xref: /linux/arch/openrisc/kernel/signal.c (revision 621cde16e49b3ecf7d59a8106a20aaebfb4a59a9)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * OpenRISC signal.c
4  *
5  * Linux architectural port borrowing liberally from similar works of
6  * others.  All original copyrights apply as per the original source
7  * declaration.
8  *
9  * Modifications for the OpenRISC architecture:
10  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
11  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
12  */
13 
14 #include <linux/sched.h>
15 #include <linux/mm.h>
16 #include <linux/smp.h>
17 #include <linux/kernel.h>
18 #include <linux/signal.h>
19 #include <linux/errno.h>
20 #include <linux/wait.h>
21 #include <linux/ptrace.h>
22 #include <linux/unistd.h>
23 #include <linux/stddef.h>
24 #include <linux/resume_user_mode.h>
25 
26 #include <asm/fpu.h>
27 #include <asm/processor.h>
28 #include <asm/syscall.h>
29 #include <asm/ucontext.h>
30 #include <linux/uaccess.h>
31 
32 struct rt_sigframe {
33 	struct siginfo info;
34 	struct ucontext uc;
35 	unsigned char retcode[16];	/* trampoline code */
36 };
37 
38 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs);
39 
40 asmlinkage int do_work_pending(struct pt_regs *regs, unsigned int thread_flags,
41 			       int syscall);
42 
43 #ifdef CONFIG_FPU
restore_fp_state(struct sigcontext __user * sc)44 static long restore_fp_state(struct sigcontext __user *sc)
45 {
46 	long err;
47 
48 	err = __copy_from_user(&current->thread.fpcsr, &sc->fpcsr, sizeof(unsigned long));
49 	if (unlikely(err))
50 		return err;
51 
52 	/* Restore the FPU state */
53 	restore_fpu(current);
54 
55 	return 0;
56 }
57 
save_fp_state(struct sigcontext __user * sc)58 static long save_fp_state(struct sigcontext __user *sc)
59 {
60 	long err;
61 
62 	/* Sync the user FPU state so we can copy to sigcontext */
63 	save_fpu(current);
64 
65 	err = __copy_to_user(&sc->fpcsr, &current->thread.fpcsr, sizeof(unsigned long));
66 
67 	return err;
68 }
69 #else
70 #define save_fp_state(sc) (0)
71 #define restore_fp_state(sc) (0)
72 #endif
73 
restore_sigcontext(struct pt_regs * regs,struct sigcontext __user * sc)74 static int restore_sigcontext(struct pt_regs *regs,
75 			      struct sigcontext __user *sc)
76 {
77 	int err = 0;
78 
79 	/* Always make any pending restarted system calls return -EINTR */
80 	current->restart_block.fn = do_no_restart_syscall;
81 
82 	/*
83 	 * Restore the regs from &sc->regs.
84 	 * (sc is already checked since the sigframe was
85 	 *  checked in sys_sigreturn previously)
86 	 */
87 	err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long));
88 	err |= __copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long));
89 	err |= __copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long));
90 	err |= restore_fp_state(sc);
91 
92 	/* make sure the SM-bit is cleared so user-mode cannot fool us */
93 	regs->sr &= ~SPR_SR_SM;
94 
95 	regs->orig_gpr11 = -1;	/* Avoid syscall restart checks */
96 
97 	/* TODO: the other ports use regs->orig_XX to disable syscall checks
98 	 * after this completes, but we don't use that mechanism. maybe we can
99 	 * use it now ?
100 	 */
101 
102 	return err;
103 }
104 
_sys_rt_sigreturn(struct pt_regs * regs)105 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
106 {
107 	struct rt_sigframe __user *frame = (struct rt_sigframe __user *)regs->sp;
108 	sigset_t set;
109 
110 	/*
111 	 * Since we stacked the signal on a dword boundary,
112 	 * then frame should be dword aligned here.  If it's
113 	 * not, then the user is trying to mess with us.
