1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  linux/arch/x86_64/ia32/ia32_signal.c
4 *
5 *  Copyright (C) 1991, 1992  Linus Torvalds
6 *
7 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
8 *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
9 *  2000-12-*   x86-64 compatibility mode signal handling by Andi Kleen
10 */
11
12#include <linux/sched.h>
13#include <linux/sched/task_stack.h>
14#include <linux/mm.h>
15#include <linux/smp.h>
16#include <linux/kernel.h>
17#include <linux/errno.h>
18#include <linux/wait.h>
19#include <linux/unistd.h>
20#include <linux/stddef.h>
21#include <linux/personality.h>
22#include <linux/compat.h>
23#include <linux/binfmts.h>
24#include <linux/syscalls.h>
25#include <asm/ucontext.h>
26#include <linux/uaccess.h>
27#include <asm/fpu/internal.h>
28#include <asm/fpu/signal.h>
29#include <asm/ptrace.h>
30#include <asm/ia32_unistd.h>
31#include <asm/user32.h>
32#include <uapi/asm/sigcontext.h>
33#include <asm/proto.h>
34#include <asm/vdso.h>
35#include <asm/sigframe.h>
36#include <asm/sighandling.h>
37#include <asm/smap.h>
38
39static 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/*
58 * Do a signal return; undo the signal stack.
59 */
60static int ia32_restore_sigcontext(struct pt_regs *regs,
61				   struct sigcontext_32 __user *usc)
62{
63	struct sigcontext_32 sc;
64
65	/* Always make any pending restarted system calls return -EINTR */
66	current->restart_block.fn = do_no_restart_syscall;
67
68	if (unlikely(copy_from_user(&sc, usc, sizeof(sc))))
69		return -EFAULT;
70
71	/* Get only the ia32 registers. */
72	regs->bx = sc.bx;
73	regs->cx = sc.cx;
74	regs->dx = sc.dx;
75	regs->si = sc.si;
76	regs->di = sc.di;
77	regs->bp = sc.bp;
78	regs->ax = sc.ax;
79	regs->sp = sc.sp;
80	regs->ip = sc.ip;
81
82	/* Get CS/SS and force CPL3 */
83	regs->cs = sc.cs | 0x03;
84	regs->ss = sc.ss | 0x03;
85
86	regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
87	/* disable syscall checks */
88	regs->orig_ax = -1;
89
90	/*
91	 * Reload fs and gs if they have changed in the signal
92	 * handler.  This does not handle long fs/gs base changes in
93	 * the handler, but does not clobber them at least in the
94	 * normal case.
95	 */
96	reload_segments(&sc);
97	return fpu__restore_sig(compat_ptr(sc.fpstate), 1);
98}
99
100COMPAT_SYSCALL_DEFINE0(sigreturn)
101{
102	struct pt_regs *regs = current_pt_regs();
103	struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
104	sigset_t set;
105
106	if (!access_ok(frame, sizeof(*frame)))
107		goto badframe;
108	if (__get_user(set.sig[0], &frame->sc.oldmask)
109	    || __get_user(((__u32 *)&set)[1], &frame->extramask[0]))
110		goto badframe;
111
112	set_current_blocked(&set);
113
114	if (ia32_restore_sigcontext(regs, &frame->sc))
115		goto badframe;
116	return regs->ax;
117
118badframe:
119	signal_fault(regs, frame, "32bit sigreturn");
120	return 0;
121}
122
123COMPAT_SYSCALL_DEFINE0(rt_sigreturn)
124{
125	struct pt_regs *regs = current_pt_regs();
126	struct rt_sigframe_ia32 __user *frame;
127	sigset_t set;
128
129	frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
130
131	if (!access_ok(frame, sizeof(*frame)))
132		goto badframe;
133	if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
134		goto badframe;
135
136	set_current_blocked(&set);
137
138	if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
139		goto badframe;
140
141	if (compat_restore_altstack(&frame->uc.uc_stack))
142		goto badframe;
143
144	return regs->ax;
145
146badframe:
147	signal_fault(regs, frame, "32bit rt sigreturn");
148	return 0;
149}
150
151/*
152 * Set up a signal frame.
