syscalls: hopefully fix fork syscall

src/tasking/switch.asm

@@ -33,9 +33,6 @@ switchProcess:
 
 
 trapret:
-    ; Восстанавливаем общие регистры из trap frame
-    ;popal           ; edi, esi, ebp, oesp, ebx, edx, ecx, eax
-
     ; Восстанавливаем сегментные регистры
     pop gs
     pop fs
@@ -44,9 +41,6 @@ trapret:
 
     popad
 
-    ; Пропускаем trapno и err
-    add esp, 8      ; trapno (4 байта) + err (4 байта)
-
-
     ; Теперь ESP указывает на eip, cs, eflags, esp, ss
+    ; (interrupt and error fields removed from TrapFrame)
     iret

src/tasking/syscalls.c

@@ -86,8 +86,16 @@ int sys_fork(TrapFrame *tf)
         destroy_page_dir(new_pd);
         return -1;
     }
-    Process* child = (Process*)((uint32_t)p_physical + 0xC0000000);
-    map_page(p_physical, (void*)child, PAGE_PRESENT | PAGE_RW);
+    
+    // Map the Process structure page into the CHILD's page directory
+    map_page_in_directory(new_pd, p_physical, (void*)phys_to_virt((uint32_t)p_physical), PAGE_PRESENT | PAGE_RW);
+
+    // Also map the same page into the current (parent) page directory so the
+    // kernel can access and initialize it now via the kernel virtual mapping.
+    map_page(p_physical, (void*)phys_to_virt((uint32_t)p_physical), PAGE_PRESENT | PAGE_RW);
+
+    // Get virtual address for initialization (kernel mapping) and clear it
+    Process* child = (Process*)phys_to_virt((uint32_t)p_physical);
     memset(child, 0, sizeof(Process));
 
     child->pid = ++pid_counter;
@@ -102,27 +110,58 @@ int sys_fork(TrapFrame *tf)
         debug_log("Failed to allocate kernel stack\n");
         return -1;
     }
-    child->kstack = (char*)((uint32_t)kstack_physical + 0xC0000000);
-    map_page(kstack_physical, child->kstack, PAGE_PRESENT | PAGE_RW);
+    
+    // Map the kernel stack in the CHILD's page directory
+    map_page_in_directory(new_pd, kstack_physical, (void*)phys_to_virt((uint32_t)kstack_physical), PAGE_PRESENT | PAGE_RW);
+
+    // Also map kernel stack into the current PD so the kernel can write to it
+    map_page(kstack_physical, (void*)phys_to_virt((uint32_t)kstack_physical), PAGE_PRESENT | PAGE_RW);
+
+    child->kstack = (char*)phys_to_virt((uint32_t)kstack_physical);
     debug_log("child->kstack: %X\n", child->kstack);
 
+    child->kstack_top = (uint32_t)child->kstack + KSTACKSIZE;
+
     uint8_t* sp = (uint8_t*)(child->kstack + KSTACKSIZE);
 
     // 1. Place the TrapFrame on the child's stack.
     sp -= sizeof(TrapFrame);
     child->tf = (TrapFrame*)sp;
+    // Debug: print parent's trapframe before copying
+    debug_log("parent tf @ %X\n", tf);
+    debug_log("parent tf->eip=%X cs=%X eflags=%X user_esp=%X user_ss=%X\n",
+              tf->eip, tf->cs, tf->eflags, tf->usermode_esp, tf->usermode_ss);
+    debug_log("parent tf regs: eax=%X ebx=%X ecx=%X edx=%X edi=%X esi=%X ebp=%X esp=%X\n",
+              tf->eax, tf->ebx, tf->ecx, tf->edx, tf->edi, tf->esi, tf->ebp, tf->esp);
 
-    memcpy(&child->tf->gs, &tf->gs, 12 * sizeof(uint32_t));
-    uint32_t* parent_cpu_state_ptr = (uint32_t*)&tf->interrupt;
-    child->tf->eip          = parent_cpu_state_ptr[0];
-    child->tf->cs           = parent_cpu_state_ptr[1];
-    child->tf->eflags       = parent_cpu_state_ptr[2];
-    child->tf->usermode_esp = parent_cpu_state_ptr[3];
-    child->tf->usermode_ss  = parent_cpu_state_ptr[4];
+    // Copy the trapframe contents from the parent into the child's trapframe
+    memcpy(child->tf, tf, sizeof(TrapFrame));
+    /* Copy instruction pointer and segment registers from parent trapframe */
+    child->tf->eip          = tf->eip;
+    child->tf->cs           = tf->cs;
+    child->tf->eflags       = tf->eflags;
+    child->tf->usermode_esp = tf->usermode_esp;
+    child->tf->usermode_ss  = tf->usermode_ss;
 
-    child->tf->eax = 0;       // Child returns 0
+     /* Ensure saved kernel-ESP in the saved-registers block points
+         to the location right after the saved registers (where the
+         iret frame starts). popad will restore ESP from this field,
+         so it must point to the iret frame, not the user-mode ESP. */
+     child->tf->esp = (uint32_t)child->tf + offsetof(TrapFrame, eip);
+
+     child->tf->eax = 0;       // Child returns 0
     debug_log("Parent returns PID: %X, Child returns 0\n", child->pid);
 
+    // Debug: dump important trapframe and stack info for the child
+    debug_log("child->tf @ %X\n", child->tf);
+    debug_log("child->tf->eip=%X cs=%X eflags=%X user_esp=%X user_ss=%X\n",
+              child->tf->eip, child->tf->cs, child->tf->eflags,
+              child->tf->usermode_esp, child->tf->usermode_ss);
+    debug_log("child->tf regs: eax=%X ebx=%X ecx=%X edx=%X edi=%X esi=%X ebp=%X esp=%X\n",
+              child->tf->eax, child->tf->ebx, child->tf->ecx, child->tf->edx,
+              child->tf->edi, child->tf->esi, child->tf->ebp, child->tf->esp);
+    debug_log("child->kstack=%X kstack_top=%X kesp=%X\n", child->kstack, child->kstack_top, child->kesp);
+
     sp -= sizeof(Context);
     child->context = (Context*)sp;
     memset(child->context, 0, sizeof(Context));