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 */
force_valid_ss(struct pt_regs * regs)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
restore_sigcontext(struct pt_regs * regs,struct sigcontext __user * sc,unsigned long uc_flags)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
setup_sigcontext(struct sigcontext __user * sc,void __user * fpstate,struct pt_regs * regs,unsigned long mask)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 */
align_sigframe(unsigned long sp)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 *
get_sigframe(struct k_sigaction * ka,struct pt_regs * regs,size_t frame_size,void __user ** fpstate)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 bool nested_altstack = on_sig_stack(regs->sp);
245 bool entering_altstack = false;
246 unsigned long math_size = 0;
247 unsigned long sp = regs->sp;
248 unsigned long buf_fx = 0;
249 int ret;
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 /*
258 * This checks nested_altstack via sas_ss_flags(). Sensible
259 * programs use SS_AUTODISARM, which disables that check, and
260 * programs that don't use SS_AUTODISARM get compatible.
261 */
262 if (sas_ss_flags(sp) == 0) {
263 sp = current->sas_ss_sp + current->sas_ss_size;
264 entering_altstack = true;
265 }
266 } else if (IS_ENABLED(CONFIG_X86_32) &&
267 !nested_altstack &&
268 regs->ss != __USER_DS &&
269 !(ka->sa.sa_flags & SA_RESTORER) &&
270 ka->sa.sa_restorer) {
271 /* This is the legacy signal stack switching. */
272 sp = (unsigned long) ka->sa.sa_restorer;
273 entering_altstack = true;
274 }
275
276 sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
277 &buf_fx, &math_size);
278 *fpstate = (void __user *)sp;
279
280 sp = align_sigframe(sp - frame_size);
281
282 /*
283 * If we are on the alternate signal stack and would overflow it, don't.
284 * Return an always-bogus address instead so we will die with SIGSEGV.
285 */
286 if (unlikely((nested_altstack || entering_altstack) &&
287 !__on_sig_stack(sp))) {
288
289 if (show_unhandled_signals && printk_ratelimit())
290 pr_info("%s[%d] overflowed sigaltstack\n",
291 current->comm, task_pid_nr(current));
292
293 return (void __user *)-1L;
294 }
295
296 /* save i387 and extended state */
297 ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
298 if (ret < 0)
299 return (void __user *)-1L;
300
301 return (void __user *)sp;
302 }
303
304 #ifdef CONFIG_X86_32
305 static const struct {
306 u16 poplmovl;
307 u32 val;
308 u16 int80;
309 } __attribute__((packed)) retcode = {
310 0xb858, /* popl %eax; movl $..., %eax */
311 __NR_sigreturn,
312 0x80cd, /* int $0x80 */
313 };
314
315 static const struct {
316 u8 movl;
317 u32 val;
318 u16 int80;
319 u8 pad;
320 } __attribute__((packed)) rt_retcode = {
321 0xb8, /* movl $..., %eax */
322 __NR_rt_sigreturn,
323 0x80cd, /* int $0x80 */
324 0
325 };
326
327 static int
__setup_frame(int sig,struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)328 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
329 struct pt_regs *regs)
330 {
331 struct sigframe __user *frame;
332 void __user *restorer;
333 int err = 0;
334 void __user *fpstate = NULL;
335
336 frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
337
338 if (!access_ok(frame, sizeof(*frame)))
339 return -EFAULT;
340
341 if (__put_user(sig, &frame->sig))
342 return -EFAULT;
343
344 if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
345 return -EFAULT;
346
347 if (_NSIG_WORDS > 1) {
348 if (__copy_to_user(&frame->extramask, &set->sig[1],
349 sizeof(frame->extramask)))
350 return -EFAULT;
351 }
352
353 if (current->mm->context.vdso)
354 restorer = current->mm->context.vdso +
355 vdso_image_32.sym___kernel_sigreturn;
356 else
357 restorer = &frame->retcode;
358 if (ksig->ka.sa.sa_flags & SA_RESTORER)
359 restorer = ksig->ka.sa.sa_restorer;
360
361 /* Set up to return from userspace. */
362 err |= __put_user(restorer, &frame->pretcode);
363
364 /*
365 * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
366 *
367 * WE DO NOT USE IT ANY MORE! It's only left here for historical
368 * reasons and because gdb uses it as a signature to notice
369 * signal handler stack frames.
