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/signal.h>
11#include <asm/fpu/regset.h>
12#include <asm/fpu/xstate.h>
13
14#include <asm/sigframe.h>
15#include <asm/trapnr.h>
16#include <asm/trace/fpu.h>
17
18#include "context.h"
19#include "internal.h"
20#include "legacy.h"
21#include "xstate.h"
22
23/*
24 * Check for the presence of extended state information in the
25 * user fpstate pointer in the sigcontext.
26 */
27static inline bool check_xstate_in_sigframe(struct fxregs_state __user *fxbuf,
28 struct _fpx_sw_bytes *fx_sw)
29{
30 void __user *fpstate = fxbuf;
31 unsigned int magic2;
32
33 if (__copy_from_user(to: fx_sw, from: &fxbuf->sw_reserved[0], n: sizeof(*fx_sw)))
34 return false;
35
36 /* Check for the first magic field */
37 if (fx_sw->magic1 != FP_XSTATE_MAGIC1)
38 goto setfx;
39
40 /*
41 * Check for the presence of second magic word at the end of memory
42 * layout. This detects the case where the user just copied the legacy
43 * fpstate layout with out copying the extended state information
44 * in the memory layout.
45 */
46 if (__get_user(magic2, (__u32 __user *)(fpstate + x86_task_fpu(current)->fpstate->user_size)))
47 return false;
48
49 if (likely(magic2 == FP_XSTATE_MAGIC2))
50 return true;
51setfx:
52 trace_x86_fpu_xstate_check_failed(fpu: x86_task_fpu(current));
53
54 /* Set the parameters for fx only state */
55 fx_sw->magic1 = 0;
56 fx_sw->xstate_size = sizeof(struct fxregs_state);
57 fx_sw->xfeatures = XFEATURE_MASK_FPSSE;
58 return true;
59}
60
61/*
62 * Signal frame handlers.
63 */
64static inline bool save_fsave_header(struct task_struct *tsk, void __user *buf)
65{
66 if (use_fxsr()) {
67 struct xregs_state *xsave = &x86_task_fpu(task: tsk)->fpstate->regs.xsave;
68 struct user_i387_ia32_struct env;
69 struct _fpstate_32 __user *fp = buf;
70
71 fpregs_lock();
72 if (!test_thread_flag(TIF_NEED_FPU_LOAD))
73 fxsave(fx: &x86_task_fpu(task: tsk)->fpstate->regs.fxsave);
74 fpregs_unlock();
75
76 convert_from_fxsr(env: &env, tsk);
77
78 if (__copy_to_user(to: buf, from: &env, n: sizeof(env)) ||
79 __put_user(xsave->i387.swd, &fp->status) ||
80 __put_user(X86_FXSR_MAGIC, &fp->magic))
81 return false;
82 } else {
83 struct fregs_state __user *fp = buf;
84 u32 swd;
85
86 if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
87 return false;
88 }
89
90 return true;
91}
92
93/*
94 * Prepare the SW reserved portion of the fxsave memory layout, indicating
95 * the presence of the extended state information in the memory layout
96 * pointed to by the fpstate pointer in the sigcontext.
97 * This is saved when ever the FP and extended state context is
98 * saved on the user stack during the signal handler delivery to the user.
99 */
100static inline void save_sw_bytes(struct _fpx_sw_bytes *sw_bytes, bool ia32_frame,
101 struct fpstate *fpstate)
102{
103 sw_bytes->magic1 = FP_XSTATE_MAGIC1;
104 sw_bytes->extended_size = fpstate->user_size + FP_XSTATE_MAGIC2_SIZE;
105 sw_bytes->xfeatures = fpstate->user_xfeatures;
106 sw_bytes->xstate_size = fpstate->user_size;
107
108 if (ia32_frame)
109 sw_bytes->extended_size += sizeof(struct fregs_state);
110}
111
112static inline bool save_xstate_epilog(void __user *buf, int ia32_frame,
113 struct fpstate *fpstate)
114{
115 struct xregs_state __user *x = buf;
116 struct _fpx_sw_bytes sw_bytes = {};
117 int err;
118
119 /* Setup the bytes not touched by the [f]xsave and reserved for SW. */
120 save_sw_bytes(sw_bytes: &sw_bytes, ia32_frame, fpstate);
121 err = __copy_to_user(to: &x->i387.sw_reserved, from: &sw_bytes, n: sizeof(sw_bytes));
122
123 if (!use_xsave())
124 return !err;
125
126 err |= __put_user(FP_XSTATE_MAGIC2,
127 (__u32 __user *)(buf + fpstate->user_size));
128
129 /*
130 * For legacy compatible, we always set FP/SSE bits in the bit
131 * vector while saving the state to the user context. This will
132 * enable us capturing any changes(during sigreturn) to
133 * the FP/SSE bits by the legacy applications which don't touch
134 * xfeatures in the xsave header.
