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 = &current->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