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Linux/arch/x86/kernel/signal.c

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  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  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
  7  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
  8  *  2000-2002   x86-64 support by Andi Kleen
  9  */
 10 
 11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 12 
 13 #include <linux/sched.h>
 14 #include <linux/sched/task_stack.h>
 15 #include <linux/mm.h>
 16 #include <linux/smp.h>
 17 #include <linux/kernel.h>
 18 #include <linux/errno.h>
 19 #include <linux/wait.h>
 20 #include <linux/tracehook.h>
 21 #include <linux/unistd.h>
 22 #include <linux/stddef.h>
 23 #include <linux/personality.h>
 24 #include <linux/uaccess.h>
 25 #include <linux/user-return-notifier.h>
 26 #include <linux/uprobes.h>
 27 #include <linux/context_tracking.h>
 28 #include <linux/syscalls.h>
 29 
 30 #include <asm/processor.h>
 31 #include <asm/ucontext.h>
 32 #include <asm/fpu/internal.h>
 33 #include <asm/fpu/signal.h>
 34 #include <asm/vdso.h>
 35 #include <asm/mce.h>
 36 #include <asm/sighandling.h>
 37 #include <asm/vm86.h>
 38 
 39 #ifdef CONFIG_X86_64
 40 #include <asm/proto.h>
 41 #include <asm/ia32_unistd.h>
 42 #endif /* CONFIG_X86_64 */
 43 
 44 #include <asm/syscall.h>
 45 #include <asm/syscalls.h>
 46 
 47 #include <asm/sigframe.h>
 48 #include <asm/signal.h>
 49 
 50 #define COPY(x)                 do {                    \
 51         get_user_ex(regs->x, &sc->x);                   \
 52 } while (0)
 53 
 54 #define GET_SEG(seg)            ({                      \
 55         unsigned short tmp;                             \
 56         get_user_ex(tmp, &sc->seg);                     \
 57         tmp;                                            \
 58 })
 59 
 60 #define COPY_SEG(seg)           do {                    \
 61         regs->seg = GET_SEG(seg);                       \
 62 } while (0)
 63 
 64 #define COPY_SEG_CPL3(seg)      do {                    \
 65         regs->seg = GET_SEG(seg) | 3;                   \
 66 } while (0)
 67 
 68 #ifdef CONFIG_X86_64
 69 /*
 70  * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
 71  * alone.  Using this generally makes no sense unless
 72  * user_64bit_mode(regs) would return true.
 73  */
 74 static void force_valid_ss(struct pt_regs *regs)
 75 {
 76         u32 ar;
 77         asm volatile ("lar %[old_ss], %[ar]\n\t"
 78                       "jz 1f\n\t"               /* If invalid: */
 79                       "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
 80                       "1:"
 81                       : [ar] "=r" (ar)
 82                       : [old_ss] "rm" ((u16)regs->ss));
 83 
 84         /*
 85          * For a valid 64-bit user context, we need DPL 3, type
 86          * read-write data or read-write exp-down data, and S and P
 87          * set.  We can't use VERW because VERW doesn't check the
 88          * P bit.
 89          */
 90         ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
 91         if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
 92             ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
 93                 regs->ss = __USER_DS;
 94 }
 95 #endif
 96 
 97 static int restore_sigcontext(struct pt_regs *regs,
 98                               struct sigcontext __user *sc,
 99                               unsigned long uc_flags)
100 {
101         unsigned long buf_val;
102         void __user *buf;
103         unsigned int tmpflags;
104         unsigned int err = 0;
105 
106         /* Always make any pending restarted system calls return -EINTR */
107         current->restart_block.fn = do_no_restart_syscall;
108 
109         get_user_try {
110 
111 #ifdef CONFIG_X86_32
112                 set_user_gs(regs, GET_SEG(gs));
113                 COPY_SEG(fs);
114                 COPY_SEG(es);
115                 COPY_SEG(ds);
116 #endif /* CONFIG_X86_32 */
117 
118                 COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
119                 COPY(dx); COPY(cx); COPY(ip); COPY(ax);
120 
121 #ifdef CONFIG_X86_64
122                 COPY(r8);
123                 COPY(r9);
124                 COPY(r10);
125                 COPY(r11);
126                 COPY(r12);
127                 COPY(r13);
128                 COPY(r14);
129                 COPY(r15);
130 #endif /* CONFIG_X86_64 */
131 
132                 COPY_SEG_CPL3(cs);
133                 COPY_SEG_CPL3(ss);
134 
135                 get_user_ex(tmpflags, &sc->flags);
136                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
137                 regs->orig_ax = -1;             /* disable syscall checks */
138 
139                 get_user_ex(buf_val, &sc->fpstate);
140                 buf = (void __user *)buf_val;
141         } get_user_catch(err);
142 
143 #ifdef CONFIG_X86_64
144         /*
145          * Fix up SS if needed for the benefit of old DOSEMU and
146          * CRIU.
