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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 #ifdef CONFIG_X86_64
136                 /*
137                  * Fix up SS if needed for the benefit of old DOSEMU and
138                  * CRIU.
139                  */
140                 if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) &&
141                              user_64bit_mode(regs)))
142                         force_valid_ss(regs);
143 #endif
144 
145                 get_user_ex(tmpflags, &sc->flags);
146                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
147                 regs->orig_ax = -1;             /* disable syscall checks */
148 
149                 get_user_ex(buf_val, &sc->fpstate);
150                 buf = (void __user *)buf_val;
151         } get_user_catch(err);
152 
153         err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
154 
155         force_iret();
156 
157         return err;
158 }
159 
160 int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
161                      struct pt_regs *regs, unsigned long mask)
162 {
163         int err = 0;
164 
165         put_user_try {
166 
167 #ifdef CONFIG_X86_32
168                 put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
169                 put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
170                 put_user_ex(regs->es, (unsigned int __user *)&sc->es);
171                 put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);
172 #endif /* CONFIG_X86_32 */
173 
174                 put_user_ex(regs->di, &sc->di);
175                 put_user_ex(regs->si, &sc->si);
176                 put_user_ex(regs->bp, &sc->bp);
177                 put_user_ex(regs->sp, &sc->sp);
178                 put_user_ex(regs->bx, &sc->bx);
179                 put_user_ex(regs->dx, &sc->dx);
180                 put_user_ex(regs->cx, &sc->cx);
181                 put_user_ex(regs->ax, &sc->ax);
182 #ifdef CONFIG_X86_64
183                 put_user_ex(regs->r8, &sc->r8);
184                 put_user_ex(regs->r9, &sc->r9);
185                 put_user_ex(regs->r10, &sc->r10);
186                 put_user_ex(regs->r11, &sc->r11);
187                 put_user_ex(regs->r12, &sc->r12);
188                 put_user_ex(regs->r13, &sc->r13);
189                 put_user_ex(regs->r14, &sc->r14);
190                 put_user_ex(regs->r15, &sc->r15);
191 #endif /* CONFIG_X86_64 */
192 
193                 put_user_ex(current->thread.trap_nr, &sc->trapno);
194                 put_user_ex(current->thread.error_code, &sc->err);
195                 put_user_ex(regs->ip, &sc->ip);
196 #ifdef CONFIG_X86_32
197                 put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
198                 put_user_ex(regs->flags, &sc->flags);
199                 put_user_ex(regs->sp, &sc->sp_at_signal);
200                 put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);
201 #else /* !CONFIG_X86_32 */
202                 put_user_ex(regs->flags, &sc->flags);
203                 put_user_ex(regs->cs, &sc->cs);
204                 put_user_ex(0, &sc->gs);
205                 put_user_ex(0, &sc->fs);
206                 put_user_ex(regs->ss, &sc->ss);
207 #endif /* CONFIG_X86_32 */
208 
209                 put_user_ex(fpstate, &sc->fpstate);
210 
211                 /* non-iBCS2 extensions.. */
212                 put_user_ex(mask, &sc->oldmask);
213                 put_user_ex(current->thread.cr2, &sc->cr2);
214         } put_user_catch(err);
215 
216         return err;
217 }
218 
219 /*
220  * Set up a signal frame.
221  */
222 
223 /*
224  * Determine which stack to use..
225  */
226 static unsigned long align_sigframe(unsigned long sp)
227 {
228 #ifdef CONFIG_X86_32
229         /*
230          * Align the stack pointer according to the i386 ABI,
231          * i.e. so that on function entry ((sp + 4) & 15) == 0.
232          */
233         sp = ((sp + 4) & -16ul) - 4;
234 #else /* !CONFIG_X86_32 */
235         sp = round_down(sp, 16) - 8;
236 #endif
237         return sp;
238 }
239 
240 static void __user *
241 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
242              void __user **fpstate)
243 {
244         /* Default to using normal stack */
245         unsigned long math_size = 0;
246         unsigned long sp = regs->sp;
247         unsigned long buf_fx = 0;
248         int onsigstack = on_sig_stack(sp);
249         struct fpu *fpu = &current->thread.fpu;
250 
251         /* redzone */
252         if (IS_ENABLED(CONFIG_X86_64))
253                 sp -= 128;
254 
255         /* This is the X/Open sanctioned signal stack switching.  */
256         if (ka->sa.sa_flags & SA_ONSTACK) {
257                 if (sas_ss_flags(sp) == 0)
258                         sp = current->sas_ss_sp + current->sas_ss_size;
259         } else if (IS_ENABLED(CONFIG_X86_32) &&
260                    !onsigstack &&
261                    regs->ss != __USER_DS &&
262                    !(ka->sa.sa_flags & SA_RESTORER) &&
263                    ka->sa.sa_restorer) {
264                 /* This is the legacy signal stack switching. */
265                 sp = (unsigned long) ka->sa.sa_restorer;
266         }
267 
268         if (fpu->initialized) {
269                 sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
270                                           &buf_fx, &math_size);
271                 *fpstate = (void __user *)sp;
272         }
273 
274         sp = align_sigframe(sp - frame_size);
275 
276         /*
277          * If we are on the alternate signal stack and would overflow it, don't.
