1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 1991, 1992 Linus Torvalds 4 * Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs 5 */ 6 7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 8 9 #include <linux/kernel.h> 10 #include <linux/errno.h> 11 #include <linux/unistd.h> 12 #include <linux/uaccess.h> 13 #include <linux/syscalls.h> 14 15 #include <asm/ucontext.h> 16 #include <asm/fpu/signal.h> 17 #include <asm/sighandling.h> 18 19 #include <asm/syscall.h> 20 #include <asm/sigframe.h> 21 #include <asm/signal.h> 22 23 /* 24 * If regs->ss will cause an IRET fault, change it. Otherwise leave it 25 * alone. Using this generally makes no sense unless 26 * user_64bit_mode(regs) would return true. 27 */ 28 static void force_valid_ss(struct pt_regs *regs) 29 { 30 u32 ar; 31 asm volatile ("lar %[old_ss], %[ar]\n\t" 32 "jz 1f\n\t" /* If invalid: */ 33 "xorl %[ar], %[ar]\n\t" /* set ar = 0 */ 34 "1:" 35 : [ar] "=r" (ar) 36 : [old_ss] "rm" ((u16)regs->ss)); 37 38 /* 39 * For a valid 64-bit user context, we need DPL 3, type 40 * read-write data or read-write exp-down data, and S and P 41 * set. We can't use VERW because VERW doesn't check the 42 * P bit. 43 */ 44 ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK; 45 if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) && 46 ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN)) 47 regs->ss = __USER_DS; 48 } 49 50 static bool restore_sigcontext(struct pt_regs *regs, 51 struct sigcontext __user *usc, 52 unsigned long uc_flags) 53 { 54 struct sigcontext sc; 55 56 /* Always make any pending restarted system calls return -EINTR */ 57 current->restart_block.fn = do_no_restart_syscall; 58 59 if (copy_from_user(&sc, usc, offsetof(struct sigcontext, reserved1))) 60 return false; 61 62 regs->bx = sc.bx; 63 regs->cx = sc.cx; 64 regs->dx = sc.dx; 65 regs->si = sc.si; 66 regs->di = sc.di; 67 regs->bp = sc.bp; 68 regs->ax = sc.ax; 69 regs->sp = sc.sp; 70 regs->ip = sc.ip; 71 regs->r8 = sc.r8; 72 regs->r9 = sc.r9; 73 regs->r10 = sc.r10; 74 regs->r11 = sc.r11; 75 regs->r12 = sc.r12; 76 regs->r13 = sc.r13; 77 regs->r14 = sc.r14; 78 regs->r15 = sc.r15; 79 80 /* Get CS/SS and force CPL3 */ 81 regs->cs = sc.cs | 0x03; 82 regs->ss = sc.ss | 0x03; 83 84 regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS); 85 /* disable syscall checks */ 86 regs->orig_ax = -1; 87 88 /* 89 * Fix up SS if needed for the benefit of old DOSEMU and 90 * CRIU. 91 */ 92 if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs))) 93 force_valid_ss(regs); 94 95 return fpu__restore_sig((void __user *)sc.fpstate, 0); 96 } 97 98 static __always_inline int 99 __unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate, 100 struct pt_regs *regs, unsigned long mask) 101 { 102 unsafe_put_user(regs->di, &sc->di, Efault); 103 unsafe_put_user(regs->si, &sc->si, Efault); 104 unsafe_put_user(regs->bp, &sc->bp, Efault); 105 unsafe_put_user(regs->sp, &sc->sp, Efault); 106 unsafe_put_user(regs->bx, &sc->bx, Efault); 107 unsafe_put_user(regs->dx, &sc->dx, Efault); 108 unsafe_put_user(regs->cx, &sc->cx, Efault); 109 unsafe_put_user(regs->ax, &sc->ax, Efault); 110 unsafe_put_user(regs->r8, &sc->r8, Efault); 111 unsafe_put_user(regs->r9, &sc->r9, Efault); 112 unsafe_put_user(regs->r10, &sc->r10, Efault); 113 unsafe_put_user(regs->r11, &sc->r11, Efault); 114 unsafe_put_user(regs->r12, &sc->r12, Efault); 115 unsafe_put_user(regs->r13, &sc->r13, Efault); 116 unsafe_put_user(regs->r14, &sc->r14, Efault); 117 unsafe_put_user(regs->r15, &sc->r15, Efault); 118 119 unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault); 120 unsafe_put_user(current->thread.error_code, &sc->err, Efault); 121 unsafe_put_user(regs->ip, &sc->ip, Efault); 122 unsafe_put_user(regs->flags, &sc->flags, Efault); 123 unsafe_put_user(regs->cs, &sc->cs, Efault); 124 unsafe_put_user(0, &sc->gs, Efault); 125 unsafe_put_user(0, &sc->fs, Efault); 126 