1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * FPU signal frame handling routines.
4 */
5
6 #include <linux/compat.h>
7 #include <linux/cpu.h>
8 #include <linux/pagemap.h>
9
10 #include <asm/fpu/internal.h>
11 #include <asm/fpu/signal.h>
12 #include <asm/fpu/regset.h>
13 #include <asm/fpu/xstate.h>
14
15 #include <asm/sigframe.h>
16 #include <asm/trace/fpu.h>
17
18 static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
19
20 /*
21 * Check for the presence of extended state information in the
22 * user fpstate pointer in the sigcontext.
23 */
check_for_xstate(struct fxregs_state __user * buf,void __user * fpstate,struct _fpx_sw_bytes * fx_sw)24 static inline int check_for_xstate(struct fxregs_state __user *buf,
25 void __user *fpstate,
26 struct _fpx_sw_bytes *fx_sw)
27 {
28 int min_xstate_size = sizeof(struct fxregs_state) +
29 sizeof(struct xstate_header);
30 unsigned int magic2;
31
32 if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
33 return -1;
34
35 /* Check for the first magic field and other error scenarios. */
36 if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
37 fx_sw->xstate_size < min_xstate_size ||
38 fx_sw->xstate_size > fpu_user_xstate_size ||
39 fx_sw->xstate_size > fx_sw->extended_size)
40 return -1;
41
42 /*
43 * Check for the presence of second magic word at the end of memory
44 * layout. This detects the case where the user just copied the legacy
45 * fpstate layout with out copying the extended state information
46 * in the memory layout.
47 */
48 if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
49 || magic2 != FP_XSTATE_MAGIC2)
50 return -1;
51
52 return 0;
53 }
54
55 /*
56 * Signal frame handlers.
57 */
save_fsave_header(struct task_struct * tsk,void __user * buf)58 static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
59 {
60 if (use_fxsr()) {
61 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
62 struct user_i387_ia32_struct env;
63 struct _fpstate_32 __user *fp = buf;
64
65 fpregs_lock();
66 if (!test_thread_flag(TIF_NEED_FPU_LOAD))
67 copy_fxregs_to_kernel(&tsk->thread.fpu);
68 fpregs_unlock();
69
70 convert_from_fxsr(&env, tsk);
71
72 if (__copy_to_user(buf, &env, sizeof(env)) ||
73 __put_user(xsave->i387.swd, &fp->status) ||
74 __put_user(X86_FXSR_MAGIC, &fp->magic))
75 return -1;
76 } else {
77 struct fregs_state __user *fp = buf;
78 u32 swd;
79 if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
80 return -1;
81 }
82
83 return 0;
84 }
85
save_xstate_epilog(void __user * buf,int ia32_frame)86 static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
87 {
88 struct xregs_state __user *x = buf;
89 struct _fpx_sw_bytes *sw_bytes;
90 u32 xfeatures;
91 int err;
92
93 /* Setup the bytes not touched by the [f]xsave and reserved for SW. */
94 sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
95 err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
96
97 if (!use_xsave())
98 return err;
99
100 err |= __put_user(FP_XSTATE_MAGIC2,
101 (__u32 __user *)(buf + fpu_user_xstate_size));
102
103 /*
104 * Read the xfeatures which we copied (directly from the cpu or
105 * from the state in task struct) to the user buffers.
106 */
107 err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
108
109 /*
110 * For legacy compatible, we always set FP/SSE bits in the bit
111 * vector while saving the state to the user context. This will
112 * enable us capturing any changes(during sigreturn) to
113 * the FP/SSE bits by the legacy applications which don't touch
114 * xfeatures in the xsave header.
115 *
116 * xsave aware apps can change the xfeatures in the xsave
117 * header as well as change any contents in the memory layout.
118 * xrestore as part of sigreturn will capture all the changes.
119 */
120 xfeatures |= XFEATURE_MASK_FPSSE;
121
122 err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
123
124 return err;
125 }
126
copy_fpregs_to_sigframe(struct xregs_state __user * buf)127 static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
128 {
129 int err;
130
131 if (use_xsave())
132 err = copy_xregs_to_user(buf);
133 else if (use_fxsr())
134 err = copy_fxregs_to_user((struct fxregs_state __user *) buf);
135 else
136 err = copy_fregs_to_user((struct fregs_state __user *) buf);
137
138 if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
139 err = -EFAULT;
140 return err;
141 }
142
143 /*
144 * Save the fpu, extended register state to the user signal frame.
