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Linux/arch/x86/kernel/signal.c

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  1 /*
  2  *  Copyright (C) 1991, 1992  Linus Torvalds
  3  *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
  4  *
  5  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
  6  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
  7  *  2000-2002   x86-64 support by Andi Kleen
  8  */
  9 
 10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 11 
 12 #include <linux/sched.h>
 13 #include <linux/mm.h>
 14 #include <linux/smp.h>
 15 #include <linux/kernel.h>
 16 #include <linux/errno.h>
 17 #include <linux/wait.h>
 18 #include <linux/tracehook.h>
 19 #include <linux/unistd.h>
 20 #include <linux/stddef.h>
 21 #include <linux/personality.h>
 22 #include <linux/uaccess.h>
 23 #include <linux/user-return-notifier.h>
 24 #include <linux/uprobes.h>
 25 #include <linux/context_tracking.h>
 26 
 27 #include <asm/processor.h>
 28 #include <asm/ucontext.h>
 29 #include <asm/fpu/internal.h>
 30 #include <asm/fpu/signal.h>
 31 #include <asm/vdso.h>
 32 #include <asm/mce.h>
 33 #include <asm/sighandling.h>
 34 #include <asm/vm86.h>
 35 
 36 #ifdef CONFIG_X86_64
 37 #include <asm/proto.h>
 38 #include <asm/ia32_unistd.h>
 39 #endif /* CONFIG_X86_64 */
 40 
 41 #include <asm/syscall.h>
 42 #include <asm/syscalls.h>
 43 
 44 #include <asm/sigframe.h>
 45 
 46 #define COPY(x)                 do {                    \
 47         get_user_ex(regs->x, &sc->x);                   \
 48 } while (0)
 49 
 50 #define GET_SEG(seg)            ({                      \
 51         unsigned short tmp;                             \
 52         get_user_ex(tmp, &sc->seg);                     \
 53         tmp;                                            \
 54 })
 55 
 56 #define COPY_SEG(seg)           do {                    \
 57         regs->seg = GET_SEG(seg);                       \
 58 } while (0)
 59 
 60 #define COPY_SEG_CPL3(seg)      do {                    \
 61         regs->seg = GET_SEG(seg) | 3;                   \
 62 } while (0)
 63 
 64 #ifdef CONFIG_X86_64
 65 /*
 66  * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
 67  * alone.  Using this generally makes no sense unless
 68  * user_64bit_mode(regs) would return true.
 69  */
 70 static void force_valid_ss(struct pt_regs *regs)
 71 {
 72         u32 ar;
 73         asm volatile ("lar %[old_ss], %[ar]\n\t"
 74                       "jz 1f\n\t"               /* If invalid: */
 75                       "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
 76                       "1:"
 77                       : [ar] "=r" (ar)
 78                       : [old_ss] "rm" ((u16)regs->ss));
 79 
 80         /*
 81          * For a valid 64-bit user context, we need DPL 3, type
 82          * read-write data or read-write exp-down data, and S and P
 83          * set.  We can't use VERW because VERW doesn't check the
 84          * P bit.
 85          */
 86         ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
 87         if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
 88             ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
 89                 regs->ss = __USER_DS;
 90 }
 91 #endif
 92 
 93 static int restore_sigcontext(struct pt_regs *regs,
 94                               struct sigcontext __user *sc,
 95                               unsigned long uc_flags)
 96 {
 97         unsigned long buf_val;
 98         void __user *buf;
 99         unsigned int tmpflags;
100         unsigned int err = 0;
101 
102         /* Always make any pending restarted system calls return -EINTR */
103         current->restart_block.fn = do_no_restart_syscall;
104 
105         get_user_try {
106 
107 #ifdef CONFIG_X86_32
108                 set_user_gs(regs, GET_SEG(gs));
109                 COPY_SEG(fs);
110                 COPY_SEG(es);
111                 COPY_SEG(ds);
112 #endif /* CONFIG_X86_32 */
113 
114                 COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
115                 COPY(dx); COPY(cx); COPY(ip); COPY(ax);
116 
117 #ifdef CONFIG_X86_64
118                 COPY(r8);
119                 COPY(r9);
120                 COPY(r10);
121                 COPY(r11);
122                 COPY(r12);
123                 COPY(r13);
124                 COPY(r14);
125                 COPY(r15);
126 #endif /* CONFIG_X86_64 */
127 
128                 COPY_SEG_CPL3(cs);
129                 COPY_SEG_CPL3(ss);
130 
131 #ifdef CONFIG_X86_64
132                 /*
133                  * Fix up SS if needed for the benefit of old DOSEMU and
134                  * CRIU.
