From 2fc03e597e97d2139490a303b95e5ad807ee4239 Mon Sep 17 00:00:00 2001
From: Loic Guegan <manzerbredes@mailbox.org>
Date: Wed, 14 Apr 2021 14:13:44 +0200
Subject: Improve task loading

---
 src/core/paging.c    | 38 ++++++++++++++++++++++----------------
 src/core/paging.h    |  3 ++-
 src/core/scheduler.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 src/core/scheduler.h |  1 +
 4 files changed, 69 insertions(+), 17 deletions(-)

(limited to 'src/core')

diff --git a/src/core/paging.c b/src/core/paging.c
index 8f12866..0fab46a 100644
--- a/src/core/paging.c
+++ b/src/core/paging.c
@@ -88,24 +88,30 @@ char* paging_allocate_next_page(){
     asm("hlt");
 }
 
-
-char *paging_allocate(int p){
+// TODO: Take p into account
+int *paging_allocate(int p){
+    // ----- Allow kernel access during interruption
     int *page_dir=(int*)paging_allocate_next_page();
-    int *page_table;
-    int current_page_entry=0;
-    int current_dir_entry=0;
-    while(current_page_entry<p){
-        if(current_page_entry%1024 == 0){
-            current_dir_entry++;
-            page_table=(int*)paging_allocate_next_page();
-            page_dir[current_dir_entry]=(int)page_table;
-        }
-        int entry=current_page_entry%1024;
-        page_table[current_page_entry]=(int)paging_allocate_next_page();
-        current_page_entry++;
-        print("Jean\n");
+    int *k_page_table=(int*)paging_allocate_next_page();
+    // Init page directory
+    page_dir[0]=(int)k_page_table|3;
+    // Init page table 0
+    int addr_offset=0;
+    for(int i=0;i<1024;i++){
+        k_page_table[i]=addr_offset;
+        k_page_table[i]|=3; // Permission
+        addr_offset+=PAGING_PAGE_SIZE; // 4Ko pages
     }
-    print("end");
+  
+    // ----- Task table
+    int *u_page_table=(int*)paging_allocate_next_page();
+    page_dir[1]=(int)u_page_table|7; // 1024*1024*4096/4
+    u_page_table[0]=(int)page_dir|7;
+    u_page_table[1]=(int)k_page_table|7;
+    u_page_table[2]=(int)u_page_table|7;
+    u_page_table[3]=(int)paging_allocate_next_page()|7;
+
+    return page_dir;
 }
 
 void paging_page_fault(){
diff --git a/src/core/paging.h b/src/core/paging.h
index 1526101..58a33b2 100644
--- a/src/core/paging.h
+++ b/src/core/paging.h
@@ -9,6 +9,7 @@
 #else
     #define PAGING_MAX_DIR_ENTRY PAGING_MAX_PAGES/1024
 #endif
+#define PADDR(entry) (entry&0xFFFFF000)
 
 /**
  * Configure and enable paging
@@ -26,7 +27,7 @@ void paging_set_usage(int addr,char state);
  * Create a new page directory containing
  * p pages.
  */
-char *paging_allocate(int p);
+int *paging_allocate(int p);
 void paging_dump(int min,int max);
 /**
  * Handler of page fault
diff --git a/src/core/scheduler.c b/src/core/scheduler.c
index 0f2b724..7b1c421 100644
--- a/src/core/scheduler.c
+++ b/src/core/scheduler.c
@@ -1,4 +1,7 @@
 #include "libc/stdio.h"
+#include "gdt.h"
+#include "mem.h"
+#include "paging.h"
 
 char show_tics=0;
 
@@ -17,4 +20,45 @@ void clock(){
       putchar('.');
   }
   schedule();
+}
+
+void run_task(int *page_dir, void *task, int task_size){
+    // Compute various addresses
+    int*pt_addr=PADDR(page_dir[1]);
+    void *entry_point=(void*)(PADDR(pt_addr[3]));
+    void *ustack=(void*)((int)entry_point+0xFF);
+
+    // Load the task into memory
+    memcpy(task,entry_point, task_size);
+  
+    // Load page directory
+    asm(
+      "mov %0, %%eax           \n\t"
+      "mov %%eax,%%cr3         \n\t"
+    :: "b"(page_dir)
+    );
+
+     // Setup users adresses
+ 
+    // Switch to user task
+    asm (
+    "cli                      \n\t" // Ensure we do not get interrupted
+    "movl %%ss, %%eax         \n\t"
+    "movl %%eax, %0           \n\t" // Save kernel ss segment into the TSS
+    "movl %%esp, %1           \n\t" // Save kernel esp into the TSS BEFORE setting up the stack
+    "pushl $0x33              \n\t" // Push task ss which is 0x30 along with prlv which is 0x3
+    "pushl %2                 \n\t" // Push task esp
+    "pushfl                   \n\t" // Retrieve flags
+    "popl %%eax               \n\t"
+    "orl $0x200, %%eax        \n\t" // Enable interrupt for the user task
+    "and $0xffffbfff, %%eax   \n\t" // Clear the NT flags
+    "push %%eax               \n\t" // Push task flags
+    "push $0x23               \n\t" // Push task cs which is 0x20 along with prlv which is 0x3
+    "push %3                  \n\t" // Push task entry point
+    "mov $0x2B, %%eax         \n\t" // GDT entry 0x28 along with prlv which is 0x3
+    "mov %%eax, %%ds          \n\t" // Setting up user data segment
+    "iret                     \n\t" // Launch user task
+    : "=m" (TSS.ss0), "=m" (TSS.esp0)
+    : "b" (ustack), "c" (entry_point)
+  );
 }
\ No newline at end of file
diff --git a/src/core/scheduler.h b/src/core/scheduler.h
index ec0caf1..8495e77 100644
--- a/src/core/scheduler.h
+++ b/src/core/scheduler.h
@@ -5,5 +5,6 @@ extern char show_tics;
 
 void clock();
 void schedule();
+void run_task(int *page_dir, void *task, int task_size);
 
 #endif
\ No newline at end of file
-- 
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