1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Signal Handling for ARC
4 *
5 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
6 *
7 * vineetg: Jan 2010 (Restarting of timer related syscalls)
8 *
9 * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK)
10 * -do_signal() supports TIF_RESTORE_SIGMASK
11 * -do_signal() no longer needs oldset, required by OLD sys_sigsuspend
12 * -sys_rt_sigsuspend() now comes from generic code, so discard arch
13 * implementation
14 * -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed
15 * -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves
16 * the job to do_signal()
17 *
18 * vineetg: July 2009
19 * -Modified Code to support the uClibc provided userland sigreturn stub
20 * to avoid kernel synthesizing it on user stack at runtime, costing TLB
21 * probes and Cache line flushes.
22 *
23 * vineetg: July 2009
24 * -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs
25 * in done in block copy rather than one word at a time.
26 * This saves around 2K of code and improves LMBench lat_sig <catch>
27 *
28 * rajeshwarr: Feb 2009
29 * - Support for Realtime Signals
30 *
31 * vineetg: Aug 11th 2008: Bug #94183
32 * -ViXS were still seeing crashes when using insmod to load drivers.
33 * It turned out that the code to change Execute permssions for TLB entries
34 * of user was not guarded for interrupts (mod_tlb_permission)
35 * This was causing TLB entries to be overwritten on unrelated indexes
36 *
37 * Vineetg: July 15th 2008: Bug #94183
38 * -Exception happens in Delay slot of a JMP, and before user space resumes,
39 * Signal is delivered (Ctrl + C) = >SIGINT.
40 * setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler
41 * to run, but doesn't clear the Delay slot bit from status32. As a result,
42 * on resuming user mode, signal handler branches off to BTA of orig JMP
43 * -FIX: clear the DE bit from status32 in setup_frame( )
44 *
45 * Rahul Trivedi, Kanika Nema: Codito Technologies 2004
46 */
47
48 #include <linux/signal.h>
49 #include <linux/ptrace.h>
50 #include <linux/personality.h>
51 #include <linux/uaccess.h>
52 #include <linux/syscalls.h>
53 #include <linux/resume_user_mode.h>
54 #include <linux/sched/task_stack.h>
55
56 #include <asm/ucontext.h>
57 #include <asm/entry.h>
58
59 struct rt_sigframe {
60 struct siginfo info;
61 struct ucontext uc;
62 #define MAGIC_SIGALTSTK 0x07302004
63 unsigned int sigret_magic;
64 };
65
66 static int save_arcv2_regs(struct sigcontext __user *mctx, struct pt_regs *regs)
67 {
68 int err = 0;
69 #ifndef CONFIG_ISA_ARCOMPACT
70 struct user_regs_arcv2 v2abi;
71
72 v2abi.r30 = regs->r30;
73 #ifdef CONFIG_ARC_HAS_ACCL_REGS
74 v2abi.r58 = regs->r58;
75 v2abi.r59 = regs->r59;
76 #else
77 v2abi.r58 = v2abi.r59 = 0;
78 #endif
79 err = __copy_to_user(&mctx->v2abi, (void const *)&v2abi, sizeof(v2abi));
80 #endif
81 return err;
82 }
83
84 static int restore_arcv2_regs(struct sigcontext __user *mctx, struct pt_regs *regs)
85 {
86 int err = 0;
87 #ifndef CONFIG_ISA_ARCOMPACT
88 struct user_regs_arcv2 v2abi;
89
90 err = __copy_from_user(&v2abi, &mctx->v2abi, sizeof(v2abi));
91
92 regs->r30 = v2abi.r30;
93 #ifdef CONFIG_ARC_HAS_ACCL_REGS
94 regs->r58 = v2abi.r58;
95 regs->r59 = v2abi.r59;
96 #endif
97 #endif
