1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
4 *  Chen Liqin <liqin.chen@sunplusct.com>
5 *  Lennox Wu <lennox.wu@sunplusct.com>
6 * Copyright (C) 2012 Regents of the University of California
7 */
8
9#include <linux/compat.h>
10#include <linux/signal.h>
11#include <linux/uaccess.h>
12#include <linux/syscalls.h>
13#include <linux/resume_user_mode.h>
14#include <linux/linkage.h>
15#include <linux/entry-common.h>
16
17#include <asm/ucontext.h>
18#include <asm/vdso.h>
19#include <asm/signal.h>
20#include <asm/signal32.h>
21#include <asm/switch_to.h>
22#include <asm/vector.h>
23#include <asm/csr.h>
24#include <asm/cacheflush.h>
25
26unsigned long signal_minsigstksz __ro_after_init;
27
28extern u32 __user_rt_sigreturn[2];
29static size_t riscv_v_sc_size __ro_after_init;
30
31#define DEBUG_SIG 0
32
33struct rt_sigframe {
34	struct siginfo info;
35	struct ucontext uc;
36#ifndef CONFIG_MMU
37	u32 sigreturn_code[2];
38#endif
39};
40
41#ifdef CONFIG_FPU
42static long restore_fp_state(struct pt_regs *regs,
43			     union __riscv_fp_state __user *sc_fpregs)
44{
45	long err;
46	struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
47
48	err = __copy_from_user(&current->thread.fstate, state, sizeof(*state));
49	if (unlikely(err))
50		return err;
51
52	fstate_restore(current, regs);
53	return 0;
54}
55
56static long save_fp_state(struct pt_regs *regs,
57			  union __riscv_fp_state __user *sc_fpregs)
58{
59	long err;
60	struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
61
62	fstate_save(current, regs);
63	err = __copy_to_user(state, &current->thread.fstate, sizeof(*state));
64	return err;
65}
66#else
67#define save_fp_state(task, regs) (0)
68#define restore_fp_state(task, regs) (0)
69#endif
70
71#ifdef CONFIG_RISCV_ISA_V
72
73static long save_v_state(struct pt_regs *regs, void __user **sc_vec)
74{
75	struct __riscv_ctx_hdr __user *hdr;
76	struct __sc_riscv_v_state __user *state;
77	void __user *datap;
78	long err;
79
80	hdr = *sc_vec;
81	/* Place state to the user's signal context space after the hdr */
82	state = (struct __sc_riscv_v_state __user *)(hdr + 1);
83	/* Point datap right after the end of __sc_riscv_v_state */
84	datap = state + 1;
85
86	/* datap is designed to be 16 byte aligned for better performance */
87	WARN_ON(unlikely(!IS_ALIGNED((unsigned long)datap, 16)));
88
89	get_cpu_vector_context();
90	riscv_v_vstate_save(&current->thread.vstate, regs);
91	put_cpu_vector_context();
92
93	/* Copy everything of vstate but datap. */
94	err = __copy_to_user(&state->v_state, &current->thread.vstate,
95			     offsetof(struct __riscv_v_ext_state, datap));
96	/* Copy the pointer datap itself. */
97	err |= __put_user((__force void *)datap, &state->v_state.datap);
98	/* Copy the whole vector content to user space datap. */
99	err |= __copy_to_user(datap, current->thread.vstate.datap, riscv_v_vsize);
100	/* Copy magic to the user space after saving  all vector conetext */
101	err |= __put_user(RISCV_V_MAGIC, &hdr->magic);
102	err |= __put_user(riscv_v_sc_size, &hdr->size);
103	if (unlikely(err))
104		return err;
105
106	/* Only progress the sv_vec if everything has done successfully  */
107	*sc_vec += riscv_v_sc_size;
108	return 0;
109}
110
111/*
112 * Restore Vector extension context from the user's signal frame. This function
113 * assumes a valid extension header. So magic and size checking must be done by
114 * the caller.
115 */
116static long __restore_v_state(struct pt_regs *regs, void __user *sc_vec)
117{
118	long err;
119	struct __sc_riscv_v_state __user *state = sc_vec;
120	void __user *datap;
121
122	/*
123	 * Mark the vstate as clean prior performing the actual copy,
124	 * to avoid getting the vstate incorrectly clobbered by the
125	 *  discarded vector state.
