1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * OpenRISC signal.c 4 * 5 * Linux architectural port borrowing liberally from similar works of 6 * others. All original copyrights apply as per the original source 7 * declaration. 8 * 9 * Modifications for the OpenRISC architecture: 10 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com> 11 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se> 12 */ 13 14 #include <linux/sched.h> 15 #include <linux/mm.h> 16 #include <linux/smp.h> 17 #include <linux/kernel.h> 18 #include <linux/signal.h> 19 #include <linux/errno.h> 20 #include <linux/wait.h> 21 #include <linux/ptrace.h> 22 #include <linux/unistd.h> 23 #include <linux/stddef.h> 24 #include <linux/resume_user_mode.h> 25 26 #include <asm/processor.h> 27 #include <asm/syscall.h> 28 #include <asm/ucontext.h> 29 #include <linux/uaccess.h> 30 31 struct rt_sigframe { 32 struct siginfo info; 33 struct ucontext uc; 34 unsigned char retcode[16]; /* trampoline code */ 35 }; 36 37 static int restore_sigcontext(struct pt_regs *regs, 38 struct sigcontext __user *sc) 39 { 40 int err = 0; 41 42 /* Always make any pending restarted system calls return -EINTR */ 43 current->restart_block.fn = do_no_restart_syscall; 44 45 /* 46 * Restore the regs from &sc->regs. 47 * (sc is already checked since the sigframe was 48 * checked in sys_sigreturn previously) 49 */ 50 err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long)); 51 err |= __copy_from_user(®s->pc, &sc->regs.pc, sizeof(unsigned long)); 52 err |= __copy_from_user(®s->sr, &sc->regs.sr, sizeof(unsigned long)); 53 err |= __copy_from_user(®s->fpcsr, &sc->fpcsr, sizeof(unsigned long)); 54 55 /* make sure the SM-bit is cleared so user-mode cannot fool us */ 56 regs->sr &= ~SPR_SR_SM; 57 58 regs->orig_gpr11 = -1; /* Avoid syscall restart checks */ 59 60 /* TODO: the other ports use regs->orig_XX to disable syscall checks 61 * after this completes, but we don't use that mechanism. maybe we can 62 * use it now ? 63 */ 64 65 return err; 66 } 67 68 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs) 69 { 70 struct rt_sigframe __user *frame = (struct rt_sigframe __user *)regs->sp; 71 sigset_t set; 72 73 /* 74 * Since we stacked the signal on a dword boundary, 75 * then frame should be dword aligned here. If it's 76 * not, then the user is trying to mess with us. 77 */ 78 if (((unsigned long)frame) & 3) 79 goto badframe; 80 81 if (!access_ok(frame, sizeof(*frame))) 82 goto badframe; 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->gpr[11]; 95 96 badframe: 97 force_sig(SIGSEGV); 98 return 0; 99 } 100 101 /* 102 * Set up a signal frame. 103 */ 104 105 static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc) 106 { 107 int err = 0; 108 109 /* copy the regs */ 110 /* There should be no need to save callee-saved registers here... 111 * ...but we save them anyway. Revisit this 112 */ 113 err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long)); 114 err |= __copy_to_user(&sc->regs.pc, ®s->pc, sizeof(unsigned long)); 115 err |= __copy_to_user(&sc->regs.sr, ®s->sr, sizeof(unsigned long)); 116 err |= __copy_to_user(&sc->fpcsr, ®s->fpcsr, sizeof(unsigned long)); 117 118 return err; 119 } 120 121 static inline unsigned long align_sigframe(unsigned long sp) 122 { 123 return sp & ~3UL; 124 } 125 126 /* 127 * Work out where the signal frame should go. It's either on the user stack 128 * or the alternate stack. 129 */ 130 131 static inline void __user *get_sigframe(struct ksignal *ksig, 132 struct pt_regs *regs, size_t frame_size) 133 { 134 unsigned long sp = regs->sp; 135 136 /* redzone */ 137 sp -= STACK_FRAME_OVERHEAD; 138 sp = sigsp(sp, ksig); 139 sp = align_sigframe(sp - frame_size); 140 141 return (void __user *)sp; 142 } 143 144 /* grab and setup a signal frame. 145 * 146 * basically we stack a lot of state info, and arrange for the 147 * user-mode program to return to the kernel using either a 148 * trampoline which performs the syscall sigreturn, or a provided 149 * user-mode trampoline. 