1// SPDX-License-Identifier: GPL-2.0
  2
  3#include <linux/signal.h>
  4#include <linux/uaccess.h>
  5#include <linux/syscalls.h>
  6#include <linux/resume_user_mode.h>
  7
  8#include <asm/traps.h>
  9#include <asm/ucontext.h>
 10#include <asm/vdso.h>
 11
 12#include <abi/regdef.h>
 13
 14#ifdef CONFIG_CPU_HAS_FPU
 15#include <abi/fpu.h>
 16static int restore_fpu_state(struct sigcontext __user *sc)
 17{
 18	int err = 0;
 19	struct user_fp user_fp;
 20
 21	err = __copy_from_user(&user_fp, &sc->sc_user_fp, sizeof(user_fp));
 22
 23	restore_from_user_fp(&user_fp);
 24
 25	return err;
 26}
 27
 28static int save_fpu_state(struct sigcontext __user *sc)
 29{
 30	struct user_fp user_fp;
 31
 32	save_to_user_fp(&user_fp);
 33
 34	return __copy_to_user(&sc->sc_user_fp, &user_fp, sizeof(user_fp));
 35}
 36#else
 37#define restore_fpu_state(sigcontext)	(0)
 38#define save_fpu_state(sigcontext)	(0)
 39#endif
 40
 41struct rt_sigframe {
 42	/*
 43	 * pad[3] is compatible with the same struct defined in
 44	 * gcc/libgcc/config/csky/linux-unwind.h
 45	 */
 46	int pad[3];
 47	struct siginfo info;
 48	struct ucontext uc;
 49};
 50
 51static long restore_sigcontext(struct pt_regs *regs,
 52	struct sigcontext __user *sc)
 53{
 54	int err = 0;
 55	unsigned long sr = regs->sr;
 56
 57	/* sc_pt_regs is structured the same as the start of pt_regs */
 58	err |= __copy_from_user(regs, &sc->sc_pt_regs, sizeof(struct pt_regs));
 59
 60	/* BIT(0) of regs->sr is Condition Code/Carry bit */
 61	regs->sr = (sr & ~1) | (regs->sr & 1);
 62
 63	/* Restore the floating-point state. */
 64	err |= restore_fpu_state(sc);
 65
 66	return err;
 67}
 68
 69SYSCALL_DEFINE0(rt_sigreturn)
 70{
 71	struct pt_regs *regs = current_pt_regs();
 72	struct rt_sigframe __user *frame;
 73	sigset_t set;
 74
 75	/* Always make any pending restarted system calls return -EINTR */
 76	current->restart_block.fn = do_no_restart_syscall;
 77
 78	frame = (struct rt_sigframe __user *)regs->usp;
 79
 80	if (!access_ok(frame, sizeof(*frame)))
 81		goto badframe;
 82
 83	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 84		goto badframe;
 85
 86	set_current_blocked(&set);
 87
 88	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 89		goto badframe;
 90
 91	if (restore_altstack(&frame->uc.uc_stack))
 92		goto badframe;
 93
 94	return regs->a0;
 95
 96badframe:
 97	force_sig(SIGSEGV);
 98	return 0;
 99}
100
101static int setup_sigcontext(struct rt_sigframe __user *frame,
102	struct pt_regs *regs)
103{
104	struct sigcontext __user *sc = &frame->uc.uc_mcontext;
105	int err = 0;
106
107	err |= __copy_to_user(&sc->sc_pt_regs, regs, sizeof(struct pt_regs));
108	err |= save_fpu_state(sc);
109
110	return err;
111}
112
113static inline void __user *get_sigframe(struct ksignal *ksig,
114	struct pt_regs *regs, size_t framesize)
115{
116	unsigned long sp;
117	/* Default to using normal stack */
118	sp = regs->usp;
119
120	/*
121	 * If we are on the alternate signal stack and would overflow it, don't.
122	 * Return an always-bogus address instead so we will die with SIGSEGV.