126	 */
127	riscv_v_vstate_set_restore(current, regs);
128
129	/* Copy everything of __sc_riscv_v_state except datap. */
130	err = __copy_from_user(&current->thread.vstate, &state->v_state,
131			       offsetof(struct __riscv_v_ext_state, datap));
132	if (unlikely(err))
133		return err;
134
135	/* Copy the pointer datap itself. */
136	err = __get_user(datap, &state->v_state.datap);
137	if (unlikely(err))
138		return err;
139	/*
140	 * Copy the whole vector content from user space datap. Use
141	 * copy_from_user to prevent information leak.
142	 */
143	return copy_from_user(current->thread.vstate.datap, datap, riscv_v_vsize);
144}
145#else
146#define save_v_state(task, regs) (0)
147#define __restore_v_state(task, regs) (0)
148#endif
149
150static long restore_sigcontext(struct pt_regs *regs,
151	struct sigcontext __user *sc)
152{
153	void __user *sc_ext_ptr = &sc->sc_extdesc.hdr;
154	__u32 rsvd;
155	long err;
156	/* sc_regs is structured the same as the start of pt_regs */
157	err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs));
158	if (unlikely(err))
159		return err;
160
161	/* Restore the floating-point state. */
162	if (has_fpu()) {
163		err = restore_fp_state(regs, &sc->sc_fpregs);
164		if (unlikely(err))
165			return err;
166	}
167
168	/* Check the reserved word before extensions parsing */
169	err = __get_user(rsvd, &sc->sc_extdesc.reserved);
170	if (unlikely(err))
171		return err;
172	if (unlikely(rsvd))
173		return -EINVAL;
174
175	while (!err) {
176		__u32 magic, size;
177		struct __riscv_ctx_hdr __user *head = sc_ext_ptr;
178
179		err |= __get_user(magic, &head->magic);
180		err |= __get_user(size, &head->size);
181		if (unlikely(err))
182			return err;
183
184		sc_ext_ptr += sizeof(*head);
185		switch (magic) {
186		case END_MAGIC:
187			if (size != END_HDR_SIZE)
188				return -EINVAL;
189
190			return 0;
191		case RISCV_V_MAGIC:
192			if (!has_vector() || !riscv_v_vstate_query(regs) ||
193			    size != riscv_v_sc_size)
194				return -EINVAL;
195
196			err = __restore_v_state(regs, sc_ext_ptr);
197			break;
198		default:
199			return -EINVAL;
200		}
201		sc_ext_ptr = (void __user *)head + size;
202	}
203	return err;
204}
205
206static size_t get_rt_frame_size(bool cal_all)
207{
208	struct rt_sigframe __user *frame;
209	size_t frame_size;
210	size_t total_context_size = 0;
211
212	frame_size = sizeof(*frame);
213
214	if (has_vector()) {
215		if (cal_all || riscv_v_vstate_query(task_pt_regs(current)))
216			total_context_size += riscv_v_sc_size;
217	}
218	/*
219	 * Preserved a __riscv_ctx_hdr for END signal context header if an
220	 * extension uses __riscv_extra_ext_header
221	 */
222	if (total_context_size)
223		total_context_size += sizeof(struct __riscv_ctx_hdr);
224
225	frame_size += total_context_size;
226
227	frame_size = round_up(frame_size, 16);
228	return frame_size;
229}
230
231SYSCALL_DEFINE0(rt_sigreturn)
232{
233	struct pt_regs *regs = current_pt_regs();
234	struct rt_sigframe __user *frame;
235	struct task_struct *task;
236	sigset_t set;
237	size_t frame_size = get_rt_frame_size(false);
238
239	/* Always make any pending restarted system calls return -EINTR */
240	current->restart_block.fn = do_no_restart_syscall;
241
242	frame = (struct rt_sigframe __user *)regs->sp;
243
244	if (!access_ok(frame, frame_size))
245		goto badframe;
246
247	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
248		goto badframe;
249
250	set_current_blocked(&set);
251
252	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
253		goto badframe;
254
255	if (restore_altstack(&frame->uc.uc_stack))
256		goto badframe;
257
258	regs->cause = -1UL;
259
260	return regs->a0;
