			/* fallthrough */
230		case -ERESTARTNOINTR:
231			/* Reload caller-saves to restore r0..r5 and r10. */
232			regs->flags |= PT_FLAGS_CALLER_SAVES;
233			regs->regs[0] = regs->orig_r0;
234			regs->pc -= 8;
235		}
236	}
237
238	/* Set up the stack frame */
239#ifdef CONFIG_COMPAT
240	if (is_compat_task())
241		ret = compat_setup_rt_frame(ksig, oldset, regs);
242	else
243#endif
244		ret = setup_rt_frame(ksig, oldset, regs);
245
246	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
247}
248
249/*
250 * Note that 'init' is a special process: it doesn't get signals it doesn't
251 * want to handle. Thus you cannot kill init even with a SIGKILL even by
252 * mistake.
253 */
254void do_signal(struct pt_regs *regs)
255{
256	struct ksignal ksig;
257
258	/*
259	 * i386 will check if we're coming from kernel mode and bail out
260	 * here.  In my experience this just turns weird crashes into
261	 * weird spin-hangs.  But if we find a case where this seems
262	 * helpful, we can reinstate the check on "!user_mode(regs)".
263	 */
264
265	if (get_signal(&ksig)) {
266		/* Whee! Actually deliver the signal.  */
267		handle_signal(&ksig, regs);
268		goto done;
269	}
270
271	/* Did we come from a system call? */
272	if (regs->faultnum == INT_SWINT_1) {
273		/* Restart the system call - no handlers present */
274		switch (regs->regs[0]) {
275		case -ERESTARTNOHAND:
276		case -ERESTARTSYS:
277		case -ERESTARTNOINTR:
278			regs->flags |= PT_FLAGS_CALLER_SAVES;
279			regs->regs[0] = regs->orig_r0;
280			regs->pc -= 8;
281			break;
282
283		case -ERESTART_RESTARTBLOCK:
284			regs->flags |= PT_FLAGS_CALLER_SAVES;
285			regs->regs[TREG_SYSCALL_NR] = __NR_restart_syscall;
286			regs->pc -= 8;
287			break;
288		}
289	}
290
291	/* If there's no signal to deliver, just put the saved sigmask back. */
292	restore_saved_sigmask();
293
294done:
295	/* Avoid double syscall restart if there are nested signals. */
296	regs->faultnum = INT_SWINT_1_SIGRETURN;
297}
298
299int show_unhandled_signals = 1;
300
301static int __init crashinfo(char *str)
302{
303	const char *word;
304
305	if (*str == '\0')
306		show_unhandled_signals = 2;
307	else if (*str != '=' || kstrtoint(++str, 0, &show_unhandled_signals) != 0)
308		return 0;
309
310	switch (show_unhandled_signals) {
311	case 0:
312		word = "No";
313		break;
314	case 1:
315		word = "One-line";
316		break;
317	default:
318		word = "Detailed";
319		break;
320	}
321	pr_info("%s crash reports will be generated on the console\n", word);
322	return 1;
323}
324__setup("crashinfo", crashinfo);
325
326static void dump_mem(void __user *address)
327{
328	void __user *addr;
329	enum { region_size = 256, bytes_per_line = 16 };
330	int i, j, k;
331	int found_readable_mem = 0;
332
333	if (!access_ok(VERIFY_READ, address, 1)) {
334		pr_err("Not dumping at address 0x%lx (kernel address)\n",
335		       (unsigned long)address);
336		return;
337	}
338
339	addr = (void __user *)
340		(((unsigned long)address & -bytes_per_line) - region_size/2);
341	if (addr > address)
342		addr = NULL;
343	for (i = 0; i < region_size;
344	     addr += bytes_per_line, i += bytes_per_line) {
345		unsigned char buf[bytes_per_line];
346		char line[100];
347		if (copy_from_user(buf, addr, bytes_per_line))
348			continue;
349		if (!found_readable_mem) {
350			pr_err("Dumping memory around address 0x%lx:\n",
351			       (unsigned long)address);
352			found_readable_mem = 1;
353		}
354		j = sprintf(line, REGFMT ":", (unsigned long)addr);
355		for (k = 0; k < bytes_per_line; ++k)
356			j += sprintf(&line[j], " %02x", buf[k]);
357		pr_err("%s\n", line);
358	}
359	if (!found_readable_mem)
360		pr_err("No readable memory around address 0x%lx\n",
361		       (unsigned long)address);
362}
363
364void trace_unhandled_signal(const char *type, struct pt_regs *regs,
365			    unsigned long address, int sig)
366{
367	struct task_struct *tsk = current;
368
369	if (show_unhandled_signals == 0)
370		return;
371
372	/* If the signal is handled, don't show it here. */
373	if (!is_global_init(tsk)) {
374		void __user *handler =
375			tsk->sighand->action[sig-1].sa.sa_handler;
376		if (handler != SIG_IGN && handler != SIG_DFL)
377			return;
378	}
379
380	/* Rate-limit the one-line output, not the detailed output. */
381	if (show_unhandled_signals <= 1 && !printk_ratelimit())
382		return;
383
384	printk("%s%s[%d]: %s at %lx pc "REGFMT" signal %d",
385	       task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
386	       tsk->comm, task_pid_nr(tsk), type, address, regs->pc, sig);
387
388	print_vma_addr(KERN_CONT " in ", regs->pc);
389
390	printk(KERN_CONT "\n");
391
392	if (show_unhandled_signals > 1) {
393		switch (sig) {
394		case SIGILL:
395		case SIGFPE:
396		case SIGSEGV:
397		case SIGBUS:
398			pr_err("User crash: signal %d, trap %ld, address 0x%lx\n",
399			       sig, regs->faultnum, address);
400			show_regs(regs);
401			dump_mem((void __user *)address);
402			break;
403		default:
404			pr_err("User crash: signal %d, trap %ld\n",
405			       sig, regs->faultnum);
406			break;
407		}
408	}
409}
410