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1/*
2 * Signal Handling for ARC
3 *
4 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * vineetg: Jan 2010 (Restarting of timer related syscalls)
11 *
12 * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK)
13 * -do_signal() supports TIF_RESTORE_SIGMASK
14 * -do_signal() no loner needs oldset, required by OLD sys_sigsuspend
15 * -sys_rt_sigsuspend() now comes from generic code, so discard arch implemen
16 * -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed
17 * -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves
18 * the job to do_signal()
19 *
20 * vineetg: July 2009
21 * -Modified Code to support the uClibc provided userland sigreturn stub
22 * to avoid kernel synthesing it on user stack at runtime, costing TLB
23 * probes and Cache line flushes.
24 *
25 * vineetg: July 2009
26 * -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs
27 * in done in block copy rather than one word at a time.
28 * This saves around 2K of code and improves LMBench lat_sig <catch>
29 *
30 * rajeshwarr: Feb 2009
31 * - Support for Realtime Signals
32 *
33 * vineetg: Aug 11th 2008: Bug #94183
34 * -ViXS were still seeing crashes when using insmod to load drivers.
35 * It turned out that the code to change Execute permssions for TLB entries
36 * of user was not guarded for interrupts (mod_tlb_permission)
37 * This was cauing TLB entries to be overwritten on unrelated indexes
38 *
39 * Vineetg: July 15th 2008: Bug #94183
40 * -Exception happens in Delay slot of a JMP, and before user space resumes,
41 * Signal is delivered (Ctrl + C) = >SIGINT.
42 * setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler
43 * to run, but doesn't clear the Delay slot bit from status32. As a result,
44 * on resuming user mode, signal handler branches off to BTA of orig JMP
45 * -FIX: clear the DE bit from status32 in setup_frame( )
46 *
47 * Rahul Trivedi, Kanika Nema: Codito Technologies 2004
48 */
49
50#include <linux/signal.h>
51#include <linux/ptrace.h>
52#include <linux/personality.h>
53#include <linux/uaccess.h>
54#include <linux/syscalls.h>
55#include <linux/tracehook.h>
56#include <asm/ucontext.h>
57
58struct rt_sigframe {
59 struct siginfo info;
60 struct ucontext uc;
61#define MAGIC_SIGALTSTK 0x07302004
62 unsigned int sigret_magic;
63};
64
65static int
66stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs,
67 sigset_t *set)
68{
69 int err;
70 err = __copy_to_user(&(sf->uc.uc_mcontext.regs), regs,
71 sizeof(sf->uc.uc_mcontext.regs.scratch));
72 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t));
73
74 return err;
75}
76
77static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf)
78{
79 sigset_t set;
80 int err;
81
82 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
83 if (!err)
84 set_current_blocked(&set);
85
86 err |= __copy_from_user(regs, &(sf->uc.uc_mcontext.regs),
87 sizeof(sf->uc.uc_mcontext.regs.scratch));
88
89 return err;
90}
91
92static inline int is_do_ss_needed(unsigned int magic)
93{
94 if (MAGIC_SIGALTSTK == magic)
95 return 1;
96 else
97 return 0;
98}
99
100SYSCALL_DEFINE0(rt_sigreturn)
101{
102 struct rt_sigframe __user *sf;
103 unsigned int magic;
104 struct pt_regs *regs = current_pt_regs();
105
106 /* Always make any pending restarted system calls return -EINTR */
107 current_thread_info()->restart_block.fn = do_no_restart_syscall;
108
109 /* Since we stacked the signal on a word boundary,
110 * then 'sp' should be word aligned here. If it's
111 * not, then the user is trying to mess with us.
