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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
9#include <asm/fpu/internal.h>
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/trace/fpu.h>
16
17static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
18
19/*
20 * Check for the presence of extended state information in the
21 * user fpstate pointer in the sigcontext.
22 */
23static inline int check_for_xstate(struct fxregs_state __user *buf,
24 void __user *fpstate,
25 struct _fpx_sw_bytes *fx_sw)
26{
27 int min_xstate_size = sizeof(struct fxregs_state) +
28 sizeof(struct xstate_header);
29 unsigned int magic2;
30
31 if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
32 return -1;
33
34 /* Check for the first magic field and other error scenarios. */
35 if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
36 fx_sw->xstate_size < min_xstate_size ||
37 fx_sw->xstate_size > fpu_user_xstate_size ||
38 fx_sw->xstate_size > fx_sw->extended_size)
39 return -1;
40
41 /*
42 * Check for the presence of second magic word at the end of memory
43 * layout. This detects the case where the user just copied the legacy
44 * fpstate layout with out copying the extended state information
45 * in the memory layout.
46 */
47 if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
48 || magic2 != FP_XSTATE_MAGIC2)
49 return -1;
50
51 return 0;
52}
53
54/*
55 * Signal frame handlers.
56 */
57static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
58{
59 if (use_fxsr()) {
60 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
61 struct user_i387_ia32_struct env;
62 struct _fpstate_32 __user *fp = buf;
63
64 convert_from_fxsr(&env, tsk);
65
66 if (__copy_to_user(buf, &env, sizeof(env)) ||
67 __put_user(xsave->i387.swd, &fp->status) ||
68 __put_user(X86_FXSR_MAGIC, &fp->magic))
69 return -1;
70 } else {
71 struct fregs_state __user *fp = buf;
72 u32 swd;
73 if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
74 return -1;
75 }
76
77 return 0;
78}
79
80static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
81{
82 struct xregs_state __user *x = buf;
83 struct _fpx_sw_bytes *sw_bytes;
84 u32 xfeatures;
85 int err;
86
87 /* Setup the bytes not touched by the [f]xsave and reserved for SW. */
88 sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
89 err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
90
91 if (!use_xsave())
92 return err;
93
94 err |= __put_user(FP_XSTATE_MAGIC2,
95 (__u32 *)(buf + fpu_user_xstate_size));
96
97 /*
98 * Read the xfeatures which we copied (directly from the cpu or
99 * from the state in task struct) to the user buffers.
100 */
101 err |= __get_user(xfeatures, (__u32 *)&x->header.xfeatures);
102
103 /*
104 * For legacy compatible, we always set FP/SSE bits in the bit
105 * vector while saving the state to the user context. This will
106 * enable us capturing any changes(during sigreturn) to
107 * the FP/SSE bits by the legacy applications which don't touch
108 * xfeatures in the xsave header.
109 *
110 * xsave aware apps can change the xfeatures in the xsave
111 * header as well as change any contents in the memory layout.
112 * xrestore as part of sigreturn will capture all the changes.
113 */
114 xfeatures |= XFEATURE_MASK_FPSSE;
115
116 err |= __put_user(xfeatures, (__u32 *)&x->header.xfeatures);
117
118 return err;
119}
120
121static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
122{
123 int err;
124
125 if (use_xsave())
126 err = copy_xregs_to_user(buf);
127 else if (use_fxsr())
128 err = copy_fxregs_to_user((struct fxregs_state __user *) buf);
129 else
130 err = copy_fregs_to_user((struct fregs_state __user *) buf);
131
132 if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
133 err = -EFAULT;
134 return err;
135}
136
137/*
138 * Save the fpu, extended register state to the user signal frame.
139 *
140 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
141 * state is copied.
142 * 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
143 *
144 * buf == buf_fx for 64-bit frames and 32-bit fsave frame.
145 * buf != buf_fx for 32-bit frames with fxstate.
146 *
147 * If the fpu, extended register state is live, save the state directly
148 * to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise,
149 * copy the thread's fpu state to the user frame starting at 'buf_fx'.
150 *
151 * If this is a 32-bit frame with fxstate, put a fsave header before
152 * the aligned state at 'buf_fx'.
153 *
154 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
155 * indicating the absence/presence of the extended state to the user.
