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//! `sadness-generator` is a simple crate that provides multiple ways to make
//! any program it is executed in very sad.
#![allow(unsafe_code)]
use std::arch::asm;
/// How you would like your sadness.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum SadnessFlavor {
/// `SIGABRT`
///
/// Note that on Windows, [`std::process::abort`], the canonical way to
/// abort processes in Rust, uses the [fastfail](https://docs.microsoft.com/en-us/cpp/intrinsics/fastfail?view=msvc-170)
/// intrinsic, which neither raises a `SIGABRT` signal, nor issue a Windows
/// exception. The method in this library always uses `libc::abort`
Abort,
/// * `SIGSEGV` on Linux
/// * `EXCEPTION_ACCESS_VIOLATION` on Windows
/// * `EXC_BAD_ACCESS` on Macos
Segfault,
/// * `SIGFPE` on Linux
/// * `EXCEPTION_INT_DIVIDE_BY_ZERO` on Windows
/// * `EXC_ARITHMETIC` on Macos
DivideByZero,
/// * `SIGILL` on Linux
/// * `EXCEPTION_ILLEGAL_INSTRUCTION` on Windows
/// * `EXC_BAD_INSTRUCTION` on Macos
Illegal,
/// * `SIGBUS` on Linux
/// * `EXC_BAD_ACCESS` on Macos
#[cfg(unix)]
Bus,
/// * `SIGTRAP` on Linux
/// * `EXCEPTION_BREAKPOINT` on Windows
/// * `EXC_BREAKPOINT` on Macos
Trap,
/// * `SIGSEGV` on Linux
/// * `EXCEPTION_STACK_OVERFLOW` on Windows
/// * `EXC_BAD_ACCESS` on Macos
StackOverflow {
/// Raises the signal/exception from a non-[`std::thread::Thread`]
non_rust_thread: bool,
/// If using a native thread and there is a signal handler that longjumps,
/// we can't wait on the thread as we would normally as it would deadlock
long_jumps: bool,
},
/// Raises a [purecall](https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/purecall?view=msvc-170)
/// exception
#[cfg(windows)]
Purecall,
/// Raises a [invalid parameter](https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/invalid-parameter-functions?view=msvc-170)
/// exception
#[cfg(windows)]
InvalidParameter,
/// Raises an `EXC_GUARD` exception on Macos by placing a guard on a
/// file descriptor then attempting to perform the operation that was guarded
#[cfg(target_os = "macos")]
Guard,
}
impl SadnessFlavor {
/// This only ends one way. Sadness.
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
pub unsafe fn make_sad(self) -> ! {
match self {
Self::Abort => raise_abort(),
Self::Segfault => raise_segfault(),
Self::DivideByZero => raise_floating_point_exception(),
Self::Illegal => raise_illegal_instruction(),
#[cfg(unix)]
Self::Bus => raise_bus(),
Self::Trap => raise_trap(),
#[allow(unused_variables)]
Self::StackOverflow {
non_rust_thread,
long_jumps,
} => {
if !non_rust_thread {
raise_stack_overflow()
} else {
#[cfg(unix)]
{
raise_stack_overflow_in_non_rust_thread(long_jumps)
}
#[cfg(windows)]
{
raise_stack_overflow()
}
}
}
#[cfg(windows)]
Self::Purecall => raise_purecall(),
#[cfg(windows)]
Self::InvalidParameter => raise_invalid_parameter(),
#[cfg(target_os = "macos")]
Self::Guard => raise_guard_exception(),
}
}
}
/// [`SadnessFlavor::Abort`]
///
/// # Safety
///
/// This is not safe. It intentionally emits `SIGABRT`.
