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
32struct rt_sigframe {
33 struct siginfo info;
34 struct ucontext uc;
35 unsigned char retcode[16]; /* trampoline code */
36};
37
38asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs);
39
40asmlinkage int do_work_pending(struct pt_regs *regs, unsigned int thread_flags,
41 int syscall);
42
43#ifdef CONFIG_FPU
44static 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
58static 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
74static 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(to: regs, from: sc->regs.gpr, n: 32 * sizeof(unsigned long));
88 err |= __copy_from_user(to: &regs->pc, from: &sc->regs.pc, n: sizeof(unsigned long));
89 err |= __copy_from_user(to: &regs->sr, from: &sc->regs.sr, n: 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
105asmlinkage 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(to: &set, from: &frame->uc.uc_sigmask, n: sizeof(set)))
121 goto badframe;
122
123 set_current_blocked(&set);
124
125 if (restore_sigcontext(regs, sc: &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
133badframe:
134 force_sig(SIGSEGV);
135 return 0;
136}
137
138/*
139 * Set up a signal frame.
140 */
141
142static 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(to: sc->regs.gpr, from: regs, n: 32 * sizeof(unsigned long));
151 err |= __copy_to_user(to: &sc->regs.pc, from: &regs->pc, n: sizeof(unsigned long));
152 err |= __copy_to_user(to: &sc->regs.sr, from: &regs->sr, n: sizeof(unsigned long));
153 err |= save_fp_state(sc);
154
155 return err;
156}
157
158static 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
168static 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: 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 */
188static 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, frame_size: 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(to: &frame->info, from: &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, sc: &frame->uc.uc_mcontext);
209
210 err |= __copy_to_user(to: &frame->uc.uc_sigmask, from: set, n: 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
242static inline void
243handle_signal(struct ksignal *ksig, struct pt_regs *regs)
244{
245 int ret;
246
247 rseq_signal_deliver(ksig, regs);
248
249 ret = setup_rt_frame(ksig, set: sigmask_to_save(), regs);
250
251 signal_setup_done(failed: ret, ksig, test_thread_flag(TIF_SINGLESTEP));
252}
253
254/*
255 * Note that 'init' is a special process: it doesn't get signals it doesn't
256 * want to handle. Thus you cannot kill init even with a SIGKILL even by
257 * mistake.
258 *
259 * Also note that the regs structure given here as an argument, is the latest
260 * pushed pt_regs. It may or may not be the same as the first pushed registers
261 * when the initial usermode->kernelmode transition took place. Therefore
262 * we can use user_mode(regs) to see if we came directly from kernel or user
263 * mode below.
264 */
265
266static int do_signal(struct pt_regs *regs, int syscall)
267{
268 struct ksignal ksig;
269 unsigned long continue_addr = 0;
270 unsigned long restart_addr = 0;
271 unsigned long retval = 0;
272 int restart = 0;
273
274 if (syscall) {
275 continue_addr = regs->pc;
276 restart_addr = continue_addr - 4;
277 retval = regs->gpr[11];
278
279 /*
280 * Setup syscall restart here so that a debugger will
281 * see the already changed PC.
282 */
283 switch (retval) {
284 case -ERESTART_RESTARTBLOCK:
285 restart = -2;
286 fallthrough;
287 case -ERESTARTNOHAND:
288 case -ERESTARTSYS:
289 case -ERESTARTNOINTR:
290 restart++;
291 regs->gpr[11] = regs->orig_gpr11;
292 regs->pc = restart_addr;
293 break;
294 }
295 }
296
297 /*
298 * Get the signal to deliver. During the call to get_signal the
299 * debugger may change all our registers so we may need to revert
300 * the decision to restart the syscall; specifically, if the PC is
301 * changed, don't restart the syscall.
302 */
303 if (get_signal(ksig: &ksig)) {
304 if (unlikely(restart) && regs->pc == restart_addr) {
305 if (retval == -ERESTARTNOHAND ||
306 retval == -ERESTART_RESTARTBLOCK
307 || (retval == -ERESTARTSYS
308 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
309 /* No automatic restart */
310 regs->gpr[11] = -EINTR;
311 regs->pc = continue_addr;
312 }
313 }
314 handle_signal(ksig: &ksig, regs);
315 } else {
316 /* no handler */
317 restore_saved_sigmask();
318 /*
319 * Restore pt_regs PC as syscall restart will be handled by
320 * kernel without return to userspace
321 */
322 if (unlikely(restart) && regs->pc == restart_addr) {
323 regs->pc = continue_addr;
324 return restart;
325 }
326 }
327
328 return 0;
329}
330
331asmlinkage int
332do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
333{
334 do {
335 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
336 schedule();
337 } else {
338 if (unlikely(!user_mode(regs)))
339 return 0;
340 local_irq_enable();
341 if (thread_flags & (_TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL)) {
342 int restart = do_signal(regs, syscall);
343 if (unlikely(restart)) {
344 /*
345 * Restart without handlers.
346 * Deal with it without leaving
347 * the kernel space.
348 */
349 return restart;
350 }
351 syscall = 0;
352 } else {
353 resume_user_mode_work(regs);
354 }
355 }
356 local_irq_disable();
357 thread_flags = read_thread_flags();
358 } while (thread_flags & _TIF_WORK_MASK);
359 return 0;
360}
361

source code of linux/arch/openrisc/kernel/signal.c