src/kernel --> src/

src/arch/syscalls.asm

@@ -0,0 +1,94 @@
+; Copyright (c) 2023-2026 Chris (boreddevnl)
+; This software is released under the GNU General Public License v3.0. See LICENSE file for details.
+; This header needs to maintain in any file it is present in, as per the GPL license terms.
+global syscall_entry
+extern syscall_handler_c
+
+section .text
+
+; Syscall ABI:
+; RDI = syscall_num
+; RSI = arg1
+; RDX = arg2
+; R10 = arg3
+; R8  = arg4
+; R9  = arg5
+
+syscall_entry:
+    ; 1. Switch to Kernel Stack safely
+    ; Note: For true SMP safety, we need per-CPU storage (via swapgs).
+    ; For now, we use a global scratch which is only safe because we mask interrupts on entry.
+    mov [rel user_rsp_scratch], rsp
+    mov rsp, [rel kernel_syscall_stack]
+
+    ; 2. Build iretq frame (compatible with registers_t)
+    push 0x1B           ; SS (User Data)
+    push qword [rel user_rsp_scratch] ; RSP
+    push r11            ; RFLAGS (captured by syscall)
+    push 0x23           ; CS (User Code)
+    push rcx            ; RIP (return address from syscall)
+    
+    push 0              ; err_code
+    push 0              ; int_no (can be used for syscall vector)
+    
+    ; 3. Save all registers in registers_t order
+    push rax
+    push rbx
+    push rcx
+    push rdx
+    push rsi
+    push rdi
+    push rbp
+    push r8
+    push r9
+    push r10
+    push r11
+    push r12
+    push r13
+    push r14
+    push r15
+    
+    ; Save SSE/FPU state
+    sub rsp, 512
+    fxsave [rsp]
+
+    ; 4. Call C handler with registers_t*
+    mov rdi, rsp
+    call syscall_handler_c
+
+    ; 5. Switch to the resulting RSP (might be different if task switched)
+    mov rsp, rax
+
+    ; Restore SSE/FPU state
+    fxrstor [rsp]
+    add rsp, 512
+
+    ; 6. Restore and return via iretq
+    pop r15
+    pop r14
+    pop r13
+    pop r12
+    pop r11
+    pop r10
+    pop r9
+    pop r8
+    pop rbp
+    pop rdi
+    pop rsi
+    pop rdx
+    pop rcx
+    pop rbx
+    pop rax
+    add rsp, 16 ; drop int_no/err_code
+    
+    ; Debug: check RIP before iretq
+    ; We can't easily print from here without destroying registers, 
+    ; but we can at least check if it's canonical.
+    
+    iretq
+
+section .bss
+global kernel_syscall_stack
+global user_rsp_scratch
+kernel_syscall_stack: resq 1
+user_rsp_scratch: resq 1