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 <arch/interrupts.h>
 37
 38#define DEBUG_SIG 0
 39
 40#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
 41
 42SYSCALL_DEFINE3(sigaltstack, const stack_t __user *, uss,
 43		stack_t __user *, uoss, struct pt_regs *, regs)
 44{
 45	return do_sigaltstack(uss, uoss, regs->sp);
 46}
 47
 48
 49/*
 50 * Do a signal return; undo the signal stack.
 51 */
 52
 53int restore_sigcontext(struct pt_regs *regs,
 54		       struct sigcontext __user *sc)
 55{
 56	int err = 0;
 57	int i;
 58
 59	/* Always make any pending restarted system calls return -EINTR */
 60	current_thread_info()->restart_block.fn = do_no_restart_syscall;
 61
 62	/*
 63	 * Enforce that sigcontext is like pt_regs, and doesn't mess
 64	 * up our stack alignment rules.
 65	 */
 66	BUILD_BUG_ON(sizeof(struct sigcontext) != sizeof(struct pt_regs));
 67	BUILD_BUG_ON(sizeof(struct sigcontext) % 8 != 0);
 68
 69	for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
 70		err |= __get_user(regs->regs[i], &sc->gregs[i]);
 71
 72	/* Ensure that the PL is always set to USER_PL. */
 73	regs->ex1 = PL_ICS_EX1(USER_PL, EX1_ICS(regs->ex1));
 74
 75	regs->faultnum = INT_SWINT_1_SIGRETURN;
 76
 77	return err;
 78}
 79
 80void signal_fault(const char *type, struct pt_regs *regs,
 81		  void __user *frame, int sig)
 82{
 83	trace_unhandled_signal(type, regs, (unsigned long)frame, SIGSEGV);
 84	force_sigsegv(sig, current);
 85}
 86
 87/* The assembly shim for this function arranges to ignore the return value. */
 88SYSCALL_DEFINE1(rt_sigreturn, struct pt_regs *, regs)
 89{
 90	struct rt_sigframe __user *frame =
 91		(struct rt_sigframe __user *)(regs->sp);
 92	sigset_t set;
 93
 94	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 95		goto badframe;
 96	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 97		goto badframe;
 98
 99	sigdelsetmask(&set, ~_BLOCKABLE);
100	spin_lock_irq(&current->sighand->siglock);
101	current->blocked = set;
102	recalc_sigpending();
103	spin_unlock_irq(&current->sighand->siglock);
104
105	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
106		goto badframe;
107
108	if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
109		goto badframe;
110
111	return 0;
112
113badframe:
114	signal_fault("bad sigreturn frame", regs, frame, 0);
115	return 0;
116}
117
118/*
119 * Set up a signal frame.
120 */
121
122int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
123{
124	int i, err = 0;
125
126	for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
127		err |= __put_user(regs->regs[i], &sc->gregs[i]);
128
129	return err;
130}
131
132/*
133 * Determine which stack to use..
134 */
135static inline void __user *get_sigframe(struct k_sigaction *ka,
136					struct pt_regs *regs,
137					size_t frame_size)
138{
139	unsigned long sp;
140
141	/* Default to using normal stack */
142	sp = regs->sp;
143
144	/*
145	 * If we are on the alternate signal stack and would overflow
146	 * it, don't.  Return an always-bogus address instead so we
147	 * will die with SIGSEGV.
148	 */
149	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
150		return (void __user __force *)-1UL;
151
152	/* This is the X/Open sanctioned signal stack switching.  */
153	if (ka->sa.sa_flags & SA_ONSTACK) {
154		if (sas_ss_flags(sp) == 0)
155			sp = current->sas_ss_sp + current->sas_ss_size;
156	}
157
158	sp -= frame_size;
159	/*
160	 * Align the stack pointer according to the TILE ABI,
161	 * i.e. so that on function entry (sp & 15) == 0.
162	 */
163	sp &= -16UL;
164	return (void __user *) sp;
165}
166
167static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
168			   sigset_t *set, struct pt_regs *regs)
169{
170	unsigned long restorer;
171	struct rt_sigframe __user *frame;
172	int err = 0;
173	int usig;
174
175	frame = get_sigframe(ka, regs, sizeof(*frame));
176
177	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
178		goto give_sigsegv;
179
180	usig = current_thread_info()->exec_domain
181		&& current_thread_info()->exec_domain->signal_invmap
182		&& sig < 32
183		? current_thread_info()->exec_domain->signal_invmap[sig]
184		: sig;
185
186	/* Always write at least the signal number for the stack backtracer. */
187	if (ka->sa.sa_flags & SA_SIGINFO) {
188		/* At sigreturn time, restore the callee-save registers too. */
189		err |= copy_siginfo_to_user(&frame->info, info);
190		regs->flags |= PT_FLAGS_RESTORE_REGS;
191	} else {
192		err |= __put_user(info->si_signo, &frame->info.si_signo);
193	}
194
195	/* Create the ucontext.  */
196	err |= __clear_user(&frame->save_area, sizeof(frame->save_area));
197	err |= __put_user(0, &frame->uc.uc_flags);
198	err |= __put_user(NULL, &frame->uc.uc_link);
199	err |= __put_user((void __user *)(current->sas_ss_sp),
200			  &frame->uc.uc_stack.ss_sp);
201	err |= __put_user(sas_ss_flags(regs->sp),
202			  &frame->uc.uc_stack.ss_flags);
203	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
204	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs);
205	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
206	if (err)
207		goto give_sigsegv;
208
209	restorer = VDSO_BASE;
210	if (ka->sa.sa_flags & SA_RESTORER)
211		restorer = (unsigned long) ka->sa.sa_restorer;
212
213	/*
214	 * Set up registers for signal handler.