156 */
157int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
158{
159 struct fpu *fpu = ¤t->thread.fpu;
160 struct xregs_state *xsave = &fpu->state.xsave;
161 struct task_struct *tsk = current;
162 int ia32_fxstate = (buf != buf_fx);
163
164 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
165 IS_ENABLED(CONFIG_IA32_EMULATION));
166
167 if (!access_ok(VERIFY_WRITE, buf, size))
168 return -EACCES;
169
170 if (!static_cpu_has(X86_FEATURE_FPU))
171 return fpregs_soft_get(current, NULL, 0,
172 sizeof(struct user_i387_ia32_struct), NULL,
173 (struct _fpstate_32 __user *) buf) ? -1 : 1;
174
175 if (fpu->initialized || using_compacted_format()) {
176 /* Save the live register state to the user directly. */
177 if (copy_fpregs_to_sigframe(buf_fx))
178 return -1;
179 /* Update the thread's fxstate to save the fsave header. */
180 if (ia32_fxstate)
181 copy_fxregs_to_kernel(fpu);
182 } else {
183 /*
184 * It is a *bug* if kernel uses compacted-format for xsave
185 * area and we copy it out directly to a signal frame. It
186 * should have been handled above by saving the registers
187 * directly.
188 */
189 if (boot_cpu_has(X86_FEATURE_XSAVES)) {
190 WARN_ONCE(1, "x86/fpu: saving compacted-format xsave area to a signal frame!\n");
191 return -1;
192 }
193
194 fpstate_sanitize_xstate(fpu);
195 if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size))
196 return -1;
197 }
198
199 /* Save the fsave header for the 32-bit frames. */
200 if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
201 return -1;
202
203 if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
204 return -1;
205
206 return 0;
207}
208
209static inline void
210sanitize_restored_xstate(struct task_struct *tsk,
211 struct user_i387_ia32_struct *ia32_env,
212 u64 xfeatures, int fx_only)
213{
214 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
215 struct xstate_header *header = &xsave->header;
216
217 if (use_xsave()) {
218 /*
219 * Note: we don't need to zero the reserved bits in the
220 * xstate_header here because we either didn't copy them at all,
221 * or we checked earlier that they aren't set.
222 */
223
224 /*
225 * Init the state that is not present in the memory
226 * layout and not enabled by the OS.
227 */
228 if (fx_only)
229 header->xfeatures = XFEATURE_MASK_FPSSE;
230 else
231 header->xfeatures &= xfeatures;
232 }
233
234 if (use_fxsr()) {
235 /*
236 * mscsr reserved bits must be masked to zero for security
237 * reasons.
238 */
239 xsave->i387.mxcsr &= mxcsr_feature_mask;
240
241 convert_to_fxsr(tsk, ia32_env);
242 }
243}
244
245/*
246 * Restore the extended state if present. Otherwise, restore the FP/SSE state.
247 */
248static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
249{
250 if (use_xsave()) {
251 if ((unsigned long)buf % 64 || fx_only) {
252 u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
253 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
254 return copy_user_to_fxregs(buf);
255 } else {
256 u64 init_bv = xfeatures_mask & ~xbv;
257 if (unlikely(init_bv))
258 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
259 return copy_user_to_xregs(buf, xbv);
260 }
261 } else if (use_fxsr()) {
262 return copy_user_to_fxregs(buf);
263 } else
264 return copy_user_to_fregs(buf);
265}
266
267static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
268{
269 int ia32_fxstate = (buf != buf_fx);
270 struct task_struct *tsk = current;
271 struct fpu *fpu = &tsk->thread.fpu;
272 int state_size = fpu_kernel_xstate_size;
273 u64 xfeatures = 0;
274 int fx_only = 0;
275
276 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
277 IS_ENABLED(CONFIG_IA32_EMULATION));
278
279 if (!buf) {
280 fpu__clear(fpu);
281 return 0;
282 }
283
284 if (!access_ok(VERIFY_READ, buf, size))
285 return -EACCES;
286
287 fpu__initialize(fpu);
288
289 if (!static_cpu_has(X86_FEATURE_FPU))
290 return fpregs_soft_set(current, NULL,
291 0, sizeof(struct user_i387_ia32_struct),
292 NULL, buf) != 0;
293
294 if (use_xsave()) {
295 struct _fpx_sw_bytes fx_sw_user;
296 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
297 /*
298 * Couldn't find the extended state information in the
299 * memory layout. Restore just the FP/SSE and init all
300 * the other extended state.
