signal_32.c

  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/*
 37 * The first GDT descriptor is reserved as 'NULL descriptor'.  As bits 0
 38 * and 1 of a segment selector, i.e., the RPL bits, are NOT used to index
 39 * GDT, selector values 0~3 all point to the NULL descriptor, thus values
 40 * 0, 1, 2 and 3 are all valid NULL selector values.
 41 *
 42 * However IRET zeros ES, FS, GS, and DS segment registers if any of them
 43 * is found to have any nonzero NULL selector value, which can be used by
 44 * userspace in pre-FRED systems to spot any interrupt/exception by loading
 45 * a nonzero NULL selector and waiting for it to become zero.  Before FRED
 46 * there was nothing software could do to prevent such an information leak.
 47 *
 48 * ERETU, the only legit instruction to return to userspace from kernel
 49 * under FRED, by design does NOT zero any segment register to avoid this
 50 * problem behavior.
 51 *
 52 * As such, leave NULL selector values 0~3 unchanged.
 53 */
 54static inline u16 fixup_rpl(u16 sel)
 55{
 56	return sel <= 3 ? sel : sel | 3;
 57}
 58
 59#ifdef CONFIG_IA32_EMULATION
 60#include <asm/unistd_32_ia32.h>
 61
 62static inline void reload_segments(struct sigcontext_32 *sc)
 63{
 64	u16 cur;
 65
 66	/*
 67	 * Reload fs and gs if they have changed in the signal
 68	 * handler.  This does not handle long fs/gs base changes in
 69	 * the handler, but does not clobber them at least in the
 70	 * normal case.
 71	 */
 72	savesegment(gs, cur);
 73	if (fixup_rpl(sc->gs) != cur)
 74		load_gs_index(fixup_rpl(sc->gs));
 75	savesegment(fs, cur);
 76	if (fixup_rpl(sc->fs) != cur)
 77		loadsegment(fs, fixup_rpl(sc->fs));
 78
 79	savesegment(ds, cur);
 80	if (fixup_rpl(sc->ds) != cur)
 81		loadsegment(ds, fixup_rpl(sc->ds));
 82	savesegment(es, cur);
 83	if (fixup_rpl(sc->es) != cur)
 84		loadsegment(es, fixup_rpl(sc->es));
 85}
 86
 87#define sigset32_t			compat_sigset_t
 88#define siginfo32_t			compat_siginfo_t
 89#define restore_altstack32		compat_restore_altstack
 90#define unsafe_save_altstack32		unsafe_compat_save_altstack
 91
 92#else
 93
 94#define sigset32_t			sigset_t
 95#define siginfo32_t			siginfo_t
 96#define __NR_ia32_sigreturn		__NR_sigreturn
 97#define __NR_ia32_rt_sigreturn		__NR_rt_sigreturn
 98#define restore_altstack32		restore_altstack
 99#define unsafe_save_altstack32		unsafe_save_altstack
100#define __copy_siginfo_to_user32	copy_siginfo_to_user
101
102#endif
103
104/*
105 * Do a signal return; undo the signal stack.