370 */
371 err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
372
373 if (err)
374 return -EFAULT;
375
376 /* Set up registers for signal handler */
377 regs->sp = (unsigned long)frame;
378 regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
379 regs->ax = (unsigned long)sig;
380 regs->dx = 0;
381 regs->cx = 0;
382
383 regs->ds = __USER_DS;
384 regs->es = __USER_DS;
385 regs->ss = __USER_DS;
386 regs->cs = __USER_CS;
387
388 return 0;
389 }
390
__setup_rt_frame(int sig,struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)391 static int __setup_rt_frame(int sig, struct ksignal *ksig,
392 sigset_t *set, struct pt_regs *regs)
393 {
394 struct rt_sigframe __user *frame;
395 void __user *restorer;
396 int err = 0;
397 void __user *fpstate = NULL;
398
399 frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
400
401 if (!access_ok(frame, sizeof(*frame)))
402 return -EFAULT;
403
404 put_user_try {
405 put_user_ex(sig, &frame->sig);
406 put_user_ex(&frame->info, &frame->pinfo);
407 put_user_ex(&frame->uc, &frame->puc);
408
409 /* Create the ucontext. */
410 if (static_cpu_has(X86_FEATURE_XSAVE))
411 put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
412 else
413 put_user_ex(0, &frame->uc.uc_flags);
414 put_user_ex(0, &frame->uc.uc_link);
415 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
416
417 /* Set up to return from userspace. */
418 restorer = current->mm->context.vdso +
419 vdso_image_32.sym___kernel_rt_sigreturn;
420 if (ksig->ka.sa.sa_flags & SA_RESTORER)
421 restorer = ksig->ka.sa.sa_restorer;
422 put_user_ex(restorer, &frame->pretcode);
423
424 /*
425 * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
426 *
427 * WE DO NOT USE IT ANY MORE! It's only left here for historical
428 * reasons and because gdb uses it as a signature to notice
429 * signal handler stack frames.
430 */
431 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
432 } put_user_catch(err);
433
434 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
435 err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
436 regs, set->sig[0]);
437 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
438
439 if (err)
440 return -EFAULT;
441
442 /* Set up registers for signal handler */
443 regs->sp = (unsigned long)frame;
444 regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
445 regs->ax = (unsigned long)sig;
446 regs->dx = (unsigned long)&frame->info;
447 regs->cx = (unsigned long)&frame->uc;
448
449 regs->ds = __USER_DS;
450 regs->es = __USER_DS;
451 regs->ss = __USER_DS;
452 regs->cs = __USER_CS;
453
454 return 0;
455 }
456 #else /* !CONFIG_X86_32 */
frame_uc_flags(struct pt_regs * regs)457 static unsigned long frame_uc_flags(struct pt_regs *regs)
458 {
459 unsigned long flags;
460
461 if (boot_cpu_has(X86_FEATURE_XSAVE))
462 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
463 else
464 flags = UC_SIGCONTEXT_SS;
465
466 if (likely(user_64bit_mode(regs)))
467 flags |= UC_STRICT_RESTORE_SS;
468
469 return flags;
470 }
471
__setup_rt_frame(int sig,struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)472 static int __setup_rt_frame(int sig, struct ksignal *ksig,
473 sigset_t *set, struct pt_regs *regs)
474 {
475 struct rt_sigframe __user *frame;
476 void __user *fp = NULL;
477 unsigned long uc_flags;
478 int err = 0;
479
480 frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
481
482 if (!access_ok(frame, sizeof(*frame)))
483 return -EFAULT;
484
485 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
486 if (copy_siginfo_to_user(&frame->info, &ksig->info))
487 return -EFAULT;
488 }
489
490 uc_flags = frame_uc_flags(regs);
491
492 put_user_try {
493 /* Create the ucontext. */
494 put_user_ex(uc_flags, &frame->uc.uc_flags);
495 put_user_ex(0, &frame->uc.uc_link);
496 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
497
498 /* Set up to return from userspace. If provided, use a stub
499 already in userspace. */
500 /* x86-64 should always use SA_RESTORER. */
501 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
502 put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
503 } else {
504 /* could use a vstub here */
505 err |= -EFAULT;
506 }
507 } put_user_catch(err);
508
509 err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
510 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
511
512 if (err)
513 return -EFAULT;
514
515 /* Set up registers for signal handler */
516 regs->di = sig;
517 /* In case the signal handler was declared without prototypes */
518 regs->ax = 0;
519
520 /* This also works for non SA_SIGINFO handlers because they expect the
521 next argument after the signal number on the stack. */
522 regs->si = (unsigned long)&frame->info;
523 regs->dx = (unsigned long)&frame->uc;
524 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
525
526 regs->sp = (unsigned long)frame;
527
528 /*
529 * Set up the CS and SS registers to run signal handlers in
530 * 64-bit mode, even if the handler happens to be interrupting
531 * 32-bit or 16-bit code.
