context switch core

switch_context.c

void __fastcall change_context(Process* current, Process* next) {
    (void)current;
    run_proc= next;
}


void switch_context(Interrupt_frame* current_iframe) {
    Process* current_p = running_proc();
    Process* next_p    = next_proc();
    if (current_p == next_p) {
        return;
    }

    Thread* current_t  = &current_p->thread;
    Thread* next_t     = &next_p->thread;
    current_t->iframe  = current_iframe;

    if (next_p->pdt != NULL && pdt_process != next_p) {
        /*
         * Next Memory space is user space.
         * So, change pdt.
         */
        set_cpu_pdt(get_page_phys_addr(&next_p->pdt_page));
        pdt_process = next_p;
        axel_s.tss->esp0 = ECAST_UINT32(next_p->km_stack);
    }

    __asm__ volatile(
            "pushfl                             \n"  // Store eflags
            "movl  $next_turn, %[current_ip]    \n"  // Store ip
            "movl  %%esp,      %[current_sp]    \n"  // Store sp
            "movl  %[current_proc], %%ecx       \n"  // Set second argument
            "movl  %[next_proc],    %%edx       \n"  // Set first argument
            "movl  %[next_sp], %%esp            \n"  // Restore sp
            "pushl %[next_ip]                   \n"  // Restore ip (set return address)
            "jmp change_context                 \n"  // Change context

            ".globl next_turn                   \n"
            "next_turn:                         \n"

            "popfl                              \n"  // Restore eflags

            :   [current_ip] "=m"(current_t->ip),
                [current_sp] "=m"(current_t->sp)
            :   [next_ip] "r"(next_t->ip),
                [next_sp] "r"(next_t->sp),
                [current_proc] "m"(current_p),
                [next_proc] "m"(next_p)
            :   "memory", "%ecx", "%edx"
    );
}