Linux Syscalls from Function Pointer Types

A procedural macro for generating a linux syscall inline assembly from the parameters and return type of a function pointer. Was designed for use with my executable packer project.

Planned Features

• Handle never return type
• Support for unnamed parameters
• Legacy syscalls via int 0x80

Example Usage

From rpx/stub/src/linux/syscall.rs

use proc_syscall::syscall;
/// arch/x86/entry/syscalls/syscall_64.tbl
#[cfg(target_arch = "x86_64")]
pub enum SysNum {    
	Exit = 60,    
	Execveat = 322,
}

#[syscall(SysNum::Execveat)]
pub type SysExecveat = fn(
	dir_fd: u32,
	path_name: *const u8,
	argv: *const *const u8,
	envp: *const *const u8,
	flags: u32,) -> u32;

#[syscall(SysNum::Execveat as usize)]
pub type SysExit = fn(code: i32) -> !;

Expands to:

#[inline(always)]
#[cfg(target_arch = "x86_64")]
pub unsafe fn sys_execveat(
	dir_fd: u32, 
	path_name: *const u8, 
	argv: *const *const u8,
	envp: *const *const u8,
	flags: u32,
	) -> u32 {
		let mut rax = SysNum::Execveat as _;
		asm!("syscall", 
			inout("rax") rax, 
			in ("rdi") dir_fd, 
			in ("rsi") path_name, 
			in ("rdx") argv, 
			in ("r10") envp, 
			in ("r8") flags, 
			clobber_abi("system"),               
			options(nostack)
		);
		rax        
}        

#[inline(always)]
#[cfg(target_arch = "x86_64")]
pub unsafe fn sys_exit(code: i32) -> ! {
	let rax = SysNum::Execveat as usize;
	asm!("syscall", 
		in ("rax") rax, 
		in ("rdi") code, 
		clobber_abi("system"),              
		options(noreturn, nostack)
	);
}