106 */
107static bool ia32_restore_sigcontext(struct pt_regs *regs,
108				    struct sigcontext_32 __user *usc)
109{
110	struct sigcontext_32 sc;
111
112	/* Always make any pending restarted system calls return -EINTR */
113	current->restart_block.fn = do_no_restart_syscall;
114
115	if (unlikely(copy_from_user(&sc, usc, sizeof(sc))))
116		return false;
117
118	/* Get only the ia32 registers. */
119	regs->bx = sc.bx;
120	regs->cx = sc.cx;
121	regs->dx = sc.dx;
122	regs->si = sc.si;
123	regs->di = sc.di;
124	regs->bp = sc.bp;
125	regs->ax = sc.ax;
126	regs->sp = sc.sp;
127	regs->ip = sc.ip;
128
129	/* Get CS/SS and force CPL3 */
130	regs->cs = sc.cs | 0x03;
131	regs->ss = sc.ss | 0x03;
132
133	regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
134	/* disable syscall checks */
135	regs->orig_ax = -1;
136
137#ifdef CONFIG_IA32_EMULATION
138	reload_segments(&sc);
139#else
140	loadsegment(gs, fixup_rpl(sc.gs));
141	regs->fs = fixup_rpl(sc.fs);
142	regs->es = fixup_rpl(sc.es);
143	regs->ds = fixup_rpl(sc.ds);
144#endif
145
146	return fpu__restore_sig(compat_ptr(sc.fpstate), 1);
147}
148
149SYSCALL32_DEFINE0(sigreturn)
150{
151	struct pt_regs *regs = current_pt_regs();
152	struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
153	sigset_t set;
154
155	prevent_single_step_upon_eretu(regs);
156
157	if (!access_ok(frame, sizeof(*frame)))
158		goto badframe;
159	if (__get_user(set.sig[0], &frame->sc.oldmask)
160	    || __get_user(((__u32 *)&set)[1], &frame->extramask[0]))
161		goto badframe;
162
163	set_current_blocked(&set);
164
165	if (!ia32_restore_sigcontext(regs, &frame->sc))
166		goto badframe;
167	return regs->ax;
168
169badframe:
170	signal_fault(regs, frame, "32bit sigreturn");
171	return 0;
172}
173
174SYSCALL32_DEFINE0(rt_sigreturn)
175{
176	struct pt_regs *regs = current_pt_regs();
177	struct rt_sigframe_ia32 __user *frame;
178	sigset_t set;
179
180	prevent_single_step_upon_eretu(regs);
181
182	frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
183
184	if (!access_ok(frame, sizeof(*frame)))
185		goto badframe;
186	if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
187		goto badframe;
188
189	set_current_blocked(&set);
190
191	if (!ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
192		goto badframe;
193
194	if (restore_altstack32(&frame->uc.uc_stack))
195		goto badframe;
196
197	return regs->ax;
198
199badframe:
200	signal_fault(regs, frame, "32bit rt sigreturn");
201	return 0;
202}
203
204/*
205 * Set up a signal frame.
206 */
207
208#define get_user_seg(seg)	({ unsigned int v; savesegment(seg, v); v; })
209
210static __always_inline int
211__unsafe_setup_sigcontext32(struct sigcontext_32 __user *sc,
212			    void __user *fpstate,
213			    struct pt_regs *regs, unsigned int mask)
214{
215	unsafe_put_user(get_user_seg(gs), (unsigned int __user *)&sc->gs, Efault);
216#ifdef CONFIG_IA32_EMULATION
217	unsafe_put_user(get_user_seg(fs), (unsigned int __user *)&sc->fs, Efault);
218	unsafe_put_user(get_user_seg(ds), (unsigned int __user *)&sc->ds, Efault);
219	unsafe_put_user(get_user_seg(es), (unsigned int __user *)&sc->es, Efault);
220#else
221	unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
222	unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
223	unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
224#endif
225
226	unsafe_put_user(regs->di, &sc->di, Efault);
227	unsafe_put_user(regs->si, &sc->si, Efault);
228	unsafe_put_user(regs->bp, &sc->bp, Efault);
229	unsafe_put_user(regs->sp, &sc->sp, Efault);
230	unsafe_put_user(regs->bx, &sc->bx, Efault);
231	unsafe_put_user(regs->dx, &sc->dx, Efault);
232	unsafe_put_user(regs->cx, &sc->cx, Efault);
233	unsafe_put_user(regs->ax, &sc->ax, Efault);
234	unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
235	unsafe_put_user(current->thread.error_code, &sc->err, Efault);
236	unsafe_put_user(regs->ip, &sc->ip, Efault);
237	unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
238	unsafe_put_user(regs->flags, &sc->flags, Efault);
239	unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
