1/*
  2 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
  3 *  Chen Liqin <liqin.chen@sunplusct.com>
  4 *  Lennox Wu <lennox.wu@sunplusct.com>
  5 * Copyright (C) 2012 Regents of the University of California
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License as published by
  9 * the Free Software Foundation; either version 2 of the License, or
 10 * (at your option) any later version.
 11 *
 12 * This program is distributed in the hope that it will be useful,
 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15 * GNU General Public License for more details.
 16 *
 17 * You should have received a copy of the GNU General Public License
 18 * along with this program; if not, see the file COPYING, or write
 19 * to the Free Software Foundation, Inc.,
 20 */
 21
 22#include <linux/signal.h>
 23#include <linux/uaccess.h>
 24#include <linux/syscalls.h>
 25#include <linux/tracehook.h>
 26#include <linux/linkage.h>
 27
 28#include <asm/ucontext.h>
 29#include <asm/vdso.h>
 30#include <asm/switch_to.h>
 31#include <asm/csr.h>
 32
 33#define DEBUG_SIG 0
 34
 35struct rt_sigframe {
 36	struct siginfo info;
 37	struct ucontext uc;
 38};
 39
 40static long restore_d_state(struct pt_regs *regs,
 41	struct __riscv_d_ext_state __user *state)
 42{
 43	long err;
 44	err = __copy_from_user(&current->thread.fstate, state, sizeof(*state));
 45	if (likely(!err))
 46		fstate_restore(current, regs);
 47	return err;
 48}
 49
 50static long save_d_state(struct pt_regs *regs,
 51	struct __riscv_d_ext_state __user *state)
 52{
 53	fstate_save(current, regs);
 54	return __copy_to_user(state, &current->thread.fstate, sizeof(*state));
 55}
 56
 57static long restore_sigcontext(struct pt_regs *regs,
 58	struct sigcontext __user *sc)
 59{
 60	long err;
 61	size_t i;
 62	/* sc_regs is structured the same as the start of pt_regs */
 63	err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs));
 64	if (unlikely(err))
 65		return err;
 66	/* Restore the floating-point state. */
 67	err = restore_d_state(regs, &sc->sc_fpregs.d);
 68	if (unlikely(err))
 69		return err;
 70	/* We support no other extension state at this time. */
 71	for (i = 0; i < ARRAY_SIZE(sc->sc_fpregs.q.reserved); i++) {
 72		u32 value;
 73		err = __get_user(value, &sc->sc_fpregs.q.reserved[i]);
 74		if (unlikely(err))
 75			break;
 76		if (value != 0)
 77			return -EINVAL;
 78	}
 79	return err;
 80}
 81
 82SYSCALL_DEFINE0(rt_sigreturn)
 83{
 84	struct pt_regs *regs = current_pt_regs();
 85	struct rt_sigframe __user *frame;
 86	struct task_struct *task;
 87	sigset_t set;
 88
 89	/* Always make any pending restarted system calls return -EINTR */
 90	current->restart_block.fn = do_no_restart_syscall;
 91
 92	frame = (struct rt_sigframe __user *)regs->sp;
 93
 94	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 95		goto badframe;
 96
 97	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 98		goto badframe;
 99
100	set_current_blocked(&set);
101
102	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
103		goto badframe;
104
105	if (restore_altstack(&frame->uc.uc_stack))
106		goto badframe;
107
108	return regs->a0;
109
110badframe:
111	task = current;
112	if (show_unhandled_signals) {
113		pr_info_ratelimited(
114			"%s[%d]: bad frame in %s: frame=%p pc=%p sp=%p\n",
115			task->comm, task_pid_nr(task), __func__,
116			frame, (void *)regs->sepc, (void *)regs->sp);
117	}
118	force_sig(SIGSEGV, task);
119	return 0;
120}
121
122static long setup_sigcontext(struct rt_sigframe __user *frame,
123	struct pt_regs *regs)
124{
125	struct sigcontext __user *sc = &frame->uc.uc_mcontext;
126	long err;
127	size_t i;
128	/* sc_regs is structured the same as the start of pt_regs */
129	err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs));
130	/* Save the floating-point state. */
131	err |= save_d_state(regs, &sc->sc_fpregs.d);
132	/* We support no other extension state at this time. */
133	for (i = 0; i < ARRAY_SIZE(sc->sc_fpregs.q.reserved); i++)
134		err |= __put_user(0, &sc->sc_fpregs.q.reserved[i]);
135	return err;
136}
137
138static inline void __user *get_sigframe(struct ksignal *ksig,
139	struct pt_regs *regs, size_t framesize)
140{
141	unsigned long sp;
142	/* Default to using normal stack */
143	sp = regs->sp;
144
145	/*
146	 * If we are on the alternate signal stack and would overflow it, don't.
