From 59038fc67c20a1f04e5d2fd5f9a444e707d1d3ea Mon Sep 17 00:00:00 2001
From: Miguel <m.i@gmx.at>
Date: Wed, 22 Aug 2018 00:52:30 +0200
Subject: userspace and kernelspace taskswitching

---
 asm/pit.s          | 50 ++++++++++++++++++++++++++++----------------------
 asm/task.s         | 37 +++++++++++++++++++++++++++++++------
 kernel/gdt.c       | 10 +---------
 kernel/kernel.h    |  1 +
 kernel/mem.c       |  1 -
 kernel/scheduler.c | 25 ++-----------------------
 kernel/usermode.c  | 23 +++++++++++++++++------
 7 files changed, 80 insertions(+), 67 deletions(-)

diff --git a/asm/pit.s b/asm/pit.s
index ab8dcdb..c25e9a1 100644
--- a/asm/pit.s
+++ b/asm/pit.s
@@ -12,32 +12,38 @@ pit_get_ticks:
 
 pit_interrupt_handler:
 
-    // increase tick counter
-    push %eax
-    mov $ticks, %eax
-    incl (%eax)
-    pop %eax
-
-    ////
-
-    pusha          //Push all standard registers
-
-    mov %esp, %eax	//save current stack pointer (pointing to registers!)
-
-    movl $stack_top, %esp	//use stack from multiboot.s(16Kb)
+    push %eax // persist
 
-    // call our scheduler passing it the old stack addres (pointing to pushed registers (pusha))
-    push %eax   
-    call task_switch_next 
-
-    // the scheduler returned the new stack pointer (after taskswitch)
-    mov %eax, %esp   //Replace the stack with what the C code gave us
+    // INC TICK COUNTER
+    mov $ticks, %eax    
+    incl (%eax)
 
-    // acknowlege irq
-    mov $0x20,%al   
+    // ACK IRQ
+    mov $0x20,%al
     out %al,$0x20   
+
+    pop %eax // load original
     
-    popa           //Put the standard registers back
+    ///////
+
+    pusha          //Push all standard registers
+    push %ds       //Push data segment
+    push %es       //etc...
+    push %fs
+    push %gs
+
+    mov %esp, %eax          // remember current %esp
+    movl $stack_top, %esp   // switch to our small scheduler stack
+
+    push %eax               // set original %esp as param and... 
+    call task_switch_next   // call scheduler
+    mov  %eax, %esp         // use %esp we got from scheduler
+
+    pop %gs
+    pop %fs
+    pop %es
+    pop %ds
+    popa           
 
     iret
 
diff --git a/asm/task.s b/asm/task.s
index 7611d4a..c29bdae 100644
--- a/asm/task.s
+++ b/asm/task.s
@@ -2,15 +2,21 @@
 task_pusha:
 
     pushf
-
-    push $0x8
+    push $0x8	   // code segment
     push $userfunc
 
     pusha
+
+    push %ds
+    push %es
+    push %fs
+    push %gs
+
 	/*
+
 	now stack looks like:
 
-	param			 // esp+48
+	param			 // esp+64
 	returnaddy		
 
 	eflags			
@@ -26,9 +32,14 @@ task_pusha:
 	esi			
 	edi			
 
+	ds
+	es
+	fs
+	gs
+
 	*/
 
-    mov 48(%esp),%eax // get address of alternative stack where we want to simulate the pusha
+    mov 64(%esp),%eax // get address of alternative stack where we want to simulate the pusha
 
     mov (%esp),%ecx
     mov %ecx,(%eax)
@@ -66,10 +77,24 @@ task_pusha:
     mov 44(%esp),%ecx
     mov %ecx,44(%eax)
 
+    mov 48(%esp),%ecx
+    mov %ecx,48(%eax)
+
+    mov 52(%esp),%ecx
+    mov %ecx,52(%eax)
+
+    mov 56(%esp),%ecx
+    mov %ecx,56(%eax)
+
+    pop %gs
+    pop %fs
+    pop %es
+    pop %ds
+
+    popa
+
     pop %eax
     pop %eax
     pop %eax
 
-    popa
-
     ret
diff --git a/kernel/gdt.c b/kernel/gdt.c
index 06a0949..88478c7 100644
--- a/kernel/gdt.c
+++ b/kernel/gdt.c
@@ -1,7 +1,6 @@
 // http://wiki.osdev.org/GDT_Tutorial
-#include "lib/logger/log.h"
+#define FOOLOS_MODULE_NAME "gdt"
 #include "usermode.h"
-#define FOOLOS_MODULE_NAME "GDT"
 
 #include <stdint.h>
 #define GDT_SIZE 6
@@ -85,13 +84,10 @@ void encodeGdtEntry(uint8_t *target, GDT source)
 6   db 11001111b    ;flags & seg.limit
 7   db 0x0	    ;base
     */
-
-
 }
 
 void gdt_init()
 {
-    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"setting up Global Descriptor Table");
     //selector 0x0
     myGDT[0].base=0;
     myGDT[0].limit=0;
@@ -122,15 +118,11 @@ void gdt_init()
     myGDT[5].limit=sizeof(tss_struct); //tss end?
     myGDT[5].type=0x89;
 
