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/signal.h>
28#include <asm/ptrace.h>
29#include <asm/ia32_unistd.h>
30#include <asm/user32.h>
31#include <uapi/asm/sigcontext.h>
32#include <asm/proto.h>
33#include <asm/vdso.h>
34#include <asm/sigframe.h>
35#include <asm/sighandling.h>
36#include <asm/smap.h>
37
38static inline void reload_segments(struct sigcontext_32 *sc)
39{
40 unsigned int cur;
41
42 savesegment(gs, cur);
43 if ((sc->gs | 0x03) != cur)
44 load_gs_index(sc->gs | 0x03);
45 savesegment(fs, cur);
46 if ((sc->fs | 0x03) != cur)
47 loadsegment(fs, sc->fs | 0x03);
48 savesegment(ds, cur);
49 if ((sc->ds | 0x03) != cur)
50 loadsegment(ds, sc->ds | 0x03);
51 savesegment(es, cur);
52 if ((sc->es | 0x03) != cur)
53 loadsegment(es, sc->es | 0x03);
54}
55
56/*
57 * Do a signal return; undo the signal stack.
58 */
59static bool ia32_restore_sigcontext(struct pt_regs *regs,
60 struct sigcontext_32 __user *usc)
61{
62 struct sigcontext_32 sc;
63
64 /* Always make any pending restarted system calls return -EINTR */
65 current->restart_block.fn = do_no_restart_syscall;
66
67 if (unlikely(copy_from_user(&sc, usc, sizeof(sc))))
68 return false;
69
70 /* Get only the ia32 registers. */
71 regs->bx = sc.bx;
72 regs->cx = sc.cx;
73 regs->dx = sc.dx;
74 regs->si = sc.si;
75 regs->di = sc.di;
76 regs->bp = sc.bp;
77 regs->ax = sc.ax;
78 regs->sp = sc.sp;
79 regs->ip = sc.ip;
80
81 /* Get CS/SS and force CPL3 */
82 regs->cs = sc.cs | 0x03;
83 regs->ss = sc.ss | 0x03;
84
85 regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
86 /* disable syscall checks */
87 regs->orig_ax = -1;
88
89 /*
90 * Reload fs and gs if they have changed in the signal
91 * handler. This does not handle long fs/gs base changes in
92 * the handler, but does not clobber them at least in the
93 * normal case.
94 */
95 reload_segments(&sc);
96 return fpu__restore_sig(compat_ptr(sc.fpstate), 1);
97}
98
99COMPAT_SYSCALL_DEFINE0(sigreturn)
100{
101 struct pt_regs *regs = current_pt_regs();
102 struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
103 sigset_t set;
104
105 if (!access_ok(frame, sizeof(*frame)))
106 goto badframe;
107 if (__get_user(set.sig[0], &frame->sc.oldmask)
108 || __get_user(((__u32 *)&set)[1], &frame->extramask[0]))
109 goto badframe;
110
111 set_current_blocked(&set);
112
113 if (!ia32_restore_sigcontext(regs, &frame->sc))
114 goto badframe;
115 return regs->ax;
116
117badframe:
118 signal_fault(regs, frame, "32bit sigreturn");
119 return 0;
120}
121
122COMPAT_SYSCALL_DEFINE0(rt_sigreturn)
123{
124 struct pt_regs *regs = current_pt_regs();
125 struct rt_sigframe_ia32 __user *frame;
126 sigset_t set;
127
128 frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
129
130 if (!access_ok(frame, sizeof(*frame)))
131 goto badframe;
132 if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
133 goto badframe;
134
135 set_current_blocked(&set);
136
137 if (!ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
138 goto badframe;
139
140 if (compat_restore_altstack(&frame->uc.uc_stack))
141 goto badframe;
142
143 return regs->ax;
144
145badframe:
146 signal_fault(regs, frame, "32bit rt sigreturn");
147 return 0;
148}
149
150/*
151 * Set up a signal frame.