unsafe_put_user(regs->ss, &sc->ss, Efault); 127 128 unsafe_put_user(fpstate, (unsigned long __user *)&sc->fpstate, Efault); 129 130 /* non-iBCS2 extensions.. */ 131 unsafe_put_user(mask, &sc->oldmask, Efault); 132 unsafe_put_user(current->thread.cr2, &sc->cr2, Efault); 133 return 0; 134 Efault: 135 return -EFAULT; 136 } 137 138 #define unsafe_put_sigcontext(sc, fp, regs, set, label) \ 139 do { \ 140 if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0])) \ 141 goto label; \ 142 } while(0); 143 144 #define unsafe_put_sigmask(set, frame, label) \ 145 unsafe_put_user(*(__u64 *)(set), \ 146 (__u64 __user *)&(frame)->uc.uc_sigmask, \ 147 label) 148 149 static unsigned long frame_uc_flags(struct pt_regs *regs) 150 { 151 unsigned long flags; 152 153 if (boot_cpu_has(X86_FEATURE_XSAVE)) 154 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS; 155 else 156 flags = UC_SIGCONTEXT_SS; 157 158 if (likely(user_64bit_mode(regs))) 159 flags |= UC_STRICT_RESTORE_SS; 160 161 return flags; 162 } 163 164 int x64_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs) 165 { 166 sigset_t *set = sigmask_to_save(); 167 struct rt_sigframe __user *frame; 168 void __user *fp = NULL; 169 unsigned long uc_flags; 170 171 /* x86-64 should always use SA_RESTORER. */ 172 if (!(ksig->ka.sa.sa_flags & SA_RESTORER)) 173 return -EFAULT; 174 175 frame = get_sigframe(ksig, regs, sizeof(struct rt_sigframe), &fp); 176 uc_flags = frame_uc_flags(regs); 177 178 if (!user_access_begin(frame, sizeof(*frame))) 179 return -EFAULT; 180 181 /* Create the ucontext. */ 182 unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault); 183 unsafe_put_user(0, &frame->uc.uc_link, Efault); 184 unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault); 185 186 /* Set up to return from userspace. If provided, use a stub 187 already in userspace. */ 188 unsafe_put_user(ksig->ka.sa.sa_restorer, &frame->pretcode, Efault); 189 unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault); 190 unsafe_put_sigmask(set, frame, Efault); 191 user_access_end(); 192 193 if (ksig->ka.sa.sa_flags & SA_SIGINFO) { 194 if (copy_siginfo_to_user(&frame->info, &ksig->info)) 195 return -EFAULT; 196 } 197 198 /* Set up registers for signal handler */ 199 regs->di = ksig->sig; 200 /* In case the signal handler was declared without prototypes */ 201 regs->ax = 0; 202 203 /* This also works for non SA_SIGINFO handlers because they expect the 204 next argument after the signal number on the stack. */ 205 regs->si = (unsigned long)&frame->info; 206 regs->dx = (unsigned long)&frame->uc; 207 regs->ip = (unsigned long) ksig->ka.sa.sa_handler; 208 209 regs->sp = (unsigned long)frame; 210 211 /* 212 * Set up the CS and SS registers to run signal handlers in 213 * 64-bit mode, even if the handler happens to be interrupting 214 * 32-bit or 16-bit code. 215 * 216 * SS is subtle. In 64-bit mode, we don't need any particular 217 * SS descriptor, but we do need SS to be valid. It's possible 218 * that the old SS is entirely bogus -- this can happen if the 219 * signal we're trying to deliver is #GP or #SS caused by a bad 220 * SS value. We also have a compatibility issue here: DOSEMU 221 * relies on the contents of the SS register indicating the 222 * SS value at the time of the signal, even though that code in 223 * DOSEMU predates sigreturn's ability to restore SS. (DOSEMU 224 * avoids relying on sigreturn to restore SS; instead it uses 225 * a trampoline.) So we do our best: if the old SS was valid, 226 * we keep it. Otherwise we replace it. 227 */ 228 regs->cs = __USER_CS; 229 230 if (unlikely(regs->ss != __USER_DS)) 231 force_valid_ss(regs); 232 233 return 0; 234 235 Efault: 236 user_access_end(); 237 return -EFAULT; 238 } 239 240 /* 241 * Do a signal return; undo the signal stack. 