arch/x86/ia32/ia32_signal.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/arch/x86_64/ia32/ia32_signal.c
   4  *
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  *
   7  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
   8  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
   9  *  2000-12-*   x86-64 compatibility mode signal handling by Andi Kleen
  10  */
  11
  12 #include <linux/sched.h>
  13 #include <linux/sched/task_stack.h>
  14 #include <linux/mm.h>
  15 #include <linux/smp.h>
  16 #include <linux/kernel.h>
  17 #include <linux/errno.h>
  18 #include <linux/wait.h>
  19 #include <linux/unistd.h>
  20 #include <linux/stddef.h>
  21 #include <linux/personality.h>
  22 #include <linux/compat.h>
  23 #include <linux/binfmts.h>
  24 #include <linux/syscalls.h>
  25 #include <asm/ucontext.h>
  26 #include <linux/uaccess.h>
  27 #include <asm/fpu/internal.h>
  28 #include <asm/fpu/signal.h>
  29 #include <asm/ptrace.h>
  30 #include <asm/ia32_unistd.h>
  31 #include <asm/user32.h>
  32 #include <uapi/asm/sigcontext.h>
  33 #include <asm/proto.h>
  34 #include <asm/vdso.h>
  35 #include <asm/sigframe.h>
  36 #include <asm/sighandling.h>
  37 #include <asm/smap.h>
  38
  39 static inline void reload_segments(struct sigcontext_32 *sc)
  40 {
  41         unsigned int cur;
  42
  43         savesegment(gs, cur);
  44         if ((sc->gs | 0x03) != cur)
  45                 load_gs_index(sc->gs | 0x03);
  46         savesegment(fs, cur);
  47         if ((sc->fs | 0x03) != cur)
  48                 loadsegment(fs, sc->fs | 0x03);
  49         savesegment(ds, cur);
  50         if ((sc->ds | 0x03) != cur)
  51                 loadsegment(ds, sc->ds | 0x03);
  52         savesegment(es, cur);
  53         if ((sc->es | 0x03) != cur)
  54                 loadsegment(es, sc->es | 0x03);
  55 }
  56
  57 /*
  58  * Do a signal return; undo the signal stack.
  59  */
  60 static int ia32_restore_sigcontext(struct pt_regs *regs,
  61                                    struct sigcontext_32 __user *usc)
  62 {
  63         struct sigcontext_32 sc;
  64
  65         /* Always make any pending restarted system calls return -EINTR */
  66         current->restart_block.fn = do_no_restart_syscall;
  67
  68         if (unlikely(copy_from_user(&sc, usc, sizeof(sc))))
  69                 return -EFAULT;
  70
  71         /* Get only the ia32 registers. */
  72         regs->bx = sc.bx;
  73         regs->cx = sc.cx;
  74         regs->dx = sc.dx;
  75         regs->si = sc.si;
  76         regs->di = sc.di;
  77         regs->bp = sc.bp;
  78         regs->ax = sc.ax;
  79         regs->sp = sc.sp;
  80         regs->ip = sc.ip;
  81
  82         /* Get CS/SS and force CPL3 */
  83         regs->cs = sc.cs | 0x03;
  84         regs->ss = sc.ss | 0x03;
  85
  86         regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
  87         /* disable syscall checks */
  88         regs->orig_ax = -1;
  89
  90         /*
  91          * Reload fs and gs if they have changed in the signal
  92          * handler.  This does not handle long fs/gs base changes in
  93          * the handler, but does not clobber them at least in the
  94          * normal case.
  95          */
  96         reload_segments(&sc);
  97         return fpu__restore_sig(compat_ptr(sc.fpstate), 1);
  98 }
  99
 100 COMPAT_SYSCALL_DEFINE0(sigreturn)
 101 {
 102         struct pt_regs *regs = current_pt_regs();
 103         struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
 104         sigset_t set;
 105
 106         if (!access_ok(frame, sizeof(*frame)))
 107                 goto badframe;
 108         if (__get_user(set.sig[0], &frame->sc.oldmask)
 109             || __get_user(((__u32 *)&set)[1], &frame->extramask[0]))
 110                 goto badframe;
 111
 112         set_current_blocked(&set);
 113
 114         if (ia32_restore_sigcontext(regs, &frame->sc))
 115                 goto badframe;
 116         return regs->ax;
 117
 118 badframe:
 119         signal_fault(regs, frame, "32bit sigreturn");
 120         return 0;
 121 }
 122
 123 COMPAT_SYSCALL_DEFINE0(rt_sigreturn)
 124 {
 125         struct pt_regs *regs = current_pt_regs();
 126         struct rt_sigframe_ia32 __user *frame;
 127         sigset_t set;
 128
 129         frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
 130
 131         if (!access_ok(frame, sizeof(*frame)))
 132                 goto badframe;
 133         if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
 134                 goto badframe;
 135
 136         set_current_blocked(&set);
 137
 138         if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
 139                 goto badframe;
 140
 141         if (compat_restore_altstack(&frame->uc.uc_stack))
 142                 goto badframe;
 143
 144         return regs->ax;
 145
 146 badframe:
 147         signal_fault(regs, frame, "32bit rt sigreturn");
 148         return 0;
 149 }
 150
 151 /*
 152  * Set up a signal frame.