240	unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
241
242	unsafe_put_user(ptr_to_compat(fpstate), &sc->fpstate, Efault);
243
244	/* non-iBCS2 extensions.. */
245	unsafe_put_user(mask, &sc->oldmask, Efault);
246	unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
247	return 0;
248
249Efault:
250	return -EFAULT;
251}
252
253#define unsafe_put_sigcontext32(sc, fp, regs, set, label)		\
254do {									\
255	if (__unsafe_setup_sigcontext32(sc, fp, regs, set->sig[0]))	\
256		goto label;						\
257} while(0)
258
259int ia32_setup_frame(struct ksignal *ksig, struct pt_regs *regs)
260{
261	sigset32_t *set = (sigset32_t *) sigmask_to_save();
262	struct sigframe_ia32 __user *frame;
263	void __user *restorer;
264	void __user *fp = NULL;
265
266	/* copy_to_user optimizes that into a single 8 byte store */
267	static const struct {
268		u16 poplmovl;
269		u32 val;
270		u16 int80;
271	} __attribute__((packed)) code = {
272		0xb858,		 /* popl %eax ; movl $...,%eax */
273		__NR_ia32_sigreturn,
274		0x80cd,		/* int $0x80 */
275	};
276
277	frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
278
279	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
280		restorer = ksig->ka.sa.sa_restorer;
281	} else {
282		/* Return stub is in 32bit vsyscall page */
283		if (current->mm->context.vdso)
284			restorer = current->mm->context.vdso +
285				vdso_image_32.sym___kernel_sigreturn;
286		else
287			restorer = &frame->retcode;
288	}
289
290	if (!user_access_begin(frame, sizeof(*frame)))
291		return -EFAULT;
292
293	unsafe_put_user(ksig->sig, &frame->sig, Efault);
294	unsafe_put_sigcontext32(&frame->sc, fp, regs, set, Efault);
295	unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
296	unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
297	/*
298	 * These are actually not used anymore, but left because some
299	 * gdb versions depend on them as a marker.
300	 */
301	unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
302	user_access_end();
303
304	/* Set up registers for signal handler */
305	regs->sp = (unsigned long) frame;
306	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
307
308	/* Make -mregparm=3 work */
309	regs->ax = ksig->sig;
310	regs->dx = 0;
311	regs->cx = 0;
312
313#ifdef CONFIG_IA32_EMULATION
314	loadsegment(ds, __USER_DS);
315	loadsegment(es, __USER_DS);
316#else
317	regs->ds = __USER_DS;
318	regs->es = __USER_DS;
319#endif
320
321	regs->cs = __USER32_CS;
322	regs->ss = __USER_DS;
323
324	return 0;
325Efault:
326	user_access_end();
327	return -EFAULT;
328}
329
330int ia32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
331{
332	sigset32_t *set = (sigset32_t *) sigmask_to_save();
333	struct rt_sigframe_ia32 __user *frame;
334	void __user *restorer;
335	void __user *fp = NULL;
336
337	/* unsafe_put_user optimizes that into a single 8 byte store */
338	static const struct {
339		u8 movl;
340		u32 val;
341		u16 int80;
342		u8  pad;
343	} __attribute__((packed)) code = {
344		0xb8,
345		__NR_ia32_rt_sigreturn,
346		0x80cd,
347		0,
348	};
349
350	frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
351
352	if (!user_access_begin(frame, sizeof(*frame)))
353		return -EFAULT;
354
355	unsafe_put_user(ksig->sig, &frame->sig, Efault);
356	unsafe_put_user(ptr_to_compat(&frame->info), &frame->pinfo, Efault);
357	unsafe_put_user(ptr_to_compat(&frame->uc), &frame->puc, Efault);
358
359	/* Create the ucontext.  */
360	if (static_cpu_has(X86_FEATURE_XSAVE))
361		unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
362	else
363		unsafe_put_user(0, &frame->uc.uc_flags, Efault);
364	unsafe_put_user(0, &frame->uc.uc_link, Efault);
365	unsafe_save_altstack32(&frame->uc.uc_stack, regs->sp, Efault);
366
367	if (ksig->ka.sa.sa_flags & SA_RESTORER)
368		restorer = ksig->ka.sa.sa_restorer;
369	else
370		restorer = current->mm->context.vdso +
371			vdso_image_32.sym___kernel_rt_sigreturn;
372	unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
373
374	/*
375	 * Not actually used anymore, but left because some gdb
376	 * versions need it.