145 *
146 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
147 * state is copied.
148 * 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
149 *
150 * buf == buf_fx for 64-bit frames and 32-bit fsave frame.
151 * buf != buf_fx for 32-bit frames with fxstate.
152 *
153 * Try to save it directly to the user frame with disabled page fault handler.
154 * If this fails then do the slow path where the FPU state is first saved to
155 * task's fpu->state and then copy it to the user frame pointed to by the
156 * aligned pointer 'buf_fx'.
157 *
158 * If this is a 32-bit frame with fxstate, put a fsave header before
159 * the aligned state at 'buf_fx'.
160 *
161 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
162 * indicating the absence/presence of the extended state to the user.
163 */
copy_fpstate_to_sigframe(void __user * buf,void __user * buf_fx,int size)164 int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
165 {
166 struct task_struct *tsk = current;
167 int ia32_fxstate = (buf != buf_fx);
168 int ret;
169
170 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
171 IS_ENABLED(CONFIG_IA32_EMULATION));
172
173 if (!static_cpu_has(X86_FEATURE_FPU)) {
174 struct user_i387_ia32_struct fp;
175 fpregs_soft_get(current, NULL, (struct membuf){.p = &fp,
176 .left = sizeof(fp)});
177 return copy_to_user(buf, &fp, sizeof(fp)) ? -EFAULT : 0;
178 }
179
180 if (!access_ok(buf, size))
181 return -EACCES;
182 retry:
183 /*
184 * Load the FPU registers if they are not valid for the current task.
185 * With a valid FPU state we can attempt to save the state directly to
186 * userland's stack frame which will likely succeed. If it does not,
187 * resolve the fault in the user memory and try again.
188 */
189 fpregs_lock();
190 if (test_thread_flag(TIF_NEED_FPU_LOAD))
191 __fpregs_load_activate();
192
193 pagefault_disable();
194 ret = copy_fpregs_to_sigframe(buf_fx);
195 pagefault_enable();
196 fpregs_unlock();
197
198 if (ret) {
199 if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
200 goto retry;
201 return -EFAULT;
202 }
203
204 /* Save the fsave header for the 32-bit frames. */
205 if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
206 return -1;
207
208 if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
209 return -1;
210
211 return 0;
212 }
213
214 static inline void
sanitize_restored_user_xstate(union fpregs_state * state,struct user_i387_ia32_struct * ia32_env,u64 user_xfeatures,int fx_only)215 sanitize_restored_user_xstate(union fpregs_state *state,
216 struct user_i387_ia32_struct *ia32_env,
217 u64 user_xfeatures, int fx_only)
218 {
219 struct xregs_state *xsave = &state->xsave;
220 struct xstate_header *header = &xsave->header;
221
222 if (use_xsave()) {
223 /*
224 * Clear all feature bits which are not set in
225 * user_xfeatures and clear all extended features
226 * for fx_only mode.
227 */
228 u64 mask = fx_only ? XFEATURE_MASK_FPSSE : user_xfeatures;
229
230 /*
231 * Supervisor state has to be preserved. The sigframe
232 * restore can only modify user features, i.e. @mask
233 * cannot contain them.
234 */
235 header->xfeatures &= mask | xfeatures_mask_supervisor();
236 }
237
238 if (use_fxsr()) {
239 /*
240 * mscsr reserved bits must be masked to zero for security
241 * reasons.
242 */
243 xsave->i387.mxcsr &= mxcsr_feature_mask;
244
245 if (ia32_env)
246 convert_to_fxsr(&state->fxsave, ia32_env);
247 }
248 }
249
250 /*
251 * Restore the extended state if present. Otherwise, restore the FP/SSE state.