242 */ 243 SYSCALL_DEFINE0(rt_sigreturn) 244 { 245 struct pt_regs *regs = current_pt_regs(); 246 struct rt_sigframe __user *frame; 247 sigset_t set; 248 unsigned long uc_flags; 249 250 frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long)); 251 if (!access_ok(frame, sizeof(*frame))) 252 goto badframe; 253 if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask)) 254 goto badframe; 255 if (__get_user(uc_flags, &frame->uc.uc_flags)) 256 goto badframe; 257 258 set_current_blocked(&set); 259 260 if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) 261 goto badframe; 262 263 if (restore_altstack(&frame->uc.uc_stack)) 264 goto badframe; 265 266 return regs->ax; 267 268 badframe: 269 signal_fault(regs, frame, "rt_sigreturn"); 270 return 0; 271 } 272 273 #ifdef CONFIG_X86_X32_ABI 274 static int x32_copy_siginfo_to_user(struct compat_siginfo __user *to, 275 const struct kernel_siginfo *from) 276 { 277 struct compat_siginfo new; 278 279 copy_siginfo_to_external32(&new, from); 280 if (from->si_signo == SIGCHLD) { 281 new._sifields._sigchld_x32._utime = from->si_utime; 282 new._sifields._sigchld_x32._stime = from->si_stime; 283 } 284 if (copy_to_user(to, &new, sizeof(struct compat_siginfo))) 285 return -EFAULT; 286 return 0; 287 } 288 289 int copy_siginfo_to_user32(struct compat_siginfo __user *to, 290 const struct kernel_siginfo *from) 291 { 292 if (in_x32_syscall()) 293 return x32_copy_siginfo_to_user(to, from); 294 return __copy_siginfo_to_user32(to, from); 295 } 296 297 int x32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs) 298 { 299 compat_sigset_t *set = (compat_sigset_t *) sigmask_to_save(); 300 struct rt_sigframe_x32 __user *frame; 301 unsigned long uc_flags; 302 void __user *restorer; 303 void __user *fp = NULL; 304 305 if (!(ksig->ka.sa.sa_flags & SA_RESTORER)) 306 return -EFAULT; 307 308 frame = get_sigframe(ksig, regs, sizeof(*frame), &fp); 309 310 uc_flags = frame_uc_flags(regs); 311 312 if (!user_access_begin(frame, sizeof(*frame))) 313 return -EFAULT; 314 315 /* Create the ucontext. */ 316 unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault); 317 unsafe_put_user(0, &frame->uc.uc_link, Efault); 318 unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault); 319 unsafe_put_user(0, &frame->uc.uc__pad0, Efault); 320 restorer = ksig->ka.sa.sa_restorer; 321 unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault); 322 unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault); 323 unsafe_put_sigmask(set, frame, Efault); 324 user_access_end(); 325 326 if (ksig->ka.sa.sa_flags & SA_SIGINFO) { 327 if (x32_copy_siginfo_to_user(&frame->info, &ksig->info)) 328 return -EFAULT; 329 } 330 331 /* Set up registers for signal handler */ 332 regs->sp = (unsigned long) frame; 333 regs->ip = (unsigned long) ksig->ka.sa.sa_handler; 334 335 /* We use the x32 calling convention here... */ 336 regs->di = ksig->sig; 337 regs->si = (unsigned long) &frame->info; 338 regs->dx = (unsigned long) &frame->uc; 339 340 loadsegment(ds, __USER_DS); 341 loadsegment(es, __USER_DS); 342 343 regs->cs = __USER_CS; 344 regs->ss = __USER_DS; 345 346 return 0; 347 348 Efault: 349 user_access_end(); 350 return -EFAULT; 351 } 352 353 COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn) 354 { 355 struct pt_regs *regs = current_pt_regs(); 356 struct rt_sigframe_x32 __user *frame; 357 sigset_t set; 358 unsigned long uc_flags; 359 360 frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8); 361 362 if (!access_ok(frame, sizeof(*frame))) 363 goto badframe; 364 if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask)) 365 goto badframe; 366 if (__get_user(uc_flags, &frame->uc.uc_flags)) 367 goto badframe; 368 369 set_current_blocked(&set); 370 371 if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) 372 goto badframe; 373 374 if (compat_restore_altstack(&frame->uc.uc_stack)) 375 goto badframe; 376 377 return regs->ax; 378 379 badframe: 380 signal_fault(regs, frame, "x32 rt_sigreturn"); 381 return 0; 382 } 383 #endif /* CONFIG_X86_X32_ABI */ 384