1 // SPDX-License-Identifier: GPL-2.0
3 * FPU signal frame handling routines.
6 #include <linux/compat.h>
8 #include <linux/pagemap.h>
10 #include <asm/fpu/internal.h>
11 #include <asm/fpu/signal.h>
12 #include <asm/fpu/regset.h>
13 #include <asm/fpu/xstate.h>
15 #include <asm/sigframe.h>
16 #include <asm/trace/fpu.h>
18 static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
21 * Check for the presence of extended state information in the
22 * user fpstate pointer in the sigcontext.
24 static inline int check_for_xstate(struct fxregs_state __user *buf,
26 struct _fpx_sw_bytes *fx_sw)
28 int min_xstate_size = sizeof(struct fxregs_state) +
29 sizeof(struct xstate_header);
32 if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
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)
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.
48 if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
49 || magic2 != FP_XSTATE_MAGIC2)
56 * Signal frame handlers.
58 static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
61 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
62 struct user_i387_ia32_struct env;
63 struct _fpstate_32 __user *fp = buf;
66 if (!test_thread_flag(TIF_NEED_FPU_LOAD))
67 copy_fxregs_to_kernel(&tsk->thread.fpu);
70 convert_from_fxsr(&env, tsk);
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))
77 struct fregs_state __user *fp = buf;
79 if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
86 static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
88 struct xregs_state __user *x = buf;
89 struct _fpx_sw_bytes *sw_bytes;
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));
100 err |= __put_user(FP_XSTATE_MAGIC2,
101 (__u32 __user *)(buf + fpu_user_xstate_size));
104 * Read the xfeatures which we copied (directly from the cpu or
105 * from the state in task struct) to the user buffers.
107 err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
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.
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.
120 xfeatures |= XFEATURE_MASK_FPSSE;
122 err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
127 static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
132 err = copy_xregs_to_user(buf);
134 err = copy_fxregs_to_user((struct fxregs_state __user *) buf);
136 err = copy_fregs_to_user((struct fregs_state __user *) buf);
138 if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
144 * Save the fpu, extended register state to the user signal frame.
146 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
148 * 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
150 * buf == buf_fx for 64-bit frames and 32-bit fsave frame.
151 * buf != buf_fx for 32-bit frames with fxstate.
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'.
158 * If this is a 32-bit frame with fxstate, put a fsave header before
159 * the aligned state at 'buf_fx'.
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.
164 int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
166 struct task_struct *tsk = current;
167 int ia32_fxstate = (buf != buf_fx);
170 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
171 IS_ENABLED(CONFIG_IA32_EMULATION));
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;
180 if (!access_ok(buf, size))
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.
190 if (test_thread_flag(TIF_NEED_FPU_LOAD))
191 __fpregs_load_activate();
194 ret = copy_fpregs_to_sigframe(buf_fx);
199 if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
204 /* Save the fsave header for the 32-bit frames. */
205 if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
208 if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
215 sanitize_restored_user_xstate(union fpregs_state *state,
216 struct user_i387_ia32_struct *ia32_env,
217 u64 user_xfeatures, int fx_only)
219 struct xregs_state *xsave = &state->xsave;
220 struct xstate_header *header = &xsave->header;
224 * Clear all feature bits which are not set in
225 * user_xfeatures and clear all extended features
228 u64 mask = fx_only ? XFEATURE_MASK_FPSSE : user_xfeatures;
231 * Supervisor state has to be preserved. The sigframe
232 * restore can only modify user features, i.e. @mask
233 * cannot contain them.
235 header->xfeatures &= mask | xfeatures_mask_supervisor();
240 * mscsr reserved bits must be masked to zero for security
243 xsave->i387.mxcsr &= mxcsr_feature_mask;
246 convert_to_fxsr(&state->fxsave, ia32_env);
251 * Restore the extended state if present. Otherwise, restore the FP/SSE state.
