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