147          */
148         if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
149                 force_valid_ss(regs);
150 #endif
151 
152         err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
153 
154         force_iret();
155 
156         return err;
157 }
158 
159 int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
160                      struct pt_regs *regs, unsigned long mask)
161 {
162         int err = 0;
163 
164         put_user_try {
165 
166 #ifdef CONFIG_X86_32
167                 put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
168                 put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
169                 put_user_ex(regs->es, (unsigned int __user *)&sc->es);
170                 put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);
171 #endif /* CONFIG_X86_32 */
172 
173                 put_user_ex(regs->di, &sc->di);
174                 put_user_ex(regs->si, &sc->si);
175                 put_user_ex(regs->bp, &sc->bp);
176                 put_user_ex(regs->sp, &sc->sp);
177                 put_user_ex(regs->bx, &sc->bx);
178                 put_user_ex(regs->dx, &sc->dx);
179                 put_user_ex(regs->cx, &sc->cx);
180                 put_user_ex(regs->ax, &sc->ax);
181 #ifdef CONFIG_X86_64
182                 put_user_ex(regs->r8, &sc->r8);
183                 put_user_ex(regs->r9, &sc->r9);
184                 put_user_ex(regs->r10, &sc->r10);
185                 put_user_ex(regs->r11, &sc->r11);
186                 put_user_ex(regs->r12, &sc->r12);
187                 put_user_ex(regs->r13, &sc->r13);
188                 put_user_ex(regs->r14, &sc->r14);
189                 put_user_ex(regs->r15, &sc->r15);
190 #endif /* CONFIG_X86_64 */
191 
192                 put_user_ex(current->thread.trap_nr, &sc->trapno);
193                 put_user_ex(current->thread.error_code, &sc->err);
194                 put_user_ex(regs->ip, &sc->ip);
195 #ifdef CONFIG_X86_32
196                 put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
197                 put_user_ex(regs->flags, &sc->flags);
198                 put_user_ex(regs->sp, &sc->sp_at_signal);
199                 put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);
200 #else /* !CONFIG_X86_32 */
201                 put_user_ex(regs->flags, &sc->flags);
202                 put_user_ex(regs->cs, &sc->cs);
203                 put_user_ex(0, &sc->gs);
204                 put_user_ex(0, &sc->fs);
205                 put_user_ex(regs->ss, &sc->ss);
206 #endif /* CONFIG_X86_32 */
207 
208                 put_user_ex(fpstate, (unsigned long __user *)&sc->fpstate);
209 
210                 /* non-iBCS2 extensions.. */
211                 put_user_ex(mask, &sc->oldmask);
212                 put_user_ex(current->thread.cr2, &sc->cr2);
213         } put_user_catch(err);
214 
215         return err;
216 }
217 
218 /*
219  * Set up a signal frame.
220  */
221 
222 /*
223  * Determine which stack to use..
224  */
225 static unsigned long align_sigframe(unsigned long sp)
226 {
227 #ifdef CONFIG_X86_32
228         /*
229          * Align the stack pointer according to the i386 ABI,
230          * i.e. so that on function entry ((sp + 4) & 15) == 0.
