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Linux/arch/openrisc/kernel/signal.c

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  1 /*
  2  * OpenRISC signal.c
  3  *
  4  * Linux architectural port borrowing liberally from similar works of
  5  * others.  All original copyrights apply as per the original source
  6  * declaration.
  7  *
  8  * Modifications for the OpenRISC architecture:
  9  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
 10  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
 11  *
 12  *      This program is free software; you can redistribute it and/or
 13  *      modify it under the terms of the GNU General Public License
 14  *      as published by the Free Software Foundation; either version
 15  *      2 of the License, or (at your option) any later version.
 16  */
 17 
 18 #include <linux/sched.h>
 19 #include <linux/mm.h>
 20 #include <linux/smp.h>
 21 #include <linux/kernel.h>
 22 #include <linux/signal.h>
 23 #include <linux/errno.h>
 24 #include <linux/wait.h>
 25 #include <linux/ptrace.h>
 26 #include <linux/unistd.h>
 27 #include <linux/stddef.h>
 28 #include <linux/tracehook.h>
 29 
 30 #include <asm/processor.h>
 31 #include <asm/syscall.h>
 32 #include <asm/ucontext.h>
 33 #include <asm/uaccess.h>
 34 
 35 #define DEBUG_SIG 0
 36 
 37 struct rt_sigframe {
 38         struct siginfo info;
 39         struct ucontext uc;
 40         unsigned char retcode[16];      /* trampoline code */
 41 };
 42 
 43 static int restore_sigcontext(struct pt_regs *regs,
 44                               struct sigcontext __user *sc)
 45 {
 46         int err = 0;
 47 
 48         /* Always make any pending restarted system calls return -EINTR */
 49         current->restart_block.fn = do_no_restart_syscall;
 50 
 51         /*
 52          * Restore the regs from &sc->regs.
 53          * (sc is already checked for VERIFY_READ since the sigframe was
 54          *  checked in sys_sigreturn previously)
 55          */
 56         err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long));
 57         err |= __copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long));
 58         err |= __copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long));
 59 
 60         /* make sure the SM-bit is cleared so user-mode cannot fool us */
 61         regs->sr &= ~SPR_SR_SM;
 62 
 63         regs->orig_gpr11 = -1;  /* Avoid syscall restart checks */
 64 
 65         /* TODO: the other ports use regs->orig_XX to disable syscall checks
 66          * after this completes, but we don't use that mechanism. maybe we can
 67          * use it now ?
 68          */
 69 
 70         return err;
 71 }
 72 
 73 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
 74 {
 75         struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
 76         sigset_t set;
 77 
 78         /*
 79          * Since we stacked the signal on a dword boundary,
 80          * then frame should be dword aligned here.  If it's
 81          * not, then the user is trying to mess with us.
 82          */
 83         if (((long)frame) & 3)
 84                 goto badframe;
 85 
 86         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 87                 goto badframe;
 88         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 89                 goto badframe;
 90 
 91         set_current_blocked(&set);
 92 
 93         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 94                 goto badframe;
 95 
 96         if (restore_altstack(&frame->uc.uc_stack))
 97                 goto badframe;
 98 
 99         return regs->gpr[11];
100 
101 badframe:
102         force_sig(SIGSEGV, current);
103         return 0;
104 }
105 
106 /*
107  * Set up a signal frame.
108  */
109 
110 static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
111 {
112         int err = 0;
113 
114         /* copy the regs */
115         /* There should be no need to save callee-saved registers here...
116          * ...but we save them anyway.  Revisit this
117          */
118         err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
119         err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
120         err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
121 
122         return err;
123 }
124 
125 static inline unsigned long align_sigframe(unsigned long sp)
126 {
127         return sp & ~3UL;
128 }
129 
130 /*
131  * Work out where the signal frame should go.  It's either on the user stack
132  * or the alternate stack.
133  */
134 
135 static inline void __user *get_sigframe(struct ksignal *ksig,
136                                         struct pt_regs *regs, size_t frame_size)
137 {
138         unsigned long sp = regs->sp;
139 
140         /* redzone */
141         sp -= STACK_FRAME_OVERHEAD;
142         sp = sigsp(sp, ksig);
143         sp = align_sigframe(sp - frame_size);
144 
145         return (void __user *)sp;
146 }
147 
148 /* grab and setup a signal frame.
149  *
150  * basically we stack a lot of state info, and arrange for the
151  * user-mode program to return to the kernel using either a
152  * trampoline which performs the syscall sigreturn, or a provided
153  * user-mode trampoline.
