Macro syscall 

macro_rules! syscall {
    ([ro] $sysno:expr, $arg0:expr, $arg1:expr, $arg2:expr, $arg3:expr, $arg4:expr, $arg5:expr $(,)?) => { ... };
    ([ro] $sysno:expr, $arg0:expr, $arg1:expr, $arg2:expr, $arg3:expr, $arg4:expr $(,)?) => { ... };
    ([ro] $sysno:expr, $arg0:expr, $arg1:expr, $arg2:expr, $arg3:expr $(,)?) => { ... };
    ([ro] $sysno:expr, $arg0:expr, $arg1:expr, $arg2:expr $(,)?) => { ... };
    ([ro] $sysno:expr, $arg0:expr, $arg1:expr $(,)?) => { ... };
    ([!] $sysno:expr, $arg0:expr $(,)?) => { ... };
    ([ro] $sysno:expr, $arg0:expr $(,)?) => { ... };
    ([ro] $sysno:expr $(,)?) => { ... };
    ($sysno:expr, $arg0:expr, $arg1:expr, $arg2:expr, $arg3:expr, $arg4:expr, $arg5:expr $(,)?) => { ... };
    ($sysno:expr, $arg0:expr, $arg1:expr, $arg2:expr, $arg3:expr, $arg4:expr $(,)?) => { ... };
    ($sysno:expr, $arg0:expr, $arg1:expr, $arg2:expr, $arg3:expr $(,)?) => { ... };
    ($sysno:expr, $arg0:expr, $arg1:expr, $arg2:expr $(,)?) => { ... };
    ($sysno:expr, $arg0:expr, $arg1:expr $(,)?) => { ... };
    ($sysno:expr, $arg0:expr $(,)?) => { ... };
    ($sysno:expr $(,)?) => { ... };
}

Available on (Linux or Android) and (x86-64 and little-endian and 64-bit, or AArch64 and 64-bit, or ARM and 32-bit, or x86 and little-endian and 32-bit), or Linux and (x86-64 and little-endian and 32-bit, or RISC-V RV64 and little-endian and 64-bit, or RISC-V RV32 and little-endian and 32-bit, or MIPS and 32-bit, or MIPS-64 and 64-bit, or s390x and big-endian and 64-bit, or LoongArch LA64 and little-endian and 64-bit, or PowerPC and big-endian and 32-bit, or PowerPC-64 and 64-bit) only.

Make a syscall and returns a Result<usize, Errno>

Accept a Sysno as the first parameter and a variable number of arguments (0 to 6). It calls syscallN under the hood where N is the number of arguments.

The are two variations:

• [ro]: use the _readonly version of syscallN.
• [!]: use the _noreturn version of syscall1 (useful for exit).

Use the previous tags if you what are you doing, otherwise you can omit them.

Example

use linux_syscalls::{Errno, Sysno, syscall};

let mut buf: [u8; 1024] = [0; 1024];
let buf = loop {
    match unsafe { syscall!(Sysno::read, 0, buf.as_mut_ptr(), buf.len()) } {
        Ok(n) => break &buf[..n],
        Err(Errno::EINTR) => (),
        Err(err) => return Err(err),
    }
};

// [ro] because write do not change the memory.
unsafe { syscall!([ro] Sysno::write, 1, buf.as_ptr(), buf.len())? };

// [!] because exit do not return.
unsafe { syscall!([!] Sysno::exit, 0) };