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>
restore_fpu_state(struct sigcontext __user * sc)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
save_fpu_state(struct sigcontext __user * sc)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
restore_sigcontext(struct pt_regs * regs,struct sigcontext __user * sc)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(regs, &sc->sc_pt_regs, 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
SYSCALL_DEFINE0(rt_sigreturn)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(&set, &frame->uc.uc_sigmask, sizeof(set)))
84 goto badframe;
85
86 set_current_blocked(&set);
87
88 if (restore_sigcontext(regs, &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
setup_sigcontext(struct rt_sigframe __user * frame,struct pt_regs * regs)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(&sc->sc_pt_regs, regs, sizeof(struct pt_regs));
108 err |= save_fpu_state(sc);
109
110 return err;
111 }
112
get_sigframe(struct ksignal * ksig,struct pt_regs * regs,size_t framesize)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
setup_rt_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)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, sizeof(*frame));
143 if (!access_ok(frame, sizeof(*frame)))
144 return -EFAULT;
145
146 err |= copy_siginfo_to_user(&frame->info, &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(&frame->uc.uc_sigmask, set, 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
handle_signal(struct ksignal * ksig,struct pt_regs * regs)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, oldset, regs);
209
210 signal_setup_done(ret, ksig, 0);
211 }
212
do_signal(struct pt_regs * regs)213 static void do_signal(struct pt_regs *regs)
214 {
215 struct ksignal ksig;
216
217 if (get_signal(&ksig)) {
218 /* Actually deliver the signal */
219 handle_signal(&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 */
do_notify_resume(struct pt_regs * regs,unsigned long thread_info_flags)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