123	 */
124	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
125		return (void __user __force *)(-1UL);
126
127	/* This is the X/Open sanctioned signal stack switching. */
128	sp = sigsp(sp, ksig) - framesize;
129
130	/* Align the stack frame. */
131	sp &= -8UL;
132
133	return (void __user *)sp;
134}
135
136static int
137setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
138{
139	struct rt_sigframe __user *frame;
140	int err = 0;
141
142	frame = get_sigframe(ksig, regs, sizeof(*frame));
143	if (!access_ok(frame, sizeof(*frame)))
144		return -EFAULT;
145
146	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
147
148	/* Create the ucontext. */
149	err |= __put_user(0, &frame->uc.uc_flags);
150	err |= __put_user(NULL, &frame->uc.uc_link);
151	err |= __save_altstack(&frame->uc.uc_stack, regs->usp);
152	err |= setup_sigcontext(frame, regs);
153	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
154	if (err)
155		return -EFAULT;
156
157	/* Set up to return from userspace. */
158	regs->lr = (unsigned long)VDSO_SYMBOL(
159		current->mm->context.vdso, rt_sigreturn);
160
161	/*
162	 * Set up registers for signal handler.
163	 * Registers that we don't modify keep the value they had from
164	 * user-space at the time we took the signal.
165	 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
166	 * since some things rely on this (e.g. glibc's debug/segfault.c).
167	 */
168	regs->pc  = (unsigned long)ksig->ka.sa.sa_handler;
169	regs->usp = (unsigned long)frame;
170	regs->a0  = ksig->sig;				/* a0: signal number */
171	regs->a1  = (unsigned long)(&(frame->info));	/* a1: siginfo pointer */
172	regs->a2  = (unsigned long)(&(frame->uc));	/* a2: ucontext pointer */
173
174	return 0;
175}
176
177static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
178{
179	sigset_t *oldset = sigmask_to_save();
180	int ret;
181
182	/* Are we from a system call? */
183	if (in_syscall(regs)) {
184		/* Avoid additional syscall restarting via ret_from_exception */
185		forget_syscall(regs);
186
187		/* If so, check system call restarting.. */
188		switch (regs->a0) {
189		case -ERESTART_RESTARTBLOCK:
190		case -ERESTARTNOHAND:
191			regs->a0 = -EINTR;
192			break;
193
194		case -ERESTARTSYS:
195			if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
196				regs->a0 = -EINTR;
197				break;
198			}
199			fallthrough;
200		case -ERESTARTNOINTR:
201			regs->a0 = regs->orig_a0;
202			regs->pc -= TRAP0_SIZE;
203			break;
204		}
205	}
206
207	/* Set up the stack frame */
208	ret = setup_rt_frame(ksig, oldset, regs);
209
210	signal_setup_done(ret, ksig, 0);
211}
212
213static void do_signal(struct pt_regs *regs)
214{
215	struct ksignal ksig;
216
217	if (get_signal(&ksig)) {
218		/* Actually deliver the signal */
219		handle_signal(&ksig, regs);
220		return;
221	}
222
223	/* Did we come from a system call? */
224	if (in_syscall(regs)) {
225		/* Avoid additional syscall restarting via ret_from_exception */
226		forget_syscall(regs);
227
228		/* Restart the system call - no handlers present */
229		switch (regs->a0) {
230		case -ERESTARTNOHAND:
231		case -ERESTARTSYS:
232		case -ERESTARTNOINTR:
233			regs->a0 = regs->orig_a0;
234			regs->pc -= TRAP0_SIZE;
235			break;
236		case -ERESTART_RESTARTBLOCK:
237			regs->a0 = regs->orig_a0;
238			regs_syscallid(regs) = __NR_restart_syscall;
239			regs->pc -= TRAP0_SIZE;
240			break;
241		}
242	}
243
244	/*
245	 * If there is no signal to deliver, we just put the saved
246	 * sigmask back.
247	 */
248	restore_saved_sigmask();
249}
250
251/*
252 * notification of userspace execution resumption
253 * - triggered by the _TIF_WORK_MASK flags
254 */
255asmlinkage void do_notify_resume(struct pt_regs *regs,
256	unsigned long thread_info_flags)
257{
258	if (thread_info_flags & _TIF_UPROBE)
259		uprobe_notify_resume(regs);
260
261	/* Handle pending signal delivery */
262	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
263		do_signal(regs);
264
265	if (thread_info_flags & _TIF_NOTIFY_RESUME)
266		resume_user_mode_work(regs);
267}