301 */
302 state_size = sizeof(struct fxregs_state);
303 fx_only = 1;
304 trace_x86_fpu_xstate_check_failed(fpu);
305 } else {
306 state_size = fx_sw_user.xstate_size;
307 xfeatures = fx_sw_user.xfeatures;
308 }
309 }
310
311 if (ia32_fxstate) {
312 /*
313 * For 32-bit frames with fxstate, copy the user state to the
314 * thread's fpu state, reconstruct fxstate from the fsave
315 * header. Validate and sanitize the copied state.
316 */
317 struct fpu *fpu = &tsk->thread.fpu;
318 struct user_i387_ia32_struct env;
319 int err = 0;
320
321 /*
322 * Drop the current fpu which clears fpu->initialized. This ensures
323 * that any context-switch during the copy of the new state,
324 * avoids the intermediate state from getting restored/saved.
325 * Thus avoiding the new restored state from getting corrupted.
326 * We will be ready to restore/save the state only after
327 * fpu->initialized is again set.
328 */
329 fpu__drop(fpu);
330
331 if (using_compacted_format()) {
332 err = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
333 } else {
334 err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
335
336 if (!err && state_size > offsetof(struct xregs_state, header))
337 err = validate_xstate_header(&fpu->state.xsave.header);
338 }
339
340 if (err || __copy_from_user(&env, buf, sizeof(env))) {
341 fpstate_init(&fpu->state);
342 trace_x86_fpu_init_state(fpu);
343 err = -1;
344 } else {
345 sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
346 }
347
348 fpu->initialized = 1;
349 preempt_disable();
350 fpu__restore(fpu);
351 preempt_enable();
352
353 return err;
354 } else {
355 /*
356 * For 64-bit frames and 32-bit fsave frames, restore the user
357 * state to the registers directly (with exceptions handled).
358 */
359 user_fpu_begin();
360 if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
361 fpu__clear(fpu);
362 return -1;
363 }
364 }
365
366 return 0;
367}
368
369static inline int xstate_sigframe_size(void)
370{
371 return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
372 fpu_user_xstate_size;
373}
374
375/*
376 * Restore FPU state from a sigframe:
377 */
378int fpu__restore_sig(void __user *buf, int ia32_frame)
379{
380 void __user *buf_fx = buf;
381 int size = xstate_sigframe_size();
382
383 if (ia32_frame && use_fxsr()) {
384 buf_fx = buf + sizeof(struct fregs_state);
385 size += sizeof(struct fregs_state);
386 }
387
388 return __fpu__restore_sig(buf, buf_fx, size);
389}
390
391unsigned long
392fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
393 unsigned long *buf_fx, unsigned long *size)
394{
395 unsigned long frame_size = xstate_sigframe_size();
396
397 *buf_fx = sp = round_down(sp - frame_size, 64);
398 if (ia32_frame && use_fxsr()) {
399 frame_size += sizeof(struct fregs_state);
400 sp -= sizeof(struct fregs_state);
401 }
402
403 *size = frame_size;
404
405 return sp;
406}
407/*
408 * Prepare the SW reserved portion of the fxsave memory layout, indicating
409 * the presence of the extended state information in the memory layout
410 * pointed by the fpstate pointer in the sigcontext.
411 * This will be saved when ever the FP and extended state context is
412 * saved on the user stack during the signal handler delivery to the user.
413 */
414void fpu__init_prepare_fx_sw_frame(void)
415{
416 int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
417
418 fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
419 fx_sw_reserved.extended_size = size;
420 fx_sw_reserved.xfeatures = xfeatures_mask;
421 fx_sw_reserved.xstate_size = fpu_user_xstate_size;
422
423 if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
424 IS_ENABLED(CONFIG_X86_32)) {
425 int fsave_header_size = sizeof(struct fregs_state);
426
427 fx_sw_reserved_ia32 = fx_sw_reserved;
428 fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
429 }
430}
431
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 __ro_after_init;
19static struct _fpx_sw_bytes fx_sw_reserved_ia32 __ro_after_init;
20
21/*
22 * Check for the presence of extended state information in the
23 * user fpstate pointer in the sigcontext.
