Context switch to one thread implemented

Author: sooriravindra

.gitignore

@@ -8,3 +8,4 @@ obj/*
 kernel
 *.img
 *.iso
+.gdb_history

include/sys/task.h

@@ -0,0 +1,19 @@
+#ifndef _TASK_H
+#define _TASK_H
+typedef struct _regstruct
+{
+    uint64_t rbp;
+    uint64_t rax;
+    uint64_t rbx;
+    uint64_t rcx;
+    uint64_t rdx;
+    uint64_t rsp;
+    uint64_t flags;
+} __attribute__((packed)) reg_struct;
+
+typedef struct _taskstruct
+{
+    reg_struct regs;
+} __attribute__((packed)) task_struct;
+void trial_sched();
+#endif

sys/main.c

@@ -7,6 +7,7 @@
 #include <sys/kprintf.h>
 #include <sys/pci.h>
 #include <sys/tarfs.h>
+#include <sys/task.h>
 #include <sys/vma.h>
 
 #define INITIAL_STACK_SIZE 4096
@@ -49,6 +50,8 @@ start(uint32_t* modulep, void* physbase, void* physfree)
             vma_pagelist_add_addresses(smap->base, smap->base + smap->length);
         }
     }
+    kprintf("physfree %p\n", (uint64_t)physfree);
+    kprintf("tarfs in [%p:%p]\n", &_binary_tarfs_start, &_binary_tarfs_end);
     vma_pagelist_create(physfree);
     vma_create_pagetables();
     kprintf("physfree %p\n", (uint64_t)physfree);
@@ -57,6 +60,7 @@ start(uint32_t* modulep, void* physbase, void* physfree)
     register_idt();
     pic_init();
     enable_interrupts(TRUE);
+    trial_sched();
     /*
     ahci_discovery();
     ahci_readwrite_test();

sys/sched.s

@@ -0,0 +1,29 @@
+.globl switch_to
+switch_to:
+// rdi: me
+// rsi: next
+    movq %rbp,  0(%rdi)
+    movq %rax,  8(%rdi)
+    movq %rbx, 16(%rdi)
+    movq %rcx, 24(%rdi)
+    movq %rdx, 32(%rdi)
+
+    pushf 
+    pop 48(%rdi)
+
+    push %rdi
+    movq %rsp, 40(%rdi)
+
+    movq 40(%rsi), %rsp
+    pop %rdi
+
+    movq  0(%rdi), %rbp
+    movq  8(%rdi), %rax
+    movq 16(%rdi), %rbx
+    movq 24(%rdi), %rcx
+    movq 32(%rdi), %rdx
+    push 48(%rdi)
+    popf
+
+    retq
+.end

sys/task.c

@@ -0,0 +1,45 @@
+#include <sys/defs.h>
+#include <sys/kprintf.h>
+#include <sys/task.h>
+
+extern void switch_to(task_struct*, task_struct*);
+uint8_t second_stack[4096] __attribute__((aligned(16)));
+task_struct tasks[2];
+task_struct *me, *next;
+
+void
+yield()
+{
+    switch_to(me, next);
+}
+
+void
+thread2()
+{
+    kprintf("Thread X! Hello from the other side\n");
+    while (1)
+        ;
+    yield();
+}
+
+void
+trial_sched()
+{
+    me = &tasks[0];
+    next = &tasks[1];
+    uint64_t* stack_top;
+    stack_top = (uint64_t*)&second_stack[4096];
+    stack_top--;
+    stack_top--;
+    stack_top--;
+    stack_top--;
+    stack_top--;
+    stack_top--;
+    *stack_top = (uint64_t)thread2;
+    stack_top--;
+    *stack_top = (uint64_t)next;
+    next->regs.rsp = (uint64_t)stack_top;
+    next->regs.rbp = (uint64_t)stack_top;
+    yield();
+    kprintf("Thread 1! Hello from the other side\n");
+}

sys/vma.c

@@ -3,7 +3,7 @@
 
 #define VMA_KERNMEM 0xffffffff80000000
 #define VMA_VIDEO (VMA_KERNMEM + 0x800000) // 2nd part is 2048 * PAGESIZE
-#define PAGELIST_ENTRIES (1024 * 256)
+#define PAGELIST_ENTRIES (1024 * 1024)
 #define PAGE_SIZE 4096
 #define TABLE_ENTRIES 512
 
@@ -99,8 +99,8 @@ vma_create_pagetables()
     // Self referencing trick
     pml4_table[TABLE_ENTRIES - 1] = ((uint64_t)pml4_table) | 0x3;
 
-    //TODO Remove this hard coding of 2048. Map only physbase to physfree
-    for (int i = 0; i < 2048; i++) {
+    // TODO Remove this hard coding of 2048. Map only physbase to physfree
+    for (int i = 0; i < 4735; i++) {
         v_addr = VMA_KERNMEM + i * (PAGE_SIZE);
         pdp_table = vma_add_table_mapping(pml4_table, VMA_PML4_OFFSET(v_addr));
         pd_table =
@@ -111,7 +111,8 @@ vma_create_pagetables()
         pt_table[VMA_PAGE_TABLE_OFFSET(v_addr)] = (0x0 + i * (PAGE_SIZE)) | 0x3;
     }
 
-    //TODO add new function to create the mapping making the following code generic
+    // TODO add new function to create the mapping making the following code
+    // generic
     v_addr = VMA_VIDEO;
     pdp_table = vma_add_table_mapping(pml4_table, VMA_PML4_OFFSET(v_addr));
     pd_table = vma_add_table_mapping(pdp_table, VMA_PD_POINTER_OFFSET(v_addr));