215	 * Registers that we don't modify keep the value they had from
216	 * user-space at the time we took the signal.
217	 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
218	 * since some things rely on this (e.g. glibc's debug/segfault.c).
219	 */
220	regs->pc = (unsigned long) ka->sa.sa_handler;
221	regs->ex1 = PL_ICS_EX1(USER_PL, 1); /* set crit sec in handler */
222	regs->sp = (unsigned long) frame;
223	regs->lr = restorer;
224	regs->regs[0] = (unsigned long) usig;
225	regs->regs[1] = (unsigned long) &frame->info;
226	regs->regs[2] = (unsigned long) &frame->uc;
227	regs->flags |= PT_FLAGS_CALLER_SAVES;
228
229	/*
230	 * Notify any tracer that was single-stepping it.
231	 * The tracer may want to single-step inside the
232	 * handler too.
233	 */
234	if (test_thread_flag(TIF_SINGLESTEP))
235		ptrace_notify(SIGTRAP);
236
237	return 0;
238
239give_sigsegv:
240	signal_fault("bad setup frame", regs, frame, sig);
241	return -EFAULT;
242}
243
244/*
245 * OK, we're invoking a handler
246 */
247
248static int handle_signal(unsigned long sig, siginfo_t *info,
249			 struct k_sigaction *ka, sigset_t *oldset,
250			 struct pt_regs *regs)
251{
252	int ret;
253
254	/* Are we from a system call? */
255	if (regs->faultnum == INT_SWINT_1) {
256		/* If so, check system call restarting.. */
257		switch (regs->regs[0]) {
258		case -ERESTART_RESTARTBLOCK:
259		case -ERESTARTNOHAND:
260			regs->regs[0] = -EINTR;
261			break;
262
263		case -ERESTARTSYS:
264			if (!(ka->sa.sa_flags & SA_RESTART)) {
265				regs->regs[0] = -EINTR;
266				break;
267			}
268			/* fallthrough */
269		case -ERESTARTNOINTR:
270			/* Reload caller-saves to restore r0..r5 and r10. */
271			regs->flags |= PT_FLAGS_CALLER_SAVES;
272			regs->regs[0] = regs->orig_r0;
273			regs->pc -= 8;
274		}
275	}
276
277	/* Set up the stack frame */
278#ifdef CONFIG_COMPAT
279	if (is_compat_task())
280		ret = compat_setup_rt_frame(sig, ka, info, oldset, regs);
281	else
282#endif
283		ret = setup_rt_frame(sig, ka, info, oldset, regs);
284	if (ret == 0) {
285		/* This code is only called from system calls or from
286		 * the work_pending path in the return-to-user code, and
287		 * either way we can re-enable interrupts unconditionally.
288		 */
289		spin_lock_irq(&current->sighand->siglock);
290		sigorsets(&current->blocked,
291			  &current->blocked, &ka->sa.sa_mask);
292		if (!(ka->sa.sa_flags & SA_NODEFER))
293			sigaddset(&current->blocked, sig);
294		recalc_sigpending();
295		spin_unlock_irq(&current->sighand->siglock);
296	}
297
298	return ret;
299}
300
301/*
302 * Note that 'init' is a special process: it doesn't get signals it doesn't
303 * want to handle. Thus you cannot kill init even with a SIGKILL even by
304 * mistake.
305 */
306void do_signal(struct pt_regs *regs)
307{
308	siginfo_t info;
309	int signr;
310	struct k_sigaction ka;
311	sigset_t *oldset;
312
313	/*
314	 * i386 will check if we're coming from kernel mode and bail out
315	 * here.  In my experience this just turns weird crashes into
316	 * weird spin-hangs.  But if we find a case where this seems
317	 * helpful, we can reinstate the check on "!user_mode(regs)".
318	 */
319
320	if (current_thread_info()->status & TS_RESTORE_SIGMASK)
321		oldset = &current->saved_sigmask;
322	else
323		oldset = &current->blocked;
324
325	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
326	if (signr > 0) {
327		/* Whee! Actually deliver the signal.  */
328		if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
329			/*
330			 * A signal was successfully delivered; the saved
331			 * sigmask will have been stored in the signal frame,
332			 * and will be restored by sigreturn, so we can simply
333			 * clear the TS_RESTORE_SIGMASK flag.