150 */ 151 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set, 152 struct pt_regs *regs) 153 { 154 struct rt_sigframe __user *frame; 155 unsigned long return_ip; 156 int err = 0; 157 158 frame = get_sigframe(ksig, regs, sizeof(*frame)); 159 160 if (!access_ok(frame, sizeof(*frame))) 161 return -EFAULT; 162 163 /* Create siginfo. */ 164 if (ksig->ka.sa.sa_flags & SA_SIGINFO) 165 err |= copy_siginfo_to_user(&frame->info, &ksig->info); 166 167 /* Create the ucontext. */ 168 err |= __put_user(0, &frame->uc.uc_flags); 169 err |= __put_user(NULL, &frame->uc.uc_link); 170 err |= __save_altstack(&frame->uc.uc_stack, regs->sp); 171 err |= setup_sigcontext(regs, &frame->uc.uc_mcontext); 172 173 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)); 174 175 if (err) 176 return -EFAULT; 177 178 /* trampoline - the desired return ip is the retcode itself */ 179 return_ip = (unsigned long)&frame->retcode; 180 /* This is: 181 l.ori r11,r0,__NR_sigreturn 182 l.sys 1 183 */ 184 err |= __put_user(0xa960, (short __user *)(frame->retcode + 0)); 185 err |= __put_user(__NR_rt_sigreturn, (short __user *)(frame->retcode + 2)); 186 err |= __put_user(0x20000001, (unsigned long __user *)(frame->retcode + 4)); 187 err |= __put_user(0x15000000, (unsigned long __user *)(frame->retcode + 8)); 188 189 if (err) 190 return -EFAULT; 191 192 /* Set up registers for signal handler */ 193 regs->pc = (unsigned long)ksig->ka.sa.sa_handler; /* what we enter NOW */ 194 regs->gpr[9] = (unsigned long)return_ip; /* what we enter LATER */ 195 regs->gpr[3] = (unsigned long)ksig->sig; /* arg 1: signo */ 196 regs->gpr[4] = (unsigned long)&frame->info; /* arg 2: (siginfo_t*) */ 197 regs->gpr[5] = (unsigned long)&frame->uc; /* arg 3: ucontext */ 198 199 /* actually move the usp to reflect the stacked frame */ 200 regs->sp = (unsigned long)frame; 201 202 return 0; 203 } 204 205 static inline void 206 handle_signal(struct ksignal *ksig, struct pt_regs *regs) 207 { 208 int ret; 209 210 ret = setup_rt_frame(ksig, sigmask_to_save(), regs); 211 212 signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP)); 213 } 214 215 /* 216 * Note that 'init' is a special process: it doesn't get signals it doesn't 217 * want to handle. Thus you cannot kill init even with a SIGKILL even by 218 * mistake. 219 * 220 * Also note that the regs structure given here as an argument, is the latest 221 * pushed pt_regs. It may or may not be the same as the first pushed registers 222 * when the initial usermode->kernelmode transition took place. Therefore 223 * we can use user_mode(regs) to see if we came directly from kernel or user 224 * mode below. 225 */ 226 227 int do_signal(struct pt_regs *regs, int syscall) 228 { 229 struct ksignal ksig; 230 unsigned long continue_addr = 0; 231 unsigned long restart_addr = 0; 232 unsigned long retval = 0; 233 int restart = 0; 234 235 if (syscall) { 236 continue_addr = regs->pc; 237 restart_addr = continue_addr - 4; 238 retval = regs->gpr[11]; 239 240 /* 241 * Setup syscall restart here so that a debugger will 242 * see the already changed PC. 243 */ 244 switch (retval) { 245 case -ERESTART_RESTARTBLOCK: 246 restart = -2; 247 fallthrough; 248 case -ERESTARTNOHAND: 249 case -ERESTARTSYS: 250 case -ERESTARTNOINTR: 251 restart++; 252 regs->gpr[11] = regs->orig_gpr11; 253 regs->pc = restart_addr; 254 break; 255 } 256 } 257 258 /* 259 * Get the signal to deliver. During the call to get_signal the 260 * debugger may change all our registers so we may need to revert 261 * the decision to restart the syscall; specifically, if the PC is 262 * changed, don't restart the syscall. 263 */ 264 if (get_signal(&ksig)) { 265 if (unlikely(restart) && regs->pc == restart_addr) { 266 if (retval == -ERESTARTNOHAND || 267 retval == -ERESTART_RESTARTBLOCK 268 || (retval == -ERESTARTSYS 269 && !(ksig.ka.sa.sa_flags & SA_RESTART))) { 270 /* No automatic restart */ 271 regs->gpr[11] = -EINTR; 272 regs->pc = continue_addr; 273 } 274 } 275 handle_signal(&ksig, regs); 276 } else { 277 /* no handler */ 278 restore_saved_sigmask(); 279 /* 280 * Restore pt_regs PC as syscall restart will be handled by 281 * kernel without return to userspace 282 */ 283 if (unlikely(restart) && regs->pc == restart_addr) { 284 regs->pc = continue_addr; 285 return restart; 286 } 287 } 288 289 return 0; 290 } 291 292 asmlinkage int 293 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) 294 { 295 do { 296 if (likely(thread_flags & _TIF_NEED_RESCHED)) { 297 schedule(); 298 } else { 299 if (unlikely(!user_mode(regs))) 300 return 0; 301 local_irq_enable(); 302 if (thread_flags & (_TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL)) { 303 int restart = do_signal(regs, syscall); 304 if (unlikely(restart)) { 305 /* 306 * Restart without handlers. 307 * Deal with it without leaving 308 * the kernel space. 309 */ 310 return restart; 311 } 312 syscall = 0; 313 } else { 314 resume_user_mode_work(regs); 315 } 316 } 317 local_irq_disable(); 318 thread_flags = read_thread_flags(); 319 } while (thread_flags & _TIF_WORK_MASK); 320 return 0; 321 } 322