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 /* 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 } 212 213 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 */ 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