xref: /linux/arch/x86/kernel/signal_32.c (revision 621cde16e49b3ecf7d59a8106a20aaebfb4a59a9)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  Copyright (C) 1991, 1992  Linus Torvalds
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  *  2000-12-*   x86-64 compatibility mode signal handling by Andi Kleen
8  */
9 
10 #include <linux/sched.h>
11 #include <linux/sched/task_stack.h>
12 #include <linux/mm.h>
13 #include <linux/smp.h>
14 #include <linux/kernel.h>
15 #include <linux/errno.h>
16 #include <linux/wait.h>
17 #include <linux/unistd.h>
18 #include <linux/stddef.h>
19 #include <linux/personality.h>
20 #include <linux/compat.h>
21 #include <linux/binfmts.h>
22 #include <linux/syscalls.h>
23 #include <asm/ucontext.h>
24 #include <linux/uaccess.h>
25 #include <asm/fpu/signal.h>
26 #include <asm/ptrace.h>
27 #include <asm/user32.h>
28 #include <uapi/asm/sigcontext.h>
29 #include <asm/proto.h>
30 #include <asm/vdso.h>
31 #include <asm/sigframe.h>
32 #include <asm/sighandling.h>
33 #include <asm/smap.h>
34 #include <asm/gsseg.h>
35 
36 #ifdef CONFIG_IA32_EMULATION
37 #include <asm/unistd_32_ia32.h>
38 
reload_segments(struct sigcontext_32 * sc)39 static inline void reload_segments(struct sigcontext_32 *sc)
40 {
41 	unsigned int cur;
42 
43 	savesegment(gs, cur);
44 	if ((sc->gs | 0x03) != cur)
45 		load_gs_index(sc->gs | 0x03);
46 	savesegment(fs, cur);
47 	if ((sc->fs | 0x03) != cur)
48 		loadsegment(fs, sc->fs | 0x03);
49 	savesegment(ds, cur);
50 	if ((sc->ds | 0x03) != cur)
51 		loadsegment(ds, sc->ds | 0x03);
52 	savesegment(es, cur);
53 	if ((sc->es | 0x03) != cur)
54 		loadsegment(es, sc->es | 0x03);
55 }
56 
57 #define sigset32_t			compat_sigset_t
58 #define siginfo32_t			compat_siginfo_t
59 #define restore_altstack32		compat_restore_altstack
60 #define unsafe_save_altstack32		unsafe_compat_save_altstack
61 
62 #else
63 
64 #define sigset32_t			sigset_t
65 #define siginfo32_t			siginfo_t
66 #define __NR_ia32_sigreturn		__NR_sigreturn
67 #define __NR_ia32_rt_sigreturn		__NR_rt_sigreturn
68 #define restore_altstack32		restore_altstack
69 #define unsafe_save_altstack32		unsafe_save_altstack
70 #define __copy_siginfo_to_user32	copy_siginfo_to_user
71 
72 #endif
73 
74 /*
75  * Do a signal return; undo the signal stack.
76  */
ia32_restore_sigcontext(struct pt_regs * regs,struct sigcontext_32 __user * usc)77 static bool ia32_restore_sigcontext(struct pt_regs *regs,
78 				    struct sigcontext_32 __user *usc)
79 {
80 	struct sigcontext_32 sc;
81 
82 	/* Always make any pending restarted system calls return -EINTR */
83 	current->restart_block.fn = do_no_restart_syscall;
84 
85 	if (unlikely(copy_from_user(&sc, usc, sizeof(sc))))
86 		return false;
87 
88 	/* Get only the ia32 registers. */
89 	regs->bx = sc.bx;
90 	regs->cx = sc.cx;
91 	regs->dx = sc.dx;
92 	regs->si = sc.si;
93 	regs->di = sc.di;
94 	regs->bp = sc.bp;
95 	regs->ax = sc.ax;
96 	regs->sp = sc.sp;
97 	regs->ip = sc.ip;
98 
99 	/* Get CS/SS and force CPL3 */
100 	regs->cs = sc.cs | 0x03;
101 	regs->ss = sc.ss | 0x03;
102 
103 	regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
104 	/* disable syscall checks */
105 	regs->orig_ax = -1;
106 
107 #ifdef CONFIG_IA32_EMULATION
108 	/*
109 	 * Reload fs and gs if they have changed in the signal
110 	 * handler.  This does not handle long fs/gs base changes in
111 	 * the handler, but does not clobber them at least in the
112 	 * normal case.