98 return err;
99 }
100
101 static int
102 stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs,
103 sigset_t *set)
104 {
105 int err;
106 struct user_regs_struct uregs;
107
108 uregs.scratch.bta = regs->bta;
109 uregs.scratch.lp_start = regs->lp_start;
110 uregs.scratch.lp_end = regs->lp_end;
111 uregs.scratch.lp_count = regs->lp_count;
112 uregs.scratch.status32 = regs->status32;
113 uregs.scratch.ret = regs->ret;
114 uregs.scratch.blink = regs->blink;
115 uregs.scratch.fp = regs->fp;
116 uregs.scratch.gp = regs->r26;
117 uregs.scratch.r12 = regs->r12;
118 uregs.scratch.r11 = regs->r11;
119 uregs.scratch.r10 = regs->r10;
120 uregs.scratch.r9 = regs->r9;
121 uregs.scratch.r8 = regs->r8;
122 uregs.scratch.r7 = regs->r7;
123 uregs.scratch.r6 = regs->r6;
124 uregs.scratch.r5 = regs->r5;
125 uregs.scratch.r4 = regs->r4;
126 uregs.scratch.r3 = regs->r3;
127 uregs.scratch.r2 = regs->r2;
128 uregs.scratch.r1 = regs->r1;
129 uregs.scratch.r0 = regs->r0;
130 uregs.scratch.sp = regs->sp;
131
132 err = __copy_to_user(&(sf->uc.uc_mcontext.regs.scratch), &uregs.scratch,
133 sizeof(sf->uc.uc_mcontext.regs.scratch));
134
135 if (is_isa_arcv2())
136 err |= save_arcv2_regs(&(sf->uc.uc_mcontext), regs);
137
138 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t));
139
140 return err ? -EFAULT : 0;
141 }
142
143 static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf)
144 {
145 sigset_t set;
146 int err;
147 struct user_regs_struct uregs;
148
149 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
150 err |= __copy_from_user(&uregs.scratch,
151 &(sf->uc.uc_mcontext.regs.scratch),
152 sizeof(sf->uc.uc_mcontext.regs.scratch));
153
154 if (is_isa_arcv2())
155 err |= restore_arcv2_regs(&(sf->uc.uc_mcontext), regs);
156
157 if (err)
158 return -EFAULT;
159
160 set_current_blocked(&set);
161 regs->bta = uregs.scratch.bta;
162 regs->lp_start = uregs.scratch.lp_start;
163 regs->lp_end = uregs.scratch.lp_end;
164 regs->lp_count = uregs.scratch.lp_count;
165 regs->status32 = uregs.scratch.status32;
166 regs->ret = uregs.scratch.ret;
167 regs->blink = uregs.scratch.blink;
168 regs->fp = uregs.scratch.fp;
169 regs->r26 = uregs.scratch.gp;
170 regs->r12 = uregs.scratch.r12;
171 regs->r11 = uregs.scratch.r11;
172 regs->r10 = uregs.scratch.r10;
173 regs->r9 = uregs.scratch.r9;
174 regs->r8 = uregs.scratch.r8;
175 regs->r7 = uregs.scratch.r7;
176 regs->r6 = uregs.scratch.r6;
177 regs->r5 = uregs.scratch.r5;
178 regs->r4 = uregs.scratch.r4;
179 regs->r3 = uregs.scratch.r3;
180 regs->r2 = uregs.scratch.r2;
181 regs->r1 = uregs.scratch.r1;
182 regs->r0 = uregs.scratch.r0;
183 regs->sp = uregs.scratch.sp;
184
185 return 0;
186 }
187
188 static inline int is_do_ss_needed(unsigned int magic)
189 {
190 if (MAGIC_SIGALTSTK == magic)
191 return 1;
192 else
193 return 0;
194 }
195
196 SYSCALL_DEFINE0(rt_sigreturn)
197 {
198 struct rt_sigframe __user *sf;
199 unsigned int magic;
200 struct pt_regs *regs = current_pt_regs();
201
202 /* Always make any pending restarted system calls return -EINTR */
203 current->restart_block.fn = do_no_restart_syscall;
204
205 /* Since we stacked the signal on a word boundary,
206 * then 'sp' should be word aligned here. If it's
207 * not, then the user is trying to mess with us.
