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
restore_sigcontext(struct pt_regs * regs,struct sigcontext __user * sc)45 int restore_sigcontext(struct pt_regs *regs,
46 struct sigcontext __user *sc)
47 {
48 int err = 0;
49 int i;
50
51 /* Always make any pending restarted system calls return -EINTR */
52 current->restart_block.fn = do_no_restart_syscall;
53
54 /*
55 * Enforce that sigcontext is like pt_regs, and doesn't mess
56 * up our stack alignment rules.
57 */
58 BUILD_BUG_ON(sizeof(struct sigcontext) != sizeof(struct pt_regs));
59 BUILD_BUG_ON(sizeof(struct sigcontext) % 8 != 0);
60
61 for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
62 err |= __get_user(regs->regs[i], &sc->gregs[i]);
63
64 /* Ensure that the PL is always set to USER_PL. */
65 regs->ex1 = PL_ICS_EX1(USER_PL, EX1_ICS(regs->ex1));
66
67 regs->faultnum = INT_SWINT_1_SIGRETURN;
68
69 return err;
70 }
71
signal_fault(const char * type,struct pt_regs * regs,void __user * frame,int sig)72 void signal_fault(const char *type, struct pt_regs *regs,
73 void __user *frame, int sig)
74 {
75 trace_unhandled_signal(type, regs, (unsigned long)frame, SIGSEGV);
76 force_sigsegv(sig, current);
77 }
78
79 /* The assembly shim for this function arranges to ignore the return value. */
SYSCALL_DEFINE0(rt_sigreturn)80 SYSCALL_DEFINE0(rt_sigreturn)
81 {
82 struct pt_regs *regs = current_pt_regs();
83 struct rt_sigframe __user *frame =
84 (struct rt_sigframe __user *)(regs->sp);
85 sigset_t set;
86
87 if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
88 goto badframe;
89 if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
90 goto badframe;
91
92 set_current_blocked(&set);
93
94 if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
95 goto badframe;
96
97 if (restore_altstack(&frame->uc.uc_stack))
98 goto badframe;
99
100 return 0;
101
102 badframe:
103 signal_fault("bad sigreturn frame", regs, frame, 0);
104 return 0;
105 }
106
107 /*
108 * Set up a signal frame.
109 */
110
setup_sigcontext(struct sigcontext __user * sc,struct pt_regs * regs)111 int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
112 {
113 int i, err = 0;
114
115 for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
116 err |= __put_user(regs->regs[i], &sc->gregs[i]);
117
118 return err;
119 }
120
121 /*
122 * Determine which stack to use..
123 */
get_sigframe(struct k_sigaction * ka,struct pt_regs * regs,size_t frame_size)124 static inline void __user *get_sigframe(struct k_sigaction *ka,
125 struct pt_regs *regs,
126 size_t frame_size)
127 {
128 unsigned long sp;
129
130 /* Default to using normal stack */
131 sp = regs->sp;
132
133 /*
134 * If we are on the alternate signal stack and would overflow
135 * it, don't. Return an always-bogus address instead so we
136 * will die with SIGSEGV.
137 */
138 if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
139 return (void __user __force *)-1UL;
140
141 /* This is the X/Open sanctioned signal stack switching. */
142 if (ka->sa.sa_flags & SA_ONSTACK) {
143 if (sas_ss_flags(sp) == 0)
144 sp = current->sas_ss_sp + current->sas_ss_size;
145 }
146
147 sp -= frame_size;
148 /*
149 * Align the stack pointer according to the TILE ABI,
150 * i.e. so that on function entry (sp & 15) == 0.