113 	 */
114 	reload_segments(&sc);
115 #else
116 	loadsegment(gs, sc.gs);
117 	regs->fs = sc.fs;
118 	regs->es = sc.es;
119 	regs->ds = sc.ds;
120 #endif
121 
122 	return fpu__restore_sig(compat_ptr(sc.fpstate), 1);
123 }
124 
SYSCALL32_DEFINE0(sigreturn)125 SYSCALL32_DEFINE0(sigreturn)
126 {
127 	struct pt_regs *regs = current_pt_regs();
128 	struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
129 	sigset_t set;
130 
131 	if (!access_ok(frame, sizeof(*frame)))
132 		goto badframe;
133 	if (__get_user(set.sig[0], &frame->sc.oldmask)
134 	    || __get_user(((__u32 *)&set)[1], &frame->extramask[0]))
135 		goto badframe;
136 
137 	set_current_blocked(&set);
138 
139 	if (!ia32_restore_sigcontext(regs, &frame->sc))
140 		goto badframe;
141 	return regs->ax;
142 
143 badframe:
144 	signal_fault(regs, frame, "32bit sigreturn");
145 	return 0;
146 }
147 
SYSCALL32_DEFINE0(rt_sigreturn)148 SYSCALL32_DEFINE0(rt_sigreturn)
149 {
150 	struct pt_regs *regs = current_pt_regs();
151 	struct rt_sigframe_ia32 __user *frame;
152 	sigset_t set;
153 
154 	frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
155 
156 	if (!access_ok(frame, sizeof(*frame)))
157 		goto badframe;
158 	if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
159 		goto badframe;
160 
161 	set_current_blocked(&set);
162 
163 	if (!ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
164 		goto badframe;
165 
166 	if (restore_altstack32(&frame->uc.uc_stack))
167 		goto badframe;
168 
169 	return regs->ax;
170 
171 badframe:
172 	signal_fault(regs, frame, "32bit rt sigreturn");
173 	return 0;
174 }
175 
176 /*
177  * Set up a signal frame.
178  */
179 
180 #define get_user_seg(seg)	({ unsigned int v; savesegment(seg, v); v; })
181 
182 static __always_inline int
__unsafe_setup_sigcontext32(struct sigcontext_32 __user * sc,void __user * fpstate,struct pt_regs * regs,unsigned int mask)183 __unsafe_setup_sigcontext32(struct sigcontext_32 __user *sc,
184 			    void __user *fpstate,
185 			    struct pt_regs *regs, unsigned int mask)
186 {
187 	unsafe_put_user(get_user_seg(gs), (unsigned int __user *)&sc->gs, Efault);
188 #ifdef CONFIG_IA32_EMULATION
189 	unsafe_put_user(get_user_seg(fs), (unsigned int __user *)&sc->fs, Efault);
190 	unsafe_put_user(get_user_seg(ds), (unsigned int __user *)&sc->ds, Efault);
191 	unsafe_put_user(get_user_seg(es), (unsigned int __user *)&sc->es, Efault);
192 #else
193 	unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
194 	unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
195 	unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
196 #endif
197 
198 	unsafe_put_user(regs->di, &sc->di, Efault);
199 	unsafe_put_user(regs->si, &sc->si, Efault);
200 	unsafe_put_user(regs->bp, &sc->bp, Efault);
201 	unsafe_put_user(regs->sp, &sc->sp, Efault);
202 	unsafe_put_user(regs->bx, &sc->bx, Efault);
203 	unsafe_put_user(regs->dx, &sc->dx, Efault);
204 	unsafe_put_user(regs->cx, &sc->cx, Efault);
205 	unsafe_put_user(regs->ax, &sc->ax, Efault);
206 	unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
207 	unsafe_put_user(current->thread.error_code, &sc->err, Efault);
208 	unsafe_put_user(regs->ip, &sc->ip, Efault);
209 	unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
210 	unsafe_put_user(regs->flags, &sc->flags, Efault);
211 	unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
212 	unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
213 
214 	unsafe_put_user(ptr_to_compat(fpstate), &sc->fpstate, Efault);
215 
216 	/* non-iBCS2 extensions.. */
217 	unsafe_put_user(mask, &sc->oldmask, Efault);
218 	unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
219 	return 0;
220 
221 Efault:
222 	return -EFAULT;
223 }
224 
225 #define unsafe_put_sigcontext32(sc, fp, regs, set, label)		\
226 do {									\
227 	if (__unsafe_setup_sigcontext32(sc, fp, regs, set->sig[0]))	\
