1// SPDX-License-Identifier: GPL-2.0-or-later
  2
  3#include <linux/compat.h>
  4#include <linux/signal.h>
  5#include <linux/uaccess.h>
  6#include <linux/syscalls.h>
  7#include <linux/linkage.h>
  8
  9#include <asm/csr.h>
 10#include <asm/signal32.h>
 11#include <asm/switch_to.h>
 12#include <asm/ucontext.h>
 13#include <asm/vdso.h>
 14
 15#define COMPAT_DEBUG_SIG 0
 16
 17struct compat_sigcontext {
 18	struct compat_user_regs_struct sc_regs;
 19	union __riscv_fp_state sc_fpregs;
 20};
 21
 22struct compat_ucontext {
 23	compat_ulong_t		uc_flags;
 24	struct compat_ucontext	*uc_link;
 25	compat_stack_t		uc_stack;
 26	sigset_t		uc_sigmask;
 27	/* There's some padding here to allow sigset_t to be expanded in the
 28	 * future.  Though this is unlikely, other architectures put uc_sigmask
 29	 * at the end of this structure and explicitly state it can be
 30	 * expanded, so we didn't want to box ourselves in here. */
 31	__u8		  __unused[1024 / 8 - sizeof(sigset_t)];
 32	/* We can't put uc_sigmask at the end of this structure because we need
 33	 * to be able to expand sigcontext in the future.  For example, the
 34	 * vector ISA extension will almost certainly add ISA state.  We want
 35	 * to ensure all user-visible ISA state can be saved and restored via a
 36	 * ucontext, so we're putting this at the end in order to allow for
 37	 * infinite extensibility.  Since we know this will be extended and we
 38	 * assume sigset_t won't be extended an extreme amount, we're
 39	 * prioritizing this. */
 40	struct compat_sigcontext uc_mcontext;
 41};
 42
 43struct compat_rt_sigframe {
 44	struct compat_siginfo info;
 45	struct compat_ucontext uc;
 46};
 47
 48#ifdef CONFIG_FPU
 49static long compat_restore_fp_state(struct pt_regs *regs,
 50	union __riscv_fp_state __user *sc_fpregs)
 51{
 52	long err;
 53	struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
 54	size_t i;
 55
 56	err = __copy_from_user(&current->thread.fstate, state, sizeof(*state));
 57	if (unlikely(err))
 58		return err;
 59
 60	fstate_restore(current, regs);
 61
 62	/* We support no other extension state at this time. */
 63	for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
 64		u32 value;
 65
 66		err = __get_user(value, &sc_fpregs->q.reserved[i]);
 67		if (unlikely(err))
 68			break;
 69		if (value != 0)
 70			return -EINVAL;
 71	}
 72
 73	return err;
 74}
 75
 76static long compat_save_fp_state(struct pt_regs *regs,
 77			  union __riscv_fp_state __user *sc_fpregs)
 78{
 79	long err;
 80	struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
 81	size_t i;
 82
 83	fstate_save(current, regs);
 84	err = __copy_to_user(state, &current->thread.fstate, sizeof(*state));
 85	if (unlikely(err))
 86		return err;
 87
 88	/* We support no other extension state at this time. */
 89	for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
 90		err = __put_user(0, &sc_fpregs->q.reserved[i]);
 91		if (unlikely(err))
 92			break;
 93	}
 94
 95	return err;
 96}
 97#else
 98#define compat_save_fp_state(task, regs) (0)
 99#define compat_restore_fp_state(task, regs) (0)
100#endif
101
102static long compat_restore_sigcontext(struct pt_regs *regs,
103	struct compat_sigcontext __user *sc)
104{
105	long err;
106	struct compat_user_regs_struct cregs;
107
108	/* sc_regs is structured the same as the start of pt_regs */
109	err = __copy_from_user(&cregs, &sc->sc_regs, sizeof(sc->sc_regs));
110
111	cregs_to_regs(&cregs, regs);
112
113	/* Restore the floating-point state. */
114	if (has_fpu())
115		err |= compat_restore_fp_state(regs, &sc->sc_fpregs);
116	return err;
117}
118
119COMPAT_SYSCALL_DEFINE0(rt_sigreturn)
120{
121	struct pt_regs *regs = current_pt_regs();
122	struct compat_rt_sigframe __user *frame;
123	struct task_struct *task;
