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/* $OpenBSD: uthread_machdep.c,v 1.5 2006/04/06 15:27:08 kurt Exp $ */
/* David Leonard, <d@csee.uq.edu.au>. Public domain. */
/*
* Machine-dependent thread state functions for OpenBSD/i386.
*/
#include <sys/param.h>
#include <sys/sysctl.h>
#include <machine/cpu.h>
#include <pthread.h>
#include "pthread_private.h"
struct frame {
int fr_gs;
int fr_fs;
int fr_es;
int fr_ds;
int fr_edi;
int fr_esi;
int fr_ebp;
int fr_esp;
int fr_ebx;
int fr_edx;
int fr_ecx;
int fr_eax;
int fr_eip;
int fr_cs; /* XXX unreachable? */
};
#define copyreg(reg, lval) \
__asm__("mov %%" #reg ", %0" : "=g"(lval))
static int _thread_machdep_osfxsr(void);
static int
_thread_machdep_osfxsr(void)
{
int mib[] = { CTL_MACHDEP, CPU_OSFXSR };
static int sse = -1;
size_t len;
int val;
if (sse == -1) {
len = sizeof (val);
if (sysctl(mib, 2, &val, &len, NULL, 0) == -1)
return (0);
if (val)
sse = 1;
else
sse = 0;
}
return (sse);
}
/*
* Given a stack and an entry function, initialise a state
* structure that can be later switched to.
*/
void
_thread_machdep_init(struct _machdep_state* statep, void *base, int len,
void (*entry)(void))
{
struct frame *f;
/* Locate the initial frame, aligned at the top of the stack */
f = (struct frame *)(((int)base + len - sizeof *f) & ~15);
/* Set up initial frame */
f->fr_esp = (int)&f->fr_edi;
copyreg(cs, f->fr_cs);
copyreg(ds, f->fr_ds);
copyreg(es, f->fr_es);
copyreg(fs, f->fr_fs);
copyreg(gs, f->fr_gs);
f->fr_ebp = (int)-1;
f->fr_eip = (int)entry;
statep->esp = (int)f;
_thread_machdep_save_float_state(statep);
/*
* The current thread float state is saved into the new thread stack.
* Later pthread_create calls _thread_kern_sched which saves the current
* thread float state again into its own stack. However all float state
* saves must be balanced with a restore on i386 due to the fninit().
* Restore the current thread float state here so that the next save
* gets the correct state.
*/
_thread_machdep_restore_float_state(statep);
}
/*
* Floating point save restore copied from code in npx.c
* (without really understanding what it does).
*/
#define fldcw(addr) __asm("fldcw %0" : : "m" (*addr))
#define fnsave(addr) __asm("fnsave %0" : "=m" (*addr))
#define fninit() __asm("fninit")
#define frstor(addr) __asm("frstor %0" : : "m" (*addr))
#define fxsave(addr) __asm("fxsave %0" : "=m" (*addr))
#define fxrstor(addr) __asm("fxrstor %0" : : "m" (*addr))
#define fwait() __asm("fwait")
void
_thread_machdep_save_float_state(struct _machdep_state *ms)
{
union savefpu *addr = &ms->fpreg;
if (_thread_machdep_osfxsr()) {
fwait();
fxsave(&addr->sv_xmm);
fninit();
} else
fnsave(&addr->sv_87);
fwait();
}
void
_thread_machdep_restore_float_state(struct _machdep_state *ms)
{
union savefpu *addr = &ms->fpreg;
if (_thread_machdep_osfxsr()) {
fxrstor(&addr->sv_xmm);
fwait();
} else
frstor(&addr->sv_87);
}
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