228 		goto label;						\
229 } while(0)
230 
ia32_setup_frame(struct ksignal * ksig,struct pt_regs * regs)231 int ia32_setup_frame(struct ksignal *ksig, struct pt_regs *regs)
232 {
233 	sigset32_t *set = (sigset32_t *) sigmask_to_save();
234 	struct sigframe_ia32 __user *frame;
235 	void __user *restorer;
236 	void __user *fp = NULL;
237 
238 	/* copy_to_user optimizes that into a single 8 byte store */
239 	static const struct {
240 		u16 poplmovl;
241 		u32 val;
242 		u16 int80;
243 	} __attribute__((packed)) code = {
244 		0xb858,		 /* popl %eax ; movl $...,%eax */
245 		__NR_ia32_sigreturn,
246 		0x80cd,		/* int $0x80 */
247 	};
248 
249 	frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
250 
251 	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
252 		restorer = ksig->ka.sa.sa_restorer;
253 	} else {
254 		/* Return stub is in 32bit vsyscall page */
255 		if (current->mm->context.vdso)
256 			restorer = current->mm->context.vdso +
257 				vdso_image_32.sym___kernel_sigreturn;
258 		else
259 			restorer = &frame->retcode;
260 	}
261 
262 	if (!user_access_begin(frame, sizeof(*frame)))
263 		return -EFAULT;
264 
265 	unsafe_put_user(ksig->sig, &frame->sig, Efault);
266 	unsafe_put_sigcontext32(&frame->sc, fp, regs, set, Efault);
267 	unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
268 	unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
269 	/*
270 	 * These are actually not used anymore, but left because some
271 	 * gdb versions depend on them as a marker.
272 	 */
273 	unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
274 	user_access_end();
275 
276 	/* Set up registers for signal handler */
277 	regs->sp = (unsigned long) frame;
278 	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
279 
280 	/* Make -mregparm=3 work */
281 	regs->ax = ksig->sig;
282 	regs->dx = 0;
283 	regs->cx = 0;
284 
285 #ifdef CONFIG_IA32_EMULATION
286 	loadsegment(ds, __USER_DS);
287 	loadsegment(es, __USER_DS);
288 #else
289 	regs->ds = __USER_DS;
290 	regs->es = __USER_DS;
291 #endif
292 
293 	regs->cs = __USER32_CS;
294 	regs->ss = __USER_DS;
295 
296 	return 0;
297 Efault:
298 	user_access_end();
299 	return -EFAULT;
300 }
301 
ia32_setup_rt_frame(struct ksignal * ksig,struct pt_regs * regs)302 int ia32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
303 {
304 	sigset32_t *set = (sigset32_t *) sigmask_to_save();
305 	struct rt_sigframe_ia32 __user *frame;
306 	void __user *restorer;
307 	void __user *fp = NULL;
308 
309 	/* unsafe_put_user optimizes that into a single 8 byte store */
310 	static const struct {
311 		u8 movl;
312 		u32 val;
313 		u16 int80;
314 		u8  pad;
315 	} __attribute__((packed)) code = {
316 		0xb8,
317 		__NR_ia32_rt_sigreturn,
318 		0x80cd,
319 		0,
320 	};
321 
322 	frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
323 
324 	if (!user_access_begin(frame, sizeof(*frame)))
325 		return -EFAULT;
326 
327 	unsafe_put_user(ksig->sig, &frame->sig, Efault);
328 	unsafe_put_user(ptr_to_compat(&frame->info), &frame->pinfo, Efault);
329 	unsafe_put_user(ptr_to_compat(&frame->uc), &frame->puc, Efault);
330 
331 	/* Create the ucontext.  */
332 	if (static_cpu_has(X86_FEATURE_XSAVE))
333 		unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
334 	else
335 		unsafe_put_user(0, &frame->uc.uc_flags, Efault);
336 	unsafe_put_user(0, &frame->uc.uc_link, Efault);
337 	unsafe_save_altstack32(&frame->uc.uc_stack, regs->sp, Efault);
338 
339 	if (ksig->ka.sa.sa_flags & SA_RESTORER)
340 		restorer = ksig->ka.sa.sa_restorer;
341 	else
342 		restorer = current->mm->context.vdso +
343 			vdso_image_32.sym___kernel_rt_sigreturn;
344 	unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
345 
346 	/*
347 	 * Not actually used anymore, but left because some gdb
348 	 * versions need it.