278          * Return an always-bogus address instead so we will die with SIGSEGV.
279          */
280         if (onsigstack && !likely(on_sig_stack(sp)))
281                 return (void __user *)-1L;
282 
283         /* save i387 and extended state */
284         if (fpu->initialized &&
285             copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0)
286                 return (void __user *)-1L;
287 
288         return (void __user *)sp;
289 }
290 
291 #ifdef CONFIG_X86_32
292 static const struct {
293         u16 poplmovl;
294         u32 val;
295         u16 int80;
296 } __attribute__((packed)) retcode = {
297         0xb858,         /* popl %eax; movl $..., %eax */
298         __NR_sigreturn,
299         0x80cd,         /* int $0x80 */
300 };
301 
302 static const struct {
303         u8  movl;
304         u32 val;
305         u16 int80;
306         u8  pad;
307 } __attribute__((packed)) rt_retcode = {
308         0xb8,           /* movl $..., %eax */
309         __NR_rt_sigreturn,
310         0x80cd,         /* int $0x80 */
311         0
312 };
313 
314 static int
315 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
316               struct pt_regs *regs)
317 {
318         struct sigframe __user *frame;
319         void __user *restorer;
320         int err = 0;
321         void __user *fpstate = NULL;
322 
323         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
324 
325         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
326                 return -EFAULT;
327 
328         if (__put_user(sig, &frame->sig))
329                 return -EFAULT;
330 
331         if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
332                 return -EFAULT;
333 
334         if (_NSIG_WORDS > 1) {
335                 if (__copy_to_user(&frame->extramask, &set->sig[1],
336                                    sizeof(frame->extramask)))
337                         return -EFAULT;
338         }
339 
340         if (current->mm->context.vdso)
341                 restorer = current->mm->context.vdso +
342                         vdso_image_32.sym___kernel_sigreturn;
343         else
344                 restorer = &frame->retcode;
345         if (ksig->ka.sa.sa_flags & SA_RESTORER)
346                 restorer = ksig->ka.sa.sa_restorer;
347 
348         /* Set up to return from userspace.  */
349         err |= __put_user(restorer, &frame->pretcode);
350 
351         /*
352          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
353          *
354          * WE DO NOT USE IT ANY MORE! It's only left here for historical
355          * reasons and because gdb uses it as a signature to notice
356          * signal handler stack frames.
357          */
358         err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
359 
360         if (err)
361                 return -EFAULT;
362 
363         /* Set up registers for signal handler */
364         regs->sp = (unsigned long)frame;
365         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
366         regs->ax = (unsigned long)sig;
367         regs->dx = 0;
368         regs->cx = 0;
369 
370         regs->ds = __USER_DS;
371         regs->es = __USER_DS;
372         regs->ss = __USER_DS;
373         regs->cs = __USER_CS;
374 
375         return 0;
376 }
377 
378 static int __setup_rt_frame(int sig, struct ksignal *ksig,
379                             sigset_t *set, struct pt_regs *regs)
380 {
381         struct rt_sigframe __user *frame;
382         void __user *restorer;
383         int err = 0;
384         void __user *fpstate = NULL;
385 
386         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
387 
388         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
389                 return -EFAULT;
390 
391         put_user_try {
392                 put_user_ex(sig, &frame->sig);
393                 put_user_ex(&frame->info, &frame->pinfo);
394                 put_user_ex(&frame->uc, &frame->puc);
395 
396                 /* Create the ucontext.  */
397                 if (boot_cpu_has(X86_FEATURE_XSAVE))
398                         put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
399                 else
400                         put_user_ex(0, &frame->uc.uc_flags);
401                 put_user_ex(0, &frame->uc.uc_link);
402                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
403 
404                 /* Set up to return from userspace.  */
405                 restorer = current->mm->context.vdso +
406                         vdso_image_32.sym___kernel_rt_sigreturn;
407                 if (ksig->ka.sa.sa_flags & SA_RESTORER)
408                         restorer = ksig->ka.sa.sa_restorer;
409                 put_user_ex(restorer, &frame->pretcode);
410 
411                 /*
412                  * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
413                  *
414                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
415                  * reasons and because gdb uses it as a signature to notice
416                  * signal handler stack frames.
