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(¤t->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, ¤t->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
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