135 *
136 * xsave aware apps can change the xfeatures in the xsave
137 * header as well as change any contents in the memory layout.
138 * xrestore as part of sigreturn will capture all the changes.
139 */
140 err |= set_xfeature_in_sigframe(xbuf: x, XFEATURE_MASK_FPSSE);
141
142 return !err;
143}
144
145static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf, u32 pkru)
146{
147 if (use_xsave())
148 return xsave_to_user_sigframe(buf, pkru);
149
150 if (use_fxsr())
151 return fxsave_to_user_sigframe(fx: (struct fxregs_state __user *) buf);
152 else
153 return fnsave_to_user_sigframe(fx: (struct fregs_state __user *) buf);
154}
155
156/*
157 * Save the fpu, extended register state to the user signal frame.
158 *
159 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
160 * state is copied.
161 * 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
162 *
163 * buf == buf_fx for 64-bit frames and 32-bit fsave frame.
164 * buf != buf_fx for 32-bit frames with fxstate.
165 *
166 * Save it directly to the user frame with disabled page fault handler. If
167 * that faults, try to clear the frame which handles the page fault.
168 *
169 * If this is a 32-bit frame with fxstate, put a fsave header before
170 * the aligned state at 'buf_fx'.
171 *
172 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
173 * indicating the absence/presence of the extended state to the user.
174 */
175bool copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size, u32 pkru)
176{
177 struct task_struct *tsk = current;
178 struct fpstate *fpstate = x86_task_fpu(task: tsk)->fpstate;
179 bool ia32_fxstate = (buf != buf_fx);
180 int ret;
181
182 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
183 IS_ENABLED(CONFIG_IA32_EMULATION));
184
185 if (!static_cpu_has(X86_FEATURE_FPU)) {
186 struct user_i387_ia32_struct fp;
187
188 fpregs_soft_get(current, NULL, (struct membuf){.p = &fp,
189 .left = sizeof(fp)});
190 return !copy_to_user(to: buf, from: &fp, n: sizeof(fp));
191 }
192
193 if (!access_ok(buf, size))
194 return false;
195
196 if (use_xsave()) {
197 struct xregs_state __user *xbuf = buf_fx;
198
199 /*
200 * Clear the xsave header first, so that reserved fields are
201 * initialized to zero.
202 */
203 if (__clear_user(addr: &xbuf->header, size: sizeof(xbuf->header)))
204 return false;
205 }
206retry:
207 /*
208 * Load the FPU registers if they are not valid for the current task.
209 * With a valid FPU state we can attempt to save the state directly to
210 * userland's stack frame which will likely succeed. If it does not,
211 * resolve the fault in the user memory and try again.
212 */
213 fpregs_lock();
214 if (test_thread_flag(TIF_NEED_FPU_LOAD))
215 fpregs_restore_userregs();
216
217 pagefault_disable();
218 ret = copy_fpregs_to_sigframe(buf: buf_fx, pkru);
219 pagefault_enable();
220 fpregs_unlock();
221
222 if (ret) {
223 if (!__clear_user(addr: buf_fx, size: fpstate->user_size))
224 goto retry;
225 return false;
226 }
227
228 /* Save the fsave header for the 32-bit frames. */
229 if ((ia32_fxstate || !use_fxsr()) && !save_fsave_header(tsk, buf))
230 return false;
231
232 if (use_fxsr() && !save_xstate_epilog(buf: buf_fx, ia32_frame: ia32_fxstate, fpstate))
233 return false;
234
235 return true;
236}
237
238static int __restore_fpregs_from_user(void __user *buf, u64 ufeatures,
239 u64 xrestore, bool fx_only)
240{
241 if (use_xsave()) {
242 u64 init_bv = ufeatures & ~xrestore;
243 int ret;
244
245 if (likely(!fx_only))
246 ret = xrstor_from_user_sigframe(buf, mask: xrestore);
247 else
248 ret = fxrstor_from_user_sigframe(fx: buf);
249
250 if (!ret && unlikely(init_bv))
251 os_xrstor(fpstate: &init_fpstate, mask: init_bv);
252 return ret;
253 } else if (use_fxsr()) {
254 return fxrstor_from_user_sigframe(fx: buf);
255 } else {
256 return frstor_from_user_sigframe(fx: buf);
257 }
258}
259
260/*
261 * Attempt to restore the FPU registers directly from user memory.
262 * Pagefaults are handled and any errors returned are fatal.