349 	 */
350 	unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
351 	unsafe_put_sigcontext32(&frame->uc.uc_mcontext, fp, regs, set, Efault);
352 	unsafe_put_user(*(__u64 *)set, (__u64 __user *)&frame->uc.uc_sigmask, Efault);
353 	user_access_end();
354 
355 	if (__copy_siginfo_to_user32(&frame->info, &ksig->info))
356 		return -EFAULT;
357 
358 	/* Set up registers for signal handler */
359 	regs->sp = (unsigned long) frame;
360 	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
361 
362 	/* Make -mregparm=3 work */
363 	regs->ax = ksig->sig;
364 	regs->dx = (unsigned long) &frame->info;
365 	regs->cx = (unsigned long) &frame->uc;
366 
367 #ifdef CONFIG_IA32_EMULATION
368 	loadsegment(ds, __USER_DS);
369 	loadsegment(es, __USER_DS);
370 #else
371 	regs->ds = __USER_DS;
372 	regs->es = __USER_DS;
373 #endif
374 
375 	regs->cs = __USER32_CS;
376 	regs->ss = __USER_DS;
377 
378 	return 0;
379 Efault:
380 	user_access_end();
381 	return -EFAULT;
382 }
383 
384 /*
385  * The siginfo_t structure and handing code is very easy
386  * to break in several ways.  It must always be updated when new
387  * updates are made to the main siginfo_t, and
388  * copy_siginfo_to_user32() must be updated when the
389  * (arch-independent) copy_siginfo_to_user() is updated.
390  *
391  * It is also easy to put a new member in the siginfo_t
392  * which has implicit alignment which can move internal structure
393  * alignment around breaking the ABI.  This can happen if you,
394  * for instance, put a plain 64-bit value in there.
395  */
396 
397 /*
398 * If adding a new si_code, there is probably new data in
399 * the siginfo.  Make sure folks bumping the si_code
400 * limits also have to look at this code.  Make sure any
401 * new fields are handled in copy_siginfo_to_user32()!
402 */
403 static_assert(NSIGILL  == 11);
404 static_assert(NSIGFPE  == 15);
405 static_assert(NSIGSEGV == 10);
406 static_assert(NSIGBUS  == 5);
407 static_assert(NSIGTRAP == 6);
408 static_assert(NSIGCHLD == 6);
409 static_assert(NSIGSYS  == 2);
410 
411 /* This is part of the ABI and can never change in size: */
412 static_assert(sizeof(siginfo32_t) == 128);
413 
414 /* This is a part of the ABI and can never change in alignment */
415 static_assert(__alignof__(siginfo32_t) == 4);
416 
417 /*
418 * The offsets of all the (unioned) si_fields are fixed
419 * in the ABI, of course.  Make sure none of them ever
420 * move and are always at the beginning:
421 */
422 static_assert(offsetof(siginfo32_t, _sifields) == 3 * sizeof(int));
423 
424 static_assert(offsetof(siginfo32_t, si_signo) == 0);
425 static_assert(offsetof(siginfo32_t, si_errno) == 4);
426 static_assert(offsetof(siginfo32_t, si_code)  == 8);
427 
428 /*
429 * Ensure that the size of each si_field never changes.
430 * If it does, it is a sign that the
431 * copy_siginfo_to_user32() code below needs to updated
432 * along with the size in the CHECK_SI_SIZE().
