1 /* 2 * Copyright (C) 1994 Linus Torvalds 3 * 4 * Pentium III FXSR, SSE support 5 * General FPU state handling cleanups 6 * Gareth Hughes <gareth@valinux.com>, May 2000 7 * x86-64 work by Andi Kleen 2002 8 */ 9 10 #ifndef _ASM_X86_I387_H 11 #define _ASM_X86_I387_H 12 13 #ifndef __ASSEMBLY__ 14 15 #include <linux/sched.h> 16 #include <linux/hardirq.h> 17 18 struct pt_regs; 19 struct user_i387_struct; 20 21 extern int init_fpu(struct task_struct *child); 22 extern int dump_fpu(struct pt_regs *, struct user_i387_struct *); 23 extern void math_state_restore(void); 24 25 extern bool irq_fpu_usable(void); 26 extern void kernel_fpu_begin(void); 27 extern void kernel_fpu_end(void); 28 29 /* 30 * Some instructions like VIA's padlock instructions generate a spurious 31 * DNA fault but don't modify SSE registers. And these instructions 32 * get used from interrupt context as well. To prevent these kernel instructions 33 * in interrupt context interacting wrongly with other user/kernel fpu usage, we 34 * should use them only in the context of irq_ts_save/restore() 35 */ irq_ts_save(void)36static inline int irq_ts_save(void) 37 { 38 /* 39 * If in process context and not atomic, we can take a spurious DNA fault. 40 * Otherwise, doing clts() in process context requires disabling preemption 41 * or some heavy lifting like kernel_fpu_begin() 42 */ 43 if (!in_atomic()) 44 return 0; 45 46 if (read_cr0() & X86_CR0_TS) { 47 clts(); 48 return 1; 49 } 50 51 return 0; 52 } 53 irq_ts_restore(int TS_state)54static inline void irq_ts_restore(int TS_state) 55 { 56 if (TS_state) 57 stts(); 58 } 59 60 /* 61 * The question "does this thread have fpu access?" 62 * is slightly racy, since preemption could come in 63 * and revoke it immediately after the test. 64 * 65 * However, even in that very unlikely scenario, 66 * we can just assume we have FPU access - typically 67 * to save the FP state - we'll just take a #NM 68 * fault and get the FPU access back. 69 */ user_has_fpu(void)70static inline int user_has_fpu(void) 71 { 72 return current->thread.fpu.has_fpu; 73 } 74 75 extern void unlazy_fpu(struct task_struct *tsk); 76 77 #endif /* __ASSEMBLY__ */ 78 79 #endif /* _ASM_X86_I387_H */ 80