532 *
533 * SS is subtle. In 64-bit mode, we don't need any particular
534 * SS descriptor, but we do need SS to be valid. It's possible
535 * that the old SS is entirely bogus -- this can happen if the
536 * signal we're trying to deliver is #GP or #SS caused by a bad
537 * SS value. We also have a compatbility issue here: DOSEMU
538 * relies on the contents of the SS register indicating the
539 * SS value at the time of the signal, even though that code in
540 * DOSEMU predates sigreturn's ability to restore SS. (DOSEMU
541 * avoids relying on sigreturn to restore SS; instead it uses
542 * a trampoline.) So we do our best: if the old SS was valid,
543 * we keep it. Otherwise we replace it.
544 */
545 regs->cs = __USER_CS;
546
547 if (unlikely(regs->ss != __USER_DS))
548 force_valid_ss(regs);
549
550 return 0;
551 }
552 #endif /* CONFIG_X86_32 */
553
x32_setup_rt_frame(struct ksignal * ksig,compat_sigset_t * set,struct pt_regs * regs)554 static int x32_setup_rt_frame(struct ksignal *ksig,
555 compat_sigset_t *set,
556 struct pt_regs *regs)
557 {
558 #ifdef CONFIG_X86_X32_ABI
559 struct rt_sigframe_x32 __user *frame;
560 unsigned long uc_flags;
561 void __user *restorer;
562 int err = 0;
563 void __user *fpstate = NULL;
564
565 frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
566
567 if (!access_ok(frame, sizeof(*frame)))
568 return -EFAULT;
569
570 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
571 if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
572 return -EFAULT;
573 }
574
575 uc_flags = frame_uc_flags(regs);
576
577 put_user_try {
578 /* Create the ucontext. */
579 put_user_ex(uc_flags, &frame->uc.uc_flags);
580 put_user_ex(0, &frame->uc.uc_link);
581 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
582 put_user_ex(0, &frame->uc.uc__pad0);
583
584 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
585 restorer = ksig->ka.sa.sa_restorer;
586 } else {
587 /* could use a vstub here */
588 restorer = NULL;
589 err |= -EFAULT;
590 }
591 put_user_ex(restorer, (unsigned long __user *)&frame->pretcode);
592 } put_user_catch(err);
593
594 err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
595 regs, set->sig[0]);
596 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
597
598 if (err)
599 return -EFAULT;
600
601 /* Set up registers for signal handler */
602 regs->sp = (unsigned long) frame;
603 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
604
605 /* We use the x32 calling convention here... */
606 regs->di = ksig->sig;
607 regs->si = (unsigned long) &frame->info;
608 regs->dx = (unsigned long) &frame->uc;
609
610 loadsegment(ds, __USER_DS);
611 loadsegment(es, __USER_DS);
612
613 regs->cs = __USER_CS;
614 regs->ss = __USER_DS;
615 #endif /* CONFIG_X86_X32_ABI */
616
617 return 0;
618 }
619
620 /*
621 * Do a signal return; undo the signal stack.