124	sigset_t set;
125
126	/* Always make any pending restarted system calls return -EINTR */
127	current->restart_block.fn = do_no_restart_syscall;
128
129	frame = (struct compat_rt_sigframe __user *)regs->sp;
130
131	if (!access_ok(frame, sizeof(*frame)))
132		goto badframe;
133
134	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
135		goto badframe;
136
137	set_current_blocked(&set);
138
139	if (compat_restore_sigcontext(regs, &frame->uc.uc_mcontext))
140		goto badframe;
141
142	if (compat_restore_altstack(&frame->uc.uc_stack))
143		goto badframe;
144
145	return regs->a0;
146
147badframe:
148	task = current;
149	if (show_unhandled_signals) {
150		pr_info_ratelimited(
151			"%s[%d]: bad frame in %s: frame=%p pc=%p sp=%p\n",
152			task->comm, task_pid_nr(task), __func__,
153			frame, (void *)regs->epc, (void *)regs->sp);
154	}
155	force_sig(SIGSEGV);
156	return 0;
157}
158
159static long compat_setup_sigcontext(struct compat_rt_sigframe __user *frame,
160	struct pt_regs *regs)
161{
162	struct compat_sigcontext __user *sc = &frame->uc.uc_mcontext;
163	struct compat_user_regs_struct cregs;
164	long err;
165
166	regs_to_cregs(&cregs, regs);
167
168	/* sc_regs is structured the same as the start of pt_regs */
169	err = __copy_to_user(&sc->sc_regs, &cregs, sizeof(sc->sc_regs));
170	/* Save the floating-point state. */
171	if (has_fpu())
172		err |= compat_save_fp_state(regs, &sc->sc_fpregs);
173	return err;
174}
175
176static inline void __user *compat_get_sigframe(struct ksignal *ksig,
177	struct pt_regs *regs, size_t framesize)
178{
179	unsigned long sp;
180	/* Default to using normal stack */
181	sp = regs->sp;
182
183	/*
184	 * If we are on the alternate signal stack and would overflow it, don't.
185	 * Return an always-bogus address instead so we will die with SIGSEGV.
186	 */
187	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
188		return (void __user __force *)(-1UL);
189
190	/* This is the X/Open sanctioned signal stack switching. */
191	sp = sigsp(sp, ksig) - framesize;
192
193	/* Align the stack frame. */
194	sp &= ~0xfUL;
195
196	return (void __user *)sp;
197}
198
199int compat_setup_rt_frame(struct ksignal *ksig, sigset_t *set,
200	struct pt_regs *regs)
201{
202	struct compat_rt_sigframe __user *frame;
203	long err = 0;
204
205	frame = compat_get_sigframe(ksig, regs, sizeof(*frame));
206	if (!access_ok(frame, sizeof(*frame)))
207		return -EFAULT;
208
209	err |= copy_siginfo_to_user32(&frame->info, &ksig->info);
210
211	/* Create the ucontext. */
212	err |= __put_user(0, &frame->uc.uc_flags);
213	err |= __put_user(NULL, &frame->uc.uc_link);
214	err |= __compat_save_altstack(&frame->uc.uc_stack, regs->sp);
215	err |= compat_setup_sigcontext(frame, regs);
216	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
217	if (err)
218		return -EFAULT;
219
220	regs->ra = (unsigned long)COMPAT_VDSO_SYMBOL(
221			current->mm->context.vdso, rt_sigreturn);
222
223	/*
224	 * Set up registers for signal handler.
225	 * Registers that we don't modify keep the value they had from
226	 * user-space at the time we took the signal.
227	 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
228	 * since some things rely on this (e.g. glibc's debug/segfault.c).
229	 */
230	regs->epc = (unsigned long)ksig->ka.sa.sa_handler;
231	regs->sp = (unsigned long)frame;
232	regs->a0 = ksig->sig;                     /* a0: signal number */
233	regs->a1 = (unsigned long)(&frame->info); /* a1: siginfo pointer */
234	regs->a2 = (unsigned long)(&frame->uc);   /* a2: ucontext pointer */
235
236#if COMPAT_DEBUG_SIG
237	pr_info("SIG deliver (%s:%d): sig=%d pc=%p ra=%p sp=%p\n",
238		current->comm, task_pid_nr(current), ksig->sig,
239		(void *)regs->epc, (void *)regs->ra, frame);
240#endif
241
242	return 0;
243}