231          */
232         sp = ((sp + 4) & -16ul) - 4;
233 #else /* !CONFIG_X86_32 */
234         sp = round_down(sp, 16) - 8;
235 #endif
236         return sp;
237 }
238 
239 static void __user *
240 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
241              void __user **fpstate)
242 {
243         /* Default to using normal stack */
244         unsigned long math_size = 0;
245         unsigned long sp = regs->sp;
246         unsigned long buf_fx = 0;
247         int onsigstack = on_sig_stack(sp);
248         int ret;
249 
250         /* redzone */
251         if (IS_ENABLED(CONFIG_X86_64))
252                 sp -= 128;
253 
254         /* This is the X/Open sanctioned signal stack switching.  */
255         if (ka->sa.sa_flags & SA_ONSTACK) {
256                 if (sas_ss_flags(sp) == 0)
257                         sp = current->sas_ss_sp + current->sas_ss_size;
258         } else if (IS_ENABLED(CONFIG_X86_32) &&
259                    !onsigstack &&
260                    regs->ss != __USER_DS &&
261                    !(ka->sa.sa_flags & SA_RESTORER) &&
262                    ka->sa.sa_restorer) {
263                 /* This is the legacy signal stack switching. */
264                 sp = (unsigned long) ka->sa.sa_restorer;
265         }
266 
267         sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
268                                   &buf_fx, &math_size);
269         *fpstate = (void __user *)sp;
270 
271         sp = align_sigframe(sp - frame_size);
272 
273         /*
274          * If we are on the alternate signal stack and would overflow it, don't.
275          * Return an always-bogus address instead so we will die with SIGSEGV.
276          */
277         if (onsigstack && !likely(on_sig_stack(sp)))
278                 return (void __user *)-1L;
279 
280         /* save i387 and extended state */
281         ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
282         if (ret < 0)
283                 return (void __user *)-1L;
284 
285         return (void __user *)sp;
286 }
287 
288 #ifdef CONFIG_X86_32
289 static const struct {
290         u16 poplmovl;
291         u32 val;
292         u16 int80;
293 } __attribute__((packed)) retcode = {
294         0xb858,         /* popl %eax; movl $..., %eax */
295         __NR_sigreturn,
296         0x80cd,         /* int $0x80 */
297 };
298 
299 static const struct {
300         u8  movl;
301         u32 val;
302         u16 int80;
303         u8  pad;
304 } __attribute__((packed)) rt_retcode = {
305         0xb8,           /* movl $..., %eax */
306         __NR_rt_sigreturn,
307         0x80cd,         /* int $0x80 */
308         0
309 };
310 
311 static int
312 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
313               struct pt_regs *regs)
314 {
315         struct sigframe __user *frame;
316         void __user *restorer;
317         int err = 0;
318         void __user *fpstate = NULL;
319 
320         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
321 
322         if (!access_ok(frame, sizeof(*frame)))
323                 return -EFAULT;
324 
325         if (__put_user(sig, &frame->sig))
326                 return -EFAULT;
327 
328         if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
329                 return -EFAULT;
330 
331         if (_NSIG_WORDS > 1) {
332                 if (__copy_to_user(&frame->extramask, &set->sig[1],
333                                    sizeof(frame->extramask)))
334                         return -EFAULT;
335         }
336 
337         if (current->mm->context.vdso)
338                 restorer = current->mm->context.vdso +
339                         vdso_image_32.sym___kernel_sigreturn;
340         else
341                 restorer = &frame->retcode;
342         if (ksig->ka.sa.sa_flags & SA_RESTORER)
343                 restorer = ksig->ka.sa.sa_restorer;
344 
345         /* Set up to return from userspace.  */
346         err |= __put_user(restorer, &frame->pretcode);
347 
348         /*
349          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
350          *
351          * WE DO NOT USE IT ANY MORE! It's only left here for historical
352          * reasons and because gdb uses it as a signature to notice
353          * signal handler stack frames.
