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