622 */
623 #ifdef CONFIG_X86_32
SYSCALL_DEFINE0(sigreturn)624 SYSCALL_DEFINE0(sigreturn)
625 {
626 struct pt_regs *regs = current_pt_regs();
627 struct sigframe __user *frame;
628 sigset_t set;
629
630 frame = (struct sigframe __user *)(regs->sp - 8);
631
632 if (!access_ok(frame, sizeof(*frame)))
633 goto badframe;
634 if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
635 && __copy_from_user(&set.sig[1], &frame->extramask,
636 sizeof(frame->extramask))))
637 goto badframe;
638
639 set_current_blocked(&set);
640
641 /*
642 * x86_32 has no uc_flags bits relevant to restore_sigcontext.
643 * Save a few cycles by skipping the __get_user.
644 */
645 if (restore_sigcontext(regs, &frame->sc, 0))
646 goto badframe;
647 return regs->ax;
648
649 badframe:
650 signal_fault(regs, frame, "sigreturn");
651
652 return 0;
653 }
654 #endif /* CONFIG_X86_32 */
655
SYSCALL_DEFINE0(rt_sigreturn)656 SYSCALL_DEFINE0(rt_sigreturn)
657 {
658 struct pt_regs *regs = current_pt_regs();
659 struct rt_sigframe __user *frame;
660 sigset_t set;
661 unsigned long uc_flags;
662
663 frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
664 if (!access_ok(frame, sizeof(*frame)))
665 goto badframe;
666 if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
667 goto badframe;
668 if (__get_user(uc_flags, &frame->uc.uc_flags))
669 goto badframe;
670
671 set_current_blocked(&set);
672
673 if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
674 goto badframe;
675
676 if (restore_altstack(&frame->uc.uc_stack))
677 goto badframe;
678
679 return regs->ax;
680
681 badframe:
682 signal_fault(regs, frame, "rt_sigreturn");
683 return 0;
684 }
685
is_ia32_compat_frame(struct ksignal * ksig)686 static inline int is_ia32_compat_frame(struct ksignal *ksig)
687 {
688 return IS_ENABLED(CONFIG_IA32_EMULATION) &&
689 ksig->ka.sa.sa_flags & SA_IA32_ABI;
690 }
691
is_ia32_frame(struct ksignal * ksig)692 static inline int is_ia32_frame(struct ksignal *ksig)
693 {
694 return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
695 }
696
is_x32_frame(struct ksignal * ksig)697 static inline int is_x32_frame(struct ksignal *ksig)
698 {
699 return IS_ENABLED(CONFIG_X86_X32_ABI) &&
700 ksig->ka.sa.sa_flags & SA_X32_ABI;
701 }
702
703 static int
setup_rt_frame(struct ksignal * ksig,struct pt_regs * regs)704 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
705 {
706 int usig = ksig->sig;
707 sigset_t *set = sigmask_to_save();
708 compat_sigset_t *cset = (compat_sigset_t *) set;
709
710 /* Perform fixup for the pre-signal frame. */
711 rseq_signal_deliver(ksig, regs);
712
713 /* Set up the stack frame */
714 if (is_ia32_frame(ksig)) {
715 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
716 return ia32_setup_rt_frame(usig, ksig, cset, regs);
717 else
718 return ia32_setup_frame(usig, ksig, cset, regs);
719 } else if (is_x32_frame(ksig)) {
720 return x32_setup_rt_frame(ksig, cset, regs);
721 } else {
722 return __setup_rt_frame(ksig->sig, ksig, set, regs);
723 }
724 }
725
726 static void
handle_signal(struct ksignal * ksig,struct pt_regs * regs)727 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
728 {
729 bool stepping, failed;
730 struct fpu *fpu = ¤t->thread.fpu;
731
732 if (v8086_mode(regs))
733 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
734
735 /* Are we from a system call? */
736 if (syscall_get_nr(current, regs) >= 0) {
737 /* If so, check system call restarting.. */
738 switch (syscall_get_error(current, regs)) {
739 case -ERESTART_RESTARTBLOCK:
740 case -ERESTARTNOHAND:
741 regs->ax = -EINTR;
742 break;
743
744 case -ERESTARTSYS:
745 if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
746 regs->ax = -EINTR;
747 break;
748 }
749 /* fallthrough */
750 case -ERESTARTNOINTR:
751 regs->ax = regs->orig_ax;
752 regs->ip -= 2;
753 break;
754 }
755 }
756
757 /*
758 * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
759 * so that register information in the sigcontext is correct and
760 * then notify the tracer before entering the signal handler.