354          */
355         err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
356 
357         if (err)
358                 return -EFAULT;
359 
360         /* Set up registers for signal handler */
361         regs->sp = (unsigned long)frame;
362         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
363         regs->ax = (unsigned long)sig;
364         regs->dx = 0;
365         regs->cx = 0;
366 
367         regs->ds = __USER_DS;
368         regs->es = __USER_DS;
369         regs->ss = __USER_DS;
370         regs->cs = __USER_CS;
371 
372         return 0;
373 }
374 
375 static int __setup_rt_frame(int sig, struct ksignal *ksig,
376                             sigset_t *set, struct pt_regs *regs)
377 {
378         struct rt_sigframe __user *frame;
379         void __user *restorer;
380         int err = 0;
381         void __user *fpstate = NULL;
382 
383         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
384 
385         if (!access_ok(frame, sizeof(*frame)))
386                 return -EFAULT;
387 
388         put_user_try {
389                 put_user_ex(sig, &frame->sig);
390                 put_user_ex(&frame->info, &frame->pinfo);
391                 put_user_ex(&frame->uc, &frame->puc);
392 
393                 /* Create the ucontext.  */
394                 if (static_cpu_has(X86_FEATURE_XSAVE))
395                         put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
396                 else
397                         put_user_ex(0, &frame->uc.uc_flags);
398                 put_user_ex(0, &frame->uc.uc_link);
399                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
400 
401                 /* Set up to return from userspace.  */
402                 restorer = current->mm->context.vdso +
403                         vdso_image_32.sym___kernel_rt_sigreturn;
404                 if (ksig->ka.sa.sa_flags & SA_RESTORER)
405                         restorer = ksig->ka.sa.sa_restorer;
406                 put_user_ex(restorer, &frame->pretcode);
407 
408                 /*
409                  * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
410                  *
411                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
412                  * reasons and because gdb uses it as a signature to notice
413                  * signal handler stack frames.
414                  */
415                 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
416         } put_user_catch(err);
417         
418         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
419         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
420                                 regs, set->sig[0]);
421         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
422 
423         if (err)
424                 return -EFAULT;
425 
426         /* Set up registers for signal handler */
427         regs->sp = (unsigned long)frame;
428         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
429         regs->ax = (unsigned long)sig;
430         regs->dx = (unsigned long)&frame->info;
431         regs->cx = (unsigned long)&frame->uc;
432 
433         regs->ds = __USER_DS;
434         regs->es = __USER_DS;
435         regs->ss = __USER_DS;
436         regs->cs = __USER_CS;
437 
438         return 0;
439 }
440 #else /* !CONFIG_X86_32 */
441 static unsigned long frame_uc_flags(struct pt_regs *regs)
442 {
443         unsigned long flags;
444 
445         if (boot_cpu_has(X86_FEATURE_XSAVE))
446                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
447         else
448                 flags = UC_SIGCONTEXT_SS;
449 
450         if (likely(user_64bit_mode(regs)))
451                 flags |= UC_STRICT_RESTORE_SS;
452 
453         return flags;
454 }
455 
456 static int __setup_rt_frame(int sig, struct ksignal *ksig,
457                             sigset_t *set, struct pt_regs *regs)
458 {
459         struct rt_sigframe __user *frame;
460         void __user *fp = NULL;
461         unsigned long uc_flags;
462         int err = 0;
463 
464         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
465 
466         if (!access_ok(frame, sizeof(*frame)))
467                 return -EFAULT;
468 
469         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
470                 if (copy_siginfo_to_user(&frame->info, &ksig->info))
471                         return -EFAULT;
472         }
473 
474         uc_flags = frame_uc_flags(regs);
475 
476         put_user_try {
477                 /* Create the ucontext.  */
478                 put_user_ex(uc_flags, &frame->uc.uc_flags);
479                 put_user_ex(0, &frame->uc.uc_link);
480                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
481 
482                 /* Set up to return from userspace.  If provided, use a stub
483                    already in userspace.  */
484                 /* x86-64 should always use SA_RESTORER. */
485                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
486                         put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
487                 } else {
488                         /* could use a vstub here */
489                         err |= -EFAULT;
490                 }
491         } put_user_catch(err);
492 
493         err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
494         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
495 
496         if (err)
497                 return -EFAULT;
498 
499         /* Set up registers for signal handler */
500         regs->di = sig;
501         /* In case the signal handler was declared without prototypes */
502         regs->ax = 0;
503 
504         /* This also works for non SA_SIGINFO handlers because they expect the
505            next argument after the signal number on the stack. */
506         regs->si = (unsigned long)&frame->info;
507         regs->dx = (unsigned long)&frame->uc;
508         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
509 
510         regs->sp = (unsigned long)frame;
511 
512         /*
513          * Set up the CS and SS registers to run signal handlers in
514          * 64-bit mode, even if the handler happens to be interrupting
515          * 32-bit or 16-bit code.
