1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Architecture-specific signal handling support.
4  *
5  * Copyright (C) 1999-2004 Hewlett-Packard Co
6  *	David Mosberger-Tang <davidm@hpl.hp.com>
7  *
8  * Derived from i386 and Alpha versions.
9  */
10 
11 #include <linux/errno.h>
12 #include <linux/kernel.h>
13 #include <linux/mm.h>
14 #include <linux/ptrace.h>
15 #include <linux/sched.h>
16 #include <linux/signal.h>
17 #include <linux/smp.h>
18 #include <linux/stddef.h>
19 #include <linux/tty.h>
20 #include <linux/binfmts.h>
21 #include <linux/unistd.h>
22 #include <linux/wait.h>
23 
24 #include <asm/intrinsics.h>
25 #include <linux/uaccess.h>
26 #include <asm/rse.h>
27 #include <asm/sigcontext.h>
28 
29 #include "sigframe.h"
30 
31 #define DEBUG_SIG	0
32 #define STACK_ALIGN	16		/* minimal alignment for stack pointer */
33 
34 #if _NSIG_WORDS > 1
35 # define PUT_SIGSET(k,u)	__copy_to_user((u)->sig, (k)->sig, sizeof(sigset_t))
36 # define GET_SIGSET(k,u)	__copy_from_user((k)->sig, (u)->sig, sizeof(sigset_t))
37 #else
38 # define PUT_SIGSET(k,u)	__put_user((k)->sig[0], &(u)->sig[0])
39 # define GET_SIGSET(k,u)	__get_user((k)->sig[0], &(u)->sig[0])
40 #endif
41 
42 static long
restore_sigcontext(struct sigcontext __user * sc,struct sigscratch * scr)43 restore_sigcontext (struct sigcontext __user *sc, struct sigscratch *scr)
44 {
45 	unsigned long ip, flags, nat, um, cfm, rsc;
46 	long err;
47 
48 	/* Always make any pending restarted system calls return -EINTR */
49 	current->restart_block.fn = do_no_restart_syscall;
50 
51 	/* restore scratch that always needs gets updated during signal delivery: */
52 	err  = __get_user(flags, &sc->sc_flags);
53 	err |= __get_user(nat, &sc->sc_nat);
54 	err |= __get_user(ip, &sc->sc_ip);			/* instruction pointer */
55 	err |= __get_user(cfm, &sc->sc_cfm);
56 	err |= __get_user(um, &sc->sc_um);			/* user mask */
57 	err |= __get_user(rsc, &sc->sc_ar_rsc);
58 	err |= __get_user(scr->pt.ar_unat, &sc->sc_ar_unat);
59 	err |= __get_user(scr->pt.ar_fpsr, &sc->sc_ar_fpsr);
60 	err |= __get_user(scr->pt.ar_pfs, &sc->sc_ar_pfs);
61 	err |= __get_user(scr->pt.pr, &sc->sc_pr);		/* predicates */
62 	err |= __get_user(scr->pt.b0, &sc->sc_br[0]);		/* b0 (rp) */
63 	err |= __get_user(scr->pt.b6, &sc->sc_br[6]);		/* b6 */
64 	err |= __copy_from_user(&scr->pt.r1, &sc->sc_gr[1], 8);	/* r1 */
65 	err |= __copy_from_user(&scr->pt.r8, &sc->sc_gr[8], 4*8);	/* r8-r11 */
66 	err |= __copy_from_user(&scr->pt.r12, &sc->sc_gr[12], 2*8);	/* r12-r13 */
67 	err |= __copy_from_user(&scr->pt.r15, &sc->sc_gr[15], 8);	/* r15 */
68 
69 	scr->pt.cr_ifs = cfm | (1UL << 63);
70 	scr->pt.ar_rsc = rsc | (3 << 2); /* force PL3 */
71 
72 	/* establish new instruction pointer: */
73 	scr->pt.cr_iip = ip & ~0x3UL;
74 	ia64_psr(&scr->pt)->ri = ip & 0x3;
75 	scr->pt.cr_ipsr = (scr->pt.cr_ipsr & ~IA64_PSR_UM) | (um & IA64_PSR_UM);
76 
77 	scr->scratch_unat = ia64_put_scratch_nat_bits(&scr->pt, nat);
78 
79 	if (!(flags & IA64_SC_FLAG_IN_SYSCALL)) {