377	 */
378	unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
379	unsafe_put_sigcontext32(&frame->uc.uc_mcontext, fp, regs, set, Efault);
380	unsafe_put_user(*(__u64 *)set, (__u64 __user *)&frame->uc.uc_sigmask, Efault);
381	user_access_end();
382
383	if (__copy_siginfo_to_user32(&frame->info, &ksig->info))
384		return -EFAULT;
385
386	/* Set up registers for signal handler */
387	regs->sp = (unsigned long) frame;
388	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
389
390	/* Make -mregparm=3 work */
391	regs->ax = ksig->sig;
392	regs->dx = (unsigned long) &frame->info;
393	regs->cx = (unsigned long) &frame->uc;
394
395#ifdef CONFIG_IA32_EMULATION
396	loadsegment(ds, __USER_DS);
397	loadsegment(es, __USER_DS);
398#else
399	regs->ds = __USER_DS;
400	regs->es = __USER_DS;
401#endif
402
403	regs->cs = __USER32_CS;
404	regs->ss = __USER_DS;
405
406	return 0;
407Efault:
408	user_access_end();
409	return -EFAULT;
410}
411
412/*
413 * The siginfo_t structure and handing code is very easy
414 * to break in several ways.  It must always be updated when new
415 * updates are made to the main siginfo_t, and
416 * copy_siginfo_to_user32() must be updated when the
417 * (arch-independent) copy_siginfo_to_user() is updated.
418 *
419 * It is also easy to put a new member in the siginfo_t
420 * which has implicit alignment which can move internal structure
421 * alignment around breaking the ABI.  This can happen if you,
422 * for instance, put a plain 64-bit value in there.
423 */
424
425/*
426* If adding a new si_code, there is probably new data in
427* the siginfo.  Make sure folks bumping the si_code
428* limits also have to look at this code.  Make sure any
429* new fields are handled in copy_siginfo_to_user32()!
430*/
431static_assert(NSIGILL  == 11);
432static_assert(NSIGFPE  == 15);
433static_assert(NSIGSEGV == 10);
434static_assert(NSIGBUS  == 5);
435static_assert(NSIGTRAP == 6);
436static_assert(NSIGCHLD == 6);
437static_assert(NSIGSYS  == 2);
438
439/* This is part of the ABI and can never change in size: */
440static_assert(sizeof(siginfo32_t) == 128);
441
442/* This is a part of the ABI and can never change in alignment */
443static_assert(__alignof__(siginfo32_t) == 4);
444
445/*
446* The offsets of all the (unioned) si_fields are fixed
447* in the ABI, of course.  Make sure none of them ever
448* move and are always at the beginning:
449*/
450static_assert(offsetof(siginfo32_t, _sifields) == 3 * sizeof(int));
451
452static_assert(offsetof(siginfo32_t, si_signo) == 0);
453static_assert(offsetof(siginfo32_t, si_errno) == 4);
454static_assert(offsetof(siginfo32_t, si_code)  == 8);
455
456/*
457* Ensure that the size of each si_field never changes.
458* If it does, it is a sign that the
459* copy_siginfo_to_user32() code below needs to updated
460* along with the size in the CHECK_SI_SIZE().
461*
462* We repeat this check for both the generic and compat
463* siginfos.
