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 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs); 38 39 asmlinkage int do_work_pending(struct pt_regs *regs, unsigned int thread_flags, 40 int syscall); 41 42 static int restore_sigcontext(struct pt_regs *regs, 43 struct sigcontext __user *sc) 44 { 45 int err = 0; 46 47 /* Always make any pending restarted system calls return -EINTR */ 48 current->restart_block.fn = do_no_restart_syscall; 49 50 /* 51 * Restore the regs from &sc->regs. 52 * (sc is already checked since the sigframe was 53 * checked in sys_sigreturn previously) 54 */ 55 err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long)); 56 err |= __copy_from_user(®s->pc, &sc->regs.pc, sizeof(unsigned long)); 57 err |= __copy_from_user(®s->sr, &sc->regs.sr, sizeof(unsigned long)); 58 err |= __copy_from_user(®s->fpcsr, &sc->fpcsr, sizeof(unsigned long)); 59 60 /* make sure the SM-bit is cleared so user-mode cannot fool us */ 61 regs->sr &= ~SPR_SR_SM; 62 63 regs->orig_gpr11 = -1; /* Avoid syscall restart checks */ 64 65 /* TODO: the other ports use regs->orig_XX to disable syscall checks 66 * after this completes, but we don't use that mechanism. maybe we can 67 * use it now ? 68 */ 69 70 return err; 71 } 72 73 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs) 74 { 75 struct rt_sigframe __user *frame = (struct rt_sigframe __user *)regs->sp; 76 sigset_t set; 77 78 /* 79 * Since we stacked the signal on a dword boundary, 80 * then frame should be dword aligned here. If it's 81 * not, then the user is trying to mess with us. 82 */ 83 if (((unsigned long)frame) & 3) 84 goto badframe; 85 86 if (!access_ok(frame, sizeof(*frame))) 87 goto badframe; 88 if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set))) 89 goto badframe; 90 91 set_current_blocked(&set); 92 93 if (restore_sigcontext(regs, &frame->uc.uc_mcontext)) 94 goto badframe; 95 96 if (restore_altstack(&frame->uc.uc_stack)) 97 goto badframe; 98 99 return regs->gpr[11]; 100 101 badframe: 102 force_sig(SIGSEGV); 103 return 0; 104 } 105 106 /* 107 * Set up a signal frame. 108 */ 109 110 static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc) 111 { 112 int err = 0; 113 114 /* copy the regs */ 115 /* There should be no need to save callee-saved registers here... 116 * ...but we save them anyway. Revisit this 117 */ 118 err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long)); 119 err |= __copy_to_user(&sc->regs.pc, ®s->pc, sizeof(unsigned long)); 120 err |= __copy_to_user(&sc->regs.sr, ®s->sr, sizeof(unsigned long)); 121 err |= __copy_to_user(&sc->fpcsr, ®s->fpcsr, sizeof(unsigned long)); 122 123 return err; 124 } 125 126 static inline unsigned long align_sigframe(unsigned long sp) 127 { 128 return sp & ~3UL; 129 } 130 131 /* 132 * Work out where the signal frame should go. It's either on the user stack 133 * or the alternate stack. 134 */ 135 136 static inline void __user *get_sigframe(struct ksignal *ksig, 137 struct pt_regs *regs, size_t frame_size) 138 { 139 unsigned long sp = regs->sp; 140 141 /* redzone */ 142 sp -= STACK_FRAME_OVERHEAD; 143 sp = sigsp(sp, ksig); 144 sp = align_sigframe(sp - frame_size); 145 146 return (void __user *)sp; 147 } 148 149 /* grab and setup a signal frame. 150 * 151 * basically we stack a lot of state info, and arrange for the 152 * user-mode program to return to the kernel using either a 153 * trampoline which performs the syscall sigreturn, or a provided 154 * user-mode trampoline. 155 */ 156 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set, 157 struct pt_regs *regs) 158 { 159 struct rt_sigframe __user *frame; 160 unsigned long return_ip; 161 int err = 0; 162 163 frame = get_sigframe(ksig, regs, sizeof(*frame)); 164 165 if (!access_ok(frame, sizeof(*frame))) 166 return -EFAULT; 167 168 /* Create siginfo. */ 169 if (ksig->ka.sa.sa_flags & SA_SIGINFO) 170 err |= copy_siginfo_to_user(&frame->info, &ksig->info); 171 172 /* Create the ucontext. */ 173 err |= __put_user(0, &frame->uc.uc_flags); 174 err |= __put_user(NULL, &frame->uc.uc_link); 175 err |= __save_altstack(&frame->uc.uc_stack, regs->sp); 176 err |= setup_sigcontext(regs, &frame->uc.uc_mcontext); 177 178 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)); 179 180 if (err) 181 return -EFAULT; 182 