pub unsafe fn raise_abort() -> ! {
libc::abort()
}
/// This is the fixed address used to generate a segfault. It's possible that
/// this address can be mapped and writable by the your process in which case a
/// crash may not occur
#[cfg(target_pointer_width = "64")]
pub const SEGFAULT_ADDRESS: u64 = u32::MAX as u64 + 0x42;
#[cfg(target_pointer_width = "32")]
pub const SEGFAULT_ADDRESS: u32 = 0x42;
/// [`SadnessFlavor::Segfault`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
pub unsafe fn raise_segfault() -> ! {
let bad_ptr: *mut u8 = SEGFAULT_ADDRESS as _;
std::ptr::write_volatile(bad_ptr, 1);
// If we actually get here that means the address is mapped and writable
// by the current process which is...unexpected
std::process::abort()
}
/// [`SadnessFlavor::DivideByZero`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
pub unsafe fn raise_floating_point_exception() -> ! {
let ohno = {
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
{
let mut divisor: u32;
asm!(
"mov eax, 1",
"cdq",
"mov {div:e}, 0",
"idiv {div:e}",
div = out(reg) divisor
);
divisor
}
#[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
{
// Unfortunately ARM by default will not raise SIGFPE on divide
// by 0 and just return 0, so we just explicitly raise here for now
libc::raise(libc::SIGFPE);
0
}
};
println!("we won't get here because we've raised a floating point exception: {ohno}");
std::process::abort()
}
/// [`SadnessFlavor::Illegal`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
pub unsafe fn raise_illegal_instruction() -> ! {
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
asm!("ud2");
#[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
asm!("udf #0");
std::process::abort()
}
/// [`SadnessFlavor::Bus`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
#[cfg(unix)]
pub unsafe fn raise_bus() -> ! {
let mut temp_name = [0; 14];
temp_name.copy_from_slice(b"sigbus.XXXXXX\0");
let bus_fd = libc::mkstemp(temp_name.as_mut_ptr().cast());
assert!(bus_fd != -1);
let page_size = libc::sysconf(libc::_SC_PAGESIZE) as usize;
let mapping = std::slice::from_raw_parts_mut(
libc::mmap(
std::ptr::null_mut(),
128,
libc::PROT_READ | libc::PROT_WRITE,
libc::MAP_SHARED,
bus_fd,
0,
)
.cast::<u8>(),
page_size + page_size / 2,
);
libc::unlink(temp_name.as_ptr().cast());
// https://pubs.opengroup.org/onlinepubs/9699919799/functions/mmap.html
// The system shall always zero-fill any partial page at the end of
// an object. Further, the system shall never write out any modified
// portions of the last page of an object which are beyond its end.
// References within the address range starting at pa and continuing
// for len bytes to whole pages following the end of an object shall
// result in delivery of a SIGBUS signal.
mapping[20] = 20;
println!("{}", mapping[20]);
std::process::abort()
}
/// [`SadnessFlavor::Trap`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
pub unsafe fn raise_trap() -> ! {
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
asm!("int3");
#[cfg(target_arch = "arm")]
asm!(".inst 0xe7f001f0");
#[cfg(target_arch = "aarch64")]
asm!(".inst 0xd4200000");
std::process::abort()
}
/// [`SadnessFlavor::StackOverflow`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
pub unsafe fn raise_stack_overflow() -> ! {
fn recurse(data: u64) -> u64 {
let mut buff = [0u8; 256];
let mut result = data;
buff[..9].copy_from_slice(b"junk data");
for c in buff {
result += c as u64;
}
if result == 0 {
result
} else {
recurse(result) + 1
}
}
recurse(42);
std::process::abort()
}
/// [`SadnessFlavor::StackOverflow`]
///
/// This is raised inside of a non-Rust `std::thread::Thread` to ensure that
/// alternate stacks apply to all threads, even ones not created from Rust
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
#[cfg(unix)]
pub unsafe fn raise_stack_overflow_in_non_rust_thread(uses_longjmp: bool) -> ! {
let mut native: libc::pthread_t = std::mem::zeroed();
let mut attr: libc::pthread_attr_t = std::mem::zeroed();
