feat: added (dumb) sigsegv catcher, small fmt fix

Cargo.toml

@@ -21,3 +21,4 @@ serde = "1.0.159"
 serde_json = "1.0.95"
 nix = "0.26.2"
 pretty-hex = "0.3"
+signal-hook = "0.3.15"

src/runtime/builtins.rs

@@ -1,13 +1,15 @@
 use std::{ffi::c_void, num::NonZeroUsize};
 
 use mlua::{Lua, Error, Variadic, Value, ToLua};
-use nix::sys::mman::{mprotect, ProtFlags, mmap, MapFlags, munmap};
 use pox::{proc_maps::get_process_maps, tricks::fmt_path};
+use nix::sys::{mman::{mprotect, ProtFlags, mmap, MapFlags, munmap}, signal::{Signal::SIGSEGV, SigHandler}};
 
 use crate::helpers::pretty_lua;
 
 use super::{console::Console, HELPTEXT};
 
+const SIGSEGV_HOOK : AtomicBool = AtomicBool::new(false);
+
 pub fn lua_help(lua: &Lua, _args: ()) -> Result<(), Error> {
 	let console : Console = lua.globals().get("console")?;
 	console.send(HELPTEXT.into())
@@ -185,6 +187,37 @@ pub fn lua_munmap(_: &Lua, (addr, len): (usize, usize)) -> Result<(), Error> {
 	}
 }
 
+extern fn handle_sigsegv(_signal: c_int) {
+	eprintln!("Segmentation fault (ignored)");
+}
+
+pub fn lua_catch_sigsev(_: &Lua, mode: Option<bool>) -> Result<bool, Error> {
+	match mode {
+		Some(m) => match m {
+			true => {
+				let handler = SigHandler::Handler(handle_sigsegv);
+				match unsafe { nix::sys::signal::signal(SIGSEGV, handler) } {
+					Ok(_h) => {
+						SIGSEGV_HOOK.store(true, Ordering::Relaxed);
+						Ok(true)
+					},
+					Err(e) => Err(Error::RuntimeError(format!("could not set sig handler ({}): {}", e, e.desc()))),
+				}
+			},
+			false => {
+				match unsafe { nix::sys::signal::signal(SIGSEGV, SigHandler::SigDfl) } {
+					Ok(_h) => {
+						SIGSEGV_HOOK.store(false, Ordering::Relaxed);
+						Ok(false)
+					},
+					Err(e) => Err(Error::RuntimeError(format!("could not reset sig handler ({}): {}", e, e.desc()))),
+				}
+			},
+		},
+		None => Ok(SIGSEGV_HOOK.load(Ordering::Relaxed)),
+	}
+}
+
 pub fn lua_exit(_: &Lua, code: Option<i32>) -> Result<(), Error> {
 	#[allow(unreachable_code)]
 	Ok(std::process::exit(code.unwrap_or(0)))

src/runtime/mod.rs

@@ -32,6 +32,7 @@ pub fn register_builtin_fn(lua: &Lua, console: broadcast::Sender<String>) -> Res
 	lua.globals().set("mmap",     lua.create_function(lua_mmap)?)?;
 	lua.globals().set("munmap",   lua.create_function(lua_munmap)?)?;
 	lua.globals().set("mprotect", lua.create_function(lua_mprotect)?)?;
+	lua.globals().set("sigsegv",  lua.create_function(lua_catch_sigsev)?)?;
 	lua.globals().set("help",     lua.create_function(lua_help)?)?;
 	lua.globals().set("x",        lua.create_function(lua_hex)?)?;
 	lua.globals().set("b",        lua.create_function(lua_bytes)?)?;
@@ -57,8 +58,9 @@ pub const HELPTEXT : &str = "?> This is a complete lua repl
  >  procmaps([ret])                  get process memory maps as string
  >  read(addr, size)                 read {size} raw bytes at {addr}
  >  write(addr, bytes)               write given {bytes} at {addr}
- >  find(ptr, len, match, [first])   search from {ptr} to {ptr+len} any or first {match}
- >  x(number)                        show hex representation of given {number}
+ >  find(ptr, len, match, [first])   search from {ptr} to {ptr+len} for {match} and return addrs
+ >  x(number, [prefix])              show hex representation of given {number}
  >  b(string)                        return array of bytes from given {string}
+ >  sigsegv([set])                   get or set SIGSEGV handler state
  >  help()                           print these messages
 ";