261
262badframe:
263	task = current;
264	if (show_unhandled_signals) {
265		pr_info_ratelimited(
266			"%s[%d]: bad frame in %s: frame=%p pc=%p sp=%p\n",
267			task->comm, task_pid_nr(task), __func__,
268			frame, (void *)regs->epc, (void *)regs->sp);
269	}
270	force_sig(SIGSEGV);
271	return 0;
272}
273
274static long setup_sigcontext(struct rt_sigframe __user *frame,
275	struct pt_regs *regs)
276{
277	struct sigcontext __user *sc = &frame->uc.uc_mcontext;
278	struct __riscv_ctx_hdr __user *sc_ext_ptr = &sc->sc_extdesc.hdr;
279	long err;
280
281	/* sc_regs is structured the same as the start of pt_regs */
282	err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs));
283	/* Save the floating-point state. */
284	if (has_fpu())
285		err |= save_fp_state(regs, &sc->sc_fpregs);
286	/* Save the vector state. */
287	if (has_vector() && riscv_v_vstate_query(regs))
288		err |= save_v_state(regs, (void __user **)&sc_ext_ptr);
289	/* Write zero to fp-reserved space and check it on restore_sigcontext */
290	err |= __put_user(0, &sc->sc_extdesc.reserved);
291	/* And put END __riscv_ctx_hdr at the end. */
292	err |= __put_user(END_MAGIC, &sc_ext_ptr->magic);
293	err |= __put_user(END_HDR_SIZE, &sc_ext_ptr->size);
294
295	return err;
296}
297
298static inline void __user *get_sigframe(struct ksignal *ksig,
299	struct pt_regs *regs, size_t framesize)
300{
301	unsigned long sp;
302	/* Default to using normal stack */
303	sp = regs->sp;
304
305	/*
306	 * If we are on the alternate signal stack and would overflow it, don't.
307	 * Return an always-bogus address instead so we will die with SIGSEGV.
308	 */
309	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
310		return (void __user __force *)(-1UL);
311
312	/* This is the X/Open sanctioned signal stack switching. */
313	sp = sigsp(sp, ksig) - framesize;
314
315	/* Align the stack frame. */
316	sp &= ~0xfUL;
317
318	return (void __user *)sp;
319}
320
321static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
322	struct pt_regs *regs)
323{
324	struct rt_sigframe __user *frame;
325	long err = 0;
326	unsigned long __maybe_unused addr;
327	size_t frame_size = get_rt_frame_size(false);
328
329	frame = get_sigframe(ksig, regs, frame_size);
330	if (!access_ok(frame, frame_size))
331		return -EFAULT;
332
333	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
334
335	/* Create the ucontext. */
336	err |= __put_user(0, &frame->uc.uc_flags);
337	err |= __put_user(NULL, &frame->uc.uc_link);
338	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
339	err |= setup_sigcontext(frame, regs);
340	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
341	if (err)
342		return -EFAULT;
343
344	/* Set up to return from userspace. */
345#ifdef CONFIG_MMU
346	regs->ra = (unsigned long)VDSO_SYMBOL(
347		current->mm->context.vdso, rt_sigreturn);
348#else
349	/*
350	 * For the nommu case we don't have a VDSO.  Instead we push two
351	 * instructions to call the rt_sigreturn syscall onto the user stack.
352	 */
353	if (copy_to_user(&frame->sigreturn_code, __user_rt_sigreturn,
354			 sizeof(frame->sigreturn_code)))
355		return -EFAULT;
356
357	addr = (unsigned long)&frame->sigreturn_code;
358	/* Make sure the two instructions are pushed to icache. */
359	flush_icache_range(addr, addr + sizeof(frame->sigreturn_code));
360
361	regs->ra = addr;
362#endif /* CONFIG_MMU */
363
364	/*
365	 * Set up registers for signal handler.
366	 * Registers that we don't modify keep the value they had from
367	 * user-space at the time we took the signal.
368	 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
369	 * since some things rely on this (e.g. glibc's debug/segfault.c).