 153  */
 154
 155 #define get_user_seg(seg)       ({ unsigned int v; savesegment(seg, v); v; })
 156
 157 static __always_inline int
 158 __unsafe_setup_sigcontext32(struct sigcontext_32 __user *sc,
 159                             void __user *fpstate,
 160                             struct pt_regs *regs, unsigned int mask)
 161 {
 162         unsafe_put_user(get_user_seg(gs), (unsigned int __user *)&sc->gs, Efault);
 163         unsafe_put_user(get_user_seg(fs), (unsigned int __user *)&sc->fs, Efault);
 164         unsafe_put_user(get_user_seg(ds), (unsigned int __user *)&sc->ds, Efault);
 165         unsafe_put_user(get_user_seg(es), (unsigned int __user *)&sc->es, Efault);
 166
 167         unsafe_put_user(regs->di, &sc->di, Efault);
 168         unsafe_put_user(regs->si, &sc->si, Efault);
 169         unsafe_put_user(regs->bp, &sc->bp, Efault);
 170         unsafe_put_user(regs->sp, &sc->sp, Efault);
 171         unsafe_put_user(regs->bx, &sc->bx, Efault);
 172         unsafe_put_user(regs->dx, &sc->dx, Efault);
 173         unsafe_put_user(regs->cx, &sc->cx, Efault);
 174         unsafe_put_user(regs->ax, &sc->ax, Efault);
 175         unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
 176         unsafe_put_user(current->thread.error_code, &sc->err, Efault);
 177         unsafe_put_user(regs->ip, &sc->ip, Efault);
 178         unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
 179         unsafe_put_user(regs->flags, &sc->flags, Efault);
 180         unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
 181         unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
 182
 183         unsafe_put_user(ptr_to_compat(fpstate), &sc->fpstate, Efault);
 184
 185         /* non-iBCS2 extensions.. */
 186         unsafe_put_user(mask, &sc->oldmask, Efault);
 187         unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
 188         return 0;
 189
 190 Efault:
 191         return -EFAULT;
 192 }
 193
 194 #define unsafe_put_sigcontext32(sc, fp, regs, set, label)               \
 195 do {                                                                    \
 196         if (__unsafe_setup_sigcontext32(sc, fp, regs, set->sig[0]))     \
 197                 goto label;                                             \
 198 } while(0)
 199
 200 /*
 201  * Determine which stack to use..
 202  */
 203 static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
 204                                  size_t frame_size,
 205                                  void __user **fpstate)
 206 {
 207         unsigned long sp, fx_aligned, math_size;
 208
 209         /* Default to using normal stack */
 210         sp = regs->sp;
 211
 212         /* This is the X/Open sanctioned signal stack switching.  */
 213         if (ksig->ka.sa.sa_flags & SA_ONSTACK)
 214                 sp = sigsp(sp, ksig);
 215         /* This is the legacy signal stack switching. */
 216         else if (regs->ss != __USER32_DS &&
 217                 !(ksig->ka.sa.sa_flags & SA_RESTORER) &&
 218                  ksig->ka.sa.sa_restorer)
 219                 sp = (unsigned long) ksig->ka.sa.sa_restorer;
 220
 221         sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);
 222         *fpstate = (struct _fpstate_32 __user *) sp;
 223         if (copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned,
 224                                      math_size) < 0)
 225                 return (void __user *) -1L;
 226
 227         sp -= frame_size;
 228         /* Align the stack pointer according to the i386 ABI,
 229          * i.e. so that on function entry ((sp + 4) & 15) == 0. */
 230         sp = ((sp + 4) & -16ul) - 4;
 231         return (void __user *) sp;
 232 }
 233
 234 int ia32_setup_frame(int sig, struct ksignal *ksig,
 235                      compat_sigset_t *set, struct pt_regs *regs)
 236 {
 237         struct sigframe_ia32 __user *frame;
 238         void __user *restorer;
 239         void __user *fp = NULL;
 240
 241         /* copy_to_user optimizes that into a single 8 byte store */
 242         static const struct {
 243                 u16 poplmovl;
 244                 u32 val;
 245                 u16 int80;
 246         } __attribute__((packed)) code = {
 247                 0xb858,          /* popl %eax ; movl $...,%eax */
 248                 __NR_ia32_sigreturn,
 249                 0x80cd,         /* int $0x80 */
 250         };
 251
 252         frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
 253
 254         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 255                 restorer = ksig->ka.sa.sa_restorer;
 256         } else {
 257                 /* Return stub is in 32bit vsyscall page */
 258                 if (current->mm->context.vdso)
 259                         restorer = current->mm->context.vdso +
 260                                 vdso_image_32.sym___kernel_sigreturn;
 261                 else
 262                         restorer = &frame->retcode;
 263         }
 264
 265         if (!user_access_begin(frame, sizeof(*frame)))
 266                 return -EFAULT;
 267
 268         unsafe_put_user(sig, &frame->sig, Efault);
 269         unsafe_put_sigcontext32(&frame->sc, fp, regs, set, Efault);
 270         unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
 271         unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
 272         /*
 273          * These are actually not used anymore, but left because some
 274          * gdb versions depend on them as a marker.
