From 3ca8b5a232ab0fbdfa046aae79c5ef77f6b3f609 Mon Sep 17 00:00:00 2001
From: pjht <terppa05@gmail.com>
Date: Sun, 25 Aug 2019 17:32:08 -0500
Subject: [PATCH] Add a very basic exit function and fix kmalloc.

Exit function does not deallocate task memory except for the data block,
and does not are about the exit code except for logging.
---
 .gdbinit                     | 22 ----------------------
 kernel/cpu/i386/isr.c        |  2 ++
 kernel/cpu/i386/kmalloc.c    |  2 +-
 kernel/cpu/i386/tasking.c    | 23 +++++++++++++++++++++++
 kernel/cpu/tasking.h         |  1 +
 kernel/kernel.c              |  1 +
 libc/tasking.c               |  7 +++++++
 sysroot/usr/include/stdlib.h |  3 +++
 8 files changed, 38 insertions(+), 23 deletions(-)

diff --git a/.gdbinit b/.gdbinit
index 62ff712..c4c2cf0 100644
--- a/.gdbinit
+++ b/.gdbinit
@@ -1,25 +1,3 @@
 set pagination off
 target remote localhost:1234
 symbol-file kernel/kernel.elf
-add-symbol-file vfs/vfs
-b kernel/cpu/i386/tasking.c:132
-b kernel/cpu/i386/tasking.c:143
-commands 1 2
-silent
-  disable breakpoints
-  symbol-file kernel/kernel.elf
-  p task->pid
-  if task->pid==2
-    add-symbol-file vfs/vfs
-    enable breakpoints
-  else
-    enable breakpoints 1
-    c
-  end
-  c
-end
-
-b main
-commands
-  disable breakpoints 1
-end
diff --git a/kernel/cpu/i386/isr.c b/kernel/cpu/i386/isr.c
index e7337da..5a2c241 100644
--- a/kernel/cpu/i386/isr.c
+++ b/kernel/cpu/i386/isr.c
@@ -230,6 +230,8 @@ void isr_handler(registers_t r) {
         tasking_yieldToPID(r.ebx);
       } else if (r.eax==16) {
         serial_write_string((char*)r.ebx);
+      } else if (r.eax==17) {
+        tasking_exit((uint8_t)r.ebx);
       }
       break;
     }
diff --git a/kernel/cpu/i386/kmalloc.c b/kernel/cpu/i386/kmalloc.c
index 2ac51cd..a19a1dd 100644
--- a/kernel/cpu/i386/kmalloc.c
+++ b/kernel/cpu/i386/kmalloc.c
@@ -81,7 +81,7 @@ void* kmalloc(uint32_t size) {
 }
 
 void kfree(void* mem) {
-  uint32_t* info=(uint32_t*)((uint32_t)mem-12);
+  uint32_t* info=(uint32_t*)((uint32_t)mem-8);
   uint32_t num_4b_grps=info[0];
   uint32_t bmap_index=info[1];
   for (uint32_t i=0;i<num_4b_grps;i++) {
diff --git a/kernel/cpu/i386/tasking.c b/kernel/cpu/i386/tasking.c
index 34a8c52..9eb9a5b 100644
--- a/kernel/cpu/i386/tasking.c
+++ b/kernel/cpu/i386/tasking.c
@@ -145,6 +145,29 @@ void tasking_yieldToPID(uint32_t pid) {
   switch_to_task(task);
 }
 
+void tasking_exit(uint8_t code) {
+  serial_printf("PID %d is exiting with code %d.\n",currentTask->pid,code);
+  if (currentTask->prev) {
+    currentTask->prev->next=currentTask->next;
+  }
+  if (currentTask->next) {
+    currentTask->next->prev=currentTask->prev;
+  }
+  if (headTask==currentTask) {
+    if (!currentTask->next) {
+      serial_write_string("ERROR! Head task exited with no child tasks! Halting!\n");
+      vga_write_string("ERROR! Head task exited with no child tasks! Halting!\n");
+      halt();
+    }
+    headTask=currentTask->next;
+  }
+  Task* task=currentTask->next;
+  kfree(currentTask);
+  serial_printf("Exit yielding to PID %d.\n",task->pid);
+  load_smap(task->cr3);
+  switch_to_task(task);
+}
+
 uint32_t getPID() {
   return currentTask->pid;
 }
diff --git a/kernel/cpu/tasking.h b/kernel/cpu/tasking.h
index 7673c10..28cb0d3 100644
--- a/kernel/cpu/tasking.h
+++ b/kernel/cpu/tasking.h
@@ -11,4 +11,5 @@ Task* tasking_createTask(void* eip);
 Task* tasking_createTaskCr3KmodeParam(void* eip,void* cr3,char kmode,char param1_exists,uint32_t param1_arg,char param2_exists,uint32_t param2_arg);
 char isPrivleged(uint32_t pid);
 uint32_t getPID();
+void tasking_exit(uint8_t code);
 #endif
diff --git a/kernel/kernel.c b/kernel/kernel.c
index 1b25ea3..836f72a 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -106,6 +106,7 @@ void kmain(struct multiboot_boot_header_tag* hdr) {
     memcpy(initrd2,initrd,initrd_sz);
     initrd2=put_data(cr3,initrd2,initrd_sz);
     createTaskCr3Param((void*)header.entry,cr3,(uint32_t)initrd2,initrd_sz);
+    exit(1);
     for(;;) {
       yield();
     }
diff --git a/libc/tasking.c b/libc/tasking.c
index 67a47be..7ff70a8 100644
--- a/libc/tasking.c
+++ b/libc/tasking.c
@@ -34,3 +34,10 @@ void yieldToPID(uint32_t pid) {
     int $80; \
   "::"b"(pid));
 }
+
+void exit(uint8_t code) {
+  asm volatile("  \
+    mov $17, %%eax; \
+    int $80; \
+  "::"b"(code));
+}
diff --git a/sysroot/usr/include/stdlib.h b/sysroot/usr/include/stdlib.h
index 9160012..4a66d5f 100644
--- a/sysroot/usr/include/stdlib.h
+++ b/sysroot/usr/include/stdlib.h
@@ -2,11 +2,14 @@
 #define STDLIB_H
 
 #include <stddef.h>
+#include <stdint.h>
+
 #define EXIT_SUCCESS 0
 #define EXIT_FAILURE 1
 
 void* malloc(size_t size);
 void* realloc(void *mem, size_t new_sz);
 void free(void* mem);
+void exit(uint8_t code);
 
 #endif