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;
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
signal_fault(const char * type,struct pt_regs * regs,void __user * frame,int sig)69 void 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. */
SYSCALL_DEFINE0(rt_sigreturn)77 SYSCALL_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
99 badframe:
100 signal_fault("bad sigreturn frame", regs, frame, 0);
101 return 0;
102 }
103
104 /*
105 * Set up a signal frame.
106 */
107
setup_sigcontext(struct sigcontext __user * sc,struct pt_regs * regs)108 int 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 */
get_sigframe(struct k_sigaction * ka,struct pt_regs * regs,size_t frame_size)116 static 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
setup_rt_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)148 static 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
200 err:
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
handle_signal(struct ksignal * ksig,struct pt_regs * regs)210 static 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 */
do_signal(struct pt_regs * regs)254 void 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
294 done:
295 /* Avoid double syscall restart if there are nested signals. */
296 regs->faultnum = INT_SWINT_1_SIGRETURN;
297 }
298
299 int show_unhandled_signals = 1;
300
crashinfo(char * str)301 static 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
dump_mem(void __user * address)326 static 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
trace_unhandled_signal(const char * type,struct pt_regs * regs,unsigned long address,int sig)364 void 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