135                  */
136                 if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) &&
137                              user_64bit_mode(regs)))
138                         force_valid_ss(regs);
139 #endif
140 
141                 get_user_ex(tmpflags, &sc->flags);
142                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
143                 regs->orig_ax = -1;             /* disable syscall checks */
144 
145                 get_user_ex(buf_val, &sc->fpstate);
146                 buf = (void __user *)buf_val;
147         } get_user_catch(err);
148 
149         err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
150 
151         force_iret();
152 
153         return err;
154 }
155 
156 int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
157                      struct pt_regs *regs, unsigned long mask)
158 {
159         int err = 0;
160 
161         put_user_try {
162 
163 #ifdef CONFIG_X86_32
164                 put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
165                 put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
166                 put_user_ex(regs->es, (unsigned int __user *)&sc->es);
167                 put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);
168 #endif /* CONFIG_X86_32 */
169 
170                 put_user_ex(regs->di, &sc->di);
171                 put_user_ex(regs->si, &sc->si);
172                 put_user_ex(regs->bp, &sc->bp);
173                 put_user_ex(regs->sp, &sc->sp);
174                 put_user_ex(regs->bx, &sc->bx);
175                 put_user_ex(regs->dx, &sc->dx);
176                 put_user_ex(regs->cx, &sc->cx);
177                 put_user_ex(regs->ax, &sc->ax);
178 #ifdef CONFIG_X86_64
179                 put_user_ex(regs->r8, &sc->r8);
180                 put_user_ex(regs->r9, &sc->r9);
181                 put_user_ex(regs->r10, &sc->r10);
182                 put_user_ex(regs->r11, &sc->r11);
183                 put_user_ex(regs->r12, &sc->r12);
184                 put_user_ex(regs->r13, &sc->r13);
185                 put_user_ex(regs->r14, &sc->r14);
186                 put_user_ex(regs->r15, &sc->r15);
187 #endif /* CONFIG_X86_64 */
188 
189                 put_user_ex(current->thread.trap_nr, &sc->trapno);
190                 put_user_ex(current->thread.error_code, &sc->err);
191                 put_user_ex(regs->ip, &sc->ip);
192 #ifdef CONFIG_X86_32
193                 put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
194                 put_user_ex(regs->flags, &sc->flags);
195                 put_user_ex(regs->sp, &sc->sp_at_signal);
196                 put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);
197 #else /* !CONFIG_X86_32 */
198                 put_user_ex(regs->flags, &sc->flags);
199                 put_user_ex(regs->cs, &sc->cs);
200                 put_user_ex(0, &sc->gs);
201                 put_user_ex(0, &sc->fs);
202                 put_user_ex(regs->ss, &sc->ss);
203 #endif /* CONFIG_X86_32 */
204 
205                 put_user_ex(fpstate, &sc->fpstate);
206 
207                 /* non-iBCS2 extensions.. */
208                 put_user_ex(mask, &sc->oldmask);
209                 put_user_ex(current->thread.cr2, &sc->cr2);
210         } put_user_catch(err);
211 
212         return err;
213 }
214 
215 /*
216  * Set up a signal frame.
217  */
218 
219 /*
220  * Determine which stack to use..
221  */
222 static unsigned long align_sigframe(unsigned long sp)
223 {
224 #ifdef CONFIG_X86_32
225         /*
226          * Align the stack pointer according to the i386 ABI,
227          * i.e. so that on function entry ((sp + 4) & 15) == 0.
