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/*
* x86_has_fpu.c
*
* Test for an x86 FPU, and do any necessary setup.
*/
#include <inttypes.h>
#include <sys/fpu.h>
static inline uint64_t get_cr0(void)
{
uint32_t v;
asm("movl %%cr0,%0":"=r"(v));
return v;
}
static inline void set_cr0(uint32_t v)
{
asm volatile ("movl %0,%%cr0"::"r" (v));
}
#define CR0_PE 0x00000001
#define CR0_MP 0x00000002
#define CR0_EM 0x00000004
#define CR0_TS 0x00000008
#define CR0_ET 0x00000010
#define CR0_NE 0x00000020
#define CR0_WP 0x00010000
#define CR0_AM 0x00040000
#define CR0_NW 0x20000000
#define CR0_CD 0x40000000
#define CR0_PG 0x80000000
int x86_init_fpu(void)
{
uint32_t cr0;
uint16_t fsw = 0xffff;
uint16_t fcw = 0xffff;
cr0 = get_cr0();
cr0 &= ~(CR0_EM | CR0_TS);
cr0 |= CR0_MP;
set_cr0(cr0);
asm volatile ("fninit");
asm volatile ("fnstsw %0":"+m" (fsw));
if (fsw != 0)
return -1;
asm volatile ("fnstcw %0":"+m" (fcw));
if ((fcw & 0x103f) != 0x3f)
return -1;
/* Techically, this could be a 386 with a 287. We could add a check
for that here... */
return 0;
}
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