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