153 */
154
155#define get_user_seg(seg)	({ unsigned int v; savesegment(seg, v); v; })
156
157static __always_inline int
158__unsafe_setup_sigcontext32(struct sigcontext_32 __user *sc,
159			    void __user *fpstate,
160			    struct pt_regs *regs, unsigned int mask)
161{
162	unsafe_put_user(get_user_seg(gs), (unsigned int __user *)&sc->gs, Efault);
163	unsafe_put_user(get_user_seg(fs), (unsigned int __user *)&sc->fs, Efault);
164	unsafe_put_user(get_user_seg(ds), (unsigned int __user *)&sc->ds, Efault);
165	unsafe_put_user(get_user_seg(es), (unsigned int __user *)&sc->es, Efault);
166
167	unsafe_put_user(regs->di, &sc->di, Efault);
168	unsafe_put_user(regs->si, &sc->si, Efault);
169	unsafe_put_user(regs->bp, &sc->bp, Efault);
170	unsafe_put_user(regs->sp, &sc->sp, Efault);
171	unsafe_put_user(regs->bx, &sc->bx, Efault);
172	unsafe_put_user(regs->dx, &sc->dx, Efault);
173	unsafe_put_user(regs->cx, &sc->cx, Efault);
174	unsafe_put_user(regs->ax, &sc->ax, Efault);
175	unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
176	unsafe_put_user(current->thread.error_code, &sc->err, Efault);
177	unsafe_put_user(regs->ip, &sc->ip, Efault);
178	unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
179	unsafe_put_user(regs->flags, &sc->flags, Efault);
180	unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
181	unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
182
183	unsafe_put_user(ptr_to_compat(fpstate), &sc->fpstate, Efault);
184
185	/* non-iBCS2 extensions.. */
186	unsafe_put_user(mask, &sc->oldmask, Efault);
187	unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
188	return 0;
189
190Efault:
191	return -EFAULT;
192}
193
194#define unsafe_put_sigcontext32(sc, fp, regs, set, label)		\
195do {									\
196	if (__unsafe_setup_sigcontext32(sc, fp, regs, set->sig[0]))	\
197		goto label;						\
198} while(0)
199
200/*
201 * Determine which stack to use..
202 */
203static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
204				 size_t frame_size,
205				 void __user **fpstate)
206{
207	unsigned long sp, fx_aligned, math_size;
208
209	/* Default to using normal stack */
210	sp = regs->sp;
211
212	/* This is the X/Open sanctioned signal stack switching.  */
213	if (ksig->ka.sa.sa_flags & SA_ONSTACK)
214		sp = sigsp(sp, ksig);
215	/* This is the legacy signal stack switching. */
216	else if (regs->ss != __USER32_DS &&
217		!(ksig->ka.sa.sa_flags & SA_RESTORER) &&
218		 ksig->ka.sa.sa_restorer)
219		sp = (unsigned long) ksig->ka.sa.sa_restorer;
220
221	sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);
222	*fpstate = (struct _fpstate_32 __user *) sp;
223	if (copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned,
224				     math_size) < 0)
225		return (void __user *) -1L;
226
227	sp -= frame_size;
228	/* Align the stack pointer according to the i386 ABI,
229	 * i.e. so that on function entry ((sp + 4) & 15) == 0. */
230	sp = ((sp + 4) & -16ul) - 4;
231	return (void __user *) sp;
232}
233
234int ia32_setup_frame(int sig, struct ksignal *ksig,
235		     compat_sigset_t *set, struct pt_regs *regs)
236{
237	struct sigframe_ia32 __user *frame;
238	void __user *restorer;
239	void __user *fp = NULL;
240
241	/* copy_to_user optimizes that into a single 8 byte store */
242	static const struct {
243		u16 poplmovl;
244		u32 val;
245		u16 int80;
246	} __attribute__((packed)) code = {
247		0xb858,		 /* popl %eax ; movl $...,%eax */
248		__NR_ia32_sigreturn,
249		0x80cd,		/* int $0x80 */
250	};
251
252	frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
253
254	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
255		restorer = ksig->ka.sa.sa_restorer;
256	} else {
257		/* Return stub is in 32bit vsyscall page */
258		if (current->mm->context.vdso)
259			restorer = current->mm->context.vdso +
260				vdso_image_32.sym___kernel_sigreturn;
261		else
262			restorer = &frame->retcode;
263	}
264
265	if (!user_access_begin(frame, sizeof(*frame)))
266		return -EFAULT;
267
268	unsafe_put_user(sig, &frame->sig, Efault);
269	unsafe_put_sigcontext32(&frame->sc, fp, regs, set, Efault);
270	unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
271	unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
272	/*
273	 * These are actually not used anymore, but left because some
274	 * gdb versions depend on them as a marker.