183 /* trampoline - the desired return ip is the retcode itself */ 184 return_ip = (unsigned long)&frame->retcode; 185 /* This is: 186 l.ori r11,r0,__NR_sigreturn 187 l.sys 1 188 */ 189 err |= __put_user(0xa960, (short __user *)(frame->retcode + 0)); 190 err |= __put_user(__NR_rt_sigreturn, (short __user *)(frame->retcode + 2)); 191 err |= __put_user(0x20000001, (unsigned long __user *)(frame->retcode + 4)); 192 err |= __put_user(0x15000000, (unsigned long __user *)(frame->retcode + 8)); 193 194 if (err) 195 return -EFAULT; 196 197 /* Set up registers for signal handler */ 198 regs->pc = (unsigned long)ksig->ka.sa.sa_handler; /* what we enter NOW */ 199 regs->gpr[9] = (unsigned long)return_ip; /* what we enter LATER */ 200 regs->gpr[3] = (unsigned long)ksig->sig; /* arg 1: signo */ 201 regs->gpr[4] = (unsigned long)&frame->info; /* arg 2: (siginfo_t*) */ 202 regs->gpr[5] = (unsigned long)&frame->uc; /* arg 3: ucontext */ 203 204 /* actually move the usp to reflect the stacked frame */ 205 regs->sp = (unsigned long)frame; 206 207 return 0; 208 } 209 210 static inline void 211 handle_signal(struct ksignal *ksig, struct pt_regs *regs) 212 { 213 int ret; 214 215 ret = setup_rt_frame(ksig, sigmask_to_save(), regs); 216 217 signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP)); 218 } 219 220 /* 221 * Note that 'init' is a special process: it doesn't get signals it doesn't 222 * want to handle. Thus you cannot kill init even with a SIGKILL even by 223 * mistake. 224 * 225 * Also note that the regs structure given here as an argument, is the latest 226 * pushed pt_regs. It may or may not be the same as the first pushed registers 227 * when the initial usermode->kernelmode transition took place. Therefore 228 * we can use user_mode(regs) to see if we came directly from kernel or user 229 * mode below. 230 */ 231 232 static int do_signal(struct pt_regs *regs, int syscall) 233 { 234 struct ksignal ksig; 235 unsigned long continue_addr = 0; 236 unsigned long restart_addr = 0; 237 unsigned long retval = 0; 238 int restart = 0; 239 240 if (syscall) { 241 continue_addr = regs->pc; 242 restart_addr = continue_addr - 4; 243 retval = regs->gpr[11]; 244 245 /* 246 * Setup syscall restart here so that a debugger will 247 * see the already changed PC. 248 */ 249 switch (retval) { 250 case -ERESTART_RESTARTBLOCK: 251 restart = -2; 252 fallthrough; 253 case -ERESTARTNOHAND: 254 case -ERESTARTSYS: 255 case -ERESTARTNOINTR: 256 restart++; 257 regs->gpr[11] = regs->orig_gpr11; 258 regs->pc = restart_addr; 259 break; 260 } 261 } 262 263 /* 264 * Get the signal to deliver. During the call to get_signal the 265 * debugger may change all our registers so we may need to revert 266 * the decision to restart the syscall; specifically, if the PC is 267 * changed, don't restart the syscall. 268 */ 269 if (get_signal(&ksig)) { 270 if (unlikely(restart) && regs->pc == restart_addr) { 271 if (retval == -ERESTARTNOHAND || 272 retval == -ERESTART_RESTARTBLOCK 273 || (retval == -ERESTARTSYS 274 && !(ksig.ka.sa.sa_flags & SA_RESTART))) { 275 /* No automatic restart */ 276 regs->gpr[11] = -EINTR; 277 regs->pc = continue_addr; 278 } 279 } 280 handle_signal(&ksig, regs); 281 } else { 282 /* no handler */ 283 restore_saved_sigmask(); 284 /* 285 * Restore pt_regs PC as syscall restart will be handled by 286 * kernel without return to userspace 287 */ 288 if (unlikely(restart) && regs->pc == restart_addr) { 289 regs->pc = continue_addr; 290 return restart; 291 } 292 } 293 294 return 0; 295 } 296 297 asmlinkage int 298 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) 299 { 300 do { 301 if (likely(thread_flags & _TIF_NEED_RESCHED)) { 302 schedule(); 303 } else { 304 if (unlikely(!user_mode(regs))) 305 return 0; 306 local_irq_enable(); 307 if (thread_flags & (_TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL)) { 308 int restart = do_signal(regs, syscall); 309 if (unlikely(restart)) { 310 /* 311 * Restart without handlers. 312 * Deal with it without leaving 313 * the kernel space. 314 */ 315 return restart; 316 } 317 syscall = 0; 318 } else { 319 resume_user_mode_work(regs); 320 } 321 } 322 local_irq_disable(); 323 thread_flags = read_thread_flags(); 324 } while (thread_flags & _TIF_WORK_MASK); 325 return 0; 326 } 327