signal_64.c

  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
  7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  8
  9#include <linux/kernel.h>
 10#include <linux/errno.h>
 11#include <linux/unistd.h>
 12#include <linux/uaccess.h>
 13#include <linux/syscalls.h>
 14
 15#include <asm/ucontext.h>
 16#include <asm/fpu/signal.h>
 17#include <asm/sighandling.h>
 18
 19#include <asm/syscall.h>
 20#include <asm/sigframe.h>
 21#include <asm/signal.h>
 22
 23/*
 24 * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
 25 * alone.  Using this generally makes no sense unless
 26 * user_64bit_mode(regs) would return true.
 27 */
 28static void force_valid_ss(struct pt_regs *regs)
 29{
 30	u32 ar;
 31	asm volatile ("lar %[old_ss], %[ar]\n\t"
 32		      "jz 1f\n\t"		/* If invalid: */
 33		      "xorl %[ar], %[ar]\n\t"	/* set ar = 0 */
 34		      "1:"
 35		      : [ar] "=r" (ar)
 36		      : [old_ss] "rm" ((u16)regs->ss));
 37
 38	/*
 39	 * For a valid 64-bit user context, we need DPL 3, type
 40	 * read-write data or read-write exp-down data, and S and P
 41	 * set.  We can't use VERW because VERW doesn't check the
 42	 * P bit.
 43	 */
 44	ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
 45	if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
 46	    ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
 47		regs->ss = __USER_DS;
 48}
 49
 50static bool restore_sigcontext(struct pt_regs *regs,
 51			       struct sigcontext __user *usc,
 52			       unsigned long uc_flags)
 53{
 54	struct sigcontext sc;
 55
 56	/* Always make any pending restarted system calls return -EINTR */
 57	current->restart_block.fn = do_no_restart_syscall;
 58
 59	if (copy_from_user(&sc, usc, offsetof(struct sigcontext, reserved1)))
 60		return false;
 61
 62	regs->bx = sc.bx;
 63	regs->cx = sc.cx;
 64	regs->dx = sc.dx;
 65	regs->si = sc.si;
 66	regs->di = sc.di;
 67	regs->bp = sc.bp;
 68	regs->ax = sc.ax;
 69	regs->sp = sc.sp;
 70	regs->ip = sc.ip;
 71	regs->r8 = sc.r8;
 72	regs->r9 = sc.r9;
 73	regs->r10 = sc.r10;
 74	regs->r11 = sc.r11;
 75	regs->r12 = sc.r12;
 76	regs->r13 = sc.r13;
 77	regs->r14 = sc.r14;
 78	regs->r15 = sc.r15;
 79
 80	/* Get CS/SS and force CPL3 */
 81	regs->cs = sc.cs | 0x03;
 82	regs->ss = sc.ss | 0x03;
 83
 84	regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
 85	/* disable syscall checks */
 86	regs->orig_ax = -1;
 87
 88	/*
 89	 * Fix up SS if needed for the benefit of old DOSEMU and
 90	 * CRIU.