263 */
264static bool restore_fpregs_from_user(void __user *buf, u64 xrestore, bool fx_only)
265{
266 struct fpu *fpu = x86_task_fpu(current);
267 int ret;
268
269 /* Restore enabled features only. */
270 xrestore &= fpu->fpstate->user_xfeatures;
271retry:
272 fpregs_lock();
273 /* Ensure that XFD is up to date */
274 xfd_update_state(fpstate: fpu->fpstate);
275 pagefault_disable();
276 ret = __restore_fpregs_from_user(buf, ufeatures: fpu->fpstate->user_xfeatures,
277 xrestore, fx_only);
278 pagefault_enable();
279
280 if (unlikely(ret)) {
281 /*
282 * The above did an FPU restore operation, restricted to
283 * the user portion of the registers, and failed, but the
284 * microcode might have modified the FPU registers
285 * nevertheless.
286 *
287 * If the FPU registers do not belong to current, then
288 * invalidate the FPU register state otherwise the task
289 * might preempt current and return to user space with
290 * corrupted FPU registers.
291 */
292 if (test_thread_flag(TIF_NEED_FPU_LOAD))
293 __cpu_invalidate_fpregs_state();
294 fpregs_unlock();
295
296 /* Try to handle #PF, but anything else is fatal. */
297 if (ret != X86_TRAP_PF)
298 return false;
299
300 if (!fault_in_readable(uaddr: buf, size: fpu->fpstate->user_size))
301 goto retry;
302 return false;
303 }
304
305 /*
306 * Restore supervisor states: previous context switch etc has done
307 * XSAVES and saved the supervisor states in the kernel buffer from
308 * which they can be restored now.
309 *
310 * It would be optimal to handle this with a single XRSTORS, but
311 * this does not work because the rest of the FPU registers have
312 * been restored from a user buffer directly.
313 */
314 if (test_thread_flag(TIF_NEED_FPU_LOAD) && xfeatures_mask_supervisor())
315 os_xrstor_supervisor(fpstate: fpu->fpstate);
316
317 fpregs_mark_activate();
318 fpregs_unlock();
319 return true;
320}
321
322static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx,
323 bool ia32_fxstate)
324{
325 struct task_struct *tsk = current;
326 struct fpu *fpu = x86_task_fpu(task: tsk);
327 struct user_i387_ia32_struct env;
328 bool success, fx_only = false;
329 union fpregs_state *fpregs;
330 u64 user_xfeatures = 0;
331
332 if (use_xsave()) {
333 struct _fpx_sw_bytes fx_sw_user;
334
335 if (!check_xstate_in_sigframe(fxbuf: buf_fx, fx_sw: &fx_sw_user))
336 return false;
337
338 fx_only = !fx_sw_user.magic1;
339 user_xfeatures = fx_sw_user.xfeatures;
340 } else {
341 user_xfeatures = XFEATURE_MASK_FPSSE;
342 }
343
344 if (likely(!ia32_fxstate)) {
345 /* Restore the FPU registers directly from user memory. */
346 return restore_fpregs_from_user(buf: buf_fx, xrestore: user_xfeatures, fx_only);
347 }
348
349 /*
350 * Copy the legacy state because the FP portion of the FX frame has
351 * to be ignored for histerical raisins. The legacy state is folded
352 * in once the larger state has been copied.
353 */
354 if (__copy_from_user(to: &env, from: buf, n: sizeof(env)))
355 return false;
356
357 /*
358 * By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is
359 * not modified on context switch and that the xstate is considered
360 * to be loaded again on return to userland (overriding last_cpu avoids
361 * the optimisation).
362 */
363 fpregs_lock();
364 if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
365 /*
366 * If supervisor states are available then save the
367 * hardware state in current's fpstate so that the
368 * supervisor state is preserved. Save the full state for
369 * simplicity. There is no point in optimizing this by only
370 * saving the supervisor states and then shuffle them to
371 * the right place in memory. It's ia32 mode. Shrug.