151 */
152 sp &= -16UL;
153 return (void __user *) sp;
154 }
155
setup_rt_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)156 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
157 struct pt_regs *regs)
158 {
159 unsigned long restorer;
160 struct rt_sigframe __user *frame;
161 int err = 0, sig = ksig->sig;
162 int usig;
163
164 frame = get_sigframe(&ksig->ka, regs, sizeof(*frame));
165
166 if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
167 goto err;
168
169 usig = current_thread_info()->exec_domain
170 && current_thread_info()->exec_domain->signal_invmap
171 && sig < 32
172 ? current_thread_info()->exec_domain->signal_invmap[sig]
173 : sig;
174
175 /* Always write at least the signal number for the stack backtracer. */
176 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
177 /* At sigreturn time, restore the callee-save registers too. */
178 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
179 regs->flags |= PT_FLAGS_RESTORE_REGS;
180 } else {
181 err |= __put_user(ksig->info.si_signo, &frame->info.si_signo);
182 }
183
184 /* Create the ucontext. */
185 err |= __clear_user(&frame->save_area, sizeof(frame->save_area));
186 err |= __put_user(0, &frame->uc.uc_flags);
187 err |= __put_user(NULL, &frame->uc.uc_link);
188 err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
189 err |= setup_sigcontext(&frame->uc.uc_mcontext, regs);
190 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
191 if (err)
192 goto err;
193
194 restorer = VDSO_SYM(&__vdso_rt_sigreturn);
195 if (ksig->ka.sa.sa_flags & SA_RESTORER)
196 restorer = (unsigned long) ksig->ka.sa.sa_restorer;
197
198 /*
199 * Set up registers for signal handler.
200 * Registers that we don't modify keep the value they had from
201 * user-space at the time we took the signal.
202 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
203 * since some things rely on this (e.g. glibc's debug/segfault.c).
204 */
205 regs->pc = (unsigned long) ksig->ka.sa.sa_handler;
206 regs->ex1 = PL_ICS_EX1(USER_PL, 1); /* set crit sec in handler */
207 regs->sp = (unsigned long) frame;
208 regs->lr = restorer;
209 regs->regs[0] = (unsigned long) usig;
210 regs->regs[1] = (unsigned long) &frame->info;
211 regs->regs[2] = (unsigned long) &frame->uc;
212 regs->flags |= PT_FLAGS_CALLER_SAVES;
213 return 0;
214
215 err:
216 trace_unhandled_signal("bad sigreturn frame", regs,
217 (unsigned long)frame, SIGSEGV);
218 return -EFAULT;
219 }
220
221 /*
222 * OK, we're invoking a handler
223 */
224
handle_signal(struct ksignal * ksig,struct pt_regs * regs)225 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
226 {
227 sigset_t *oldset = sigmask_to_save();
228 int ret;
229
230 /* Are we from a system call? */
231 if (regs->faultnum == INT_SWINT_1) {
232 /* If so, check system call restarting.. */
233 switch (regs->regs[0]) {
234 case -ERESTART_RESTARTBLOCK:
235 case -ERESTARTNOHAND:
236 regs->regs[0] = -EINTR;
237 break;
238
239 case -ERESTARTSYS:
240 if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
241 regs->regs[0] = -EINTR;
242 break;
243 }
244 /* fallthrough */
245 case -ERESTARTNOINTR:
246 /* Reload caller-saves to restore r0..r5 and r10. */
247 regs->flags |= PT_FLAGS_CALLER_SAVES;
248 regs->regs[0] = regs->orig_r0;
249 regs->pc -= 8;
250 }
251 }
252
253 /* Set up the stack frame */
254 #ifdef CONFIG_COMPAT
255 if (is_compat_task())
256 ret = compat_setup_rt_frame(ksig, oldset, regs);
257 else
258 #endif
259 ret = setup_rt_frame(ksig, oldset, regs);
260
261 signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
262 }
263
264 /*
265 * Note that 'init' is a special process: it doesn't get signals it doesn't
266 * want to handle. Thus you cannot kill init even with a SIGKILL even by
267 * mistake.
268 */
do_signal(struct pt_regs * regs)269 void do_signal(struct pt_regs *regs)
270 {
271 struct ksignal ksig;
272
273 /*
274 * i386 will check if we're coming from kernel mode and bail out
275 * here. In my experience this just turns weird crashes into
276 * weird spin-hangs. But if we find a case where this seems
277 * helpful, we can reinstate the check on "!user_mode(regs)".
