sysv.rs

// SPDX-License-Identifier: Apache-2.0

#[derive(Default)]
#[repr(C, align(16))]
pub struct Context([usize; 8]);

impl Context {
    #[naked]
    #[inline(never)]
    pub extern "C" fn wipe() {
        unsafe {
            asm!(
                "xor     rax, rax",
                "xor     rcx, rcx",
                "xor     rdx, rdx",
                "xor     rdi, rdi",
                "xor     rsi, rsi",
                "xor     r8,  r8",
                "xor     r9,  r9",
                "xor     r10, r10",
                "xor     r11, r11",
                "add     rax, rax",
                "cld",
                "ret",
                options(noreturn)
            )
        }
    }

    #[naked]
    #[must_use]
    #[inline(never)]
    pub extern "C" fn save(&mut self) -> bool {
        unsafe {
            asm!(
                "pop    rsi",
                "mov    [rdi + 0x00], r15",
                "mov    [rdi + 0x08], r14",
                "mov    [rdi + 0x10], r13",
                "mov    [rdi + 0x18], r12",
                "mov    [rdi + 0x20], rbx",
                "mov    [rdi + 0x28], rbp",
                "mov    [rdi + 0x30], rsp",
                "mov    [rdi + 0x38], rsi",
                "mov    rax, 1",
                "jmp    rsi",
                options(noreturn)
            )
        }
    }

    #[naked]
    #[inline(never)]
    pub unsafe extern "C" fn load(&self) -> ! {
        asm!(
            "mov     rax, 0",
            "mov     r15, [rdi + 0x00]",
            "mov     r14, [rdi + 0x08]",
            "mov     r13, [rdi + 0x10]",
            "mov     r12, [rdi + 0x18]",
            "mov     rbx, [rdi + 0x20]",
            "mov     rbp, [rdi + 0x28]",
            "mov     rsp, [rdi + 0x30]",
            "jmp          [rdi + 0x38]",
            options(noreturn)
        )
    }
}