417                  */
418                 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
419         } put_user_catch(err);
420         
421         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
422         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
423                                 regs, set->sig[0]);
424         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
425 
426         if (err)
427                 return -EFAULT;
428 
429         /* Set up registers for signal handler */
430         regs->sp = (unsigned long)frame;
431         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
432         regs->ax = (unsigned long)sig;
433         regs->dx = (unsigned long)&frame->info;
434         regs->cx = (unsigned long)&frame->uc;
435 
436         regs->ds = __USER_DS;
437         regs->es = __USER_DS;
438         regs->ss = __USER_DS;
439         regs->cs = __USER_CS;
440 
441         return 0;
442 }
443 #else /* !CONFIG_X86_32 */
444 static unsigned long frame_uc_flags(struct pt_regs *regs)
445 {
446         unsigned long flags;
447 
448         if (boot_cpu_has(X86_FEATURE_XSAVE))
449                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
450         else
451                 flags = UC_SIGCONTEXT_SS;
452 
453         if (likely(user_64bit_mode(regs)))
454                 flags |= UC_STRICT_RESTORE_SS;
455 
456         return flags;
457 }
458 
459 static int __setup_rt_frame(int sig, struct ksignal *ksig,
460                             sigset_t *set, struct pt_regs *regs)
461 {
462         struct rt_sigframe __user *frame;
463         void __user *fp = NULL;
464         int err = 0;
465 
466         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
467 
468         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
469                 return -EFAULT;
470 
471         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
472                 if (copy_siginfo_to_user(&frame->info, &ksig->info))
473                         return -EFAULT;
474         }
475 
476         put_user_try {
477                 /* Create the ucontext.  */
478                 put_user_ex(frame_uc_flags(regs), &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         void __user *restorer;
545         int err = 0;
546         void __user *fpstate = NULL;
547 
548         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
549 
550         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
551                 return -EFAULT;
552 
553         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
554                 if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
555                         return -EFAULT;
556         }
557 
558         put_user_try {
559                 /* Create the ucontext.  */
560                 put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
561                 put_user_ex(0, &frame->uc.uc_link);
562                 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
563                 put_user_ex(0, &frame->uc.uc__pad0);
564 
565                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
566                         restorer = ksig->ka.sa.sa_restorer;
567                 } else {
568                         /* could use a vstub here */
569                         restorer = NULL;
570                         err |= -EFAULT;
571                 }
572                 put_user_ex(restorer, &frame->pretcode);
573         } put_user_catch(err);
574 
575         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
576                                 regs, set->sig[0]);
577         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
578 
579         if (err)
580                 return -EFAULT;
581 
582         /* Set up registers for signal handler */
583         regs->sp = (unsigned long) frame;
584         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
585 
586         /* We use the x32 calling convention here... */
587         regs->di = ksig->sig;
588         regs->si = (unsigned long) &frame->info;
589         regs->dx = (unsigned long) &frame->uc;
590 
591         loadsegment(ds, __USER_DS);
592         loadsegment(es, __USER_DS);
593 
594         regs->cs = __USER_CS;
595         regs->ss = __USER_DS;
596 #endif  /* CONFIG_X86_X32_ABI */
597 
598         return 0;
599 }
600 
601 /*
602  * Do a signal return; undo the signal stack.
603  */
604 #ifdef CONFIG_X86_32
605 SYSCALL_DEFINE0(sigreturn)
606 {
607         struct pt_regs *regs = current_pt_regs();
608         struct sigframe __user *frame;
609         sigset_t set;
610 
611         frame = (struct sigframe __user *)(regs->sp - 8);
612 
613         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
614                 goto badframe;
615         if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
616                 && __copy_from_user(&set.sig[1], &frame->extramask,
617                                     sizeof(frame->extramask))))
618                 goto badframe;
619 
620         set_current_blocked(&set);
621 
622         /*
623          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
624          * Save a few cycles by skipping the __get_user.
625          */
626         if (restore_sigcontext(regs, &frame->sc, 0))
627                 goto badframe;
628         return regs->ax;
629 
630 badframe:
631         signal_fault(regs, frame, "sigreturn");
632 
633         return 0;
634 }
635 #endif /* CONFIG_X86_32 */
636 
637 SYSCALL_DEFINE0(rt_sigreturn)
638 {
639         struct pt_regs *regs = current_pt_regs();
640         struct rt_sigframe __user *frame;
641         sigset_t set;
642         unsigned long uc_flags;
643 
644         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
645         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
646                 goto badframe;
647         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
648                 goto badframe;
649         if (__get_user(uc_flags, &frame->uc.uc_flags))
650                 goto badframe;
651 
652         set_current_blocked(&set);
653 
654         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
655                 goto badframe;
656 
657         if (restore_altstack(&frame->uc.uc_stack))
658                 goto badframe;
659 
660         return regs->ax;
661 
662 badframe:
663         signal_fault(regs, frame, "rt_sigreturn");
664         return 0;
665 }
666 
667 static inline int is_ia32_compat_frame(struct ksignal *ksig)
668 {
669         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
670                 ksig->ka.sa.sa_flags & SA_IA32_ABI;
671 }
672 
673 static inline int is_ia32_frame(struct ksignal *ksig)
674 {
675         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
676 }
677 
678 static inline int is_x32_frame(struct ksignal *ksig)
679 {
680         return IS_ENABLED(CONFIG_X86_X32_ABI) &&
681                 ksig->ka.sa.sa_flags & SA_X32_ABI;
682 }
683 
684 static int
685 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
686 {
687         int usig = ksig->sig;
688         sigset_t *set = sigmask_to_save();
689         compat_sigset_t *cset = (compat_sigset_t *) set;
690 
691         /*
692          * Increment event counter and perform fixup for the pre-signal
693          * frame.