152 */
153
154#define get_user_seg(seg) ({ unsigned int v; savesegment(seg, v); v; })
155
156static __always_inline int
157__unsafe_setup_sigcontext32(struct sigcontext_32 __user *sc,
158 void __user *fpstate,
159 struct pt_regs *regs, unsigned int mask)
160{
161 unsafe_put_user(get_user_seg(gs), (unsigned int __user *)&sc->gs, Efault);
162 unsafe_put_user(get_user_seg(fs), (unsigned int __user *)&sc->fs, Efault);
163 unsafe_put_user(get_user_seg(ds), (unsigned int __user *)&sc->ds, Efault);
164 unsafe_put_user(get_user_seg(es), (unsigned int __user *)&sc->es, Efault);
165
166 unsafe_put_user(regs->di, &sc->di, Efault);
167 unsafe_put_user(regs->si, &sc->si, Efault);
168 unsafe_put_user(regs->bp, &sc->bp, Efault);
169 unsafe_put_user(regs->sp, &sc->sp, Efault);
170 unsafe_put_user(regs->bx, &sc->bx, Efault);
171 unsafe_put_user(regs->dx, &sc->dx, Efault);
172 unsafe_put_user(regs->cx, &sc->cx, Efault);
173 unsafe_put_user(regs->ax, &sc->ax, Efault);
174 unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
175 unsafe_put_user(current->thread.error_code, &sc->err, Efault);
176 unsafe_put_user(regs->ip, &sc->ip, Efault);
177 unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
178 unsafe_put_user(regs->flags, &sc->flags, Efault);
179 unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
180 unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
181
182 unsafe_put_user(ptr_to_compat(fpstate), &sc->fpstate, Efault);
183
184 /* non-iBCS2 extensions.. */
185 unsafe_put_user(mask, &sc->oldmask, Efault);
186 unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
187 return 0;
188
189Efault:
190 return -EFAULT;
191}
192
193#define unsafe_put_sigcontext32(sc, fp, regs, set, label) \
194do { \
195 if (__unsafe_setup_sigcontext32(sc, fp, regs, set->sig[0])) \
196 goto label; \
197} while(0)
198
199/*
200 * Determine which stack to use..
201 */
202static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
203 size_t frame_size,
204 void __user **fpstate)
205{
206 unsigned long sp, fx_aligned, math_size;
207
208 /* Default to using normal stack */
209 sp = regs->sp;
210
211 /* This is the X/Open sanctioned signal stack switching. */
212 if (ksig->ka.sa.sa_flags & SA_ONSTACK)
213 sp = sigsp(sp, ksig);
214 /* This is the legacy signal stack switching. */
215 else if (regs->ss != __USER32_DS &&
216 !(ksig->ka.sa.sa_flags & SA_RESTORER) &&
217 ksig->ka.sa.sa_restorer)
218 sp = (unsigned long) ksig->ka.sa.sa_restorer;
219
220 sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);
221 *fpstate = (struct _fpstate_32 __user *) sp;
222 if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned,
223 math_size))
224 return (void __user *) -1L;
225
226 sp -= frame_size;
227 /* Align the stack pointer according to the i386 ABI,
228 * i.e. so that on function entry ((sp + 4) & 15) == 0. */
229 sp = ((sp + 4) & -16ul) - 4;
230 return (void __user *) sp;
231}
232
233int ia32_setup_frame(int sig, struct ksignal *ksig,
234 compat_sigset_t *set, struct pt_regs *regs)
235{
236 struct sigframe_ia32 __user *frame;
237 void __user *restorer;
238 void __user *fp = NULL;
239
240 /* copy_to_user optimizes that into a single 8 byte store */
241 static const struct {
242 u16 poplmovl;
243 u32 val;
244 u16 int80;
245 } __attribute__((packed)) code = {
246 0xb858, /* popl %eax ; movl $...,%eax */
247 __NR_ia32_sigreturn,
248 0x80cd, /* int $0x80 */
249 };
250
251 frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
252
253 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
254 restorer = ksig->ka.sa.sa_restorer;
255 } else {
256 /* Return stub is in 32bit vsyscall page */
257 if (current->mm->context.vdso)
258 restorer = current->mm->context.vdso +
259 vdso_image_32.sym___kernel_sigreturn;
260 else
261 restorer = &frame->retcode;
262 }
263
264 if (!user_access_begin(frame, sizeof(*frame)))
265 return -EFAULT;
266
267 unsafe_put_user(sig, &frame->sig, Efault);
268 unsafe_put_sigcontext32(&frame->sc, fp, regs, set, Efault);
269 unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
270 unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
271 /*
272 * These are actually not used anymore, but left because some
273 * gdb versions depend on them as a marker.