114 	 */
115 	if (((unsigned long)frame) & 3)
116 		goto badframe;
117 
118 	if (!access_ok(frame, sizeof(*frame)))
119 		goto badframe;
120 	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
121 		goto badframe;
122 
123 	set_current_blocked(&set);
124 
125 	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
126 		goto badframe;
127 
128 	if (restore_altstack(&frame->uc.uc_stack))
129 		goto badframe;
130 
131 	return regs->gpr[11];
132 
133 badframe:
134 	force_sig(SIGSEGV);
135 	return 0;
136 }
137 
138 /*
139  * Set up a signal frame.
140  */
141 
setup_sigcontext(struct pt_regs * regs,struct sigcontext __user * sc)142 static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
143 {
144 	int err = 0;
145 
146 	/* copy the regs */
147 	/* There should be no need to save callee-saved registers here...
148 	 * ...but we save them anyway.  Revisit this
149 	 */
150 	err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
151 	err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
152 	err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
153 	err |= save_fp_state(sc);
154 
155 	return err;
156 }
157 
align_sigframe(unsigned long sp)158 static inline unsigned long align_sigframe(unsigned long sp)
159 {
160 	return sp & ~3UL;
161 }
162 
163 /*
164  * Work out where the signal frame should go.  It's either on the user stack
165  * or the alternate stack.
166  */
167 
get_sigframe(struct ksignal * ksig,struct pt_regs * regs,size_t frame_size)168 static inline void __user *get_sigframe(struct ksignal *ksig,
169 					struct pt_regs *regs, size_t frame_size)
170 {
171 	unsigned long sp = regs->sp;
172 
173 	/* redzone */
174 	sp -= STACK_FRAME_OVERHEAD;
175 	sp = sigsp(sp, ksig);
176 	sp = align_sigframe(sp - frame_size);
177 
178 	return (void __user *)sp;
179 }
180 
181 /* grab and setup a signal frame.
182  *
183  * basically we stack a lot of state info, and arrange for the
184  * user-mode program to return to the kernel using either a
185  * trampoline which performs the syscall sigreturn, or a provided
186  * user-mode trampoline.
187  */
setup_rt_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)188 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
189 			  struct pt_regs *regs)
190 {
191 	struct rt_sigframe __user *frame;
192 	unsigned long return_ip;
193 	int err = 0;
194 
195 	frame = get_sigframe(ksig, regs, sizeof(*frame));
196 
197 	if (!access_ok(frame, sizeof(*frame)))
198 		return -EFAULT;
199 
200 	/* Create siginfo.  */
201 	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
202 		err |= copy_siginfo_to_user(&frame->info, &ksig->info);
203 
204 	/* Create the ucontext.  */
205 	err |= __put_user(0, &frame->uc.uc_flags);
206 	err |= __put_user(NULL, &frame->uc.uc_link);
207 	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
208 	err |= setup_sigcontext(regs, &frame->uc.uc_mcontext);
209 
210 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
211 
212 	if (err)
213 		return -EFAULT;
214 
215 	/* trampoline - the desired return ip is the retcode itself */
216 	return_ip = (unsigned long)&frame->retcode;
217 	/* This is:
218 		l.ori r11,r0,__NR_sigreturn
219 		l.sys 1
220 	 */
221 	err |= __put_user(0xa960,             (short __user *)(frame->retcode + 0));
222 	err |= __put_user(__NR_rt_sigreturn,  (short __user *)(frame->retcode + 2));
223 	err |= __put_user(0x20000001, (unsigned long __user *)(frame->retcode + 4));
224 	err |= __put_user(0x15000000, (unsigned long __user *)(frame->retcode + 8));
225 
226 	if (err)
227 		return -EFAULT;
228 
229 	/* Set up registers for signal handler */
230 	regs->pc = (unsigned long)ksig->ka.sa.sa_handler; /* what we enter NOW */
231 	regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
232 	regs->gpr[3] = (unsigned long)ksig->sig;           /* arg 1: signo */
233 	regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
234 	regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
235 
236 	/* actually move the usp to reflect the stacked frame */
237 	regs->sp = (unsigned long)frame;
238 
239 	return 0;
240 }
241 
242 static inline void
handle_signal(struct ksignal * ksig,struct pt_regs * regs)243 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
244 {
245 	int ret;
246 
247 	ret = setup_rt_frame(ksig, sigmask_to_save(), regs);
248 
249 	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
250 }
251 
252 /*
253  * Note that 'init' is a special process: it doesn't get signals it doesn't
254  * want to handle. Thus you cannot kill init even with a SIGKILL even by
255  * mistake.
