Enable tasks execution and syscalls

1 files changed, 28 insertions, 4 deletions

diff --git a/src/bringelle.c b/src/bringelle.c
index 5fd315b..8faaecc 100644
--- a/src/bringelle.c
+++ b/src/bringelle.c
@@ -2,10 +2,15 @@
 #include "utils/pic.h"
 #include "boot/multiboot.h"
 #include "utils/mem.h"
+#include "utils/gdt.h"
 
 char show_tics=0;
 
+extern GDT_TSS TSS;
+
 void utask(){
+  char msg[]="Message from the task :D";
+  asm("mov $0x1, %%eax;int $0x30"::"b"(msg));
   while(1);
 }
 
@@ -15,14 +20,33 @@ void bringelle(){
 
   // Kernel boot sequence
   pic_enable_interrupt();
-  print("Interrupts enabled!\n");
-
+  print("Interrupts enabled\n");
+  print("Kernel started !\n");
 
   // Utask
+  print("Launch user task ");
+  show_tics=1;
   memcpy((void*)utask,(void*)0x300000, 100); // 100 bytes seems reasonable to load utask
+  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 $0x400000          \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 $0                  \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)
+  );
 
-  print("Kernel started ");
-  show_tics=1;
   while(1);
 }