-
     // transcript to format the processor wants
     for(int i=0;i<GDT_SIZE;i++)
         encodeGdtEntry(&gdt_struct[8*i],myGDT[i]);
 
-
     // updat
     install_tss();
     setup_gdt(&gdt_struct[0],8*GDT_SIZE);
-
-
 }
diff --git a/kernel/kernel.h b/kernel/kernel.h
index 1880045..5ac10d1 100644
--- a/kernel/kernel.h
+++ b/kernel/kernel.h
@@ -11,6 +11,7 @@
 #define FIFO_MAX_RINGBUFFERS 20
 #define MAX_FIFOS 20
 #define MAX_FD 20
+#define MAX_TASKS 255
 
 #define FOOLOS_CONSOLE_AUTOBREAK    // add newline automatically at end of line
 
diff --git a/kernel/mem.c b/kernel/mem.c
index a167d8b..8b90911 100644
--- a/kernel/mem.c
+++ b/kernel/mem.c
@@ -219,7 +219,6 @@ uint32_t mem_init(multiboot_information *info)
     // we deinit everything below mem_min_block anyway
     pmmngr_deinit_region(0,mem_min_block*PMMNGR_BLOCK_SIZE);
 
-
     log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"Usable ~%d / %d MB ",mem_free_blocks*4096/1024/1024,total_mem/1024/1024);
 
     log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,
diff --git a/kernel/scheduler.c b/kernel/scheduler.c
index 4823276..d6e2c76 100644
--- a/kernel/scheduler.c
+++ b/kernel/scheduler.c
@@ -13,8 +13,6 @@
 #include "fs/fs.h"
 #include "fs/ext2.h"
 
-#define MAX_TASKS 10
-
 static volatile int volatile current_task=-1;
 
 static volatile struct task_list_struct
@@ -36,7 +34,6 @@ volatile int add_task(uint32_t esp, uint32_t vmem)
     {
 	if(task_list[i].active!=true)
 	{
-
 	    task_list[i].parent=current_task;
 	    task_list[i].vmem=vmem;
 	    task_list[i].esp=esp;
@@ -174,30 +171,12 @@ volatile void scheduler_init(pdirectory *dir)
     task_list[1].vmem=dir;
     task_list[1].esp = kballoc(4); // fresh 16kb stack from here.
 
-    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"fresh esp on: 0x%08X",1,task_list[1].esp);
-    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"fresh esp on: 0x%08X",0,task_list[0].esp);
+    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"fresh esp on: 0x%08X",task_list[1].esp+4*4096-1);
+    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"fresh esp on: 0x%08X",task_list[0].esp+4*4096-1);
 
     task_pusha(task_list[1].esp); // pusha but to alternative location
     task_pusha(task_list[0].esp); // pusha but to alternative location
 
-    /*
-    current_task=0;
-    unsigned esp, ebp, eax, ebx, ecx, edx;
-
-    asm(
-        "movl %%esp, %0;"
-        "movl %%ebp, %1;"
-        "movl %%eax, %2;"
-        "movl %%ebx, %3;"
-        "movl %%ecx, %4;"
-        "movl %%edx, %5;"
-        :"=r"(esp), "=r"(ebp), "=r"(eax), "=r"(ebx), "=r"(ecx), "=r"(edx)
-        );
-
-    // TODO: prepare stack so popa get's what it wants!
-    int i=task_fork(esp);
-    */
-
     // finally enable interrrupts so the scheduler is called (by timer)
     x86_sti(); 
 
diff --git a/kernel/usermode.c b/kernel/usermode.c
index 81dc5c1..bb614d0 100644
--- a/kernel/usermode.c
+++ b/kernel/usermode.c
@@ -15,6 +15,9 @@
 //https://wiki.osdev.org/Task_State_Segment
 tss_struct sys_tss; //Define the TSS as a global structure
 
+static volatile uint32_t c1;
+static volatile uint32_t c2;
+
 void install_tss(int cpu_no){
 
     // now fill each value
@@ -28,20 +31,28 @@ void install_tss(int cpu_no){
 
 void userfunc()
 {
+
     // we need enable here again (since the pushed eflags have it disabled)!
     x86_sti(); 
 
     // if we are pid 0, replace ourselves with /bin/init TODO: switch to usermode before!
-    if(task_get_current_pid()==0)syscall(SYSCALL_EXECVE,BIN_INIT,NULL,NULL); 
+    if(task_get_current_pid()==0)
+    {
+	//usermode(&initfunc); 
+	while(1)
+	{
+	   c2++;
+	}
+    }
 
-    // kernel worker thread
+    // kernel worker thread on pid1
     if(task_get_current_pid()==1)
     {
+	while(1)
+	{
+	    c1++;
+	}
     }
 }
 
-void switch_to_user_mode() 
-{
-    usermode(&userfunc); 
-}
 
-- 
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