 91	 */
 92	if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
 93		force_valid_ss(regs);
 94
 95	return fpu__restore_sig((void __user *)sc.fpstate, 0);
 96}
 97
 98static __always_inline int
 99__unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
100		     struct pt_regs *regs, unsigned long mask)
101{
102	unsafe_put_user(regs->di, &sc->di, Efault);
103	unsafe_put_user(regs->si, &sc->si, Efault);
104	unsafe_put_user(regs->bp, &sc->bp, Efault);
105	unsafe_put_user(regs->sp, &sc->sp, Efault);
106	unsafe_put_user(regs->bx, &sc->bx, Efault);
107	unsafe_put_user(regs->dx, &sc->dx, Efault);
108	unsafe_put_user(regs->cx, &sc->cx, Efault);
109	unsafe_put_user(regs->ax, &sc->ax, Efault);
110	unsafe_put_user(regs->r8, &sc->r8, Efault);
111	unsafe_put_user(regs->r9, &sc->r9, Efault);
112	unsafe_put_user(regs->r10, &sc->r10, Efault);
113	unsafe_put_user(regs->r11, &sc->r11, Efault);
114	unsafe_put_user(regs->r12, &sc->r12, Efault);
115	unsafe_put_user(regs->r13, &sc->r13, Efault);
116	unsafe_put_user(regs->r14, &sc->r14, Efault);
117	unsafe_put_user(regs->r15, &sc->r15, Efault);
118
119	unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
120	unsafe_put_user(current->thread.error_code, &sc->err, Efault);
121	unsafe_put_user(regs->ip, &sc->ip, Efault);
122	unsafe_put_user(regs->flags, &sc->flags, Efault);
123	unsafe_put_user(regs->cs, &sc->cs, Efault);
124	unsafe_put_user(0, &sc->gs, Efault);
125	unsafe_put_user(0, &sc->fs, Efault);
126	unsafe_put_user(regs->ss, &sc->ss, Efault);
127
128	unsafe_put_user(fpstate, (unsigned long __user *)&sc->fpstate, Efault);
129
130	/* non-iBCS2 extensions.. */
131	unsafe_put_user(mask, &sc->oldmask, Efault);
132	unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
133	return 0;
134Efault:
135	return -EFAULT;
136}
137
138#define unsafe_put_sigcontext(sc, fp, regs, set, label)			\
139do {									\
140	if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0]))	\
141		goto label;						\
142} while(0);
143
144#define unsafe_put_sigmask(set, frame, label) \
145	unsafe_put_user(*(__u64 *)(set), \
146			(__u64 __user *)&(frame)->uc.uc_sigmask, \
147			label)
148
149static unsigned long frame_uc_flags(struct pt_regs *regs)
150{
151	unsigned long flags;
152
153	if (boot_cpu_has(X86_FEATURE_XSAVE))
154		flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
155	else
156		flags = UC_SIGCONTEXT_SS;
157
158	if (likely(user_64bit_mode(regs)))
159		flags |= UC_STRICT_RESTORE_SS;
160
161	return flags;
162}
163
164int x64_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
165{
166	sigset_t *set = sigmask_to_save();
167	struct rt_sigframe __user *frame;
168	void __user *fp = NULL;
169	unsigned long uc_flags;
170
171	/* x86-64 should always use SA_RESTORER. */
172	if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
173		return -EFAULT;
174
175	frame = get_sigframe(ksig, regs, sizeof(struct rt_sigframe), &fp);
176	uc_flags = frame_uc_flags(regs);
177
178	if (!user_access_begin(frame, sizeof(*frame)))
179		return -EFAULT;
180
181	/* Create the ucontext.  */
182	unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
183	unsafe_put_user(0, &frame->uc.uc_link, Efault);
184	unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
185
186	/* Set up to return from userspace.  If provided, use a stub
187	   already in userspace.  */
188	unsafe_put_user(ksig->ka.sa.sa_restorer, &frame->pretcode, Efault);
189	unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
190	unsafe_put_sigmask(set, frame, Efault);
191	user_access_end();
192
193	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
194		if (copy_siginfo_to_user(&frame->info, &ksig->info))
195			return -EFAULT;
196	}
197
198	if (setup_signal_shadow_stack(ksig))
199		return -EFAULT;
200
201	/* Set up registers for signal handler */
202	regs->di = ksig->sig;
203	/* In case the signal handler was declared without prototypes */
204	regs->ax = 0;
205
206	/* This also works for non SA_SIGINFO handlers because they expect the
207	   next argument after the signal number on the stack. */
208	regs->si = (unsigned long)&frame->info;
209	regs->dx = (unsigned long)&frame->uc;
210	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
211
212	regs->sp = (unsigned long)frame;
213
214	/*
215	 * Set up the CS and SS registers to run signal handlers in
216	 * 64-bit mode, even if the handler happens to be interrupting
217	 * 32-bit or 16-bit code.