275	 */
276	unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
277	user_access_end();
278
279	/* Set up registers for signal handler */
280	regs->sp = (unsigned long) frame;
281	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
282
283	/* Make -mregparm=3 work */
284	regs->ax = sig;
285	regs->dx = 0;
286	regs->cx = 0;
287
288	loadsegment(ds, __USER32_DS);
289	loadsegment(es, __USER32_DS);
290
291	regs->cs = __USER32_CS;
292	regs->ss = __USER32_DS;
293
294	return 0;
295Efault:
296	user_access_end();
297	return -EFAULT;
298}
299
300int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
301			compat_sigset_t *set, struct pt_regs *regs)
302{
303	struct rt_sigframe_ia32 __user *frame;
304	void __user *restorer;
305	void __user *fp = NULL;
306
307	/* unsafe_put_user optimizes that into a single 8 byte store */
308	static const struct {
309		u8 movl;
310		u32 val;
311		u16 int80;
312		u8  pad;
313	} __attribute__((packed)) code = {
314		0xb8,
315		__NR_ia32_rt_sigreturn,
316		0x80cd,
317		0,
318	};
319
320	frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
321
322	if (!user_access_begin(frame, sizeof(*frame)))
323		return -EFAULT;
324
325	unsafe_put_user(sig, &frame->sig, Efault);
326	unsafe_put_user(ptr_to_compat(&frame->info), &frame->pinfo, Efault);
327	unsafe_put_user(ptr_to_compat(&frame->uc), &frame->puc, Efault);
328
329	/* Create the ucontext.  */
330	if (static_cpu_has(X86_FEATURE_XSAVE))
331		unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
332	else
333		unsafe_put_user(0, &frame->uc.uc_flags, Efault);
334	unsafe_put_user(0, &frame->uc.uc_link, Efault);
335	unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
336
337	if (ksig->ka.sa.sa_flags & SA_RESTORER)
338		restorer = ksig->ka.sa.sa_restorer;
339	else
340		restorer = current->mm->context.vdso +
341			vdso_image_32.sym___kernel_rt_sigreturn;
342	unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
343
344	/*
345	 * Not actually used anymore, but left because some gdb
346	 * versions need it.
347	 */
348	unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
349	unsafe_put_sigcontext32(&frame->uc.uc_mcontext, fp, regs, set, Efault);
350	unsafe_put_user(*(__u64 *)set, (__u64 *)&frame->uc.uc_sigmask, Efault);
351	user_access_end();
352
353	if (__copy_siginfo_to_user32(&frame->info, &ksig->info))
354		return -EFAULT;
355
356	/* Set up registers for signal handler */
357	regs->sp = (unsigned long) frame;
358	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
359
360	/* Make -mregparm=3 work */
361	regs->ax = sig;
362	regs->dx = (unsigned long) &frame->info;
363	regs->cx = (unsigned long) &frame->uc;
364
365	loadsegment(ds, __USER32_DS);
366	loadsegment(es, __USER32_DS);
367
368	regs->cs = __USER32_CS;
369	regs->ss = __USER32_DS;
370
371	return 0;
372Efault:
373	user_access_end();
374	return -EFAULT;
375}
376