80 		/* Restore most scratch-state only when not in syscall. */
81 		err |= __get_user(scr->pt.ar_ccv, &sc->sc_ar_ccv);		/* ar.ccv */
82 		err |= __get_user(scr->pt.b7, &sc->sc_br[7]);			/* b7 */
83 		err |= __get_user(scr->pt.r14, &sc->sc_gr[14]);			/* r14 */
84 		err |= __copy_from_user(&scr->pt.ar_csd, &sc->sc_ar25, 2*8); /* ar.csd & ar.ssd */
85 		err |= __copy_from_user(&scr->pt.r2, &sc->sc_gr[2], 2*8);	/* r2-r3 */
86 		err |= __copy_from_user(&scr->pt.r16, &sc->sc_gr[16], 16*8);	/* r16-r31 */
87 	}
88 
89 	if ((flags & IA64_SC_FLAG_FPH_VALID) != 0) {
90 		struct ia64_psr *psr = ia64_psr(&scr->pt);
91 
92 		err |= __copy_from_user(current->thread.fph, &sc->sc_fr[32], 96*16);
93 		psr->mfh = 0;	/* drop signal handler's fph contents... */
94 		preempt_disable();
95 		if (psr->dfh)
96 			ia64_drop_fpu(current);
97 		else {
98 			/* We already own the local fph, otherwise psr->dfh wouldn't be 0.  */
99 			__ia64_load_fpu(current->thread.fph);
100 			ia64_set_local_fpu_owner(current);
101 		}
102 		preempt_enable();
103 	}
104 	return err;
105 }
106 
107 long
ia64_rt_sigreturn(struct sigscratch * scr)108 ia64_rt_sigreturn (struct sigscratch *scr)
109 {
110 	extern char ia64_strace_leave_kernel, ia64_leave_kernel;
111 	struct sigcontext __user *sc;
112 	sigset_t set;
113 	long retval;
114 
115 	sc = &((struct sigframe __user *) (scr->pt.r12 + 16))->sc;
116 
117 	/*
118 	 * When we return to the previously executing context, r8 and r10 have already
119 	 * been setup the way we want them.  Indeed, if the signal wasn't delivered while
120 	 * in a system call, we must not touch r8 or r10 as otherwise user-level state
121 	 * could be corrupted.
122 	 */
123 	retval = (long) &ia64_leave_kernel;
124 	if (test_thread_flag(TIF_SYSCALL_TRACE)
125 	    || test_thread_flag(TIF_SYSCALL_AUDIT))
126 		/*
127 		 * strace expects to be notified after sigreturn returns even though the
128 		 * context to which we return may not be in the middle of a syscall.
129 		 * Thus, the return-value that strace displays for sigreturn is
130 		 * meaningless.
131 		 */
132 		retval = (long) &ia64_strace_leave_kernel;
133 
134 	if (!access_ok(sc, sizeof(*sc)))
135 		goto give_sigsegv;
136 
137 	if (GET_SIGSET(&set, &sc->sc_mask))
138 		goto give_sigsegv;
139 
140 	set_current_blocked(&set);
141 
142 	if (restore_sigcontext(sc, scr))
143 		goto give_sigsegv;
144 
145 #if DEBUG_SIG
146 	printk("SIG return (%s:%d): sp=%lx ip=%lx\n",
147 	       current->comm, current->pid, scr->pt.r12, scr->pt.cr_iip);
148 #endif
149 	if (restore_altstack(&sc->sc_stack))
150 		goto give_sigsegv;
151 	return retval;
152 
153   give_sigsegv:
154 	force_sig(SIGSEGV);
155 	return retval;
156 }
157 
158 /*
159  * This does just the minimum required setup of sigcontext.
160  * Specifically, it only installs data that is either not knowable at
161  * the user-level or that gets modified before execution in the
162  * trampoline starts.  Everything else is done at the user-level.
