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> |
16 | static 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 | |
28 | static 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 | |
41 | struct 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 | |
51 | static 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(to: regs, from: &sc->sc_pt_regs, n: 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 | |
69 | SYSCALL_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(to: &set, from: &frame->uc.uc_sigmask, n: sizeof(set))) |
84 | goto badframe; |
85 | |
86 | set_current_blocked(&set); |
87 | |
88 | if (restore_sigcontext(regs, sc: &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 | |
96 | badframe: |
97 | force_sig(SIGSEGV); |
98 | return 0; |
99 | } |
100 | |
101 | static 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(to: &sc->sc_pt_regs, from: regs, n: sizeof(struct pt_regs)); |
108 | err |= save_fpu_state(sc); |
109 | |
110 | return err; |
111 | } |
112 | |
113 | static 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 | |
136 | static int |
137 | setup_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, framesize: sizeof(*frame)); |
143 | if (!access_ok(frame, sizeof(*frame))) |
144 | return -EFAULT; |
145 | |
146 | err |= copy_siginfo_to_user(to: &frame->info, from: &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(to: &frame->uc.uc_sigmask, from: set, n: 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 | |
177 | static 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, set: oldset, regs); |
209 | |
210 | signal_setup_done(failed: ret, ksig, stepping: 0); |
211 | } |
212 | |
213 | static void do_signal(struct pt_regs *regs) |
214 | { |
215 | struct ksignal ksig; |
216 | |
217 | if (get_signal(ksig: &ksig)) { |
218 | /* Actually deliver the signal */ |
219 | handle_signal(ksig: &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 | */ |
255 | asmlinkage 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 | } |
268 | |