/* opencoreC - Fast Syscall Entry Trampoline (x86_64) */
.global syscall_entry
.extern kernel_syscall_dispatcher

/* Per-CPU scratch: user RSP saved here on syscall entry */
.section .bss
.align 8
.global cpu0_scratch_user_rsp
cpu0_scratch_user_rsp:  .quad 0

.section .text
/*
 * syscall_entry:
 * On entry (SYSCALL from Ring 3):
 *   RCX = user RIP
 *   R11 = user RFLAGS
 *   RAX = syscall number
 *   RDI,RSI,RDX,R10,R8,R9 = args
 *   RSP = user RSP
 *
 * Strategy:
 *   1. Save user RSP into scratch area
 *   2. Load kernel RSP from TSS.RSP0 via gdt.rs TSS symbol
 *   3. Build SyscallRegisters on kernel stack
 *   4. Dispatch to Rust handler
 *   5. Restore & sysretq
 */
syscall_entry:
    /* Save user RSP */
    mov [rip + cpu0_scratch_user_rsp], rsp

    /* Load kernel stack from TSS.rsp0.
     * TSS is exported as 'TSS' from gdt.rs.
     * Layout: _reserved1(u32=4 bytes), rsp0(u64=8 bytes)
     * So TSS.rsp0 is at offset 4 from TSS start.
     */
    lea rsp, [rip + TSS]
    mov rsp, [rsp + 4]

    /* Push user RIP and RFLAGS */
    push rcx
    push r11

    /* Push syscall arguments as SyscallRegisters */
    push rax
    push rdi
    push rsi
    push rdx
    push r8
    push r9
    push r10

    mov rdi, rsp
    call kernel_syscall_dispatcher

    /* Restore args */
    pop r10
    pop r9
    pop r8
    pop rdx
    pop rsi
    pop rdi
    pop rax

    /* Restore user context */
    pop r11
    pop rcx

    /* Restore user RSP */
    mov rsp, [rip + cpu0_scratch_user_rsp]

    sysretq