163  */
164 static long
setup_sigcontext(struct sigcontext __user * sc,sigset_t * mask,struct sigscratch * scr)165 setup_sigcontext (struct sigcontext __user *sc, sigset_t *mask, struct sigscratch *scr)
166 {
167 	unsigned long flags = 0, ifs, cfm, nat;
168 	long err = 0;
169 
170 	ifs = scr->pt.cr_ifs;
171 
172 	if (on_sig_stack((unsigned long) sc))
173 		flags |= IA64_SC_FLAG_ONSTACK;
174 	if ((ifs & (1UL << 63)) == 0)
175 		/* if cr_ifs doesn't have the valid bit set, we got here through a syscall */
176 		flags |= IA64_SC_FLAG_IN_SYSCALL;
177 	cfm = ifs & ((1UL << 38) - 1);
178 	ia64_flush_fph(current);
179 	if ((current->thread.flags & IA64_THREAD_FPH_VALID)) {
180 		flags |= IA64_SC_FLAG_FPH_VALID;
181 		err = __copy_to_user(&sc->sc_fr[32], current->thread.fph, 96*16);
182 	}
183 
184 	nat = ia64_get_scratch_nat_bits(&scr->pt, scr->scratch_unat);
185 
186 	err |= __put_user(flags, &sc->sc_flags);
187 	err |= __put_user(nat, &sc->sc_nat);
188 	err |= PUT_SIGSET(mask, &sc->sc_mask);
189 	err |= __put_user(cfm, &sc->sc_cfm);
190 	err |= __put_user(scr->pt.cr_ipsr & IA64_PSR_UM, &sc->sc_um);
191 	err |= __put_user(scr->pt.ar_rsc, &sc->sc_ar_rsc);
192 	err |= __put_user(scr->pt.ar_unat, &sc->sc_ar_unat);		/* ar.unat */
193 	err |= __put_user(scr->pt.ar_fpsr, &sc->sc_ar_fpsr);		/* ar.fpsr */
194 	err |= __put_user(scr->pt.ar_pfs, &sc->sc_ar_pfs);
195 	err |= __put_user(scr->pt.pr, &sc->sc_pr);			/* predicates */
196 	err |= __put_user(scr->pt.b0, &sc->sc_br[0]);			/* b0 (rp) */
197 	err |= __put_user(scr->pt.b6, &sc->sc_br[6]);			/* b6 */
198 	err |= __copy_to_user(&sc->sc_gr[1], &scr->pt.r1, 8);		/* r1 */
199 	err |= __copy_to_user(&sc->sc_gr[8], &scr->pt.r8, 4*8);		/* r8-r11 */
200 	err |= __copy_to_user(&sc->sc_gr[12], &scr->pt.r12, 2*8);	/* r12-r13 */
201 	err |= __copy_to_user(&sc->sc_gr[15], &scr->pt.r15, 8);		/* r15 */
202 	err |= __put_user(scr->pt.cr_iip + ia64_psr(&scr->pt)->ri, &sc->sc_ip);
203 
204 	if (!(flags & IA64_SC_FLAG_IN_SYSCALL)) {
205 		/* Copy scratch regs to sigcontext if the signal didn't interrupt a syscall. */
206 		err |= __put_user(scr->pt.ar_ccv, &sc->sc_ar_ccv);		/* ar.ccv */
207 		err |= __put_user(scr->pt.b7, &sc->sc_br[7]);			/* b7 */
208 		err |= __put_user(scr->pt.r14, &sc->sc_gr[14]);			/* r14 */
209 		err |= __copy_to_user(&sc->sc_ar25, &scr->pt.ar_csd, 2*8); /* ar.csd & ar.ssd */
210 		err |= __copy_to_user(&sc->sc_gr[2], &scr->pt.r2, 2*8);		/* r2-r3 */
211 		err |= __copy_to_user(&sc->sc_gr[16], &scr->pt.r16, 16*8);	/* r16-r31 */
212 	}
213 	return err;
214 }
215 
216 /*
217  * Check whether the register-backing store is already on the signal stack.
