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Minimal Hello World in Rust
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| #![feature(asm, panic_implementation)] | |
| #![no_std] | |
| #![no_main] | |
| ///! With nightly compiler, run: | |
| ///! ```sh | |
| ///! rustc -O -C panic=abort -Z pre-link-arg=-nostartfiles no-std.rs | |
| ///! ``` | |
| #[panic_implementation] | |
| #[no_mangle] | |
| pub extern "C" fn panic(_: &core::panic::PanicInfo) -> ! { | |
| loop {} | |
| } | |
| pub mod syscall { | |
| pub struct Syscall<T>(::core::marker::PhantomData<T>); | |
| macro_rules! syscall_impl { | |
| ($syscall:ident $count:ident $id:ident, $ret:ident ( $( $arg:ident ),* ) { $asm:expr }) => { | |
| pub struct $count; | |
| impl $syscall<$count> { | |
| pub unsafe fn with($id: usize $(, $arg: usize)*) -> usize { | |
| let $ret: usize; | |
| $asm; | |
| $ret | |
| } | |
| } | |
| }; | |
| } | |
| syscall_impl!(Syscall Zero id, ret () { | |
| asm!( | |
| "syscall" | |
| : "={rax}"(ret) | |
| : "{rax}"(id) | |
| : "memory" | |
| : "volatile" | |
| ) | |
| }); | |
| syscall_impl!(Syscall One id, ret (arg1) { | |
| asm!( | |
| "syscall" | |
| : "={rax}"(ret) | |
| : "{rax}"(id), "{rdi}"(arg1) | |
| : "memory" | |
| : "volatile" | |
| ) | |
| }); | |
| syscall_impl!(Syscall Two id, ret (arg1, arg2) { | |
| asm!( | |
| "syscall" | |
| : "={rax}"(ret) | |
| : "{rax}"(id), "{rdi}"(arg1), "{rsi}"(arg2) | |
| : "memory" | |
| : "volatile" | |
| ) | |
| }); | |
| syscall_impl!(Syscall Three id, ret (arg1, arg2, arg3) { | |
| asm!( | |
| "syscall" | |
| : "={rax}"(ret) | |
| : "{rax}"(id), "{rdi}"(arg1), "{rsi}"(arg2), "{rdx}"(arg3) | |
| : "memory" | |
| : "volatile" | |
| ) | |
| }); | |
| } | |
| fn exit(code: usize) -> ! { | |
| use syscall::{Syscall, One}; | |
| unsafe { | |
| Syscall::<One>::with(60, code); | |
| core::hint::unreachable_unchecked(); | |
| } | |
| } | |
| fn puts(s: &str) { | |
| use syscall::{Syscall, Three}; | |
| unsafe { | |
| Syscall::<Three>::with( | |
| 1, | |
| 0, | |
| s as *const str as *const u8 as usize, | |
| s.len() | |
| ); | |
| } | |
| } | |
| #[no_mangle] | |
| pub extern "C" fn _start() -> ! { | |
| puts("Hello, world!\n"); | |
| exit(0); | |
| } |
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| no-std: file format elf64-x86-64 | |
| Disassembly of section .text: | |
| 0000000000001000 <_start>: | |
| 1000: 48 8d 35 f9 0f 00 00 lea 0xff9(%rip),%rsi # 2000 <_start+0x1000> | |
| 1007: b8 01 00 00 00 mov $0x1,%eax | |
| 100c: 31 ff xor %edi,%edi | |
| 100e: ba 0e 00 00 00 mov $0xe,%edx | |
| 1013: 0f 05 syscall | |
| 1015: b8 3c 00 00 00 mov $0x3c,%eax | |
| 101a: 31 ff xor %edi,%edi | |
| 101c: 0f 05 syscall | |
| 101e: 0f 0b ud2 |
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