464*
465* Note: it is OK for these to grow as long as the whole
466* structure stays within the padding size (checked
467* above).
468*/
469
470#define CHECK_SI_OFFSET(name)						\
471	static_assert(offsetof(siginfo32_t, _sifields) ==		\
472		      offsetof(siginfo32_t, _sifields.name))
473
474#define CHECK_SI_SIZE(name, size)					\
475	static_assert(sizeof_field(siginfo32_t, _sifields.name) == size)
476
477CHECK_SI_OFFSET(_kill);
478CHECK_SI_SIZE  (_kill, 2*sizeof(int));
479static_assert(offsetof(siginfo32_t, si_pid) == 0xC);
480static_assert(offsetof(siginfo32_t, si_uid) == 0x10);
481
482CHECK_SI_OFFSET(_timer);
483#ifdef CONFIG_COMPAT
484/* compat_siginfo_t doesn't have si_sys_private */
485CHECK_SI_SIZE  (_timer, 3*sizeof(int));
486#else
487CHECK_SI_SIZE  (_timer, 4*sizeof(int));
488#endif
489static_assert(offsetof(siginfo32_t, si_tid)     == 0x0C);
490static_assert(offsetof(siginfo32_t, si_overrun) == 0x10);
491static_assert(offsetof(siginfo32_t, si_value)   == 0x14);
492
493CHECK_SI_OFFSET(_rt);
494CHECK_SI_SIZE  (_rt, 3*sizeof(int));
495static_assert(offsetof(siginfo32_t, si_pid)   == 0x0C);
496static_assert(offsetof(siginfo32_t, si_uid)   == 0x10);
497static_assert(offsetof(siginfo32_t, si_value) == 0x14);
498
499CHECK_SI_OFFSET(_sigchld);
500CHECK_SI_SIZE  (_sigchld, 5*sizeof(int));
501static_assert(offsetof(siginfo32_t, si_pid)    == 0x0C);
502static_assert(offsetof(siginfo32_t, si_uid)    == 0x10);
503static_assert(offsetof(siginfo32_t, si_status) == 0x14);
504static_assert(offsetof(siginfo32_t, si_utime)  == 0x18);
505static_assert(offsetof(siginfo32_t, si_stime)  == 0x1C);
506
507CHECK_SI_OFFSET(_sigfault);
508CHECK_SI_SIZE  (_sigfault, 4*sizeof(int));
509static_assert(offsetof(siginfo32_t, si_addr) == 0x0C);
510
511static_assert(offsetof(siginfo32_t, si_trapno) == 0x10);
512
513static_assert(offsetof(siginfo32_t, si_addr_lsb) == 0x10);
514
515static_assert(offsetof(siginfo32_t, si_lower) == 0x14);
516static_assert(offsetof(siginfo32_t, si_upper) == 0x18);
517
518static_assert(offsetof(siginfo32_t, si_pkey) == 0x14);
519
520static_assert(offsetof(siginfo32_t, si_perf_data) == 0x10);
521static_assert(offsetof(siginfo32_t, si_perf_type) == 0x14);
522static_assert(offsetof(siginfo32_t, si_perf_flags) == 0x18);
523
524CHECK_SI_OFFSET(_sigpoll);
525CHECK_SI_SIZE  (_sigpoll, 2*sizeof(int));
526static_assert(offsetof(siginfo32_t, si_band) == 0x0C);
527static_assert(offsetof(siginfo32_t, si_fd)   == 0x10);
528
529CHECK_SI_OFFSET(_sigsys);
530CHECK_SI_SIZE  (_sigsys, 3*sizeof(int));
531static_assert(offsetof(siginfo32_t, si_call_addr) == 0x0C);
532static_assert(offsetof(siginfo32_t, si_syscall)   == 0x10);
533static_assert(offsetof(siginfo32_t, si_arch)      == 0x14);
534
535/* any new si_fields should be added here */