334			 */
335			current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
336		}
337
338		goto done;
339	}
340
341	/* Did we come from a system call? */
342	if (regs->faultnum == INT_SWINT_1) {
343		/* Restart the system call - no handlers present */
344		switch (regs->regs[0]) {
345		case -ERESTARTNOHAND:
346		case -ERESTARTSYS:
347		case -ERESTARTNOINTR:
348			regs->flags |= PT_FLAGS_CALLER_SAVES;
349			regs->regs[0] = regs->orig_r0;
350			regs->pc -= 8;
351			break;
352
353		case -ERESTART_RESTARTBLOCK:
354			regs->flags |= PT_FLAGS_CALLER_SAVES;
355			regs->regs[TREG_SYSCALL_NR] = __NR_restart_syscall;
356			regs->pc -= 8;
357			break;
358		}
359	}
360
361	/* If there's no signal to deliver, just put the saved sigmask back. */
362	if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
363		current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
364		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
365	}
366
367done:
368	/* Avoid double syscall restart if there are nested signals. */
369	regs->faultnum = INT_SWINT_1_SIGRETURN;
370}
371
372int show_unhandled_signals = 1;
373
374static int __init crashinfo(char *str)
375{
376	unsigned long val;
377	const char *word;
378
379	if (*str == '\0')
380		val = 2;
381	else if (*str != '=' || strict_strtoul(++str, 0, &val) != 0)
382		return 0;
383	show_unhandled_signals = val;
384	switch (show_unhandled_signals) {
385	case 0:
386		word = "No";
387		break;
388	case 1:
389		word = "One-line";
390		break;
391	default:
392		word = "Detailed";
393		break;
394	}
395	pr_info("%s crash reports will be generated on the console\n", word);
396	return 1;
397}
398__setup("crashinfo", crashinfo);
399
400static void dump_mem(void __user *address)
401{
402	void __user *addr;
403	enum { region_size = 256, bytes_per_line = 16 };
404	int i, j, k;
405	int found_readable_mem = 0;
406
407	pr_err("\n");
408	if (!access_ok(VERIFY_READ, address, 1)) {
409		pr_err("Not dumping at address 0x%lx (kernel address)\n",
410		       (unsigned long)address);
411		return;
412	}
413
414	addr = (void __user *)
415		(((unsigned long)address & -bytes_per_line) - region_size/2);
416	if (addr > address)
417		addr = NULL;
418	for (i = 0; i < region_size;
419	     addr += bytes_per_line, i += bytes_per_line) {
420		unsigned char buf[bytes_per_line];
421		char line[100];
422		if (copy_from_user(buf, addr, bytes_per_line))
423			continue;
424		if (!found_readable_mem) {
425			pr_err("Dumping memory around address 0x%lx:\n",
426			       (unsigned long)address);
427			found_readable_mem = 1;
428		}
429		j = sprintf(line, REGFMT":", (unsigned long)addr);
430		for (k = 0; k < bytes_per_line; ++k)
431			j += sprintf(&line[j], " %02x", buf[k]);
432		pr_err("%s\n", line);
433	}
434	if (!found_readable_mem)
435		pr_err("No readable memory around address 0x%lx\n",
436		       (unsigned long)address);
437}
438
439void trace_unhandled_signal(const char *type, struct pt_regs *regs,
440			    unsigned long address, int sig)
441{
442	struct task_struct *tsk = current;
443
444	if (show_unhandled_signals == 0)
445		return;
446
447	/* If the signal is handled, don't show it here. */
448	if (!is_global_init(tsk)) {
449		void __user *handler =
450			tsk->sighand->action[sig-1].sa.sa_handler;
451		if (handler != SIG_IGN && handler != SIG_DFL)
452			return;
453	}
454
455	/* Rate-limit the one-line output, not the detailed output. */
456	if (show_unhandled_signals <= 1 && !printk_ratelimit())
457		return;
458
459	printk("%s%s[%d]: %s at %lx pc "REGFMT" signal %d",
460	       task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
461	       tsk->comm, task_pid_nr(tsk), type, address, regs->pc, sig);
462
463	print_vma_addr(KERN_CONT " in ", regs->pc);
464
465	printk(KERN_CONT "\n");
466
467	if (show_unhandled_signals > 1) {
468		switch (sig) {
469		case SIGILL:
470		case SIGFPE:
471		case SIGSEGV:
472		case SIGBUS:
473			pr_err("User crash: signal %d,"
474			       " trap %ld, address 0x%lx\n",
475			       sig, regs->faultnum, address);
476			show_regs(regs);
477			dump_mem((void __user *)address);
478			break;
479		default:
480			pr_err("User crash: signal %d, trap %ld\n",
481			       sig, regs->faultnum);
482			break;
483		}
484	}
485}