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
31struct rt_sigframe {
32	struct siginfo info;
33	struct ucontext uc;
34	unsigned char retcode[16];	/* trampoline code */
35};
36
37asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs);
38
39asmlinkage int do_work_pending(struct pt_regs *regs, unsigned int thread_flags,
40			       int syscall);
41
42static 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(&regs->pc, &sc->regs.pc, sizeof(unsigned long));
57	err |= __copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long));
58	err |= __copy_from_user(&regs->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
73asmlinkage 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
101badframe:
102	force_sig(SIGSEGV);
103	return 0;
104}
105
106/*
107 * Set up a signal frame.
108 */
109
110static 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, &regs->pc, sizeof(unsigned long));
120	err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
121	err |= __copy_to_user(&sc->fpcsr, &regs->fpcsr, sizeof(unsigned long));
122
123	return err;
124}
125
126static 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
136static 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 */
156static 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
210static inline void
211handle_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
232static 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
297asmlinkage int
298do_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