228          */
229         sp = ((sp + 4) & -16ul) - 4;
230 #else /* !CONFIG_X86_32 */
231         sp = round_down(sp, 16) - 8;
232 #endif
233         return sp;
234 }
235 
236 static void __user *
237 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
238              void __user **fpstate)
239 {
240         /* Default to using normal stack */
241         unsigned long math_size = 0;
242         unsigned long sp = regs->sp;
243         unsigned long buf_fx = 0;
244         int onsigstack = on_sig_stack(sp);
245         struct fpu *fpu = &current->thread.fpu;
246 
247         /* redzone */
248         if (IS_ENABLED(CONFIG_X86_64))
249                 sp -= 128;
250 
251         /* This is the X/Open sanctioned signal stack switching.  */
252         if (ka->sa.sa_flags & SA_ONSTACK) {
253                 if (sas_ss_flags(sp) == 0)
254                         sp = current->sas_ss_sp + current->sas_ss_size;
255         } else if (IS_ENABLED(CONFIG_X86_32) &&
256                    !onsigstack &&
257                    (regs->ss & 0xffff) != __USER_DS &&
258                    !(ka->sa.sa_flags & SA_RESTORER) &&
259                    ka->sa.sa_restorer) {
260                 /* This is the legacy signal stack switching. */
261                 sp = (unsigned long) ka->sa.sa_restorer;
262         }
263 
264         if (fpu->fpstate_active) {
265                 sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
266                                           &buf_fx, &math_size);
267                 *fpstate = (void __user *)sp;
268         }
269 
270         sp = align_sigframe(sp - frame_size);
271 
272         /*
273          * If we are on the alternate signal stack and would overflow it, don't.
274          * Return an always-bogus address instead so we will die with SIGSEGV.
275          */
276         if (onsigstack && !likely(on_sig_stack(sp)))
277                 return (void __user *)-1L;
278 
279         /* save i387 and extended state */
280         if (fpu->fpstate_active &&
281             copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0)
282                 return (void __user *)-1L;
283 
284         return (void __user *)sp;
285 }
286 
287 #ifdef CONFIG_X86_32
288 static const struct {
289         u16 poplmovl;
290         u32 val;
291         u16 int80;
292 } __attribute__((packed)) retcode = {
293         0xb858,         /* popl %eax; movl $..., %eax */
294         __NR_sigreturn,
295         0x80cd,         /* int $0x80 */
296 };
297 
298 static const struct {
299         u8  movl;
300         u32 val;
301         u16 int80;
302         u8  pad;
303 } __attribute__((packed)) rt_retcode = {
304         0xb8,           /* movl $..., %eax */
305         __NR_rt_sigreturn,
306         0x80cd,         /* int $0x80 */
307         0
308 };
309 
310 static int
311 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
312               struct pt_regs *regs)
313 {
314         struct sigframe __user *frame;
315         void __user *restorer;
316         int err = 0;
317         void __user *fpstate = NULL;
318 
319         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
320 
321         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
322                 return -EFAULT;
323 
324         if (__put_user(sig, &frame->sig))
325                 return -EFAULT;
326 
327         if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
328                 return -EFAULT;
329 
330         if (_NSIG_WORDS > 1) {
331                 if (__copy_to_user(&frame->extramask, &set->sig[1],
332                                    sizeof(frame->extramask)))
333                         return -EFAULT;
334         }
335 
336         if (current->mm->context.vdso)
337                 restorer = current->mm->context.vdso +
338                         vdso_image_32.sym___kernel_sigreturn;
339         else
340                 restorer = &frame->retcode;
341         if (ksig->ka.sa.sa_flags & SA_RESTORER)
342                 restorer = ksig->ka.sa.sa_restorer;
343 
344         /* Set up to return from userspace.  */
345         err |= __put_user(restorer, &frame->pretcode);
346 
347         /*
348          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
349          *
350          * WE DO NOT USE IT ANY MORE! It's only left here for historical
351          * reasons and because gdb uses it as a signature to notice
352          * signal handler stack frames.