516          *
517          * SS is subtle.  In 64-bit mode, we don't need any particular
518          * SS descriptor, but we do need SS to be valid.  It's possible
519          * that the old SS is entirely bogus -- this can happen if the
520          * signal we're trying to deliver is #GP or #SS caused by a bad
521          * SS value.  We also have a compatbility issue here: DOSEMU
522          * relies on the contents of the SS register indicating the
523          * SS value at the time of the signal, even though that code in
524          * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
525          * avoids relying on sigreturn to restore SS; instead it uses
526          * a trampoline.)  So we do our best: if the old SS was valid,
527          * we keep it.  Otherwise we replace it.
528          */
529         regs->cs = __USER_CS;
530 
531         if (unlikely(regs->ss != __USER_DS))
532                 force_valid_ss(regs);
533 
534         return 0;
535 }
536 #endif /* CONFIG_X86_32 */
537 
538 static int x32_setup_rt_frame(struct ksignal *ksig,
539                               compat_sigset_t *set,
540                               struct pt_regs *regs)
541 {
542 #ifdef CONFIG_X86_X32_ABI
543         struct rt_sigframe_x32 __user *frame;
544         unsigned long uc_flags;
545         void __user *restorer;
546         int err = 0;
547         void __user *fpstate = NULL;
548 
549         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
550 
551         if (!access_ok(frame, sizeof(*frame)))
552                 return -EFAULT;
553 
554         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
555                 if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
556                         return -EFAULT;
557         }
558 
559         uc_flags = frame_uc_flags(regs);
560 
561         put_user_try {
562                 /* Create the ucontext.  */
563                 put_user_ex(uc_flags, &frame->uc.uc_flags);
564                 put_user_ex(0, &frame->uc.uc_link);
565                 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
566                 put_user_ex(0, &frame->uc.uc__pad0);
567 
568                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
569                         restorer = ksig->ka.sa.sa_restorer;
570                 } else {
571                         /* could use a vstub here */
572                         restorer = NULL;
573                         err |= -EFAULT;
574                 }
575                 put_user_ex(restorer, (unsigned long __user *)&frame->pretcode);
576         } put_user_catch(err);
577 
578         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
579                                 regs, set->sig[0]);
580         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
581 
582         if (err)
583                 return -EFAULT;
584 
585         /* Set up registers for signal handler */
586         regs->sp = (unsigned long) frame;
587         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
588 
589         /* We use the x32 calling convention here... */
590         regs->di = ksig->sig;
591         regs->si = (unsigned long) &frame->info;
592         regs->dx = (unsigned long) &frame->uc;
593 
594         loadsegment(ds, __USER_DS);
595         loadsegment(es, __USER_DS);
596 
597         regs->cs = __USER_CS;
598         regs->ss = __USER_DS;
599 #endif  /* CONFIG_X86_X32_ABI */
600 
601         return 0;
602 }
603 
604 /*
605  * Do a signal return; undo the signal stack.
606  */
607 #ifdef CONFIG_X86_32
608 SYSCALL_DEFINE0(sigreturn)
609 {
610         struct pt_regs *regs = current_pt_regs();
611         struct sigframe __user *frame;
612         sigset_t set;
613 
614         frame = (struct sigframe __user *)(regs->sp - 8);
615 
616         if (!access_ok(frame, sizeof(*frame)))
617                 goto badframe;
618         if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
619                 && __copy_from_user(&set.sig[1], &frame->extramask,
620                                     sizeof(frame->extramask))))
621                 goto badframe;
622 
623         set_current_blocked(&set);
624 
625         /*
626          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
627          * Save a few cycles by skipping the __get_user.
