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 
17 struct compat_sigcontext {
18 	struct compat_user_regs_struct sc_regs;
19 	union __riscv_fp_state sc_fpregs;
20 };
21 
22 struct 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 
43 struct compat_rt_sigframe {
44 	struct compat_siginfo info;
45 	struct compat_ucontext uc;
46 };
47 
48 #ifdef CONFIG_FPU
49 static 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 
76 static 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 
102 static 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 
119 COMPAT_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 
147 badframe:
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 
159 static 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 
176 static 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 
199 int 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 }
244