24 */
25static inline int check_xstate_in_sigframe(struct fxregs_state __user *fxbuf,
26 struct _fpx_sw_bytes *fx_sw)
27{
28 int min_xstate_size = sizeof(struct fxregs_state) +
29 sizeof(struct xstate_header);
30 void __user *fpstate = fxbuf;
31 unsigned int magic2;
32
33 if (__copy_from_user(fx_sw, &fxbuf->sw_reserved[0], sizeof(*fx_sw)))
34 return -EFAULT;
35
36 /* Check for the first magic field and other error scenarios. */
37 if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
38 fx_sw->xstate_size < min_xstate_size ||
39 fx_sw->xstate_size > fpu_user_xstate_size ||
40 fx_sw->xstate_size > fx_sw->extended_size)
41 goto setfx;
42
43 /*
44 * Check for the presence of second magic word at the end of memory
45 * layout. This detects the case where the user just copied the legacy
46 * fpstate layout with out copying the extended state information
47 * in the memory layout.
48 */
49 if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size)))
50 return -EFAULT;
51
52 if (likely(magic2 == FP_XSTATE_MAGIC2))
53 return 0;
54setfx:
55 trace_x86_fpu_xstate_check_failed(¤t->thread.fpu);
56
57 /* Set the parameters for fx only state */
58 fx_sw->magic1 = 0;
59 fx_sw->xstate_size = sizeof(struct fxregs_state);
60 fx_sw->xfeatures = XFEATURE_MASK_FPSSE;
61 return 0;
62}
63
64/*
65 * Signal frame handlers.
66 */
67static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
68{
69 if (use_fxsr()) {
70 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
71 struct user_i387_ia32_struct env;
72 struct _fpstate_32 __user *fp = buf;
73
74 fpregs_lock();
75 if (!test_thread_flag(TIF_NEED_FPU_LOAD))
76 fxsave(&tsk->thread.fpu.state.fxsave);
77 fpregs_unlock();
78
79 convert_from_fxsr(&env, tsk);
80
81 if (__copy_to_user(buf, &env, sizeof(env)) ||
82 __put_user(xsave->i387.swd, &fp->status) ||
83 __put_user(X86_FXSR_MAGIC, &fp->magic))
84 return -1;
85 } else {
86 struct fregs_state __user *fp = buf;
87 u32 swd;
88 if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
89 return -1;
90 }
91
92 return 0;
93}
94
95static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
96{
97 struct xregs_state __user *x = buf;
98 struct _fpx_sw_bytes *sw_bytes;
99 u32 xfeatures;
100 int err;
101
102 /* Setup the bytes not touched by the [f]xsave and reserved for SW. */
103 sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
104 err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
105
106 if (!use_xsave())
107 return err;
108
109 err |= __put_user(FP_XSTATE_MAGIC2,
110 (__u32 __user *)(buf + fpu_user_xstate_size));
111
112 /*
113 * Read the xfeatures which we copied (directly from the cpu or
114 * from the state in task struct) to the user buffers.
115 */
116 err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
117
118 /*
119 * For legacy compatible, we always set FP/SSE bits in the bit
120 * vector while saving the state to the user context. This will
121 * enable us capturing any changes(during sigreturn) to
122 * the FP/SSE bits by the legacy applications which don't touch
123 * xfeatures in the xsave header.
124 *
125 * xsave aware apps can change the xfeatures in the xsave
126 * header as well as change any contents in the memory layout.
127 * xrestore as part of sigreturn will capture all the changes.
128 */
129 xfeatures |= XFEATURE_MASK_FPSSE;
130
131 err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
132
133 return err;
134}
135
136static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
137{
138 int err;
139
140 if (use_xsave())
141 err = xsave_to_user_sigframe(buf);
142 else if (use_fxsr())
143 err = fxsave_to_user_sigframe((struct fxregs_state __user *) buf);
144 else
145 err = fnsave_to_user_sigframe((struct fregs_state __user *) buf);
146
147 if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
148 err = -EFAULT;
149 return err;
150}
151
152/*
153 * Save the fpu, extended register state to the user signal frame.
154 *
155 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
156 * state is copied.
157 * 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
158 *
159 * buf == buf_fx for 64-bit frames and 32-bit fsave frame.