112 */
113 if (regs->sp & 3)
114 goto badframe;
115
116 sf = (struct rt_sigframe __force __user *)(regs->sp);
117
118 if (!access_ok(VERIFY_READ, sf, sizeof(*sf)))
119 goto badframe;
120
121 if (__get_user(magic, &sf->sigret_magic))
122 goto badframe;
123
124 if (unlikely(is_do_ss_needed(magic)))
125 if (restore_altstack(&sf->uc.uc_stack))
126 goto badframe;
127
128 if (restore_usr_regs(regs, sf))
129 goto badframe;
130
131 /* Don't restart from sigreturn */
132 syscall_wont_restart(regs);
133
134 return regs->r0;
135
136badframe:
137 force_sig(SIGSEGV, current);
138 return 0;
139}
140
141/*
142 * Determine which stack to use..
143 */
144static inline void __user *get_sigframe(struct k_sigaction *ka,
145 struct pt_regs *regs,
146 unsigned long framesize)
147{
148 unsigned long sp = regs->sp;
149 void __user *frame;
150
151 /* This is the X/Open sanctioned signal stack switching */
152 if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
153 sp = current->sas_ss_sp + current->sas_ss_size;
154
155 /* No matter what happens, 'sp' must be word
156 * aligned otherwise nasty things could happen
157 */
158
159 /* ATPCS B01 mandates 8-byte alignment */
160 frame = (void __user *)((sp - framesize) & ~7);
161
162 /* Check that we can actually write to the signal frame */
163 if (!access_ok(VERIFY_WRITE, frame, framesize))
164 frame = NULL;
165
166 return frame;
167}
168
169/*
170 * translate the signal
171 */
172static inline int map_sig(int sig)
173{
174 struct thread_info *thread = current_thread_info();
175 if (thread->exec_domain && thread->exec_domain->signal_invmap
176 && sig < 32)
177 sig = thread->exec_domain->signal_invmap[sig];
178 return sig;
179}
180
181static int
182setup_rt_frame(int signo, struct k_sigaction *ka, siginfo_t *info,
183 sigset_t *set, struct pt_regs *regs)
184{
185 struct rt_sigframe __user *sf;
186 unsigned int magic = 0;
187 int err = 0;
188
189 sf = get_sigframe(ka, regs, sizeof(struct rt_sigframe));
190 if (!sf)
191 return 1;
192
193 /*
194 * w/o SA_SIGINFO, struct ucontext is partially populated (only
195 * uc_mcontext/uc_sigmask) for kernel's normal user state preservation
196 * during signal handler execution. This works for SA_SIGINFO as well
197 * although the semantics are now overloaded (the same reg state can be
198 * inspected by userland: but are they allowed to fiddle with it ?
199 */
200 err |= stash_usr_regs(sf, regs, set);
201
202 /*
203 * SA_SIGINFO requires 3 args to signal handler:
204 * #1: sig-no (common to any handler)
205 * #2: struct siginfo
206 * #3: struct ucontext (completely populated)
207 */
208 if (unlikely(ka->sa.sa_flags & SA_SIGINFO)) {
209 err |= copy_siginfo_to_user(&sf->info, info);
210 err |= __put_user(0, &sf->uc.uc_flags);
211 err |= __put_user(NULL, &sf->uc.uc_link);
212 err |= __save_altstack(&sf->uc.uc_stack, regs->sp);
213
214 /* setup args 2 and 3 for user mode handler */
215 regs->r1 = (unsigned long)&sf->info;
216 regs->r2 = (unsigned long)&sf->uc;
217
218 /*
219 * small optim to avoid unconditonally calling do_sigaltstack
220 * in sigreturn path, now that we only have rt_sigreturn
221 */
222 magic = MAGIC_SIGALTSTK;
223 }
224
225 err |= __put_user(magic, &sf->sigret_magic);
226 if (err)
227 return err;
228
229 /* #1 arg to the user Signal handler */
230 regs->r0 = map_sig(signo);
231
232 /* setup PC of user space signal handler */
233 regs->ret = (unsigned long)ka->sa.sa_handler;
234
235 /*