218  */
219 static inline int
rbs_on_sig_stack(unsigned long bsp)220 rbs_on_sig_stack (unsigned long bsp)
221 {
222 	return (bsp - current->sas_ss_sp < current->sas_ss_size);
223 }
224 
225 static long
setup_frame(struct ksignal * ksig,sigset_t * set,struct sigscratch * scr)226 setup_frame(struct ksignal *ksig, sigset_t *set, struct sigscratch *scr)
227 {
228 	extern char __kernel_sigtramp[];
229 	unsigned long tramp_addr, new_rbs = 0, new_sp;
230 	struct sigframe __user *frame;
231 	long err;
232 
233 	new_sp = scr->pt.r12;
234 	tramp_addr = (unsigned long) __kernel_sigtramp;
235 	if (ksig->ka.sa.sa_flags & SA_ONSTACK) {
236 		int onstack = sas_ss_flags(new_sp);
237 
238 		if (onstack == 0) {
239 			new_sp = current->sas_ss_sp + current->sas_ss_size;
240 			/*
241 			 * We need to check for the register stack being on the
242 			 * signal stack separately, because it's switched
243 			 * separately (memory stack is switched in the kernel,
244 			 * register stack is switched in the signal trampoline).
245 			 */
246 			if (!rbs_on_sig_stack(scr->pt.ar_bspstore))
247 				new_rbs = ALIGN(current->sas_ss_sp,
248 						sizeof(long));
249 		} else if (onstack == SS_ONSTACK) {
250 			unsigned long check_sp;
251 
252 			/*
253 			 * If we are on the alternate signal stack and would
254 			 * overflow it, don't. Return an always-bogus address
255 			 * instead so we will die with SIGSEGV.
256 			 */
257 			check_sp = (new_sp - sizeof(*frame)) & -STACK_ALIGN;
258 			if (!likely(on_sig_stack(check_sp))) {
259 				force_sigsegv(ksig->sig);
260 				return 1;
261 			}
262 		}
263 	}
264 	frame = (void __user *) ((new_sp - sizeof(*frame)) & -STACK_ALIGN);
265 
266 	if (!access_ok(frame, sizeof(*frame))) {
267 		force_sigsegv(ksig->sig);
268 		return 1;
269 	}
270 
271 	err  = __put_user(ksig->sig, &frame->arg0);
272 	err |= __put_user(&frame->info, &frame->arg1);
273 	err |= __put_user(&frame->sc, &frame->arg2);
274 	err |= __put_user(new_rbs, &frame->sc.sc_rbs_base);
275 	err |= __put_user(0, &frame->sc.sc_loadrs);	/* initialize to zero */
276 	err |= __put_user(ksig->ka.sa.sa_handler, &frame->handler);
277 
278 	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
279 
280 	err |= __save_altstack(&frame->sc.sc_stack, scr->pt.r12);
281 	err |= setup_sigcontext(&frame->sc, set, scr);
282 
283 	if (unlikely(err)) {
284 		force_sigsegv(ksig->sig);
285 		return 1;
286 	}
287 
288 	scr->pt.r12 = (unsigned long) frame - 16;	/* new stack pointer */
289 	scr->pt.ar_fpsr = FPSR_DEFAULT;			/* reset fpsr for signal handler */
290 	scr->pt.cr_iip = tramp_addr;
291 	ia64_psr(&scr->pt)->ri = 0;			/* start executing in first slot */
292 	ia64_psr(&scr->pt)->be = 0;			/* force little-endian byte-order */
293 	/*
294 	 * Force the interruption function mask to zero.  This has no effect when a
295 	 * system-call got interrupted by a signal (since, in that case, scr->pt_cr_ifs is
296 	 * ignored), but it has the desirable effect of making it possible to deliver a
297 	 * signal with an incomplete register frame (which happens when a mandatory RSE
298 	 * load faults).  Furthermore, it has no negative effect on the getting the user's
299 	 * dirty partition preserved, because that's governed by scr->pt.loadrs.
300 	 */
301 	scr->pt.cr_ifs = (1UL << 63);
302 
303 	/*
304 	 * Note: this affects only the NaT bits of the scratch regs (the ones saved in
305 	 * pt_regs), which is exactly what we want.