 275          */
 276         unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
 277         user_access_end();
 278
 279         /* Set up registers for signal handler */
 280         regs->sp = (unsigned long) frame;
 281         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 282
 283         /* Make -mregparm=3 work */
 284         regs->ax = sig;
 285         regs->dx = 0;
 286         regs->cx = 0;
 287
 288         loadsegment(ds, __USER32_DS);
 289         loadsegment(es, __USER32_DS);
 290
 291         regs->cs = __USER32_CS;
 292         regs->ss = __USER32_DS;
 293
 294         return 0;
 295 Efault:
 296         user_access_end();
 297         return -EFAULT;
 298 }
 299
 300 int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
 301                         compat_sigset_t *set, struct pt_regs *regs)
 302 {
 303         struct rt_sigframe_ia32 __user *frame;
 304         void __user *restorer;
 305         void __user *fp = NULL;
 306
 307         /* unsafe_put_user optimizes that into a single 8 byte store */
 308         static const struct {
 309                 u8 movl;
 310                 u32 val;
 311                 u16 int80;
 312                 u8  pad;
 313         } __attribute__((packed)) code = {
 314                 0xb8,
 315                 __NR_ia32_rt_sigreturn,
 316                 0x80cd,
 317                 0,
 318         };
 319
 320         frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
 321
 322         if (!user_access_begin(frame, sizeof(*frame)))
 323                 return -EFAULT;
 324
 325         unsafe_put_user(sig, &frame->sig, Efault);
 326         unsafe_put_user(ptr_to_compat(&frame->info), &frame->pinfo, Efault);
 327         unsafe_put_user(ptr_to_compat(&frame->uc), &frame->puc, Efault);
 328
 329         /* Create the ucontext.  */
 330         if (static_cpu_has(X86_FEATURE_XSAVE))
 331                 unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
 332         else
 333                 unsafe_put_user(0, &frame->uc.uc_flags, Efault);
 334         unsafe_put_user(0, &frame->uc.uc_link, Efault);
 335         unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
 336
 337         if (ksig->ka.sa.sa_flags & SA_RESTORER)
 338                 restorer = ksig->ka.sa.sa_restorer;
 339         else
 340                 restorer = current->mm->context.vdso +
 341                         vdso_image_32.sym___kernel_rt_sigreturn;
 342         unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
 343
 344         /*
 345          * Not actually used anymore, but left because some gdb
 346          * versions need it.
 347          */
 348         unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
 349         unsafe_put_sigcontext32(&frame->uc.uc_mcontext, fp, regs, set, Efault);
 350         unsafe_put_user(*(__u64 *)set, (__u64 *)&frame->uc.uc_sigmask, Efault);
 351         user_access_end();
 352
 353         if (__copy_siginfo_to_user32(&frame->info, &ksig->info, false))
 354                 return -EFAULT;
 355
 356         /* Set up registers for signal handler */
 357         regs->sp = (unsigned long) frame;
 358         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 359
 360         /* Make -mregparm=3 work */
 361         regs->ax = sig;
 362         regs->dx = (unsigned long) &frame->info;
 363         regs->cx = (unsigned long) &frame->uc;
 364
 365         loadsegment(ds, __USER32_DS);
 366         loadsegment(es, __USER32_DS);
 367
 368         regs->cs = __USER32_CS;
 369         regs->ss = __USER32_DS;
 370
 371         return 0;
 372 Efault:
 373         user_access_end();
 374         return -EFAULT;
 375 }