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Linux/arch/tile/kernel/signal.c

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  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 
 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 
 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. */
 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 
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  */
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 
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 
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  */
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 
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 
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 
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 

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