306 	 */
307 	scr->scratch_unat = 0; /* ensure NaT bits of r12 is clear */
308 
309 #if DEBUG_SIG
310 	printk("SIG deliver (%s:%d): sig=%d sp=%lx ip=%lx handler=%p\n",
311 	       current->comm, current->pid, ksig->sig, scr->pt.r12, frame->sc.sc_ip, frame->handler);
312 #endif
313 	return 0;
314 }
315 
316 static long
handle_signal(struct ksignal * ksig,struct sigscratch * scr)317 handle_signal (struct ksignal *ksig, struct sigscratch *scr)
318 {
319 	int ret = setup_frame(ksig, sigmask_to_save(), scr);
320 
321 	if (!ret)
322 		signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
323 
324 	return ret;
325 }
326 
327 /*
328  * Note that `init' is a special process: it doesn't get signals it doesn't want to
329  * handle.  Thus you cannot kill init even with a SIGKILL even by mistake.
330  */
331 void
ia64_do_signal(struct sigscratch * scr,long in_syscall)332 ia64_do_signal (struct sigscratch *scr, long in_syscall)
333 {
334 	long restart = in_syscall;
335 	long errno = scr->pt.r8;
336 	struct ksignal ksig;
337 
338 	/*
339 	 * This only loops in the rare cases of handle_signal() failing, in which case we
340 	 * need to push through a forced SIGSEGV.
341 	 */
342 	while (1) {
343 		if (!get_signal(&ksig))
344 			break;
345 
346 		/*
347 		 * get_signal() may have run a debugger (via notify_parent())
348 		 * and the debugger may have modified the state (e.g., to arrange for an
349 		 * inferior call), thus it's important to check for restarting _after_
350 		 * get_signal().
351 		 */
352 		if ((long) scr->pt.r10 != -1)
353 			/*
354 			 * A system calls has to be restarted only if one of the error codes
355 			 * ERESTARTNOHAND, ERESTARTSYS, or ERESTARTNOINTR is returned.  If r10
356 			 * isn't -1 then r8 doesn't hold an error code and we don't need to
357 			 * restart the syscall, so we can clear the "restart" flag here.
358 			 */
359 			restart = 0;
360 
361 		if (ksig.sig <= 0)
362 			break;
363 
364 		if (unlikely(restart)) {
365 			switch (errno) {
366 			case ERESTART_RESTARTBLOCK:
367 			case ERESTARTNOHAND:
368 				scr->pt.r8 = EINTR;
369 				/* note: scr->pt.r10 is already -1 */
370 				break;
371 			case ERESTARTSYS:
372 				if ((ksig.ka.sa.sa_flags & SA_RESTART) == 0) {
373 					scr->pt.r8 = EINTR;
374 					/* note: scr->pt.r10 is already -1 */
375 					break;
376 				}
377 				fallthrough;
378 			case ERESTARTNOINTR:
379 				ia64_decrement_ip(&scr->pt);
380 				restart = 0; /* don't restart twice if handle_signal() fails... */
381 			}
382 		}
383 
384 		/*
385 		 * Whee!  Actually deliver the signal.  If the delivery failed, we need to
386 		 * continue to iterate in this loop so we can deliver the SIGSEGV...
387 		 */
388 		if (handle_signal(&ksig, scr))
389 			return;
390 	}
391 
392 	/* Did we come from a system call? */
393 	if (restart) {
394 		/* Restart the system call - no handlers present */
395 		if (errno == ERESTARTNOHAND || errno == ERESTARTSYS || errno == ERESTARTNOINTR
396 		    || errno == ERESTART_RESTARTBLOCK)
397 		{
398 			/*
399 			 * Note: the syscall number is in r15 which is saved in
400 			 * pt_regs so all we need to do here is adjust ip so that
401 			 * the "break" instruction gets re-executed.
402 			 */
403 			ia64_decrement_ip(&scr->pt);
404 			if (errno == ERESTART_RESTARTBLOCK)
405 				scr->pt.r15 = __NR_restart_syscall;
406 		}
407 	}
408 
409 	/* if there's no signal to deliver, we just put the saved sigmask
410 	 * back */
411 	restore_saved_sigmask();
412 }
413