252 */
copy_user_to_fpregs_zeroing(void __user * buf,u64 xbv,int fx_only)253 static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
254 {
255 u64 init_bv;
256 int r;
257
258 if (use_xsave()) {
259 if (fx_only) {
260 init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
261
262 r = copy_user_to_fxregs(buf);
263 if (!r)
264 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
265 return r;
266 } else {
267 init_bv = xfeatures_mask_user() & ~xbv;
268
269 r = copy_user_to_xregs(buf, xbv);
270 if (!r && unlikely(init_bv))
271 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
272 return r;
273 }
274 } else if (use_fxsr()) {
275 return copy_user_to_fxregs(buf);
276 } else
277 return copy_user_to_fregs(buf);
278 }
279
__fpu__restore_sig(void __user * buf,void __user * buf_fx,int size)280 static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
281 {
282 struct user_i387_ia32_struct *envp = NULL;
283 int state_size = fpu_kernel_xstate_size;
284 int ia32_fxstate = (buf != buf_fx);
285 struct task_struct *tsk = current;
286 struct fpu *fpu = &tsk->thread.fpu;
287 struct user_i387_ia32_struct env;
288 u64 user_xfeatures = 0;
289 int fx_only = 0;
290 int ret = 0;
291
292 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
293 IS_ENABLED(CONFIG_IA32_EMULATION));
294
295 if (!buf) {
296 fpu__clear_user_states(fpu);
297 return 0;
298 }
299
300 if (!access_ok(buf, size)) {
301 ret = -EACCES;
302 goto out;
303 }
304
305 if (!static_cpu_has(X86_FEATURE_FPU)) {
306 ret = fpregs_soft_set(current, NULL, 0,
307 sizeof(struct user_i387_ia32_struct),
308 NULL, buf);
309 goto out;
310 }
311
312 if (use_xsave()) {
313 struct _fpx_sw_bytes fx_sw_user;
314 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
315 /*
316 * Couldn't find the extended state information in the
317 * memory layout. Restore just the FP/SSE and init all
318 * the other extended state.
319 */
320 state_size = sizeof(struct fxregs_state);
321 fx_only = 1;
322 trace_x86_fpu_xstate_check_failed(fpu);
323 } else {
324 state_size = fx_sw_user.xstate_size;
325 user_xfeatures = fx_sw_user.xfeatures;
326 }
327 }
328
329 if ((unsigned long)buf_fx % 64)
330 fx_only = 1;
331
332 if (!ia32_fxstate) {
333 /*
334 * Attempt to restore the FPU registers directly from user
335 * memory. For that to succeed, the user access cannot cause
336 * page faults. If it does, fall back to the slow path below,
337 * going through the kernel buffer with the enabled pagefault
338 * handler.
339 */
340 fpregs_lock();
341 pagefault_disable();
342 ret = copy_user_to_fpregs_zeroing(buf_fx, user_xfeatures, fx_only);
343 pagefault_enable();
344 if (!ret) {
345
346 /*
347 * Restore supervisor states: previous context switch
348 * etc has done XSAVES and saved the supervisor states
349 * in the kernel buffer from which they can be restored
350 * now.
351 *
352 * We cannot do a single XRSTORS here - which would
353 * be nice - because the rest of the FPU registers are
354 * being restored from a user buffer directly. The
355 * single XRSTORS happens below, when the user buffer
356 * has been copied to the kernel one.
357 */
358 if (test_thread_flag(TIF_NEED_FPU_LOAD) &&
359 xfeatures_mask_supervisor())
360 copy_kernel_to_xregs(&fpu->state.xsave,
361 xfeatures_mask_supervisor());
362 fpregs_mark_activate();
363 fpregs_unlock();
364 return 0;
365 }
366
367 /*
368 * The above did an FPU restore operation, restricted to
369 * the user portion of the registers, and failed, but the
370 * microcode might have modified the FPU registers
371 * nevertheless.
372 *
373 * If the FPU registers do not belong to current, then
374 * invalidate the FPU register state otherwise the task might
375 * preempt current and return to user space with corrupted
376 * FPU registers.
377 *
378 * In case current owns the FPU registers then no further
379 * action is required. The fixup below will handle it
380 * correctly.
381 */
382 if (test_thread_flag(TIF_NEED_FPU_LOAD))
383 __cpu_invalidate_fpregs_state();
384
385 fpregs_unlock();
386 } else {
387 /*
388 * For 32-bit frames with fxstate, copy the fxstate so it can
389 * be reconstructed later.
390 */
391 ret = __copy_from_user(&env, buf, sizeof(env));
392 if (ret)
393 goto out;
394 envp = &env;
395 }
396
397 /*
398 * By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is
399 * not modified on context switch and that the xstate is considered
400 * to be loaded again on return to userland (overriding last_cpu avoids
401 * the optimisation).
