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(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 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 } 100 101 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 } 112 113 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, 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 } 176 177 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) 178 { 179 sigset_t *oldset = sigmask_to_save(); 180 int ret; 181 182 rseq_signal_deliver(ksig, regs); 183 184 /* Are we from a system call? */ 185 if (in_syscall(regs)) { 186 /* Avoid additional syscall restarting via ret_from_exception */ 187 forget_syscall(regs); 188 189 /* If so, check system call restarting.. */ 190 switch (regs->a0) { 191 case -ERESTART_RESTARTBLOCK: 192 case -ERESTARTNOHAND: 193 regs->a0 = -EINTR; 194 break; 195 196 case -ERESTARTSYS: 197 if (!(ksig->ka.sa.sa_flags & SA_RESTART)) { 198 regs->a0 = -EINTR; 199 break; 200 } 201 fallthrough; 202 case -ERESTARTNOINTR: 203 regs->a0 = regs->orig_a0; 204 regs->pc -= TRAP0_SIZE; 205 break; 206 } 207 } 208 209 /* Set up the stack frame */ 210 ret = setup_rt_frame(ksig, oldset, regs); 211 212 signal_setup_done(ret, ksig, 0); 213 } 214 215 static void do_signal(struct pt_regs *regs) 216 { 217 struct ksignal ksig; 218 219 if (get_signal(&ksig)) { 220 /* Actually deliver the signal */ 221 handle_signal(&ksig, regs); 222 return; 223 } 224 225 /* Did we come from a system call? */ 226 if (in_syscall(regs)) { 227 /* Avoid additional syscall restarting via ret_from_exception */ 228 forget_syscall(regs); 229 230 /* Restart the system call - no handlers present */ 231 switch (regs->a0) { 232 case -ERESTARTNOHAND: 233 case -ERESTARTSYS: 234 case -ERESTARTNOINTR: 235 regs->a0 = regs->orig_a0; 236 regs->pc -= TRAP0_SIZE; 237 break; 238 case -ERESTART_RESTARTBLOCK: 239 regs->a0 = regs->orig_a0; 240 regs_syscallid(regs) = __NR_restart_syscall; 241 regs->pc -= TRAP0_SIZE; 242 break; 243 } 244 } 245 246 /* 247 * If there is no signal to deliver, we just put the saved 248 * sigmask back. 249 */ 250 restore_saved_sigmask(); 251 } 252 253 /* 254 * notification of userspace execution resumption 255 * - triggered by the _TIF_WORK_MASK flags 256 */ 257 asmlinkage void do_notify_resume(struct pt_regs *regs, 258 unsigned long thread_info_flags) 259 { 260 if (thread_info_flags & _TIF_UPROBE) 261 uprobe_notify_resume(regs); 262 263 /* Handle pending signal delivery */ 264 if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) 265 do_signal(regs); 266 267 if (thread_info_flags & _TIF_NOTIFY_RESUME) 268 resume_user_mode_work(regs); 269 } 270