353          */
354         err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
355 
356         if (err)
357                 return -EFAULT;
358 
359         /* Set up registers for signal handler */
360         regs->sp = (unsigned long)frame;
361         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
362         regs->ax = (unsigned long)sig;
363         regs->dx = 0;
364         regs->cx = 0;
365 
366         regs->ds = __USER_DS;
367         regs->es = __USER_DS;
368         regs->ss = __USER_DS;
369         regs->cs = __USER_CS;
370 
371         return 0;
372 }
373 
374 static int __setup_rt_frame(int sig, struct ksignal *ksig,
375                             sigset_t *set, struct pt_regs *regs)
376 {
377         struct rt_sigframe __user *frame;
378         void __user *restorer;
379         int err = 0;
380         void __user *fpstate = NULL;
381 
382         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
383 
384         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
385                 return -EFAULT;
386 
387         put_user_try {
388                 put_user_ex(sig, &frame->sig);
389                 put_user_ex(&frame->info, &frame->pinfo);
390                 put_user_ex(&frame->uc, &frame->puc);
391 
392                 /* Create the ucontext.  */
393                 if (boot_cpu_has(X86_FEATURE_XSAVE))
394                         put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
395                 else
396                         put_user_ex(0, &frame->uc.uc_flags);
397                 put_user_ex(0, &frame->uc.uc_link);
398                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
399 
400                 /* Set up to return from userspace.  */
401                 restorer = current->mm->context.vdso +
402                         vdso_image_32.sym___kernel_rt_sigreturn;
403                 if (ksig->ka.sa.sa_flags & SA_RESTORER)
404                         restorer = ksig->ka.sa.sa_restorer;
405                 put_user_ex(restorer, &frame->pretcode);
406 
407                 /*
408                  * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
409                  *
410                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
411                  * reasons and because gdb uses it as a signature to notice
412                  * signal handler stack frames.
413                  */
414                 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
415         } put_user_catch(err);
416         
417         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
418         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
419                                 regs, set->sig[0]);
420         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
421 
422         if (err)
423                 return -EFAULT;
424 
425         /* Set up registers for signal handler */
426         regs->sp = (unsigned long)frame;
427         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
428         regs->ax = (unsigned long)sig;
429         regs->dx = (unsigned long)&frame->info;
430         regs->cx = (unsigned long)&frame->uc;
431 
432         regs->ds = __USER_DS;
433         regs->es = __USER_DS;
434         regs->ss = __USER_DS;
435         regs->cs = __USER_CS;
436 
437         return 0;
438 }
439 #else /* !CONFIG_X86_32 */
440 static unsigned long frame_uc_flags(struct pt_regs *regs)
441 {
442         unsigned long flags;
443 
444         if (boot_cpu_has(X86_FEATURE_XSAVE))
445                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
446         else
447                 flags = UC_SIGCONTEXT_SS;
448 
449         if (likely(user_64bit_mode(regs)))
450                 flags |= UC_STRICT_RESTORE_SS;
451 
452         return flags;
453 }
454 
455 static int __setup_rt_frame(int sig, struct ksignal *ksig,
456                             sigset_t *set, struct pt_regs *regs)
457 {
458         struct rt_sigframe __user *frame;
459         void __user *fp = NULL;
460         int err = 0;
461 
462         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
463 
464         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
465                 return -EFAULT;
466 
467         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
468                 if (copy_siginfo_to_user(&frame->info, &ksig->info))
469                         return -EFAULT;
470         }
471 
472         put_user_try {
473                 /* Create the ucontext.  */
474                 put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
475                 put_user_ex(0, &frame->uc.uc_link);
476                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
477 
478                 /* Set up to return from userspace.  If provided, use a stub
479                    already in userspace.  */
480                 /* x86-64 should always use SA_RESTORER. */
481                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
482                         put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
483                 } else {
484                         /* could use a vstub here */
485                         err |= -EFAULT;
486                 }
487         } put_user_catch(err);
488 
489         err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
490         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
491 
492         if (err)
493                 return -EFAULT;
494 
495         /* Set up registers for signal handler */
496         regs->di = sig;
497         /* In case the signal handler was declared without prototypes */
498         regs->ax = 0;
499 
500         /* This also works for non SA_SIGINFO handlers because they expect the
501            next argument after the signal number on the stack. */
502         regs->si = (unsigned long)&frame->info;
503         regs->dx = (unsigned long)&frame->uc;
504         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
505 
506         regs->sp = (unsigned long)frame;
507 
508         /*
509          * Set up the CS and SS registers to run signal handlers in
510          * 64-bit mode, even if the handler happens to be interrupting
511          * 32-bit or 16-bit code.