278 */
279
280 if (get_signal(&ksig)) {
281 /* Whee! Actually deliver the signal. */
282 handle_signal(&ksig, regs);
283 goto done;
284 }
285
286 /* Did we come from a system call? */
287 if (regs->faultnum == INT_SWINT_1) {
288 /* Restart the system call - no handlers present */
289 switch (regs->regs[0]) {
290 case -ERESTARTNOHAND:
291 case -ERESTARTSYS:
292 case -ERESTARTNOINTR:
293 regs->flags |= PT_FLAGS_CALLER_SAVES;
294 regs->regs[0] = regs->orig_r0;
295 regs->pc -= 8;
296 break;
297
298 case -ERESTART_RESTARTBLOCK:
299 regs->flags |= PT_FLAGS_CALLER_SAVES;
300 regs->regs[TREG_SYSCALL_NR] = __NR_restart_syscall;
301 regs->pc -= 8;
302 break;
303 }
304 }
305
306 /* If there's no signal to deliver, just put the saved sigmask back. */
307 restore_saved_sigmask();
308
309 done:
310 /* Avoid double syscall restart if there are nested signals. */
311 regs->faultnum = INT_SWINT_1_SIGRETURN;
312 }
313
314 int show_unhandled_signals = 1;
315
crashinfo(char * str)316 static int __init crashinfo(char *str)
317 {
318 const char *word;
319
320 if (*str == '\0')
321 show_unhandled_signals = 2;
322 else if (*str != '=' || kstrtoint(++str, 0, &show_unhandled_signals) != 0)
323 return 0;
324
325 switch (show_unhandled_signals) {
326 case 0:
327 word = "No";
328 break;
329 case 1:
330 word = "One-line";
331 break;
332 default:
333 word = "Detailed";
334 break;
335 }
336 pr_info("%s crash reports will be generated on the console\n", word);
337 return 1;
338 }
339 __setup("crashinfo", crashinfo);
340
dump_mem(void __user * address)341 static void dump_mem(void __user *address)
342 {
343 void __user *addr;
344 enum { region_size = 256, bytes_per_line = 16 };
345 int i, j, k;
346 int found_readable_mem = 0;
347
348 pr_err("\n");
349 if (!access_ok(VERIFY_READ, address, 1)) {
350 pr_err("Not dumping at address 0x%lx (kernel address)\n",
351 (unsigned long)address);
352 return;
353 }
354
355 addr = (void __user *)
356 (((unsigned long)address & -bytes_per_line) - region_size/2);
357 if (addr > address)
358 addr = NULL;
359 for (i = 0; i < region_size;
360 addr += bytes_per_line, i += bytes_per_line) {
361 unsigned char buf[bytes_per_line];
362 char line[100];
363 if (copy_from_user(buf, addr, bytes_per_line))
364 continue;
365 if (!found_readable_mem) {
366 pr_err("Dumping memory around address 0x%lx:\n",
367 (unsigned long)address);
368 found_readable_mem = 1;
369 }
370 j = sprintf(line, REGFMT":", (unsigned long)addr);
371 for (k = 0; k < bytes_per_line; ++k)
372 j += sprintf(&line[j], " %02x", buf[k]);
373 pr_err("%s\n", line);
374 }
375 if (!found_readable_mem)
376 pr_err("No readable memory around address 0x%lx\n",
377 (unsigned long)address);
378 }
379
trace_unhandled_signal(const char * type,struct pt_regs * regs,unsigned long address,int sig)380 void trace_unhandled_signal(const char *type, struct pt_regs *regs,
381 unsigned long address, int sig)
382 {
383 struct task_struct *tsk = current;
384
385 if (show_unhandled_signals == 0)
386 return;
387
388 /* If the signal is handled, don't show it here. */
389 if (!is_global_init(tsk)) {
390 void __user *handler =
391 tsk->sighand->action[sig-1].sa.sa_handler;
392 if (handler != SIG_IGN && handler != SIG_DFL)
393 return;
394 }
395
396 /* Rate-limit the one-line output, not the detailed output. */
397 if (show_unhandled_signals <= 1 && !printk_ratelimit())
398 return;
399
400 printk("%s%s[%d]: %s at %lx pc "REGFMT" signal %d",
401 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
402 tsk->comm, task_pid_nr(tsk), type, address, regs->pc, sig);
403
404 print_vma_addr(KERN_CONT " in ", regs->pc);
405
406 printk(KERN_CONT "\n");
407
408 if (show_unhandled_signals > 1) {
409 switch (sig) {
410 case SIGILL:
411 case SIGFPE:
412 case SIGSEGV:
413 case SIGBUS:
414 pr_err("User crash: signal %d,"
415 " trap %ld, address 0x%lx\n",
416 sig, regs->faultnum, address);
417 show_regs(regs);
418 dump_mem((void __user *)address);
419 break;
420 default:
421 pr_err("User crash: signal %d, trap %ld\n",
422 sig, regs->faultnum);
423 break;
424 }
425 }
426 }
427