628          */
629         if (restore_sigcontext(regs, &frame->sc, 0))
630                 goto badframe;
631         return regs->ax;
632 
633 badframe:
634         signal_fault(regs, frame, "sigreturn");
635 
636         return 0;
637 }
638 #endif /* CONFIG_X86_32 */
639 
640 SYSCALL_DEFINE0(rt_sigreturn)
641 {
642         struct pt_regs *regs = current_pt_regs();
643         struct rt_sigframe __user *frame;
644         sigset_t set;
645         unsigned long uc_flags;
646 
647         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
648         if (!access_ok(frame, sizeof(*frame)))
649                 goto badframe;
650         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
651                 goto badframe;
652         if (__get_user(uc_flags, &frame->uc.uc_flags))
653                 goto badframe;
654 
655         set_current_blocked(&set);
656 
657         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
658                 goto badframe;
659 
660         if (restore_altstack(&frame->uc.uc_stack))
661                 goto badframe;
662 
663         return regs->ax;
664 
665 badframe:
666         signal_fault(regs, frame, "rt_sigreturn");
667         return 0;
668 }
669 
670 static inline int is_ia32_compat_frame(struct ksignal *ksig)
671 {
672         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
673                 ksig->ka.sa.sa_flags & SA_IA32_ABI;
674 }
675 
676 static inline int is_ia32_frame(struct ksignal *ksig)
677 {
678         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
679 }
680 
681 static inline int is_x32_frame(struct ksignal *ksig)
682 {
683         return IS_ENABLED(CONFIG_X86_X32_ABI) &&
684                 ksig->ka.sa.sa_flags & SA_X32_ABI;
685 }
686 
687 static int
688 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
689 {
690         int usig = ksig->sig;
691         sigset_t *set = sigmask_to_save();
692         compat_sigset_t *cset = (compat_sigset_t *) set;
693 
694         /* Perform fixup for the pre-signal frame. */
695         rseq_signal_deliver(ksig, regs);
696 
697         /* Set up the stack frame */
698         if (is_ia32_frame(ksig)) {
699                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
700                         return ia32_setup_rt_frame(usig, ksig, cset, regs);
701                 else
702                         return ia32_setup_frame(usig, ksig, cset, regs);
703         } else if (is_x32_frame(ksig)) {
704                 return x32_setup_rt_frame(ksig, cset, regs);
705         } else {
706                 return __setup_rt_frame(ksig->sig, ksig, set, regs);
707         }
708 }
709 
710 static void
711 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
712 {
713         bool stepping, failed;
714         struct fpu *fpu = &current->thread.fpu;
715 
716         if (v8086_mode(regs))
717                 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
718 
719         /* Are we from a system call? */
720         if (syscall_get_nr(current, regs) >= 0) {
721                 /* If so, check system call restarting.. */
722                 switch (syscall_get_error(current, regs)) {
723                 case -ERESTART_RESTARTBLOCK:
724                 case -ERESTARTNOHAND:
725                         regs->ax = -EINTR;
726                         break;
727 
728                 case -ERESTARTSYS:
729                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
730                                 regs->ax = -EINTR;
731                                 break;
732                         }
733                 /* fallthrough */
734                 case -ERESTARTNOINTR:
735                         regs->ax = regs->orig_ax;
736                         regs->ip -= 2;
737                         break;
738                 }
739         }
740 
741         /*
742          * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
743          * so that register information in the sigcontext is correct and
744          * then notify the tracer before entering the signal handler.
745          */
746         stepping = test_thread_flag(TIF_SINGLESTEP);
747         if (stepping)
748                 user_disable_single_step(current);
749 
750         failed = (setup_rt_frame(ksig, regs) < 0);
751         if (!failed) {
752                 /*
753                  * Clear the direction flag as per the ABI for function entry.
754                  *
755                  * Clear RF when entering the signal handler, because
756                  * it might disable possible debug exception from the
757                  * signal handler.
758                  *
759                  * Clear TF for the case when it wasn't set by debugger to
760                  * avoid the recursive send_sigtrap() in SIGTRAP handler.