512          *
513          * SS is subtle.  In 64-bit mode, we don't need any particular
514          * SS descriptor, but we do need SS to be valid.  It's possible
515          * that the old SS is entirely bogus -- this can happen if the
516          * signal we're trying to deliver is #GP or #SS caused by a bad
517          * SS value.  We also have a compatbility issue here: DOSEMU
518          * relies on the contents of the SS register indicating the
519          * SS value at the time of the signal, even though that code in
520          * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
521          * avoids relying on sigreturn to restore SS; instead it uses
522          * a trampoline.)  So we do our best: if the old SS was valid,
523          * we keep it.  Otherwise we replace it.
524          */
525         regs->cs = __USER_CS;
526 
527         if (unlikely(regs->ss != __USER_DS))
528                 force_valid_ss(regs);
529 
530         return 0;
531 }
532 #endif /* CONFIG_X86_32 */
533 
534 static int x32_setup_rt_frame(struct ksignal *ksig,
535                               compat_sigset_t *set,
536                               struct pt_regs *regs)
537 {
538 #ifdef CONFIG_X86_X32_ABI
539         struct rt_sigframe_x32 __user *frame;
540         void __user *restorer;
541         int err = 0;
542         void __user *fpstate = NULL;
543 
544         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
545 
546         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
547                 return -EFAULT;
548 
549         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
550                 if (copy_siginfo_to_user32(&frame->info, &ksig->info))
551                         return -EFAULT;
552         }
553 
554         put_user_try {
555                 /* Create the ucontext.  */
556                 put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
557                 put_user_ex(0, &frame->uc.uc_link);
558                 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
559                 put_user_ex(0, &frame->uc.uc__pad0);
560 
561                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
562                         restorer = ksig->ka.sa.sa_restorer;
563                 } else {
564                         /* could use a vstub here */
565                         restorer = NULL;
566                         err |= -EFAULT;
567                 }
568                 put_user_ex(restorer, &frame->pretcode);
569         } put_user_catch(err);
570 
571         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
572                                 regs, set->sig[0]);
573         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
574 
575         if (err)
576                 return -EFAULT;
577 
578         /* Set up registers for signal handler */
579         regs->sp = (unsigned long) frame;
580         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
581 
582         /* We use the x32 calling convention here... */
583         regs->di = ksig->sig;
584         regs->si = (unsigned long) &frame->info;
585         regs->dx = (unsigned long) &frame->uc;
586 
587         loadsegment(ds, __USER_DS);
588         loadsegment(es, __USER_DS);
589 
590         regs->cs = __USER_CS;
591         regs->ss = __USER_DS;
592 #endif  /* CONFIG_X86_X32_ABI */
593 
594         return 0;
595 }
596 
597 /*
598  * Do a signal return; undo the signal stack.
599  */
600 #ifdef CONFIG_X86_32
601 asmlinkage unsigned long sys_sigreturn(void)
602 {
603         struct pt_regs *regs = current_pt_regs();
604         struct sigframe __user *frame;
605         sigset_t set;
606 
607         frame = (struct sigframe __user *)(regs->sp - 8);
608 
609         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
610                 goto badframe;
611         if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
612                 && __copy_from_user(&set.sig[1], &frame->extramask,
613                                     sizeof(frame->extramask))))
614                 goto badframe;
615 
616         set_current_blocked(&set);
617 
618         /*
619          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
620          * Save a few cycles by skipping the __get_user.