218	 *
219	 * SS is subtle.  In 64-bit mode, we don't need any particular
220	 * SS descriptor, but we do need SS to be valid.  It's possible
221	 * that the old SS is entirely bogus -- this can happen if the
222	 * signal we're trying to deliver is #GP or #SS caused by a bad
223	 * SS value.  We also have a compatibility issue here: DOSEMU
224	 * relies on the contents of the SS register indicating the
225	 * SS value at the time of the signal, even though that code in
226	 * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
227	 * avoids relying on sigreturn to restore SS; instead it uses
228	 * a trampoline.)  So we do our best: if the old SS was valid,
229	 * we keep it.  Otherwise we replace it.
230	 */
231	regs->cs = __USER_CS;
232
233	if (unlikely(regs->ss != __USER_DS))
234		force_valid_ss(regs);
235
236	return 0;
237
238Efault:
239	user_access_end();
240	return -EFAULT;
241}
242
243/*
244 * Do a signal return; undo the signal stack.
245 */
246SYSCALL_DEFINE0(rt_sigreturn)
247{
248	struct pt_regs *regs = current_pt_regs();
249	struct rt_sigframe __user *frame;
250	sigset_t set;
251	unsigned long uc_flags;
252
253	prevent_single_step_upon_eretu(regs);
254
255	frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
256	if (!access_ok(frame, sizeof(*frame)))
257		goto badframe;
258	if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
259		goto badframe;
260	if (__get_user(uc_flags, &frame->uc.uc_flags))
261		goto badframe;
262
263	set_current_blocked(&set);
264
265	if (restore_altstack(&frame->uc.uc_stack))
266		goto badframe;
267
268	if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
269		goto badframe;
270
271	if (restore_signal_shadow_stack())
272		goto badframe;
273
274	return regs->ax;
275
276badframe:
277	signal_fault(regs, frame, "rt_sigreturn");
278	return 0;
279}
280
281#ifdef CONFIG_X86_X32_ABI
282static int x32_copy_siginfo_to_user(struct compat_siginfo __user *to,
283		const struct kernel_siginfo *from)
284{
285	struct compat_siginfo new;
286
287	copy_siginfo_to_external32(&new, from);
288	if (from->si_signo == SIGCHLD) {
289		new._sifields._sigchld_x32._utime = from->si_utime;
290		new._sifields._sigchld_x32._stime = from->si_stime;
291	}
292	if (copy_to_user(to, &new, sizeof(struct compat_siginfo)))
293		return -EFAULT;
294	return 0;
295}
296
297int copy_siginfo_to_user32(struct compat_siginfo __user *to,
298			   const struct kernel_siginfo *from)
299{
300	if (in_x32_syscall())
301		return x32_copy_siginfo_to_user(to, from);
302	return __copy_siginfo_to_user32(to, from);
303}
304
305int x32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
306{
307	compat_sigset_t *set = (compat_sigset_t *) sigmask_to_save();
308	struct rt_sigframe_x32 __user *frame;
309	unsigned long uc_flags;
310	void __user *restorer;
311	void __user *fp = NULL;
312
313	if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
314		return -EFAULT;
315
316	frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
317
318	uc_flags = frame_uc_flags(regs);
319
320	if (setup_signal_shadow_stack(ksig))
321		return -EFAULT;
322
323	if (!user_access_begin(frame, sizeof(*frame)))
324		return -EFAULT;
325
326	/* Create the ucontext.  */
327	unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
328	unsafe_put_user(0, &frame->uc.uc_link, Efault);
329	unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
330	unsafe_put_user(0, &frame->uc.uc__pad0, Efault);
331	restorer = ksig->ka.sa.sa_restorer;
332	unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault);