370	 */
371	regs->epc = (unsigned long)ksig->ka.sa.sa_handler;
372	regs->sp = (unsigned long)frame;
373	regs->a0 = ksig->sig;                     /* a0: signal number */
374	regs->a1 = (unsigned long)(&frame->info); /* a1: siginfo pointer */
375	regs->a2 = (unsigned long)(&frame->uc);   /* a2: ucontext pointer */
376
377#if DEBUG_SIG
378	pr_info("SIG deliver (%s:%d): sig=%d pc=%p ra=%p sp=%p\n",
379		current->comm, task_pid_nr(current), ksig->sig,
380		(void *)regs->epc, (void *)regs->ra, frame);
381#endif
382
383	return 0;
384}
385
386static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
387{
388	sigset_t *oldset = sigmask_to_save();
389	int ret;
390
391	rseq_signal_deliver(ksig, regs);
392
393	/* Set up the stack frame */
394	if (is_compat_task())
395		ret = compat_setup_rt_frame(ksig, oldset, regs);
396	else
397		ret = setup_rt_frame(ksig, oldset, regs);
398
399	signal_setup_done(ret, ksig, 0);
400}
401
402void arch_do_signal_or_restart(struct pt_regs *regs)
403{
404	unsigned long continue_addr = 0, restart_addr = 0;
405	int retval = 0;
406	struct ksignal ksig;
407	bool syscall = (regs->cause == EXC_SYSCALL);
408
409	/* If we were from a system call, check for system call restarting */
410	if (syscall) {
411		continue_addr = regs->epc;
412		restart_addr = continue_addr - 4;
413		retval = regs->a0;
414
415		/* Avoid additional syscall restarting via ret_from_exception */
416		regs->cause = -1UL;
417
418		/*
419		 * Prepare for system call restart. We do this here so that a
420		 * debugger will see the already changed PC.
421		 */
422		switch (retval) {
423		case -ERESTARTNOHAND:
424		case -ERESTARTSYS:
425		case -ERESTARTNOINTR:
426		case -ERESTART_RESTARTBLOCK:
427			regs->a0 = regs->orig_a0;
428			regs->epc = restart_addr;
429			break;
430		}
431	}
432
433	/*
434	 * Get the signal to deliver. When running under ptrace, at this point
435	 * the debugger may change all of our registers.
436	 */
437	if (get_signal(&ksig)) {
438		/*
439		 * Depending on the signal settings, we may need to revert the
440		 * decision to restart the system call, but skip this if a
441		 * debugger has chosen to restart at a different PC.
442		 */
443		if (regs->epc == restart_addr &&
444		    (retval == -ERESTARTNOHAND ||
445		     retval == -ERESTART_RESTARTBLOCK ||
446		     (retval == -ERESTARTSYS &&
447		      !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
448			regs->a0 = -EINTR;
449			regs->epc = continue_addr;
450		}
451
452		/* Actually deliver the signal */
453		handle_signal(&ksig, regs);
454		return;
455	}
456
457	/*
458	 * Handle restarting a different system call. As above, if a debugger
459	 * has chosen to restart at a different PC, ignore the restart.
460	 */
461	if (syscall && regs->epc == restart_addr && retval == -ERESTART_RESTARTBLOCK)
462		regs->a7 = __NR_restart_syscall;
463
464	/*
465	 * If there is no signal to deliver, we just put the saved
466	 * sigmask back.
467	 */
468	restore_saved_sigmask();
469}
470
471void init_rt_signal_env(void);
472void __init init_rt_signal_env(void)
473{
474	riscv_v_sc_size = sizeof(struct __riscv_ctx_hdr) +
475			  sizeof(struct __sc_riscv_v_state) + riscv_v_vsize;
476	/*
477	 * Determine the stack space required for guaranteed signal delivery.
478	 * The signal_minsigstksz will be populated into the AT_MINSIGSTKSZ entry
479	 * in the auxiliary array at process startup.
480	 */
481	signal_minsigstksz = get_rt_frame_size(true);
482}
483
484#ifdef CONFIG_DYNAMIC_SIGFRAME
485bool sigaltstack_size_valid(size_t ss_size)
486{
487	return ss_size > get_rt_frame_size(false);
488}
489#endif /* CONFIG_DYNAMIC_SIGFRAME */
490