160 * buf != buf_fx for 32-bit frames with fxstate.
161 *
162 * Try to save it directly to the user frame with disabled page fault handler.
163 * If this fails then do the slow path where the FPU state is first saved to
164 * task's fpu->state and then copy it to the user frame pointed to by the
165 * aligned pointer 'buf_fx'.
166 *
167 * If this is a 32-bit frame with fxstate, put a fsave header before
168 * the aligned state at 'buf_fx'.
169 *
170 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
171 * indicating the absence/presence of the extended state to the user.
172 */
173int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
174{
175 struct task_struct *tsk = current;
176 int ia32_fxstate = (buf != buf_fx);
177 int ret;
178
179 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
180 IS_ENABLED(CONFIG_IA32_EMULATION));
181
182 if (!static_cpu_has(X86_FEATURE_FPU)) {
183 struct user_i387_ia32_struct fp;
184 fpregs_soft_get(current, NULL, (struct membuf){.p = &fp,
185 .left = sizeof(fp)});
186 return copy_to_user(buf, &fp, sizeof(fp)) ? -EFAULT : 0;
187 }
188
189 if (!access_ok(buf, size))
190 return -EACCES;
191retry:
192 /*
193 * Load the FPU registers if they are not valid for the current task.
194 * With a valid FPU state we can attempt to save the state directly to
195 * userland's stack frame which will likely succeed. If it does not,
196 * resolve the fault in the user memory and try again.
197 */
198 fpregs_lock();
199 if (test_thread_flag(TIF_NEED_FPU_LOAD))
200 fpregs_restore_userregs();
201
202 pagefault_disable();
203 ret = copy_fpregs_to_sigframe(buf_fx);
204 pagefault_enable();
205 fpregs_unlock();
206
207 if (ret) {
208 if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
209 goto retry;
210 return -EFAULT;
211 }
212
213 /* Save the fsave header for the 32-bit frames. */
214 if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
215 return -1;
216
217 if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
218 return -1;
219
220 return 0;
221}
222
223static int __restore_fpregs_from_user(void __user *buf, u64 xrestore,
224 bool fx_only)
225{
226 if (use_xsave()) {
227 u64 init_bv = xfeatures_mask_uabi() & ~xrestore;
228 int ret;
229
230 if (likely(!fx_only))
231 ret = xrstor_from_user_sigframe(buf, xrestore);
232 else
233 ret = fxrstor_from_user_sigframe(buf);
234
235 if (!ret && unlikely(init_bv))
236 os_xrstor(&init_fpstate.xsave, init_bv);
237 return ret;
238 } else if (use_fxsr()) {
239 return fxrstor_from_user_sigframe(buf);
240 } else {
241 return frstor_from_user_sigframe(buf);
242 }
243}
244
245/*
246 * Attempt to restore the FPU registers directly from user memory.
247 * Pagefaults are handled and any errors returned are fatal.
248 */
249static int restore_fpregs_from_user(void __user *buf, u64 xrestore,
250 bool fx_only, unsigned int size)
251{
252 struct fpu *fpu = ¤t->thread.fpu;
253 int ret;
254
255retry:
256 fpregs_lock();
257 pagefault_disable();
258 ret = __restore_fpregs_from_user(buf, xrestore, fx_only);
259 pagefault_enable();
260
261 if (unlikely(ret)) {
262 /*
263 * The above did an FPU restore operation, restricted to
264 * the user portion of the registers, and failed, but the
265 * microcode might have modified the FPU registers
266 * nevertheless.
267 *
268 * If the FPU registers do not belong to current, then
269 * invalidate the FPU register state otherwise the task
270 * might preempt current and return to user space with
271 * corrupted FPU registers.
272 */
273 if (test_thread_flag(TIF_NEED_FPU_LOAD))
274 __cpu_invalidate_fpregs_state();
275 fpregs_unlock();
276
277 /* Try to handle #PF, but anything else is fatal. */
278 if (ret != -EFAULT)
279 return -EINVAL;
280
281 ret = fault_in_pages_readable(buf, size);
282 if (!ret)
283 goto retry;
284 return ret;
285 }
286
287 /*
288 * Restore supervisor states: previous context switch etc has done
289 * XSAVES and saved the supervisor states in the kernel buffer from
290 * which they can be restored now.