433 *
434 * We repeat this check for both the generic and compat
435 * siginfos.
436 *
437 * Note: it is OK for these to grow as long as the whole
438 * structure stays within the padding size (checked
439 * above).
440 */
441 
442 #define CHECK_SI_OFFSET(name)						\
443 	static_assert(offsetof(siginfo32_t, _sifields) ==		\
444 		      offsetof(siginfo32_t, _sifields.name))
445 
446 #define CHECK_SI_SIZE(name, size)					\
447 	static_assert(sizeof_field(siginfo32_t, _sifields.name) == size)
448 
449 CHECK_SI_OFFSET(_kill);
450 CHECK_SI_SIZE  (_kill, 2*sizeof(int));
451 static_assert(offsetof(siginfo32_t, si_pid) == 0xC);
452 static_assert(offsetof(siginfo32_t, si_uid) == 0x10);
453 
454 CHECK_SI_OFFSET(_timer);
455 #ifdef CONFIG_COMPAT
456 /* compat_siginfo_t doesn't have si_sys_private */
457 CHECK_SI_SIZE  (_timer, 3*sizeof(int));
458 #else
459 CHECK_SI_SIZE  (_timer, 4*sizeof(int));
460 #endif
461 static_assert(offsetof(siginfo32_t, si_tid)     == 0x0C);
462 static_assert(offsetof(siginfo32_t, si_overrun) == 0x10);
463 static_assert(offsetof(siginfo32_t, si_value)   == 0x14);
464 
465 CHECK_SI_OFFSET(_rt);
466 CHECK_SI_SIZE  (_rt, 3*sizeof(int));
467 static_assert(offsetof(siginfo32_t, si_pid)   == 0x0C);
468 static_assert(offsetof(siginfo32_t, si_uid)   == 0x10);
469 static_assert(offsetof(siginfo32_t, si_value) == 0x14);
470 
471 CHECK_SI_OFFSET(_sigchld);
472 CHECK_SI_SIZE  (_sigchld, 5*sizeof(int));
473 static_assert(offsetof(siginfo32_t, si_pid)    == 0x0C);
474 static_assert(offsetof(siginfo32_t, si_uid)    == 0x10);
475 static_assert(offsetof(siginfo32_t, si_status) == 0x14);
476 static_assert(offsetof(siginfo32_t, si_utime)  == 0x18);
477 static_assert(offsetof(siginfo32_t, si_stime)  == 0x1C);
478 
479 CHECK_SI_OFFSET(_sigfault);
480 CHECK_SI_SIZE  (_sigfault, 4*sizeof(int));
481 static_assert(offsetof(siginfo32_t, si_addr) == 0x0C);
482 
483 static_assert(offsetof(siginfo32_t, si_trapno) == 0x10);
484 
485 static_assert(offsetof(siginfo32_t, si_addr_lsb) == 0x10);
486 
487 static_assert(offsetof(siginfo32_t, si_lower) == 0x14);
488 static_assert(offsetof(siginfo32_t, si_upper) == 0x18);
489 
490 static_assert(offsetof(siginfo32_t, si_pkey) == 0x14);
491 
492 static_assert(offsetof(siginfo32_t, si_perf_data) == 0x10);
493 static_assert(offsetof(siginfo32_t, si_perf_type) == 0x14);
494 static_assert(offsetof(siginfo32_t, si_perf_flags) == 0x18);
495 
496 CHECK_SI_OFFSET(_sigpoll);
497 CHECK_SI_SIZE  (_sigpoll, 2*sizeof(int));
498 static_assert(offsetof(siginfo32_t, si_band) == 0x0C);
499 static_assert(offsetof(siginfo32_t, si_fd)   == 0x10);
500 
501 CHECK_SI_OFFSET(_sigsys);
502 CHECK_SI_SIZE  (_sigsys, 3*sizeof(int));
503 static_assert(offsetof(siginfo32_t, si_call_addr) == 0x0C);
504 static_assert(offsetof(siginfo32_t, si_syscall)   == 0x10);
505 static_assert(offsetof(siginfo32_t, si_arch)      == 0x14);
506 
507 /* any new si_fields should be added here */
508