372 */
373 if (xfeatures_mask_supervisor())
374 os_xsave(fpstate: fpu->fpstate);
375 set_thread_flag(TIF_NEED_FPU_LOAD);
376 }
377 __fpu_invalidate_fpregs_state(fpu);
378 __cpu_invalidate_fpregs_state();
379 fpregs_unlock();
380
381 fpregs = &fpu->fpstate->regs;
382 if (use_xsave() && !fx_only) {
383 if (copy_sigframe_from_user_to_xstate(tsk, ubuf: buf_fx))
384 return false;
385 } else {
386 if (__copy_from_user(to: &fpregs->fxsave, from: buf_fx,
387 n: sizeof(fpregs->fxsave)))
388 return false;
389
390 if (IS_ENABLED(CONFIG_X86_64)) {
391 /* Reject invalid MXCSR values. */
392 if (fpregs->fxsave.mxcsr & ~mxcsr_feature_mask)
393 return false;
394 } else {
395 /* Mask invalid bits out for historical reasons (broken hardware). */
396 fpregs->fxsave.mxcsr &= mxcsr_feature_mask;
397 }
398
399 /* Enforce XFEATURE_MASK_FPSSE when XSAVE is enabled */
400 if (use_xsave())
401 fpregs->xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;
402 }
403
404 /* Fold the legacy FP storage */
405 convert_to_fxsr(fxsave: &fpregs->fxsave, env: &env);
406
407 fpregs_lock();
408 if (use_xsave()) {
409 /*
410 * Remove all UABI feature bits not set in user_xfeatures
411 * from the memory xstate header which makes the full
412 * restore below bring them into init state. This works for
413 * fx_only mode as well because that has only FP and SSE
414 * set in user_xfeatures.
415 *
416 * Preserve supervisor states!
417 */
418 u64 mask = user_xfeatures | xfeatures_mask_supervisor();
419
420 fpregs->xsave.header.xfeatures &= mask;
421 success = !os_xrstor_safe(fpstate: fpu->fpstate,
422 mask: fpu_kernel_cfg.max_features);
423 } else {
424 success = !fxrstor_safe(fx: &fpregs->fxsave);
425 }
426
427 if (likely(success))
428 fpregs_mark_activate();
429
430 fpregs_unlock();
431 return success;
432}
433
434static inline unsigned int xstate_sigframe_size(struct fpstate *fpstate)
435{
436 unsigned int size = fpstate->user_size;
437
438 return use_xsave() ? size + FP_XSTATE_MAGIC2_SIZE : size;
439}
440
441/*
442 * Restore FPU state from a sigframe:
443 */
444bool fpu__restore_sig(void __user *buf, int ia32_frame)
445{
446 struct fpu *fpu = x86_task_fpu(current);
447 void __user *buf_fx = buf;
448 bool ia32_fxstate = false;
449 bool success = false;
450 unsigned int size;
451
452 if (unlikely(!buf)) {
453 fpu__clear_user_states(fpu);
454 return true;
455 }
456
457 size = xstate_sigframe_size(fpstate: fpu->fpstate);
458
459 ia32_frame &= (IS_ENABLED(CONFIG_X86_32) ||
460 IS_ENABLED(CONFIG_IA32_EMULATION));
461
462 /*
463 * Only FXSR enabled systems need the FX state quirk.
464 * FRSTOR does not need it and can use the fast path.
465 */
466 if (ia32_frame && use_fxsr()) {
467 buf_fx = buf + sizeof(struct fregs_state);
468 size += sizeof(struct fregs_state);
469 ia32_fxstate = true;
470 }
471
472 if (!access_ok(buf, size))
473 goto out;
474
475 if (!IS_ENABLED(CONFIG_X86_64) && !cpu_feature_enabled(X86_FEATURE_FPU)) {
476 success = !fpregs_soft_set(current, NULL, 0,
477 sizeof(struct user_i387_ia32_struct),
478 NULL, buf);
479 } else {
480 success = __fpu_restore_sig(buf, buf_fx, ia32_fxstate);
481 }
482
483out:
484 if (unlikely(!success))
485 fpu__clear_user_states(fpu);
486 return success;
487}
488
489unsigned long
490fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
491 unsigned long *buf_fx, unsigned long *size)
492{
493 unsigned long frame_size = xstate_sigframe_size(fpstate: x86_task_fpu(current)->fpstate);
494
495 *buf_fx = sp = round_down(sp - frame_size, 64);
496 if (ia32_frame && use_fxsr()) {
497 frame_size += sizeof(struct fregs_state);
498 sp -= sizeof(struct fregs_state);
499 }
500
501 *size = frame_size;
502
503 return sp;
504}
505
506unsigned long __init fpu__get_fpstate_size(void)
507{
508 unsigned long ret = fpu_user_cfg.max_size;
509
510 if (use_xsave())
511 ret += FP_XSTATE_MAGIC2_SIZE;
512
513 /*
514 * This space is needed on (most) 32-bit kernels, or when a 32-bit
515 * app is running on a 64-bit kernel. To keep things simple, just
516 * assume the worst case and always include space for 'freg_state',
517 * even for 64-bit apps on 64-bit kernels. This wastes a bit of
518 * space, but keeps the code simple.
519 */
520 if ((IS_ENABLED(CONFIG_IA32_EMULATION) ||
521 IS_ENABLED(CONFIG_X86_32)) && use_fxsr())
522 ret += sizeof(struct fregs_state);
523
524 return ret;
525}
526
527