gistfile1.txt

    .code64
    .section .text
    .global thread_context_switch
# from thread: rdi = interrupt_stack_frame*, rsi = registers_t*
# to thread: rdx = const interrupt_stack_frame*, rcx = const registers_t*
thread_context_switch:
# store general purpose registers to *rdi
    mov %r15, 0(%rdi)
    mov %r14, 8(%rdi)
    mov %r13, 16(%rdi)
    mov %r12, 24(%rdi)
    mov %r11, 32(%rdi)
    mov %r10, 40(%rdi)
    mov %r9, 48(%rdi)
    mov %r8, 56(%rdi)

    mov %rdi, 64(%rdi)
    mov %rsi, 72(%rdi)
    mov %rsp, 80(%rdi)
    mov %rbp, 88(%rdi)
    mov %rdx, 96(%rdi)
    mov %rcx, 104(%rdi)
    mov %rbx, 112(%rdi)
    mov %rax, 120(%rdi)

# store interrupt stack frame to *rsi: rip, cs, rflags, rsp, ss
    pop %rax
    mov %rax, 0(%rsi)
    mov %cs, %rax
    mov %rax, 8(%rsi)
    pushfq
    pop %rax
    mov %rax, 16(%rsi)
    mov %rsp, 24(%rsi)
    mov %ss, %rax
    mov %rax, 32(%rsi)

# restore interrupt stack frame from *rdx and push to stack
# push lret stack frame: rip, cs, rsp, ss
    push 32(%rdx) # offsetof(interrupt_stack_frame_t, ss) = 32
    push 24(%rdx) # offsetof(interrupt_stack_frame_t, rsp) = 24
    push 8(%rdx) # offsetof(interrupt_stack_frame_t, cs) = 8
    push 0(%rdx) # offsetof(interrupt_stack_frame_t, rip) = 0
# push rflags to stack
    push 16(%rdx) # offsetof(interrupt_stack_frame_t, rflags) = 16

# restore general purpose registers from *rcx
    mov 0(%rcx), %r15
    mov 8(%rcx), %r14
    mov 16(%rcx), %r13
    mov 24(%rcx), %r12
    mov 32(%rcx), %r11
    mov 40(%rcx), %r10
    mov 48(%rcx), %r9
    mov 56(%rcx), %r8

    mov 64(%rcx), %rdi
    mov 72(%rcx), %rsi
# rsp is omitted
    mov 88(%rcx), %rbp
    mov 96(%rcx), %rdx
    mov 112(%rcx), %rbx
    mov 120(%rcx), %rax
    mov 104(%rcx), %rcx # rcx is restored last

# pop flags and far return
    popfq
    lretq $0