621          */
622         if (restore_sigcontext(regs, &frame->sc, 0))
623                 goto badframe;
624         return regs->ax;
625 
626 badframe:
627         signal_fault(regs, frame, "sigreturn");
628 
629         return 0;
630 }
631 #endif /* CONFIG_X86_32 */
632 
633 asmlinkage long sys_rt_sigreturn(void)
634 {
635         struct pt_regs *regs = current_pt_regs();
636         struct rt_sigframe __user *frame;
637         sigset_t set;
638         unsigned long uc_flags;
639 
640         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
641         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
642                 goto badframe;
643         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
644                 goto badframe;
645         if (__get_user(uc_flags, &frame->uc.uc_flags))
646                 goto badframe;
647 
648         set_current_blocked(&set);
649 
650         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
651                 goto badframe;
652 
653         if (restore_altstack(&frame->uc.uc_stack))
654                 goto badframe;
655 
656         return regs->ax;
657 
658 badframe:
659         signal_fault(regs, frame, "rt_sigreturn");
660         return 0;
661 }
662 
663 static inline int is_ia32_compat_frame(void)
664 {
665         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
666                test_thread_flag(TIF_IA32);
667 }
668 
669 static inline int is_ia32_frame(void)
670 {
671         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame();
672 }
673 
674 static inline int is_x32_frame(void)
675 {
676         return IS_ENABLED(CONFIG_X86_X32_ABI) && test_thread_flag(TIF_X32);
677 }
678 
679 static int
680 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
681 {
682         int usig = ksig->sig;
683         sigset_t *set = sigmask_to_save();
684         compat_sigset_t *cset = (compat_sigset_t *) set;
685 
686         /* Set up the stack frame */
687         if (is_ia32_frame()) {
688                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
689                         return ia32_setup_rt_frame(usig, ksig, cset, regs);
690                 else
691                         return ia32_setup_frame(usig, ksig, cset, regs);
692         } else if (is_x32_frame()) {
693                 return x32_setup_rt_frame(ksig, cset, regs);
694         } else {
695                 return __setup_rt_frame(ksig->sig, ksig, set, regs);
696         }
697 }
698 
699 static void
700 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
701 {
702         bool stepping, failed;
703         struct fpu *fpu = &current->thread.fpu;
704 
705         if (v8086_mode(regs))
706                 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
707 
708         /* Are we from a system call? */
709         if (syscall_get_nr(current, regs) >= 0) {
710                 /* If so, check system call restarting.. */
711                 switch (syscall_get_error(current, regs)) {
712                 case -ERESTART_RESTARTBLOCK:
713                 case -ERESTARTNOHAND:
714                         regs->ax = -EINTR;
715                         break;
716 
717                 case -ERESTARTSYS:
718                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
719                                 regs->ax = -EINTR;
720                                 break;
721                         }
722                 /* fallthrough */
723                 case -ERESTARTNOINTR:
724                         regs->ax = regs->orig_ax;
725                         regs->ip -= 2;
726                         break;
727                 }
728         }
729 
730         /*
731          * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
732          * so that register information in the sigcontext is correct and
733          * then notify the tracer before entering the signal handler.
734          */
735         stepping = test_thread_flag(TIF_SINGLESTEP);
736         if (stepping)
737                 user_disable_single_step(current);
738 
739         failed = (setup_rt_frame(ksig, regs) < 0);
740         if (!failed) {
741                 /*
742                  * Clear the direction flag as per the ABI for function entry.
743                  *
744                  * Clear RF when entering the signal handler, because
745                  * it might disable possible debug exception from the
746                  * signal handler.
747                  *
748                  * Clear TF for the case when it wasn't set by debugger to
749                  * avoid the recursive send_sigtrap() in SIGTRAP handler.
750                  */
751                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
752                 /*
753                  * Ensure the signal handler starts with the new fpu state.