761                  */
762                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
763                 /*
764                  * Ensure the signal handler starts with the new fpu state.
765                  */
766                 fpu__clear(fpu);
767         }
768         signal_setup_done(failed, ksig, stepping);
769 }
770 
771 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
772 {
773         /*
774          * This function is fundamentally broken as currently
775          * implemented.
776          *
777          * The idea is that we want to trigger a call to the
778          * restart_block() syscall and that we want in_ia32_syscall(),
779          * in_x32_syscall(), etc. to match whatever they were in the
780          * syscall being restarted.  We assume that the syscall
781          * instruction at (regs->ip - 2) matches whatever syscall
782          * instruction we used to enter in the first place.
783          *
784          * The problem is that we can get here when ptrace pokes
785          * syscall-like values into regs even if we're not in a syscall
786          * at all.
787          *
788          * For now, we maintain historical behavior and guess based on
789          * stored state.  We could do better by saving the actual
790          * syscall arch in restart_block or (with caveats on x32) by
791          * checking if regs->ip points to 'int $0x80'.  The current
792          * behavior is incorrect if a tracer has a different bitness
793          * than the tracee.
794          */
795 #ifdef CONFIG_IA32_EMULATION
796         if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
797                 return __NR_ia32_restart_syscall;
798 #endif
799 #ifdef CONFIG_X86_X32_ABI
800         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
801 #else
802         return __NR_restart_syscall;
803 #endif
804 }
805 
806 /*
807  * Note that 'init' is a special process: it doesn't get signals it doesn't
808  * want to handle. Thus you cannot kill init even with a SIGKILL even by
809  * mistake.
810  */
811 void do_signal(struct pt_regs *regs)
812 {
813         struct ksignal ksig;
814 
815         if (get_signal(&ksig)) {
816                 /* Whee! Actually deliver the signal.  */
817                 handle_signal(&ksig, regs);
818                 return;
819         }
820 
821         /* Did we come from a system call? */
822         if (syscall_get_nr(current, regs) >= 0) {
823                 /* Restart the system call - no handlers present */
824                 switch (syscall_get_error(current, regs)) {
825                 case -ERESTARTNOHAND:
826                 case -ERESTARTSYS:
827                 case -ERESTARTNOINTR:
828                         regs->ax = regs->orig_ax;
829                         regs->ip -= 2;
830                         break;
831 
832                 case -ERESTART_RESTARTBLOCK:
833                         regs->ax = get_nr_restart_syscall(regs);
834                         regs->ip -= 2;
835                         break;
836                 }
837         }
838 
839         /*
840          * If there's no signal to deliver, we just put the saved sigmask
841          * back.
842          */
843         restore_saved_sigmask();
844 }
845 
846 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
847 {
848         struct task_struct *me = current;
849 
850         if (show_unhandled_signals && printk_ratelimit()) {
851                 printk("%s"
852                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
853                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
854                        me->comm, me->pid, where, frame,
855                        regs->ip, regs->sp, regs->orig_ax);
856                 print_vma_addr(KERN_CONT " in ", regs->ip);
857                 pr_cont("\n");
858         }
859 
860         force_sig(SIGSEGV);
861 }
862 
863 #ifdef CONFIG_X86_X32_ABI
864 asmlinkage long sys32_x32_rt_sigreturn(void)
865 {
866         struct pt_regs *regs = current_pt_regs();
867         struct rt_sigframe_x32 __user *frame;
868         sigset_t set;
869         unsigned long uc_flags;
870 
871         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
872 
873         if (!access_ok(frame, sizeof(*frame)))
874                 goto badframe;
875         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
876                 goto badframe;
877         if (__get_user(uc_flags, &frame->uc.uc_flags))
878                 goto badframe;
879 
880         set_current_blocked(&set);
881 
882         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
883                 goto badframe;
884 
885         if (compat_restore_altstack(&frame->uc.uc_stack))
886                 goto badframe;
887 
888         return regs->ax;
889 
890 badframe:
891         signal_fault(regs, frame, "x32 rt_sigreturn");
892         return 0;
893 }
894 #endif
895 

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