333	unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
334	unsafe_put_sigmask(set, frame, Efault);
335	user_access_end();
336
337	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
338		if (x32_copy_siginfo_to_user(&frame->info, &ksig->info))
339			return -EFAULT;
340	}
341
342	/* Set up registers for signal handler */
343	regs->sp = (unsigned long) frame;
344	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
345
346	/* We use the x32 calling convention here... */
347	regs->di = ksig->sig;
348	regs->si = (unsigned long) &frame->info;
349	regs->dx = (unsigned long) &frame->uc;
350
351	loadsegment(ds, __USER_DS);
352	loadsegment(es, __USER_DS);
353
354	regs->cs = __USER_CS;
355	regs->ss = __USER_DS;
356
357	return 0;
358
359Efault:
360	user_access_end();
361	return -EFAULT;
362}
363
364COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
365{
366	struct pt_regs *regs = current_pt_regs();
367	struct rt_sigframe_x32 __user *frame;
368	sigset_t set;
369	unsigned long uc_flags;
370
371	prevent_single_step_upon_eretu(regs);
372
373	frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
374
375	if (!access_ok(frame, sizeof(*frame)))
376		goto badframe;
377	if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
378		goto badframe;
379	if (__get_user(uc_flags, &frame->uc.uc_flags))
380		goto badframe;
381
382	set_current_blocked(&set);
383
384	if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
385		goto badframe;
386
387	if (restore_signal_shadow_stack())
388		goto badframe;
389
390	if (compat_restore_altstack(&frame->uc.uc_stack))
391		goto badframe;
392
393	return regs->ax;
394
395badframe:
396	signal_fault(regs, frame, "x32 rt_sigreturn");
397	return 0;
398}
399#endif /* CONFIG_X86_X32_ABI */
400
401#ifdef CONFIG_COMPAT
402void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
403{
404	if (!act)
405		return;
406
407	if (in_ia32_syscall())
408		act->sa.sa_flags |= SA_IA32_ABI;
409	if (in_x32_syscall())
410		act->sa.sa_flags |= SA_X32_ABI;
411}
412#endif /* CONFIG_COMPAT */
413
414/*
415* If adding a new si_code, there is probably new data in
416* the siginfo.  Make sure folks bumping the si_code
417* limits also have to look at this code.  Make sure any
418* new fields are handled in copy_siginfo_to_user32()!
419*/
420static_assert(NSIGILL  == 11);
421static_assert(NSIGFPE  == 15);
422static_assert(NSIGSEGV == 10);
423static_assert(NSIGBUS  == 5);
424static_assert(NSIGTRAP == 6);
425static_assert(NSIGCHLD == 6);
426static_assert(NSIGSYS  == 2);
427
428/* This is part of the ABI and can never change in size: */
429static_assert(sizeof(siginfo_t) == 128);
430
431/* This is a part of the ABI and can never change in alignment */
432static_assert(__alignof__(siginfo_t) == 8);
433
434/*
435* The offsets of all the (unioned) si_fields are fixed
436* in the ABI, of course.  Make sure none of them ever
437* move and are always at the beginning:
438*/
439static_assert(offsetof(siginfo_t, si_signo) == 0);
440static_assert(offsetof(siginfo_t, si_errno) == 4);
441static_assert(offsetof(siginfo_t, si_code)  == 8);
442
443/*
444* Ensure that the size of each si_field never changes.
445* If it does, it is a sign that the
446* copy_siginfo_to_user32() code below needs to updated
447* along with the size in the CHECK_SI_SIZE().
448*
449* We repeat this check for both the generic and compat
450* siginfos.
451*
452* Note: it is OK for these to grow as long as the whole
453* structure stays within the padding size (checked
454* above).