208 */
209 if (regs->sp & 3)
210 goto badframe;
211
212 sf = (struct rt_sigframe __force __user *)(regs->sp);
213
214 if (!access_ok(sf, sizeof(*sf)))
215 goto badframe;
216
217 if (__get_user(magic, &sf->sigret_magic))
218 goto badframe;
219
220 if (unlikely(is_do_ss_needed(magic)))
221 if (restore_altstack(&sf->uc.uc_stack))
222 goto badframe;
223
224 if (restore_usr_regs(regs, sf))
225 goto badframe;
226
227 /* Don't restart from sigreturn */
228 syscall_wont_restart(regs);
229
230 /*
231 * Ensure that sigreturn always returns to user mode (in case the
232 * regs saved on user stack got fudged between save and sigreturn)
233 * Otherwise it is easy to panic the kernel with a custom
234 * signal handler and/or restorer which clobberes the status32/ret
235 * to return to a bogus location in kernel mode.
236 */
237 regs->status32 |= STATUS_U_MASK;
238
239 return regs->r0;
240
241 badframe:
242 force_sig(SIGSEGV);
243 return 0;
244 }
245
246 /*
247 * Determine which stack to use..
248 */
249 static inline void __user *get_sigframe(struct ksignal *ksig,
250 struct pt_regs *regs,
251 unsigned long framesize)
252 {
253 unsigned long sp = sigsp(regs->sp, ksig);
254 void __user *frame;
255
256 /* No matter what happens, 'sp' must be word
257 * aligned otherwise nasty things could happen
258 */
259
260 /* ATPCS B01 mandates 8-byte alignment */
261 frame = (void __user *)((sp - framesize) & ~7);
262
263 /* Check that we can actually write to the signal frame */
264 if (!access_ok(frame, framesize))
265 frame = NULL;
266
267 return frame;
268 }
269
270 static int
271 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
272 {
273 struct rt_sigframe __user *sf;
274 unsigned int magic = 0;
275 int err = 0;
276
277 sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe));
278 if (!sf)
279 return 1;
280
281 /*
282 * w/o SA_SIGINFO, struct ucontext is partially populated (only
283 * uc_mcontext/uc_sigmask) for kernel's normal user state preservation
284 * during signal handler execution. This works for SA_SIGINFO as well
285 * although the semantics are now overloaded (the same reg state can be
286 * inspected by userland: but are they allowed to fiddle with it ?
287 */
288 err |= stash_usr_regs(sf, regs, set);
289
290 /*
291 * SA_SIGINFO requires 3 args to signal handler:
292 * #1: sig-no (common to any handler)
293 * #2: struct siginfo
294 * #3: struct ucontext (completely populated)
295 */
296 if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) {
297 err |= copy_siginfo_to_user(&sf->info, &ksig->info);
298 err |= __put_user(0, &sf->uc.uc_flags);
299 err |= __put_user(NULL, &sf->uc.uc_link);
300 err |= __save_altstack(&sf->uc.uc_stack, regs->sp);
301
302 /* setup args 2 and 3 for user mode handler */
303 regs->r1 = (unsigned long)&sf->info;
304 regs->r2 = (unsigned long)&sf->uc;
305
306 /*
307 * small optim to avoid unconditionally calling do_sigaltstack
308 * in sigreturn path, now that we only have rt_sigreturn
309 */
310 magic = MAGIC_SIGALTSTK;
311 }
312
313 err |= __put_user(magic, &sf->sigret_magic);
314 if (err)
315 return err;
316
317 /* #1 arg to the user Signal handler */
318 regs->r0 = ksig->sig;
319
320 /* setup PC of user space signal handler */
321 regs->ret = (unsigned long)ksig->ka.sa.sa_handler;
322
323 /*
324 * handler returns using sigreturn stub provided already by userspace