274 */
275 unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
276 user_access_end();
277
278 /* Set up registers for signal handler */
279 regs->sp = (unsigned long) frame;
280 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
281
282 /* Make -mregparm=3 work */
283 regs->ax = sig;
284 regs->dx = 0;
285 regs->cx = 0;
286
287 loadsegment(ds, __USER32_DS);
288 loadsegment(es, __USER32_DS);
289
290 regs->cs = __USER32_CS;
291 regs->ss = __USER32_DS;
292
293 return 0;
294Efault:
295 user_access_end();
296 return -EFAULT;
297}
298
299int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
300 compat_sigset_t *set, struct pt_regs *regs)
301{
302 struct rt_sigframe_ia32 __user *frame;
303 void __user *restorer;
304 void __user *fp = NULL;
305
306 /* unsafe_put_user optimizes that into a single 8 byte store */
307 static const struct {
308 u8 movl;
309 u32 val;
310 u16 int80;
311 u8 pad;
312 } __attribute__((packed)) code = {
313 0xb8,
314 __NR_ia32_rt_sigreturn,
315 0x80cd,
316 0,
317 };
318
319 frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
320
321 if (!user_access_begin(frame, sizeof(*frame)))
322 return -EFAULT;
323
324 unsafe_put_user(sig, &frame->sig, Efault);
325 unsafe_put_user(ptr_to_compat(&frame->info), &frame->pinfo, Efault);
326 unsafe_put_user(ptr_to_compat(&frame->uc), &frame->puc, Efault);
327
328 /* Create the ucontext. */
329 if (static_cpu_has(X86_FEATURE_XSAVE))
330 unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
331 else
332 unsafe_put_user(0, &frame->uc.uc_flags, Efault);
333 unsafe_put_user(0, &frame->uc.uc_link, Efault);
334 unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
335
336 if (ksig->ka.sa.sa_flags & SA_RESTORER)
337 restorer = ksig->ka.sa.sa_restorer;
338 else
339 restorer = current->mm->context.vdso +
340 vdso_image_32.sym___kernel_rt_sigreturn;
341 unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
342
343 /*
344 * Not actually used anymore, but left because some gdb
345 * versions need it.
346 */
347 unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
348 unsafe_put_sigcontext32(&frame->uc.uc_mcontext, fp, regs, set, Efault);
349 unsafe_put_user(*(__u64 *)set, (__u64 __user *)&frame->uc.uc_sigmask, Efault);
350 user_access_end();
351
352 if (__copy_siginfo_to_user32(&frame->info, &ksig->info))
353 return -EFAULT;
354
355 /* Set up registers for signal handler */
356 regs->sp = (unsigned long) frame;
357 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
358
359 /* Make -mregparm=3 work */
360 regs->ax = sig;
361 regs->dx = (unsigned long) &frame->info;
362 regs->cx = (unsigned long) &frame->uc;
363
364 loadsegment(ds, __USER32_DS);
365 loadsegment(es, __USER32_DS);
366
367 regs->cs = __USER32_CS;
368 regs->ss = __USER32_DS;
369
370 return 0;
371Efault:
372 user_access_end();
373 return -EFAULT;
374}
375

source code of linux/arch/x86/ia32/ia32_signal.c