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