256  *
257  * Also note that the regs structure given here as an argument, is the latest
258  * pushed pt_regs. It may or may not be the same as the first pushed registers
259  * when the initial usermode->kernelmode transition took place. Therefore
260  * we can use user_mode(regs) to see if we came directly from kernel or user
261  * mode below.
262  */
263 
do_signal(struct pt_regs * regs,int syscall)264 static int do_signal(struct pt_regs *regs, int syscall)
265 {
266 	struct ksignal ksig;
267 	unsigned long continue_addr = 0;
268 	unsigned long restart_addr = 0;
269 	unsigned long retval = 0;
270 	int restart = 0;
271 
272 	if (syscall) {
273 		continue_addr = regs->pc;
274 		restart_addr = continue_addr - 4;
275 		retval = regs->gpr[11];
276 
277 		/*
278 		 * Setup syscall restart here so that a debugger will
279 		 * see the already changed PC.
280 		 */
281 		switch (retval) {
282 		case -ERESTART_RESTARTBLOCK:
283 			restart = -2;
284 			fallthrough;
285 		case -ERESTARTNOHAND:
286 		case -ERESTARTSYS:
287 		case -ERESTARTNOINTR:
288 			restart++;
289 			regs->gpr[11] = regs->orig_gpr11;
290 			regs->pc = restart_addr;
291 			break;
292 		}
293 	}
294 
295 	/*
296 	 * Get the signal to deliver.  During the call to get_signal the
297 	 * debugger may change all our registers so we may need to revert
298 	 * the decision to restart the syscall; specifically, if the PC is
299 	 * changed, don't restart the syscall.
300 	 */
301 	if (get_signal(&ksig)) {
302 		if (unlikely(restart) && regs->pc == restart_addr) {
303 			if (retval == -ERESTARTNOHAND ||
304 			    retval == -ERESTART_RESTARTBLOCK
305 			    || (retval == -ERESTARTSYS
306 			        && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
307 				/* No automatic restart */
308 				regs->gpr[11] = -EINTR;
309 				regs->pc = continue_addr;
310 			}
311 		}
312 		handle_signal(&ksig, regs);
313 	} else {
314 		/* no handler */
315 		restore_saved_sigmask();
316 		/*
317 		 * Restore pt_regs PC as syscall restart will be handled by
318 		 * kernel without return to userspace
319 		 */
320 		if (unlikely(restart) && regs->pc == restart_addr) {
321 			regs->pc = continue_addr;
322 			return restart;
323 		}
324 	}
325 
326 	return 0;
327 }
328 
329 asmlinkage int
do_work_pending(struct pt_regs * regs,unsigned int thread_flags,int syscall)330 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
331 {
332 	do {
333 		if (likely(thread_flags & _TIF_NEED_RESCHED)) {
334 			schedule();
335 		} else {
336 			if (unlikely(!user_mode(regs)))
337 				return 0;
338 			local_irq_enable();
339 			if (thread_flags & (_TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL)) {
340 				int restart = do_signal(regs, syscall);
341 				if (unlikely(restart)) {
342 					/*
343 					 * Restart without handlers.
344 					 * Deal with it without leaving
345 					 * the kernel space.
346 					 */
347 					return restart;
348 				}
349 				syscall = 0;
350 			} else {
351 				resume_user_mode_work(regs);
352 			}
353 		}
354 		local_irq_disable();
355 		thread_flags = read_thread_flags();
356 	} while (thread_flags & _TIF_WORK_MASK);
357 	return 0;
358 }
359