402 */
403 fpregs_lock();
404
405 if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
406
407 /*
408 * Supervisor states are not modified by user space input. Save
409 * current supervisor states first and invalidate the FPU regs.
410 */
411 if (xfeatures_mask_supervisor())
412 copy_supervisor_to_kernel(&fpu->state.xsave);
413 set_thread_flag(TIF_NEED_FPU_LOAD);
414 }
415 __fpu_invalidate_fpregs_state(fpu);
416 fpregs_unlock();
417
418 if (use_xsave() && !fx_only) {
419 u64 init_bv = xfeatures_mask_user() & ~user_xfeatures;
420
421 ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
422 if (ret)
423 goto out;
424
425 sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
426 fx_only);
427
428 fpregs_lock();
429 if (unlikely(init_bv))
430 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
431
432 /*
433 * Restore previously saved supervisor xstates along with
434 * copied-in user xstates.
435 */
436 ret = copy_kernel_to_xregs_err(&fpu->state.xsave,
437 user_xfeatures | xfeatures_mask_supervisor());
438
439 } else if (use_fxsr()) {
440 ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
441 if (ret) {
442 ret = -EFAULT;
443 goto out;
444 }
445
446 sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
447 fx_only);
448
449 fpregs_lock();
450 if (use_xsave()) {
451 u64 init_bv;
452
453 init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
454 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
455 }
456
457 ret = copy_kernel_to_fxregs_err(&fpu->state.fxsave);
458 } else {
459 ret = __copy_from_user(&fpu->state.fsave, buf_fx, state_size);
460 if (ret)
461 goto out;
462
463 fpregs_lock();
464 ret = copy_kernel_to_fregs_err(&fpu->state.fsave);
465 }
466 if (!ret)
467 fpregs_mark_activate();
468 else
469 fpregs_deactivate(fpu);
470 fpregs_unlock();
471
472 out:
473 if (ret)
474 fpu__clear_user_states(fpu);
475 return ret;
476 }
477
xstate_sigframe_size(void)478 static inline int xstate_sigframe_size(void)
479 {
480 return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
481 fpu_user_xstate_size;
482 }
483
484 /*
485 * Restore FPU state from a sigframe:
486 */
fpu__restore_sig(void __user * buf,int ia32_frame)487 int fpu__restore_sig(void __user *buf, int ia32_frame)
488 {
489 void __user *buf_fx = buf;
490 int size = xstate_sigframe_size();
491
492 if (ia32_frame && use_fxsr()) {
493 buf_fx = buf + sizeof(struct fregs_state);
494 size += sizeof(struct fregs_state);
495 }
496
497 return __fpu__restore_sig(buf, buf_fx, size);
498 }
499
500 unsigned long
fpu__alloc_mathframe(unsigned long sp,int ia32_frame,unsigned long * buf_fx,unsigned long * size)501 fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
502 unsigned long *buf_fx, unsigned long *size)
503 {
504 unsigned long frame_size = xstate_sigframe_size();
505
506 *buf_fx = sp = round_down(sp - frame_size, 64);
507 if (ia32_frame && use_fxsr()) {
508 frame_size += sizeof(struct fregs_state);
509 sp -= sizeof(struct fregs_state);
510 }
511
512 *size = frame_size;
513
514 return sp;
515 }
516 /*
517 * Prepare the SW reserved portion of the fxsave memory layout, indicating
518 * the presence of the extended state information in the memory layout
519 * pointed by the fpstate pointer in the sigcontext.
520 * This will be saved when ever the FP and extended state context is
521 * saved on the user stack during the signal handler delivery to the user.
522 */
fpu__init_prepare_fx_sw_frame(void)523 void fpu__init_prepare_fx_sw_frame(void)
524 {
525 int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
526
527 fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
528 fx_sw_reserved.extended_size = size;
529 fx_sw_reserved.xfeatures = xfeatures_mask_user();
530 fx_sw_reserved.xstate_size = fpu_user_xstate_size;
531
532 if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
533 IS_ENABLED(CONFIG_X86_32)) {
534 int fsave_header_size = sizeof(struct fregs_state);
535
536 fx_sw_reserved_ia32 = fx_sw_reserved;
537 fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
538 }
539 }
540
541