325 * If not, nuke the process right away
326 */
327 if(!(ksig->ka.sa.sa_flags & SA_RESTORER))
328 return 1;
329
330 regs->blink = (unsigned long)ksig->ka.sa.sa_restorer;
331
332 /* User Stack for signal handler will be above the frame just carved */
333 regs->sp = (unsigned long)sf;
334
335 /*
336 * Bug 94183, Clear the DE bit, so that when signal handler
337 * starts to run, it doesn't use BTA
338 */
339 regs->status32 &= ~STATUS_DE_MASK;
340 regs->status32 |= STATUS_L_MASK;
341
342 return err;
343 }
344
345 static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs)
346 {
347 switch (regs->r0) {
348 case -ERESTART_RESTARTBLOCK:
349 case -ERESTARTNOHAND:
350 /*
351 * ERESTARTNOHAND means that the syscall should
352 * only be restarted if there was no handler for
353 * the signal, and since we only get here if there
354 * is a handler, we don't restart
355 */
356 regs->r0 = -EINTR; /* ERESTART_xxx is internal */
357 break;
358
359 case -ERESTARTSYS:
360 /*
361 * ERESTARTSYS means to restart the syscall if
362 * there is no handler or the handler was
363 * registered with SA_RESTART
364 */
365 if (!(ka->sa.sa_flags & SA_RESTART)) {
366 regs->r0 = -EINTR;
367 break;
368 }
369 fallthrough;
370
371 case -ERESTARTNOINTR:
372 /*
373 * ERESTARTNOINTR means that the syscall should
374 * be called again after the signal handler returns.
375 * Setup reg state just as it was before doing the trap
376 * r0 has been clobbered with sys call ret code thus it
377 * needs to be reloaded with orig first arg to syscall
378 * in orig_r0. Rest of relevant reg-file:
379 * r8 (syscall num) and (r1 - r7) will be reset to
380 * their orig user space value when we ret from kernel
381 */
382 regs->r0 = regs->orig_r0;
383 regs->ret -= is_isa_arcv2() ? 2 : 4;
384 break;
385 }
386 }
387
388 /*
389 * OK, we're invoking a handler
390 */
391 static void
392 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
393 {
394 sigset_t *oldset = sigmask_to_save();
395 int failed;
396
397 /* Set up the stack frame */
398 failed = setup_rt_frame(ksig, oldset, regs);
399
400 signal_setup_done(failed, ksig, 0);
401 }
402
403 void do_signal(struct pt_regs *regs)
404 {
405 struct ksignal ksig;
406 int restart_scall;
407
408 restart_scall = in_syscall(regs) && syscall_restartable(regs);
409
410 if (test_thread_flag(TIF_SIGPENDING) && get_signal(&ksig)) {
411 if (restart_scall) {
412 arc_restart_syscall(&ksig.ka, regs);
413 syscall_wont_restart(regs); /* No more restarts */
414 }
415 handle_signal(&ksig, regs);
416 return;
417 }
418
419 if (restart_scall) {
420 /* No handler for syscall: restart it */
421 if (regs->r0 == -ERESTARTNOHAND ||
422 regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) {
423 regs->r0 = regs->orig_r0;
424 regs->ret -= is_isa_arcv2() ? 2 : 4;
425 } else if (regs->r0 == -ERESTART_RESTARTBLOCK) {
426 regs->r8 = __NR_restart_syscall;
427 regs->ret -= is_isa_arcv2() ? 2 : 4;
428 }
429 syscall_wont_restart(regs); /* No more restarts */
430 }
431
432 /* If there's no signal to deliver, restore the saved sigmask back */
433 restore_saved_sigmask();
434 }
435
436 void do_notify_resume(struct pt_regs *regs)
437 {
438 /*
439 * ASM glue guarantees that this is only called when returning to
440 * user mode
441 */
442 if (test_thread_flag(TIF_NOTIFY_RESUME))
443 resume_user_mode_work(regs);
444 }
445
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