291 *
292 * It would be optimal to handle this with a single XRSTORS, but
293 * this does not work because the rest of the FPU registers have
294 * been restored from a user buffer directly.
295 */
296 if (test_thread_flag(TIF_NEED_FPU_LOAD) && xfeatures_mask_supervisor())
297 os_xrstor(&fpu->state.xsave, xfeatures_mask_supervisor());
298
299 fpregs_mark_activate();
300 fpregs_unlock();
301 return 0;
302}
303
304static int __fpu_restore_sig(void __user *buf, void __user *buf_fx,
305 bool ia32_fxstate)
306{
307 int state_size = fpu_kernel_xstate_size;
308 struct task_struct *tsk = current;
309 struct fpu *fpu = &tsk->thread.fpu;
310 struct user_i387_ia32_struct env;
311 u64 user_xfeatures = 0;
312 bool fx_only = false;
313 int ret;
314
315 if (use_xsave()) {
316 struct _fpx_sw_bytes fx_sw_user;
317
318 ret = check_xstate_in_sigframe(buf_fx, &fx_sw_user);
319 if (unlikely(ret))
320 return ret;
321
322 fx_only = !fx_sw_user.magic1;
323 state_size = fx_sw_user.xstate_size;
324 user_xfeatures = fx_sw_user.xfeatures;
325 } else {
326 user_xfeatures = XFEATURE_MASK_FPSSE;
327 }
328
329 if (likely(!ia32_fxstate)) {
330 /*
331 * Attempt to restore the FPU registers directly from user
332 * memory. For that to succeed, the user access cannot cause page
333 * faults. If it does, fall back to the slow path below, going
334 * through the kernel buffer with the enabled pagefault handler.
335 */
336 return restore_fpregs_from_user(buf_fx, user_xfeatures, fx_only,
337 state_size);
338 }
339
340 /*
341 * Copy the legacy state because the FP portion of the FX frame has
342 * to be ignored for histerical raisins. The legacy state is folded
343 * in once the larger state has been copied.
344 */
345 ret = __copy_from_user(&env, buf, sizeof(env));
346 if (ret)
347 return ret;
348
349 /*
350 * By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is
351 * not modified on context switch and that the xstate is considered
352 * to be loaded again on return to userland (overriding last_cpu avoids
353 * the optimisation).
354 */
355 fpregs_lock();
356 if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
357 /*
358 * If supervisor states are available then save the
359 * hardware state in current's fpstate so that the
360 * supervisor state is preserved. Save the full state for
361 * simplicity. There is no point in optimizing this by only
362 * saving the supervisor states and then shuffle them to
363 * the right place in memory. It's ia32 mode. Shrug.
364 */
365 if (xfeatures_mask_supervisor())
366 os_xsave(&fpu->state.xsave);
367 set_thread_flag(TIF_NEED_FPU_LOAD);
368 }
369 __fpu_invalidate_fpregs_state(fpu);
370 __cpu_invalidate_fpregs_state();
371 fpregs_unlock();
372
373 if (use_xsave() && !fx_only) {
374 ret = copy_sigframe_from_user_to_xstate(&fpu->state.xsave, buf_fx);
375 if (ret)
376 return ret;
377 } else {
378 if (__copy_from_user(&fpu->state.fxsave, buf_fx,
379 sizeof(fpu->state.fxsave)))
380 return -EFAULT;
381
382 if (IS_ENABLED(CONFIG_X86_64)) {
383 /* Reject invalid MXCSR values. */
384 if (fpu->state.fxsave.mxcsr & ~mxcsr_feature_mask)
385 return -EINVAL;
386 } else {
387 /* Mask invalid bits out for historical reasons (broken hardware). */
388 fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;
389 }
390
391 /* Enforce XFEATURE_MASK_FPSSE when XSAVE is enabled */
392 if (use_xsave())
393 fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;
394 }
395
396 /* Fold the legacy FP storage */
397 convert_to_fxsr(&fpu->state.fxsave, &env);
398
399 fpregs_lock();
400 if (use_xsave()) {
401 /*
402 * Remove all UABI feature bits not set in user_xfeatures
403 * from the memory xstate header which makes the full
404 * restore below bring them into init state. This works for
405 * fx_only mode as well because that has only FP and SSE
406 * set in user_xfeatures.