154  */
155 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
156                           struct pt_regs *regs)
157 {
158         struct rt_sigframe *frame;
159         unsigned long return_ip;
160         int err = 0;
161 
162         frame = get_sigframe(ksig, regs, sizeof(*frame));
163 
164         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
165                 return -EFAULT;
166 
167         /* Create siginfo.  */
168         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
169                 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
170 
171         /* Create the ucontext.  */
172         err |= __put_user(0, &frame->uc.uc_flags);
173         err |= __put_user(NULL, &frame->uc.uc_link);
174         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
175         err |= setup_sigcontext(regs, &frame->uc.uc_mcontext);
176 
177         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
178 
179         if (err)
180                 return -EFAULT;
181 
182         /* trampoline - the desired return ip is the retcode itself */
183         return_ip = (unsigned long)&frame->retcode;
184         /* This is:
185                 l.ori r11,r0,__NR_sigreturn
186                 l.sys 1
187          */
188         err |= __put_user(0xa960,             (short *)(frame->retcode + 0));
189         err |= __put_user(__NR_rt_sigreturn,  (short *)(frame->retcode + 2));
190         err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
191         err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));
192 
193         if (err)
194                 return -EFAULT;
195 
196         /* TODO what is the current->exec_domain stuff and invmap ? */
197 
198         /* Set up registers for signal handler */
199         regs->pc = (unsigned long)ksig->ka.sa.sa_handler; /* what we enter NOW */
200         regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
201         regs->gpr[3] = (unsigned long)ksig->sig;           /* arg 1: signo */
202         regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
203         regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
204 
205         /* actually move the usp to reflect the stacked frame */
206         regs->sp = (unsigned long)frame;
207 
208         return 0;
209 }
210 
211 static inline void
212 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
213 {
214         int ret;
215 
216         ret = setup_rt_frame(ksig, sigmask_to_save(), regs);
217 
218         signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
219 }
220 
221 /*
222  * Note that 'init' is a special process: it doesn't get signals it doesn't
223  * want to handle. Thus you cannot kill init even with a SIGKILL even by
224  * mistake.
225  *
226  * Also note that the regs structure given here as an argument, is the latest
227  * pushed pt_regs. It may or may not be the same as the first pushed registers
228  * when the initial usermode->kernelmode transition took place. Therefore
229  * we can use user_mode(regs) to see if we came directly from kernel or user
230  * mode below.
231  */
232 
233 int do_signal(struct pt_regs *regs, int syscall)
234 {
235         struct ksignal ksig;
236         unsigned long continue_addr = 0;
237         unsigned long restart_addr = 0;
238         unsigned long retval = 0;
239         int restart = 0;
240 
241         if (syscall) {
242                 continue_addr = regs->pc;
243                 restart_addr = continue_addr - 4;
244                 retval = regs->gpr[11];
245 
246                 /*
247                  * Setup syscall restart here so that a debugger will
248                  * see the already changed PC.
249                  */
250                 switch (retval) {
251                 case -ERESTART_RESTARTBLOCK:
252                         restart = -2;
253                         /* Fall through */
254                 case -ERESTARTNOHAND:
255                 case -ERESTARTSYS:
256                 case -ERESTARTNOINTR:
257                         restart++;
258                         regs->gpr[11] = regs->orig_gpr11;
259                         regs->pc = restart_addr;
260                         break;
261                 }
262         }
263 
264         /*
265          * Get the signal to deliver.  During the call to get_signal the
266          * debugger may change all our registers so we may need to revert
267          * the decision to restart the syscall; specifically, if the PC is
268          * changed, don't restart the syscall.
269          */
270         if (get_signal(&ksig)) {
271                 if (unlikely(restart) && regs->pc == restart_addr) {
272                         if (retval == -ERESTARTNOHAND ||
273                             retval == -ERESTART_RESTARTBLOCK
274                             || (retval == -ERESTARTSYS
275                                 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
276                                 /* No automatic restart */
277                                 regs->gpr[11] = -EINTR;
278                                 regs->pc = continue_addr;
279                         }
280                 }
281                 handle_signal(&ksig, regs);
282         } else {
283                 /* no handler */
284                 restore_saved_sigmask();
285                 /*
286                  * Restore pt_regs PC as syscall restart will be handled by
287                  * kernel without return to userspace
288                  */
289                 if (unlikely(restart) && regs->pc == restart_addr) {
290                         regs->pc = continue_addr;
291                         return restart;
292                 }
293         }
294 
295         return 0;
296 }
297 
298 asmlinkage int
299 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
300 {
301         do {
302                 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
303                         schedule();
304                 } else {
305                         if (unlikely(!user_mode(regs)))
306                                 return 0;
307                         local_irq_enable();
308                         if (thread_flags & _TIF_SIGPENDING) {
309                                 int restart = do_signal(regs, syscall);
310                                 if (unlikely(restart)) {
311                                         /*
312                                          * Restart without handlers.
313                                          * Deal with it without leaving
314                                          * the kernel space.
315                                          */
316                                         return restart;
317                                 }
318                                 syscall = 0;
319                         } else {
320                                 clear_thread_flag(TIF_NOTIFY_RESUME);
321                                 tracehook_notify_resume(regs);
322                         }
323                 }
324                 local_irq_disable();
325                 thread_flags = current_thread_info()->flags;
326         } while (thread_flags & _TIF_WORK_MASK);
327         return 0;
328 }
329 

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