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Linux/arch/x86/ia32/ia32_signal.c

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  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 
 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 /*
 58  * Do a signal return; undo the signal stack.
 59  */
 60 static 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 
100 COMPAT_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 
118 badframe:
119         signal_fault(regs, frame, "32bit sigreturn");
120         return 0;
121 }
122 
123 COMPAT_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 
146 badframe:
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 
157 static __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 
190 Efault:
191         return -EFAULT;
192 }
193 
194 #define unsafe_put_sigcontext32(sc, fp, regs, set, label)               \
195 do {                                                                    \
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  */
203 static 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 
234 int 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;
295 Efault:
296         user_access_end();
297         return -EFAULT;
298 }
299 
300 int 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, false))
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;
372 Efault:
373         user_access_end();
374         return -EFAULT;
375 }
376 

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