1 /* 2 * x86_has_fpu.c 3 * 4 * Test for an x86 FPU, and do any necessary setup. 5 */ 6 7 #include <inttypes.h> 8 #include <sys/fpu.h> 9 10 static inline uint64_t get_cr0(void) 11 { 12 uint32_t v; 13 asm("movl %%cr0,%0":"=r"(v)); 14 return v; 15 } 16 17 static inline void set_cr0(uint32_t v) 18 { 19 asm volatile ("movl %0,%%cr0"::"r" (v)); 20 } 21 22 #define CR0_PE 0x00000001 23 #define CR0_MP 0x00000002 24 #define CR0_EM 0x00000004 25 #define CR0_TS 0x00000008 26 #define CR0_ET 0x00000010 27 #define CR0_NE 0x00000020 28 #define CR0_WP 0x00010000 29 #define CR0_AM 0x00040000 30 #define CR0_NW 0x20000000 31 #define CR0_CD 0x40000000 32 #define CR0_PG 0x80000000 33 34 int x86_init_fpu(void) 35 { 36 uint32_t cr0; 37 uint16_t fsw = 0xffff; 38 uint16_t fcw = 0xffff; 39 40 cr0 = get_cr0(); 41 cr0 &= ~(CR0_EM | CR0_TS); 42 cr0 |= CR0_MP; 43 set_cr0(cr0); 44 45 asm volatile ("fninit"); 46 asm volatile ("fnstsw %0":"+m" (fsw)); 47 if (fsw != 0) 48 return -1; 49 50 asm volatile ("fnstcw %0":"+m" (fcw)); 51 if ((fcw & 0x103f) != 0x3f) 52 return -1; 53 54 /* Techically, this could be a 386 with a 287. We could add a check 55 for that here... */ 56 57 return 0; 58 } 59