761 */
762 stepping = test_thread_flag(TIF_SINGLESTEP);
763 if (stepping)
764 user_disable_single_step(current);
765
766 failed = (setup_rt_frame(ksig, regs) < 0);
767 if (!failed) {
768 /*
769 * Clear the direction flag as per the ABI for function entry.
770 *
771 * Clear RF when entering the signal handler, because
772 * it might disable possible debug exception from the
773 * signal handler.
774 *
775 * Clear TF for the case when it wasn't set by debugger to
776 * avoid the recursive send_sigtrap() in SIGTRAP handler.
777 */
778 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
779 /*
780 * Ensure the signal handler starts with the new fpu state.
781 */
782 fpu__clear(fpu);
783 }
784 signal_setup_done(failed, ksig, stepping);
785 }
786
get_nr_restart_syscall(const struct pt_regs * regs)787 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
788 {
789 #ifdef CONFIG_IA32_EMULATION
790 if (current_thread_info()->status & TS_COMPAT_RESTART)
791 return __NR_ia32_restart_syscall;
792 #endif
793 #ifdef CONFIG_X86_X32_ABI
794 return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
795 #else
796 return __NR_restart_syscall;
797 #endif
798 }
799
800 /*
801 * Note that 'init' is a special process: it doesn't get signals it doesn't
802 * want to handle. Thus you cannot kill init even with a SIGKILL even by
803 * mistake.
804 */
do_signal(struct pt_regs * regs)805 void do_signal(struct pt_regs *regs)
806 {
807 struct ksignal ksig;
808
809 if (get_signal(&ksig)) {
810 /* Whee! Actually deliver the signal. */
811 handle_signal(&ksig, regs);
812 return;
813 }
814
815 /* Did we come from a system call? */
816 if (syscall_get_nr(current, regs) >= 0) {
817 /* Restart the system call - no handlers present */
818 switch (syscall_get_error(current, regs)) {
819 case -ERESTARTNOHAND:
820 case -ERESTARTSYS:
821 case -ERESTARTNOINTR:
822 regs->ax = regs->orig_ax;
823 regs->ip -= 2;
824 break;
825
826 case -ERESTART_RESTARTBLOCK:
827 regs->ax = get_nr_restart_syscall(regs);
828 regs->ip -= 2;
829 break;
830 }
831 }
832
833 /*
834 * If there's no signal to deliver, we just put the saved sigmask
835 * back.
836 */
837 restore_saved_sigmask();
838 }
839
signal_fault(struct pt_regs * regs,void __user * frame,char * where)840 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
841 {
842 struct task_struct *me = current;
843
844 if (show_unhandled_signals && printk_ratelimit()) {
845 printk("%s"
846 "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
847 task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
848 me->comm, me->pid, where, frame,
849 regs->ip, regs->sp, regs->orig_ax);
850 print_vma_addr(KERN_CONT " in ", regs->ip);
851 pr_cont("\n");
852 }
853
854 force_sig(SIGSEGV);
855 }
856
857 #ifdef CONFIG_X86_X32_ABI
sys32_x32_rt_sigreturn(void)858 asmlinkage long sys32_x32_rt_sigreturn(void)
859 {
860 struct pt_regs *regs = current_pt_regs();
861 struct rt_sigframe_x32 __user *frame;
862 sigset_t set;
863 unsigned long uc_flags;
864
865 frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
866
867 if (!access_ok(frame, sizeof(*frame)))
868 goto badframe;
869 if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
870 goto badframe;
871 if (__get_user(uc_flags, &frame->uc.uc_flags))
872 goto badframe;
873
874 set_current_blocked(&set);
875
876 if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
877 goto badframe;
878
879 if (compat_restore_altstack(&frame->uc.uc_stack))
880 goto badframe;
881
882 return regs->ax;
883
884 badframe:
885 signal_fault(regs, frame, "x32 rt_sigreturn");
886 return 0;
887 }
888 #endif
889