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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
18static 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 */
24static 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 */
58static 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
86static 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
127static 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 */
164int 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 (!access_ok(buf, size))
174 return -EACCES;
175
176 if (!static_cpu_has(X86_FEATURE_FPU))
177 return fpregs_soft_get(current, NULL, 0,
178 sizeof(struct user_i387_ia32_struct), NULL,
179 (struct _fpstate_32 __user *) buf) ? -1 : 1;
180
181retry:
182 /*
183 * Load the FPU registers if they are not valid for the current task.
184 * With a valid FPU state we can attempt to save the state directly to
185 * userland's stack frame which will likely succeed. If it does not,
186 * resolve the fault in the user memory and try again.
187 */
188 fpregs_lock();
189 if (test_thread_flag(TIF_NEED_FPU_LOAD))
190 __fpregs_load_activate();
191
192 pagefault_disable();
193 ret = copy_fpregs_to_sigframe(buf_fx);
194 pagefault_enable();
195 fpregs_unlock();
196
197 if (ret) {
198 if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
199 goto retry;
200 return -EFAULT;
201 }
202
203 /* Save the fsave header for the 32-bit frames. */
204 if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
205 return -1;
206
207 if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
208 return -1;
209
210 return 0;
211}
212
213static inline void
214sanitize_restored_xstate(union fpregs_state *state,
215 struct user_i387_ia32_struct *ia32_env,
216 u64 xfeatures, int fx_only)
217{
218 struct xregs_state *xsave = &state->xsave;
219 struct xstate_header *header = &xsave->header;
220
221 if (use_xsave()) {
222 /*
223 * Note: we don't need to zero the reserved bits in the
224 * xstate_header here because we either didn't copy them at all,
225 * or we checked earlier that they aren't set.
226 */
227
228 /*
229 * Init the state that is not present in the memory
230 * layout and not enabled by the OS.
231 */
232 if (fx_only)
233 header->xfeatures = XFEATURE_MASK_FPSSE;
234 else
235 header->xfeatures &= xfeatures;
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 */
253static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
254{
255 if (use_xsave()) {
256 if (fx_only) {
257 u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
258 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
259 return copy_user_to_fxregs(buf);
260 } else {
261 u64 init_bv = xfeatures_mask & ~xbv;
262 if (unlikely(init_bv))
263 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
264 return copy_user_to_xregs(buf, xbv);
265 }
266 } else if (use_fxsr()) {
267 return copy_user_to_fxregs(buf);
268 } else
269 return copy_user_to_fregs(buf);
270}
271
272static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
273{
274 struct user_i387_ia32_struct *envp = NULL;
275 int state_size = fpu_kernel_xstate_size;
276 int ia32_fxstate = (buf != buf_fx);
277 struct task_struct *tsk = current;
278 struct fpu *fpu = &tsk->thread.fpu;
279 struct user_i387_ia32_struct env;
280 u64 xfeatures = 0;
281 int fx_only = 0;
282 int ret = 0;
283
284 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
285 IS_ENABLED(CONFIG_IA32_EMULATION));
286
287 if (!buf) {
288 fpu__clear(fpu);
289 return 0;
290 }
291
292 if (!access_ok(buf, size))
293 return -EACCES;
294
295 if (!static_cpu_has(X86_FEATURE_FPU))
296 return fpregs_soft_set(current, NULL,
297 0, sizeof(struct user_i387_ia32_struct),
298 NULL, buf) != 0;
299
300 if (use_xsave()) {
301 struct _fpx_sw_bytes fx_sw_user;
302 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
303 /*
304 * Couldn't find the extended state information in the
305 * memory layout. Restore just the FP/SSE and init all
306 * the other extended state.
307 */
308 state_size = sizeof(struct fxregs_state);
309 fx_only = 1;
310 trace_x86_fpu_xstate_check_failed(fpu);
311 } else {
312 state_size = fx_sw_user.xstate_size;
313 xfeatures = fx_sw_user.xfeatures;
314 }
315 }
316
317 /*
318 * The current state of the FPU registers does not matter. By setting
319 * TIF_NEED_FPU_LOAD unconditionally it is ensured that the our xstate
320 * is not modified on context switch and that the xstate is considered
321 * to be loaded again on return to userland (overriding last_cpu avoids
322 * the optimisation).
