void up_initial_state(_TCB *tcb)
{
struct xcptcontext *xcp = &tcb->xcp;
/* Initialize the initial exception register context structure */
memset(xcp, 0, sizeof(struct xcptcontext));
/* Save the initial stack pointer... the value of the stackpointer before
* the "interrupt occurs." We don't know the value of REG_ESP yet..
* that depends on if a priority change is required or not.
*/
xcp->regs[REG_SP] = (uint32_t)tcb->adj_stack_ptr;
/* Save the task entry point */
xcp->regs[REG_EIP] = (uint32_t)tcb->start;
/* Set up the segment registers... assume the same segment as the caller.
* That is not a good assumption in the long run.
*/
xcp->regs[REG_DS] = up_getds();
xcp->regs[REG_CS] = up_getcs();
xcp->regs[REG_SS] = up_getss();
/* Set supervisor- or user-mode, depending on how NuttX is configured and
* what kind of thread is being started. Disable FIQs in any event
*
* If the kernel build is not selected, then all threads run in
* supervisor-mode.
*/
#ifdef CONFIG_NUTTX_KERNEL
# error "Missing logic for the CONFIG_NUTTX_KERNEL build"
#endif
/* Enable or disable interrupts, based on user configuration. If the IF
* bit is set, maskable interrupts will be enabled.
*/
#ifndef CONFIG_SUPPRESS_INTERRUPTS
xcp->regs[REG_EFLAGS] = X86_FLAGS_IF;
#endif
}
void up_savestate(uint32_t *regs)
{
uint8_t cpl;
uint8_t rpl;
/* First, just copy all of the registers */
up_copystate(regs, (uint32_t*)current_regs);
/* The RES_SP and REG_SS values will not be saved by the interrupt handling
* logic if there is no change in privilege level. In that case, we will
* have to "fudge" those values here. For now, just overwrite the REG_SP
* and REG_SS values with what we believe to be correct. Obviously, this
* will have to change in the future to support multi-segment operation.
*
* Check for a change in privilege level.
*/
rpl = regs[REG_CS] & 3;
cpl = up_getcs() & 3;
DEBUGASSERT(rpl >= cpl);
if (rpl == cpl)
{
/* No priority change, SP and SS are not present in the stack frame.
*
* The value saved in the REG_ESP will be the stackpointer value prior to
* the execution of the PUSHA. It will point at REG_IRQNO.
*/
regs[REG_SP] = current_regs[REG_ESP] + 4*BOTTOM_NOPRIO;
regs[REG_SS] = up_getss();
}
else
{
DEBUGASSERT(regs[REG_SP] == current_regs[REG_ESP] + 4*BOTTOM_PRIO);
}
}