236 * handler returns using sigreturn stub provided already by userpsace
237 */
238 BUG_ON(!(ka->sa.sa_flags & SA_RESTORER));
239 regs->blink = (unsigned long)ka->sa.sa_restorer;
240
241 /* User Stack for signal handler will be above the frame just carved */
242 regs->sp = (unsigned long)sf;
243
244 /*
245 * Bug 94183, Clear the DE bit, so that when signal handler
246 * starts to run, it doesn't use BTA
247 */
248 regs->status32 &= ~STATUS_DE_MASK;
249 regs->status32 |= STATUS_L_MASK;
250
251 return err;
252}
253
254static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs)
255{
256 switch (regs->r0) {
257 case -ERESTART_RESTARTBLOCK:
258 case -ERESTARTNOHAND:
259 /*
260 * ERESTARTNOHAND means that the syscall should
261 * only be restarted if there was no handler for
262 * the signal, and since we only get here if there
263 * is a handler, we don't restart
264 */
265 regs->r0 = -EINTR; /* ERESTART_xxx is internal */
266 break;
267
268 case -ERESTARTSYS:
269 /*
270 * ERESTARTSYS means to restart the syscall if
271 * there is no handler or the handler was
272 * registered with SA_RESTART
273 */
274 if (!(ka->sa.sa_flags & SA_RESTART)) {
275 regs->r0 = -EINTR;
276 break;
277 }
278 /* fallthrough */
279
280 case -ERESTARTNOINTR:
281 /*
282 * ERESTARTNOINTR means that the syscall should
283 * be called again after the signal handler returns.
284 * Setup reg state just as it was before doing the trap
285 * r0 has been clobbered with sys call ret code thus it
286 * needs to be reloaded with orig first arg to syscall
287 * in orig_r0. Rest of relevant reg-file:
288 * r8 (syscall num) and (r1 - r7) will be reset to
289 * their orig user space value when we ret from kernel
290 */
291 regs->r0 = regs->orig_r0;
292 regs->ret -= 4;
293 break;
294 }
295}
296
297/*
298 * OK, we're invoking a handler
299 */
300static void
301handle_signal(unsigned long sig, struct k_sigaction *ka, siginfo_t *info,
302 struct pt_regs *regs)
303{
304 sigset_t *oldset = sigmask_to_save();
305 int ret;
306
307 /* Set up the stack frame */
308 ret = setup_rt_frame(sig, ka, info, oldset, regs);
309
310 if (ret)
311 force_sigsegv(sig, current);
312 else
313 signal_delivered(sig, info, ka, regs, 0);
314}
315
316void do_signal(struct pt_regs *regs)
317{
318 struct k_sigaction ka;
319 siginfo_t info;
320 int signr;
321 int restart_scall;
322
323 signr = get_signal_to_deliver(&info, &ka, regs, NULL);
324
325 restart_scall = in_syscall(regs) && syscall_restartable(regs);
326
327 if (signr > 0) {
328 if (restart_scall) {
329 arc_restart_syscall(&ka, regs);
330 syscall_wont_restart(regs); /* No more restarts */
331 }
332 handle_signal(signr, &ka, &info, regs);
333 return;
334 }
335
336 if (restart_scall) {
337 /* No handler for syscall: restart it */
338 if (regs->r0 == -ERESTARTNOHAND ||
339 regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) {
340 regs->r0 = regs->orig_r0;
341 regs->ret -= 4;
342 } else if (regs->r0 == -ERESTART_RESTARTBLOCK) {
343 regs->r8 = __NR_restart_syscall;
344 regs->ret -= 4;
345 }
346 syscall_wont_restart(regs); /* No more restarts */
347 }
348
349 /* If there's no signal to deliver, restore the saved sigmask back */
350 restore_saved_sigmask();
351}
352
353void do_notify_resume(struct pt_regs *regs)
354{
355 /*
356 * ASM glue gaurantees that this is only called when returning to
357 * user mode
358 */
359 if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
360 tracehook_notify_resume(regs);
361}