694          */
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                 if (fpu->initialized)
767                         fpu__clear(fpu);
768         }
769         signal_setup_done(failed, ksig, stepping);
770 }
771 
772 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
773 {
774         /*
775          * This function is fundamentally broken as currently
776          * implemented.
777          *
778          * The idea is that we want to trigger a call to the
779          * restart_block() syscall and that we want in_ia32_syscall(),
780          * in_x32_syscall(), etc. to match whatever they were in the
781          * syscall being restarted.  We assume that the syscall
782          * instruction at (regs->ip - 2) matches whatever syscall
783          * instruction we used to enter in the first place.
784          *
785          * The problem is that we can get here when ptrace pokes
786          * syscall-like values into regs even if we're not in a syscall
787          * at all.
788          *
789          * For now, we maintain historical behavior and guess based on
790          * stored state.  We could do better by saving the actual
791          * syscall arch in restart_block or (with caveats on x32) by
792          * checking if regs->ip points to 'int $0x80'.  The current
793          * behavior is incorrect if a tracer has a different bitness
794          * than the tracee.
795          */
796 #ifdef CONFIG_IA32_EMULATION
797         if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
798                 return __NR_ia32_restart_syscall;
799 #endif
800 #ifdef CONFIG_X86_X32_ABI
801         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
802 #else
803         return __NR_restart_syscall;
804 #endif
805 }
806 
807 /*
808  * Note that 'init' is a special process: it doesn't get signals it doesn't
809  * want to handle. Thus you cannot kill init even with a SIGKILL even by
810  * mistake.
811  */
812 void do_signal(struct pt_regs *regs)
813 {
814         struct ksignal ksig;
815 
816         if (get_signal(&ksig)) {
817                 /* Whee! Actually deliver the signal.  */
818                 handle_signal(&ksig, regs);
819                 return;
820         }
821 
822         /* Did we come from a system call? */
823         if (syscall_get_nr(current, regs) >= 0) {
824                 /* Restart the system call - no handlers present */
825                 switch (syscall_get_error(current, regs)) {
826                 case -ERESTARTNOHAND:
827                 case -ERESTARTSYS:
828                 case -ERESTARTNOINTR:
829                         regs->ax = regs->orig_ax;
830                         regs->ip -= 2;
831                         break;
832 
833                 case -ERESTART_RESTARTBLOCK:
834                         regs->ax = get_nr_restart_syscall(regs);
835                         regs->ip -= 2;
836                         break;
837                 }
838         }
839 
840         /*
841          * If there's no signal to deliver, we just put the saved sigmask
842          * back.
843          */
844         restore_saved_sigmask();
845 }
846 
847 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
848 {
849         struct task_struct *me = current;
850 
851         if (show_unhandled_signals && printk_ratelimit()) {
852                 printk("%s"
853                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
854                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
855                        me->comm, me->pid, where, frame,
856                        regs->ip, regs->sp, regs->orig_ax);
857                 print_vma_addr(KERN_CONT " in ", regs->ip);
858                 pr_cont("\n");
859         }
860 
861         force_sig(SIGSEGV, me);
862 }
863 
864 #ifdef CONFIG_X86_X32_ABI
865 asmlinkage long sys32_x32_rt_sigreturn(void)
866 {
867         struct pt_regs *regs = current_pt_regs();
868         struct rt_sigframe_x32 __user *frame;
869         sigset_t set;
870         unsigned long uc_flags;
871 
872         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
873 
874         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
875                 goto badframe;
876         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
877                 goto badframe;
878         if (__get_user(uc_flags, &frame->uc.uc_flags))
879                 goto badframe;
880 
881         set_current_blocked(&set);
882 
883         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
884                 goto badframe;
885 
886         if (compat_restore_altstack(&frame->uc.uc_stack))
887                 goto badframe;
888 
889         return regs->ax;
890 
891 badframe:
892         signal_fault(regs, frame, "x32 rt_sigreturn");
893         return 0;
894 }
895 #endif
896 

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