void
context_switch(context_t *oldc, context_t *newc)
{
gdt_set_kernel_stack((void *)((uintptr_t)newc->c_kstack + newc->c_kstacksz));
pt_set(newc->c_pdptr);
/*
* Save the current value of the stack pointer and the frame pointer into
* the old context. Set the instruction pointer to the return address
* (whoever called us).
*/
__asm__ __volatile__(
"pushfl \n\t" /* save EFLAGS on the stack */
"pushl %%ebp \n\t"
"movl %%esp, %0 \n\t" /* save ESP into oldc */
"movl %2, %%esp \n\t" /* restore ESP from newc */
"movl $1f, %1 \n\t" /* save EIP into oldc */
"pushl %3 \n\t" /* restore EIP */
"ret \n\t"
"1:\t" /* this is where oldc starts executing later */
"popl %%ebp \n\t"
"popfl" /* restore EFLAGS */
:"=m"(oldc->c_esp), "=m"(oldc->c_eip)
:"m"(newc->c_esp), "m"(newc->c_eip)
);
}
void
context_make_active(context_t *c)
{
gdt_set_kernel_stack((void *)((uintptr_t)c->c_kstack + c->c_kstacksz));
pt_set(c->c_pdptr);
/* Switch stacks and run the thread */
__asm__ volatile(
"movl %0,%%ebp\n\t" /* update ebp */
"movl %1,%%esp\n\t" /* update esp */
"push %2\n\t" /* save eip */
"ret" /* jump to new eip */
:: "m"(c->c_ebp), "m"(c->c_esp), "m"(c->c_eip)
);
}