455*/
456
457#define CHECK_SI_OFFSET(name)						\
458	static_assert(offsetof(siginfo_t, _sifields) == 		\
459		      offsetof(siginfo_t, _sifields.name))
460#define CHECK_SI_SIZE(name, size)					\
461	static_assert(sizeof_field(siginfo_t, _sifields.name) == size)
462
463CHECK_SI_OFFSET(_kill);
464CHECK_SI_SIZE  (_kill, 2*sizeof(int));
465static_assert(offsetof(siginfo_t, si_pid) == 0x10);
466static_assert(offsetof(siginfo_t, si_uid) == 0x14);
467
468CHECK_SI_OFFSET(_timer);
469CHECK_SI_SIZE  (_timer, 6*sizeof(int));
470static_assert(offsetof(siginfo_t, si_tid)     == 0x10);
471static_assert(offsetof(siginfo_t, si_overrun) == 0x14);
472static_assert(offsetof(siginfo_t, si_value)   == 0x18);
473
474CHECK_SI_OFFSET(_rt);
475CHECK_SI_SIZE  (_rt, 4*sizeof(int));
476static_assert(offsetof(siginfo_t, si_pid)   == 0x10);
477static_assert(offsetof(siginfo_t, si_uid)   == 0x14);
478static_assert(offsetof(siginfo_t, si_value) == 0x18);
479
480CHECK_SI_OFFSET(_sigchld);
481CHECK_SI_SIZE  (_sigchld, 8*sizeof(int));
482static_assert(offsetof(siginfo_t, si_pid)    == 0x10);
483static_assert(offsetof(siginfo_t, si_uid)    == 0x14);
484static_assert(offsetof(siginfo_t, si_status) == 0x18);
485static_assert(offsetof(siginfo_t, si_utime)  == 0x20);
486static_assert(offsetof(siginfo_t, si_stime)  == 0x28);
487
488#ifdef CONFIG_X86_X32_ABI
489/* no _sigchld_x32 in the generic siginfo_t */
490static_assert(sizeof_field(compat_siginfo_t, _sifields._sigchld_x32) ==
491	      7*sizeof(int));
492static_assert(offsetof(compat_siginfo_t, _sifields) ==
493	      offsetof(compat_siginfo_t, _sifields._sigchld_x32));
494static_assert(offsetof(compat_siginfo_t, _sifields._sigchld_x32._utime)  == 0x18);
495static_assert(offsetof(compat_siginfo_t, _sifields._sigchld_x32._stime)  == 0x20);
496#endif
497
498CHECK_SI_OFFSET(_sigfault);
499CHECK_SI_SIZE  (_sigfault, 8*sizeof(int));
500static_assert(offsetof(siginfo_t, si_addr)	== 0x10);
501
502static_assert(offsetof(siginfo_t, si_trapno)	== 0x18);
503
504static_assert(offsetof(siginfo_t, si_addr_lsb)	== 0x18);
505
506static_assert(offsetof(siginfo_t, si_lower)	== 0x20);
507static_assert(offsetof(siginfo_t, si_upper)	== 0x28);
508
509static_assert(offsetof(siginfo_t, si_pkey)	== 0x20);
510
511static_assert(offsetof(siginfo_t, si_perf_data)	 == 0x18);
512static_assert(offsetof(siginfo_t, si_perf_type)	 == 0x20);
513static_assert(offsetof(siginfo_t, si_perf_flags) == 0x24);
514
515CHECK_SI_OFFSET(_sigpoll);
516CHECK_SI_SIZE  (_sigpoll, 4*sizeof(int));
517static_assert(offsetof(siginfo_t, si_band) == 0x10);
518static_assert(offsetof(siginfo_t, si_fd)   == 0x18);
519
520CHECK_SI_OFFSET(_sigsys);
521CHECK_SI_SIZE  (_sigsys, 4*sizeof(int));
522static_assert(offsetof(siginfo_t, si_call_addr) == 0x10);
523static_assert(offsetof(siginfo_t, si_syscall)   == 0x18);
524static_assert(offsetof(siginfo_t, si_arch)      == 0x1C);
525
526/* any new si_fields should be added here */