754                  */
755                 if (fpu->fpstate_active)
756                         fpu__clear(fpu);
757         }
758         signal_setup_done(failed, ksig, stepping);
759 }
760 
761 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
762 {
763         /*
764          * This function is fundamentally broken as currently
765          * implemented.
766          *
767          * The idea is that we want to trigger a call to the
768          * restart_block() syscall and that we want in_ia32_syscall(),
769          * in_x32_syscall(), etc. to match whatever they were in the
770          * syscall being restarted.  We assume that the syscall
771          * instruction at (regs->ip - 2) matches whatever syscall
772          * instruction we used to enter in the first place.
773          *
774          * The problem is that we can get here when ptrace pokes
775          * syscall-like values into regs even if we're not in a syscall
776          * at all.
777          *
778          * For now, we maintain historical behavior and guess based on
779          * stored state.  We could do better by saving the actual
780          * syscall arch in restart_block or (with caveats on x32) by
781          * checking if regs->ip points to 'int $0x80'.  The current
782          * behavior is incorrect if a tracer has a different bitness
783          * than the tracee.
784          */
785 #ifdef CONFIG_IA32_EMULATION
786         if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
787                 return __NR_ia32_restart_syscall;
788 #endif
789 #ifdef CONFIG_X86_X32_ABI
790         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
791 #else
792         return __NR_restart_syscall;
793 #endif
794 }
795 
796 /*
797  * Note that 'init' is a special process: it doesn't get signals it doesn't
798  * want to handle. Thus you cannot kill init even with a SIGKILL even by
799  * mistake.
800  */
801 void do_signal(struct pt_regs *regs)
802 {
803         struct ksignal ksig;
804 
805         if (get_signal(&ksig)) {
806                 /* Whee! Actually deliver the signal.  */
807                 handle_signal(&ksig, regs);
808                 return;
809         }
810 
811         /* Did we come from a system call? */
812         if (syscall_get_nr(current, regs) >= 0) {
813                 /* Restart the system call - no handlers present */
814                 switch (syscall_get_error(current, regs)) {
815                 case -ERESTARTNOHAND:
816                 case -ERESTARTSYS:
817                 case -ERESTARTNOINTR:
818                         regs->ax = regs->orig_ax;
819                         regs->ip -= 2;
820                         break;
821 
822                 case -ERESTART_RESTARTBLOCK:
823                         regs->ax = get_nr_restart_syscall(regs);
824                         regs->ip -= 2;
825                         break;
826                 }
827         }
828 
829         /*
830          * If there's no signal to deliver, we just put the saved sigmask
831          * back.
832          */
833         restore_saved_sigmask();
834 }
835 
836 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
837 {
838         struct task_struct *me = current;
839 
840         if (show_unhandled_signals && printk_ratelimit()) {
841                 printk("%s"
842                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
843                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
844                        me->comm, me->pid, where, frame,
845                        regs->ip, regs->sp, regs->orig_ax);
846                 print_vma_addr(" in ", regs->ip);
847                 pr_cont("\n");
848         }
849 
850         force_sig(SIGSEGV, me);
851 }
852 
853 #ifdef CONFIG_X86_X32_ABI
854 asmlinkage long sys32_x32_rt_sigreturn(void)
855 {
856         struct pt_regs *regs = current_pt_regs();
857         struct rt_sigframe_x32 __user *frame;
858         sigset_t set;
859         unsigned long uc_flags;
860 
861         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
862 
863         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
864                 goto badframe;
865         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
866                 goto badframe;
867         if (__get_user(uc_flags, &frame->uc.uc_flags))
868                 goto badframe;
869 
870         set_current_blocked(&set);
871 
872         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
873                 goto badframe;
874 
875         if (compat_restore_altstack(&frame->uc.uc_stack))
876                 goto badframe;
877 
878         return regs->ax;
879 
880 badframe:
881         signal_fault(regs, frame, "x32 rt_sigreturn");
882         return 0;
883 }
884 #endif
885 

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