253 static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
260 init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
262 r = copy_user_to_fxregs(buf);
264 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
267 init_bv = xfeatures_mask_user() & ~xbv;
269 r = copy_user_to_xregs(buf, xbv);
270 if (!r && unlikely(init_bv))
271 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
274 } else if (use_fxsr()) {
275 return copy_user_to_fxregs(buf);
277 return copy_user_to_fregs(buf);
280 static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
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;
292 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
293 IS_ENABLED(CONFIG_IA32_EMULATION));
296 fpu__clear_user_states(fpu);
300 if (!access_ok(buf, size)) {
305 if (!static_cpu_has(X86_FEATURE_FPU)) {
306 ret = fpregs_soft_set(current, NULL, 0,
307 sizeof(struct user_i387_ia32_struct),
313 struct _fpx_sw_bytes fx_sw_user;
314 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
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.
320 state_size = sizeof(struct fxregs_state);
322 trace_x86_fpu_xstate_check_failed(fpu);
324 state_size = fx_sw_user.xstate_size;
325 user_xfeatures = fx_sw_user.xfeatures;
329 if ((unsigned long)buf_fx % 64)
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
342 ret = copy_user_to_fpregs_zeroing(buf_fx, user_xfeatures, fx_only);
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
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.
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();
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
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
378 * In case current owns the FPU registers then no further
379 * action is required. The fixup below will handle it
382 if (test_thread_flag(TIF_NEED_FPU_LOAD))
383 __cpu_invalidate_fpregs_state();
388 * For 32-bit frames with fxstate, copy the fxstate so it can
389 * be reconstructed later.
391 ret = __copy_from_user(&env, buf, sizeof(env));
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
405 if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
408 * Supervisor states are not modified by user space input. Save
409 * current supervisor states first and invalidate the FPU regs.
411 if (xfeatures_mask_supervisor())
412 copy_supervisor_to_kernel(&fpu->state.xsave);
413 set_thread_flag(TIF_NEED_FPU_LOAD);
415 __fpu_invalidate_fpregs_state(fpu);
418 if (use_xsave() && !fx_only) {
419 u64 init_bv = xfeatures_mask_user() & ~user_xfeatures;
421 ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
425 sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
429 if (unlikely(init_bv))
430 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
433 * Restore previously saved supervisor xstates along with
434 * copied-in user xstates.
436 ret = copy_kernel_to_xregs_err(&fpu->state.xsave,
437 user_xfeatures | xfeatures_mask_supervisor());
439 } else if (use_fxsr()) {
440 ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
446 sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
453 init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
454 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
457 ret = copy_kernel_to_fxregs_err(&fpu->state.fxsave);
459 ret = __copy_from_user(&fpu->state.fsave, buf_fx, state_size);
464 ret = copy_kernel_to_fregs_err(&fpu->state.fsave);
467 fpregs_mark_activate();
469 fpregs_deactivate(fpu);
474 fpu__clear_user_states(fpu);
478 static inline int xstate_sigframe_size(void)
480 return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
481 fpu_user_xstate_size;
485 * Restore FPU state from a sigframe:
487 int fpu__restore_sig(void __user *buf, int ia32_frame)
489 void __user *buf_fx = buf;
490 int size = xstate_sigframe_size();
492 if (ia32_frame && use_fxsr()) {
493 buf_fx = buf + sizeof(struct fregs_state);
494 size += sizeof(struct fregs_state);
497 return __fpu__restore_sig(buf, buf_fx, size);
501 fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
502 unsigned long *buf_fx, unsigned long *size)
504 unsigned long frame_size = xstate_sigframe_size();
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);
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.
523 void fpu__init_prepare_fx_sw_frame(void)
525 int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
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;
532 if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
533 IS_ENABLED(CONFIG_X86_32)) {
534 int fsave_header_size = sizeof(struct fregs_state);
536 fx_sw_reserved_ia32 = fx_sw_reserved;
537 fx_sw_reserved_ia32.extended_size = size + fsave_header_size;