static void
restore_guest_fpustate(struct vcpu *vcpu)
{
/* flush host state to the pcb */
fpuexit(curthread);
/* restore guest FPU state */
fpu_stop_emulating();
fpurestore(vcpu->guestfpu);
/* restore guest XCR0 if XSAVE is enabled in the host */
if (rcr4() & CR4_XSAVE)
load_xcr(0, vcpu->guest_xcr0);
/*
* The FPU is now "dirty" with the guest's state so turn on emulation
* to trap any access to the FPU by the host.
*/
fpu_start_emulating();
}
/*
* Finish a fork operation, with process p2 nearly set up.
* Copy and update the pcb, set up the stack so that the child
* ready to run and return to user mode.
*/
void
cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
{
struct proc *p1;
struct pcb *pcb2;
struct mdproc *mdp1, *mdp2;
struct proc_ldt *pldt;
p1 = td1->td_proc;
if ((flags & RFPROC) == 0) {
if ((flags & RFMEM) == 0) {
/* unshare user LDT */
mdp1 = &p1->p_md;
mtx_lock(&dt_lock);
if ((pldt = mdp1->md_ldt) != NULL &&
pldt->ldt_refcnt > 1 &&
user_ldt_alloc(p1, 1) == NULL)
panic("could not copy LDT");
mtx_unlock(&dt_lock);
}
return;
}
/* Ensure that td1's pcb is up to date. */
fpuexit(td1);
update_pcb_bases(td1->td_pcb);
/* Point the pcb to the top of the stack */
pcb2 = get_pcb_td(td2);
td2->td_pcb = pcb2;
/* Copy td1's pcb */
bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
/* Properly initialize pcb_save */
pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
bcopy(get_pcb_user_save_td(td1), get_pcb_user_save_pcb(pcb2),
cpu_max_ext_state_size);
/* Point mdproc and then copy over td1's contents */
mdp2 = &p2->p_md;
bcopy(&p1->p_md, mdp2, sizeof(*mdp2));
/*
* Create a new fresh stack for the new process.
* Copy the trap frame for the return to user mode as if from a
* syscall. This copies most of the user mode register values.
*/
td2->td_frame = (struct trapframe *)td2->td_pcb - 1;
bcopy(td1->td_frame, td2->td_frame, sizeof(struct trapframe));
td2->td_frame->tf_rax = 0; /* Child returns zero */
td2->td_frame->tf_rflags &= ~PSL_C; /* success */
td2->td_frame->tf_rdx = 1;
/*
* If the parent process has the trap bit set (i.e. a debugger had
* single stepped the process to the system call), we need to clear
* the trap flag from the new frame unless the debugger had set PF_FORK
* on the parent. Otherwise, the child will receive a (likely
* unexpected) SIGTRAP when it executes the first instruction after
* returning to userland.
*/
if ((p1->p_pfsflags & PF_FORK) == 0)
td2->td_frame->tf_rflags &= ~PSL_T;
/*
* Set registers for trampoline to user mode. Leave space for the
* return address on stack. These are the kernel mode register values.
*/
pcb2->pcb_r12 = (register_t)fork_return; /* fork_trampoline argument */
pcb2->pcb_rbp = 0;
pcb2->pcb_rsp = (register_t)td2->td_frame - sizeof(void *);
pcb2->pcb_rbx = (register_t)td2; /* fork_trampoline argument */
pcb2->pcb_rip = (register_t)fork_trampoline;
/*-
* pcb2->pcb_dr*: cloned above.
* pcb2->pcb_savefpu: cloned above.
* pcb2->pcb_flags: cloned above.
* pcb2->pcb_onfault: cloned above (always NULL here?).
* pcb2->pcb_[fg]sbase: cloned above
*/
/* Setup to release spin count in fork_exit(). */
td2->td_md.md_spinlock_count = 1;
td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
td2->td_md.md_invl_gen.gen = 0;
/* As an i386, do not copy io permission bitmap. */
pcb2->pcb_tssp = NULL;
/* New segment registers. */
set_pcb_flags_raw(pcb2, PCB_FULL_IRET);
/* Copy the LDT, if necessary. */
mdp1 = &td1->td_proc->p_md;
mdp2 = &p2->p_md;
if (mdp1->md_ldt == NULL) {
mdp2->md_ldt = NULL;
return;
}
mtx_lock(&dt_lock);
if (mdp1->md_ldt != NULL) {
if (flags & RFMEM) {
mdp1->md_ldt->ldt_refcnt++;
mdp2->md_ldt = mdp1->md_ldt;
bcopy(&mdp1->md_ldt_sd, &mdp2->md_ldt_sd, sizeof(struct
system_segment_descriptor));
} else {
mdp2->md_ldt = NULL;
mdp2->md_ldt = user_ldt_alloc(p2, 0);
if (mdp2->md_ldt == NULL)
panic("could not copy LDT");
amd64_set_ldt_data(td2, 0, max_ldt_segment,
(struct user_segment_descriptor *)
mdp1->md_ldt->ldt_base);
}
} else
mdp2->md_ldt = NULL;
mtx_unlock(&dt_lock);
/*
* Now, cpu_switch() can schedule the new process.
* pcb_rsp is loaded pointing to the cpu_switch() stack frame
* containing the return address when exiting cpu_switch.
* This will normally be to fork_trampoline(), which will have
* %ebx loaded with the new proc's pointer. fork_trampoline()
* will set up a stack to call fork_return(p, frame); to complete
* the return to user-mode.
*/
}