assert_eq!(
libc::pthread_attr_setstacksize(&mut attr, 2 * 1024 * 1024),
0,
"failed to set thread stack size",
);
use std::sync;
let pair = sync::Arc::new((sync::Mutex::new(false), sync::Condvar::new()));
let tpair = pair.clone();
extern "C" fn thread_start(arg: *mut libc::c_void) -> *mut libc::c_void {
{
let tpair =
unsafe { sync::Arc::from_raw(arg as *const (sync::Mutex<bool>, sync::Condvar)) };
let (lock, cvar) = &*tpair;
let mut started = lock.lock().unwrap();
*started = true;
cvar.notify_one();
}
unsafe { raise_stack_overflow() };
}
let ret = libc::pthread_create(
&mut native,
&attr,
thread_start,
sync::Arc::into_raw(tpair) as *mut _,
);
// We might not get here, but that's ok
assert_eq!(
libc::pthread_attr_destroy(&mut attr),
0,
"failed to destroy thread attributes"
);
assert_eq!(ret, 0, "pthread_create failed");
// Note if we're doing longjmp shenanigans, we can't do thread join, that
// has to be handled by the calling code
if !uses_longjmp {
assert_eq!(
libc::pthread_join(native, std::ptr::null_mut()),
0,
"failed to join"
);
}
let (lock, cvar) = &*pair;
let mut started = lock.lock().unwrap();
while !*started {
started = cvar.wait(started).unwrap();
}
std::thread::sleep(std::time::Duration::from_millis(10));
#[allow(clippy::empty_loop)]
loop {}
}
/// [`SadnessFlavor::StackOverflow`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
#[inline]
#[cfg(unix)]
pub unsafe fn raise_stack_overflow_in_non_rust_thread_normal() -> ! {
raise_stack_overflow_in_non_rust_thread(false)
}
/// [`SadnessFlavor::StackOverflow`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
#[inline]
#[cfg(unix)]
pub unsafe fn raise_stack_overflow_in_non_rust_thread_longjmp() -> ! {
raise_stack_overflow_in_non_rust_thread(true)
}
/// [`SadnessFlavor::Purecall`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
#[cfg(target_os = "windows")]
pub unsafe fn raise_purecall() -> ! {
extern "C" {
fn _purecall() -> i32;
}
_purecall();
std::process::abort()
}
/// [`SadnessFlavor::InvalidParameter`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
#[cfg(target_os = "windows")]
pub unsafe fn raise_invalid_parameter() -> ! {
extern "C" {
fn _mbscmp(s1: *const u8, s2: *const u8) -> i32;
}
_mbscmp(std::ptr::null(), std::ptr::null());
std::process::abort()
}
/// The identifier used when guarding the file resource when raising
/// an `EXC_GUARD` exception via [`raise_guard_exception`]
#[cfg(target_os = "macos")]
pub const GUARD_ID: u64 = 0x1234567890abcdef;
/// [`SadnessFlavor::Guard`]
///
/// # Safety
///
/// This is not safe. It intentionally crashes.
#[cfg(target_os = "macos")]
pub unsafe fn raise_guard_exception() -> ! {
extern "C" {
/// <https://github.com/apple-oss-distributions/xnu/blob/e7776783b89a353188416a9a346c6cdb4928faad/bsd/sys/guarded.h#L48-L49>
fn guarded_open_np(
path: *const u8,
guard_id: *const u64,
guard_flags: u32,
flags: i32,
...
) -> i32;
}
// https://github.com/apple-oss-distributions/xnu/blob/e7776783b89a353188416a9a346c6cdb4928faad/bsd/sys/guarded.h#L67-L97
/// Forbid `close(2)`, and the implicit `close()` that a `dup2(2)` may do.
/// Forces close-on-fork to be set immutably too.
const GUARD_CLOSE: u32 = 1 << 0;
/// Forbid `dup(2)`, `dup2(2)`, and `fcntl(2)` subcodes `F_DUPFD`, `F_DUPFD_CLOEXEC`
/// on a guarded fd. Also forbids open's of a guarded fd via `/dev/fd/`
/// (an implicit dup.)
const GUARD_DUP: u32 = 1 << 1;
/// Forbid sending a guarded fd via a socket
const GUARD_SOCKET_IPC: u32 = 1 << 2;
/// Forbid creating a fileport from a guarded fd
const GUARD_FILEPORT: u32 = 1 << 3;
let fd = guarded_open_np(
b"/tmp/sadness-generator-guard.txt\0".as_ptr(),
&GUARD_ID,
GUARD_CLOSE | GUARD_DUP | GUARD_SOCKET_IPC | GUARD_FILEPORT,
libc::O_CREAT | libc::O_CLOEXEC | libc::O_RDWR,
0o666,
);
assert!(
fd != -1,
"failed to create guarded file descriptor, unable to crash"
);
// Since this operation was guarded, this will raise an EXC_GUARD exception
libc::close(fd);
std::process::abort()
}