147	 * Return an always-bogus address instead so we will die with SIGSEGV.
148	 */
149	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
150		return (void __user __force *)(-1UL);
151
152	/* This is the X/Open sanctioned signal stack switching. */
153	sp = sigsp(sp, ksig) - framesize;
154
155	/* Align the stack frame. */
156	sp &= ~0xfUL;
157
158	return (void __user *)sp;
159}
160
161
162static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
163	struct pt_regs *regs)
164{
165	struct rt_sigframe __user *frame;
166	long err = 0;
167
168	frame = get_sigframe(ksig, regs, sizeof(*frame));
169	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
170		return -EFAULT;
171
172	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
173
174	/* Create the ucontext. */
175	err |= __put_user(0, &frame->uc.uc_flags);
176	err |= __put_user(NULL, &frame->uc.uc_link);
177	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
178	err |= setup_sigcontext(frame, regs);
179	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
180	if (err)
181		return -EFAULT;
182
183	/* Set up to return from userspace. */
184	regs->ra = (unsigned long)VDSO_SYMBOL(
185		current->mm->context.vdso, rt_sigreturn);
186
187	/*
188	 * Set up registers for signal handler.
189	 * Registers that we don't modify keep the value they had from
190	 * user-space at the time we took the signal.
191	 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
192	 * since some things rely on this (e.g. glibc's debug/segfault.c).
193	 */
194	regs->sepc = (unsigned long)ksig->ka.sa.sa_handler;
195	regs->sp = (unsigned long)frame;
196	regs->a0 = ksig->sig;                     /* a0: signal number */
197	regs->a1 = (unsigned long)(&frame->info); /* a1: siginfo pointer */
198	regs->a2 = (unsigned long)(&frame->uc);   /* a2: ucontext pointer */
199
200#if DEBUG_SIG
201	pr_info("SIG deliver (%s:%d): sig=%d pc=%p ra=%p sp=%p\n",
202		current->comm, task_pid_nr(current), ksig->sig,
203		(void *)regs->sepc, (void *)regs->ra, frame);
204#endif
205
206	return 0;
207}
208
209static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
210{
211	sigset_t *oldset = sigmask_to_save();
212	int ret;
213
214	/* Are we from a system call? */
215	if (regs->scause == EXC_SYSCALL) {
216		/* If so, check system call restarting.. */
217		switch (regs->a0) {
218		case -ERESTART_RESTARTBLOCK:
219		case -ERESTARTNOHAND:
220			regs->a0 = -EINTR;
221			break;
222
223		case -ERESTARTSYS:
224			if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
225				regs->a0 = -EINTR;
226				break;
227			}
228			/* fallthrough */
229		case -ERESTARTNOINTR:
230                        regs->a0 = regs->orig_a0;
231			regs->sepc -= 0x4;
232			break;
233		}
234	}
235
236	/* Set up the stack frame */
237	ret = setup_rt_frame(ksig, oldset, regs);
238
239	signal_setup_done(ret, ksig, 0);
240}
241
242static void do_signal(struct pt_regs *regs)
243{
244	struct ksignal ksig;
245
246	if (get_signal(&ksig)) {
247		/* Actually deliver the signal */
248		handle_signal(&ksig, regs);
249		return;
250	}
251
252	/* Did we come from a system call? */
253	if (regs->scause == EXC_SYSCALL) {
254		/* Restart the system call - no handlers present */
255		switch (regs->a0) {
256		case -ERESTARTNOHAND:
257		case -ERESTARTSYS:
258		case -ERESTARTNOINTR:
259                        regs->a0 = regs->orig_a0;
260			regs->sepc -= 0x4;
261			break;
262		case -ERESTART_RESTARTBLOCK:
263                        regs->a0 = regs->orig_a0;
264			regs->a7 = __NR_restart_syscall;
265			regs->sepc -= 0x4;
266			break;
267		}
268	}
269
270	/*
271	 * If there is no signal to deliver, we just put the saved
272	 * sigmask back.
273	 */
274	restore_saved_sigmask();
275}
276
277/*
278 * notification of userspace execution resumption
279 * - triggered by the _TIF_WORK_MASK flags
280 */
281asmlinkage void do_notify_resume(struct pt_regs *regs,
282	unsigned long thread_info_flags)
283{
284	/* Handle pending signal delivery */
285	if (thread_info_flags & _TIF_SIGPENDING)
286		do_signal(regs);
287
288	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
289		clear_thread_flag(TIF_NOTIFY_RESUME);
290		tracehook_notify_resume(regs);
291	}
292}