From 6e77fbc32363253835124bab7c0b36185da1356a Mon Sep 17 00:00:00 2001
From: RaphProductions <81994075+RaphProductions@users.noreply.github.com>
Date: Sun, 11 May 2025 17:29:59 +0200
Subject: [PATCH] sched: fix a dumb stack bug inside the scheduler

---
 kernel/src/sched/sched.c         | 14 ++++++++------
 kernel/src/sys/arch/x86_64/gdt.c |  6 ++++--
 kernel/src/sys/syscall.c         |  2 +-
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/kernel/src/sched/sched.c b/kernel/src/sched/sched.c
index d358fff..907f83a 100644
--- a/kernel/src/sched/sched.c
+++ b/kernel/src/sched/sched.c
@@ -34,6 +34,8 @@ void sched_init() {
   memcpy(proc_list->name, "System\0", 7);
   proc_list->pid = -1;
   proc_list->type = SCHED_EMPTY;
+  proc_list->flags = SCHED_KERNEL_PROCESS;
+  proc_list->pm = vmm_kernel_pm;
 
   curr_proc = proc_list;
 
@@ -71,13 +73,13 @@ sched_process *sched_create(char *name, uint64_t entry_point, pagemap_t *pm,
   if (flags == SCHED_KERNEL_PROCESS) {
     proc->stack_base = stack_phys;
     proc->stack_base_physical = stack_phys;
-    proc->stack_end = proc_list->stack_base + PMM_PAGE_SIZE;
+    proc->stack_end = proc->stack_base + PMM_PAGE_SIZE;
   } else if (flags == SCHED_USER_PROCESS) {
     vmm_map_user(proc->pm, (uint64_t)stack_virt, (uint64_t)stack_phys,
                  VMM_PRESENT | VMM_WRITABLE | VMM_USER);
     proc->stack_base = stack_virt;
     proc->stack_base_physical = stack_phys;
-    proc->stack_end = proc_list->stack_base + PMM_PAGE_SIZE;
+    proc->stack_end = proc->stack_base + PMM_PAGE_SIZE;
   }
   proc->regs.rip = (uint64_t)entry_point;
 
@@ -85,8 +87,8 @@ sched_process *sched_create(char *name, uint64_t entry_point, pagemap_t *pm,
     proc->regs.cs = 0x28; // Run in kernel mode
     proc->regs.ss = 0x30;
   } else if (flags == SCHED_USER_PROCESS) {
-    proc->regs.cs = 0x43; // Run in user mode
-    proc->regs.ss = 0x3B;
+    proc->regs.cs = 0x38 | 3; // Run in user mode
+    proc->regs.ss = 0x40 | 3;
   }
   proc->regs.rflags = 0x202; // Enable interrupts
   proc->regs.rsp = (uint64_t)proc->stack_end;
@@ -153,9 +155,9 @@ void schedule(registers_t *regs) {
   if (curr_proc == NULL)
     curr_proc = proc_list;
 
-  log("sched - I choosed process %d\n", curr_proc->pid);
+  //log("sched - I choosed process %d\n", curr_proc->pid);
 
-  // log("sched - I choosed process %d\n", curr_proc->pid);
+  //log("sched - I choosed process %d (pm: %s, rip: %p)\n", curr_proc->pid, curr_proc->pm == vmm_kernel_pm ? "kernel" : "user", curr_proc->regs.rip);
   memcpy(regs, &curr_proc->regs, sizeof(registers_t));
 
   // Finally, load our pagemap
diff --git a/kernel/src/sys/arch/x86_64/gdt.c b/kernel/src/sys/arch/x86_64/gdt.c
index e528eff..61b6ae4 100644
--- a/kernel/src/sys/arch/x86_64/gdt.c
+++ b/kernel/src/sys/arch/x86_64/gdt.c
@@ -16,8 +16,8 @@ gdt_table def_table = {{
                            0x00af9b000000ffff, // 0x28 64 bit code cs
                            0x00af93000000ffff, // 0x30 64 bit data ss
 
-                           0x00aff3000000ffff, // 0x38 data ss
-                           0x00affb000000ffff, // 0x40 user mode code cs
+                           0x00affb000000ffff, // 0x38 user mode code cs
+                           0x00aff3000000ffff, // 0x40 user mode data ss
                        },
                        {}};
 
@@ -26,7 +26,9 @@ tssr tss_list[256]; // One tssr per CPU
 void gdt_init(char *kstack) {
 
   // TODO: adapt for multiprocessor kernel
+  memset(&tss_list[0], 0, sizeof(tssr));
   tss_list[0].rsp[0] = (uint64_t)kstack;
+  tss_list[0].iopb = sizeof(tssr);
   uintptr_t tss = (uintptr_t)&tss_list[0];
 
   def_table.tss_entry.length = sizeof(tss_entry);
diff --git a/kernel/src/sys/syscall.c b/kernel/src/sys/syscall.c
index c87134e..0a3567c 100644
--- a/kernel/src/sys/syscall.c
+++ b/kernel/src/sys/syscall.c
@@ -18,7 +18,7 @@ void syscall_handle(registers_t *regs) {
     return;
   }
 
-  if (curr_proc == NULL || curr_proc->regs.cs != 0x43) {
+  if (curr_proc == NULL || curr_proc->regs.cs != 0x3B) {
     log("syscall - syscall_handle was called by the kernel. is this wanted?\n");
     return;
   }