407 *
408 * Preserve supervisor states!
409 */
410 u64 mask = user_xfeatures | xfeatures_mask_supervisor();
411
412 fpu->state.xsave.header.xfeatures &= mask;
413 ret = os_xrstor_safe(&fpu->state.xsave, xfeatures_mask_all);
414 } else {
415 ret = fxrstor_safe(&fpu->state.fxsave);
416 }
417
418 if (likely(!ret))
419 fpregs_mark_activate();
420
421 fpregs_unlock();
422 return ret;
423}
424static inline int xstate_sigframe_size(void)
425{
426 return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
427 fpu_user_xstate_size;
428}
429
430/*
431 * Restore FPU state from a sigframe:
432 */
433int fpu__restore_sig(void __user *buf, int ia32_frame)
434{
435 unsigned int size = xstate_sigframe_size();
436 struct fpu *fpu = ¤t->thread.fpu;
437 void __user *buf_fx = buf;
438 bool ia32_fxstate = false;
439 int ret;
440
441 if (unlikely(!buf)) {
442 fpu__clear_user_states(fpu);
443 return 0;
444 }
445
446 ia32_frame &= (IS_ENABLED(CONFIG_X86_32) ||
447 IS_ENABLED(CONFIG_IA32_EMULATION));
448
449 /*
450 * Only FXSR enabled systems need the FX state quirk.
451 * FRSTOR does not need it and can use the fast path.
452 */
453 if (ia32_frame && use_fxsr()) {
454 buf_fx = buf + sizeof(struct fregs_state);
455 size += sizeof(struct fregs_state);
456 ia32_fxstate = true;
457 }
458
459 if (!access_ok(buf, size)) {
460 ret = -EACCES;
461 goto out;
462 }
463
464 if (!IS_ENABLED(CONFIG_X86_64) && !cpu_feature_enabled(X86_FEATURE_FPU)) {
465 ret = fpregs_soft_set(current, NULL, 0,
466 sizeof(struct user_i387_ia32_struct),
467 NULL, buf);
468 } else {
469 ret = __fpu_restore_sig(buf, buf_fx, ia32_fxstate);
470 }
471
472out:
473 if (unlikely(ret))
474 fpu__clear_user_states(fpu);
475 return ret;
476}
477
478unsigned long
479fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
480 unsigned long *buf_fx, unsigned long *size)
481{
482 unsigned long frame_size = xstate_sigframe_size();
483
484 *buf_fx = sp = round_down(sp - frame_size, 64);
485 if (ia32_frame && use_fxsr()) {
486 frame_size += sizeof(struct fregs_state);
487 sp -= sizeof(struct fregs_state);
488 }
489
490 *size = frame_size;
491
492 return sp;
493}
494
495unsigned long fpu__get_fpstate_size(void)
496{
497 unsigned long ret = xstate_sigframe_size();
498
499 /*
500 * This space is needed on (most) 32-bit kernels, or when a 32-bit
501 * app is running on a 64-bit kernel. To keep things simple, just
502 * assume the worst case and always include space for 'freg_state',
503 * even for 64-bit apps on 64-bit kernels. This wastes a bit of
504 * space, but keeps the code simple.
505 */
506 if ((IS_ENABLED(CONFIG_IA32_EMULATION) ||
507 IS_ENABLED(CONFIG_X86_32)) && use_fxsr())
508 ret += sizeof(struct fregs_state);
509
510 return ret;
511}
512
513/*
514 * Prepare the SW reserved portion of the fxsave memory layout, indicating
515 * the presence of the extended state information in the memory layout
516 * pointed by the fpstate pointer in the sigcontext.
517 * This will be saved when ever the FP and extended state context is
518 * saved on the user stack during the signal handler delivery to the user.
519 */
520void fpu__init_prepare_fx_sw_frame(void)
521{
522 int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
523
524 fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
525 fx_sw_reserved.extended_size = size;
526 fx_sw_reserved.xfeatures = xfeatures_mask_uabi();
527 fx_sw_reserved.xstate_size = fpu_user_xstate_size;
528
529 if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
530 IS_ENABLED(CONFIG_X86_32)) {
531 int fsave_header_size = sizeof(struct fregs_state);
532
533 fx_sw_reserved_ia32 = fx_sw_reserved;
534 fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
535 }
536}
537