arch/x86_64/syscall_setup.S


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.extern _kernel_task_sp
.extern syscall_handler

.global syscall_entry
.type syscall_entry @function
syscall_entry:
    swapgs
    movq %rsp, %rax
    movq (_kernel_task_bp), %rsp
    pushq %rax
    pushq %rbp
    pushq %rcx
    pushq %r11
    movq %rsp, %rbp
    call syscall_handler
    popq %r11
    popq %rcx
    popq %rbp
    popq %rsp
    swapgs
    sysretq

.global syscall_setup_syscall
.type syscall_setup_syscall @function
syscall_setup_syscall:
    movq $0xc0000080, %rcx
    rdmsr
    or $1, %eax
    wrmsr
    
    movq $0xc0000081, %rcx
    rdmsr
    mov  $0x001b0008, %edx
    wrmsr

    movq $0xc0000082, %rcx
    leaq syscall_entry, %rdx
    mov %edx, %eax
    shr $32, %rdx
    wrmsr

    retq