323 */
324 set_thread_flag(TIF_NEED_FPU_LOAD);
325 __fpu_invalidate_fpregs_state(fpu);
326
327 if ((unsigned long)buf_fx % 64)
328 fx_only = 1;
329 /*
330 * For 32-bit frames with fxstate, copy the fxstate so it can be
331 * reconstructed later.
332 */
333 if (ia32_fxstate) {
334 ret = __copy_from_user(&env, buf, sizeof(env));
335 if (ret)
336 goto err_out;
337 envp = &env;
338 } else {
339 /*
340 * Attempt to restore the FPU registers directly from user
341 * memory. For that to succeed, the user access cannot cause
342 * page faults. If it does, fall back to the slow path below,
343 * going through the kernel buffer with the enabled pagefault
344 * handler.
345 */
346 fpregs_lock();
347 pagefault_disable();
348 ret = copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only);
349 pagefault_enable();
350 if (!ret) {
351 fpregs_mark_activate();
352 fpregs_unlock();
353 return 0;
354 }
355 fpregs_unlock();
356 }
357
358
359 if (use_xsave() && !fx_only) {
360 u64 init_bv = xfeatures_mask & ~xfeatures;
361
362 if (using_compacted_format()) {
363 ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
364 } else {
365 ret = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
366
367 if (!ret && state_size > offsetof(struct xregs_state, header))
368 ret = validate_xstate_header(&fpu->state.xsave.header);
369 }
370 if (ret)
371 goto err_out;
372
373 sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
374
375 fpregs_lock();
376 if (unlikely(init_bv))
377 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
378 ret = copy_kernel_to_xregs_err(&fpu->state.xsave, xfeatures);
379
380 } else if (use_fxsr()) {
381 ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
382 if (ret) {
383 ret = -EFAULT;
384 goto err_out;
385 }
386
387 sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
388
389 fpregs_lock();
390 if (use_xsave()) {
391 u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
392 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
393 }
394
395 ret = copy_kernel_to_fxregs_err(&fpu->state.fxsave);
396 } else {
397 ret = __copy_from_user(&fpu->state.fsave, buf_fx, state_size);
398 if (ret)
399 goto err_out;
400
401 fpregs_lock();
402 ret = copy_kernel_to_fregs_err(&fpu->state.fsave);
403 }
404 if (!ret)
405 fpregs_mark_activate();
406 fpregs_unlock();
407
408err_out:
409 if (ret)
410 fpu__clear(fpu);
411 return ret;
412}
413
414static inline int xstate_sigframe_size(void)
415{
416 return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
417 fpu_user_xstate_size;
418}
419
420/*
421 * Restore FPU state from a sigframe:
422 */
423int fpu__restore_sig(void __user *buf, int ia32_frame)
424{
425 void __user *buf_fx = buf;
426 int size = xstate_sigframe_size();
427
428 if (ia32_frame && use_fxsr()) {
429 buf_fx = buf + sizeof(struct fregs_state);
430 size += sizeof(struct fregs_state);
431 }
432
433 return __fpu__restore_sig(buf, buf_fx, size);
434}
435
436unsigned long
437fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
438 unsigned long *buf_fx, unsigned long *size)
439{
440 unsigned long frame_size = xstate_sigframe_size();
441
442 *buf_fx = sp = round_down(sp - frame_size, 64);
443 if (ia32_frame && use_fxsr()) {
444 frame_size += sizeof(struct fregs_state);
445 sp -= sizeof(struct fregs_state);
446 }
447
448 *size = frame_size;
449
450 return sp;
451}
452/*
453 * Prepare the SW reserved portion of the fxsave memory layout, indicating
454 * the presence of the extended state information in the memory layout
455 * pointed by the fpstate pointer in the sigcontext.
456 * This will be saved when ever the FP and extended state context is
457 * saved on the user stack during the signal handler delivery to the user.
458 */
459void fpu__init_prepare_fx_sw_frame(void)
460{
461 int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
462
463 fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
464 fx_sw_reserved.extended_size = size;
465 fx_sw_reserved.xfeatures = xfeatures_mask;
466 fx_sw_reserved.xstate_size = fpu_user_xstate_size;
467
468 if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
469 IS_ENABLED(CONFIG_X86_32)) {
470 int fsave_header_size = sizeof(struct fregs_state);
471
472 fx_sw_reserved_ia32 = fx_sw_reserved;
473 fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
474 }
475}
476