lua: add Lua bindings

Signed-off-by: Rubicon Rowe <l1589002388@gmail.com>

.gitignore

@@ -69,3 +69,12 @@ tests/tests_*
 tests/*.log
 tests/*.trs
 test-suite.log
+
+# Cached files
+.cache/
+compile_commands.json
+
+# LuaRocks development files
+/luarocks
+/lua_modules
+/.luarocks

Makefile.am

@@ -86,6 +86,20 @@ python_crun_la_LDFLAGS = -avoid-version -module $(PYTHON_LDFLAGS)
 python_crun_la_LIBADD = libcrun.la $(PYTHON_LIBS) $(FOUND_LIBS) $(maybe_libyajl.la)
 endif
 
+if LUA_BINDINGS
+noinst_LTLIBRARIES = libcrun-bundled.la
+luaexec_LTLIBRARIES = luacrun.la
+luacrun_la_SOURCES = lua/lua_crun.c
+luacrun_la_CFLAGS = -I $(abs_top_srcdir)/libocispec/src -I $(abs_top_builddir)/libocispec/src -I $(abs_top_builddir)/src $(LUA_INCLUDE)
+luacrun_la_LDFLAGS = -avoid-version -module
+luacrun_la_LIBADD = libcrun-bundled.la $(LUA_LIB) $(FOUND_LIBS)
+
+libcrun_bundled_la_SOURCES = $(libcrun_SOURCES)
+libcrun_bundled_la_CFLAGS = -I $(abs_top_builddir)/libocispec/src -I $(abs_top_srcdir)/libocispec/src -fvisibility=hidden
+libcrun_bundled_la_LIBADD = libocispec/libocispec.la $(FOUND_LIBS) $(maybe_libyajl.la)
+libcrun_bundled_la_LDFLAGS = -Wl,--version-script=$(abs_top_srcdir)/libcrun.lds
+endif
+
 crun_CFLAGS = -I $(abs_top_builddir)/libocispec/src -I $(abs_top_srcdir)/libocispec/src -D CRUN_LIBDIR="\"$(CRUN_LIBDIR)\""
 crun_SOURCES = src/crun.c src/run.c src/delete.c src/kill.c src/pause.c src/unpause.c src/spec.c \
 		src/exec.c src/list.c src/create.c src/start.c src/state.c src/update.c src/ps.c \

README.md

@@ -176,3 +176,7 @@ $ sudo su -
 # molecule converge
 # molecule verify
 ```
+
+## Lua bindings
+
+A Lua binding is available. See [the README](lua/README.md) for more information.

configure.ac

@@ -173,6 +173,15 @@ AS_IF([test "x$with_python_bindings" = "xyes"], [
         use_fPIC=yes
 ])
 
+AC_ARG_WITH([lua-bindings], AS_HELP_STRING([--with-lua-bindings], [build the Lua bindings]))
+
+AS_IF([test "x$with_lua_bindings" = "xyes"], [
+	AX_PROG_LUA([5.4], [5.5], [], [AC_MSG_ERROR([*** lua interpreter not found])])
+	AX_LUA_HEADERS([], [AC_MSG_ERROR([*** lua headers not found])])
+	AX_LUA_LIBS([], [AC_MSG_ERROR([*** lua libs not found])])
+	use_fPIC=yes
+])
+
 AS_IF([test "x$use_fPIC" = "xyes"], [
 	# configure should not touch CFLAGS/LDFLAGS but we need it to propagate it
 	# to libocispec.
@@ -253,6 +262,7 @@ fi
 AC_SEARCH_LIBS([argp_parse], [argp], [], [AC_MSG_ERROR([*** argp functions not found - install libargp or argp_standalone])])
 
 AM_CONDITIONAL([PYTHON_BINDINGS], [test "x$with_python_bindings" = "xyes"])
+AM_CONDITIONAL([LUA_BINDINGS], [test "x$with_lua_bindings" = "xyes"])
 AM_CONDITIONAL([CRIU_SUPPORT], [test "x$have_criu" = "xyes"])
 AM_CONDITIONAL([SHARED_LIBCRUN], [test "x$enable_shared" = "xyes"])
 

lua/README.md

@@ -0,0 +1,120 @@
+# Lua binding for libcrun
+
+Bare libcrun interface for Lua.
+
+There are some problems still and the API is a subject to change.
+
+## Build
+
+Only build static archive, to be bundled with another program:
+
+````sh
+./configure --with-lua-bindings
+make && make install
+````
+
+Since the final product bundle libcrun, you don't need to link libcrun at runtime.
+
+
+For the library using at runtime, add option `--enable-shared`:
+````sh
+./configure --with-lua-bindings --enable-shared
+make && make install
+````
+
+Other options to build libcrun may affect the bundled libcrun.
+
+## Usage
+
+See `luacrun.d.tl`.
+
+## Works with your LuaRocks project
+
+You can configure the prefix as your `lua_modules` to access this library in your project.
+
+````sh
+./configure --with-lua-bindings --enable-shared --prefix $(pwd)/lua_modules
+````
+
+## Interpreter may restart?
+
+Related issue: [#695: [Python bindings] Python interpreter restarts (?) after first import of python_crun](https://github.com/containers/crun/issues/695)
+
+The lua interpreter may restart at the first open of the library (may not happen if statically linked into your program). It's side effect of [a protection (click for the code)](https://github.com/containers/crun/blob/923447b691dbd7c5bffbaee1427460d62d848047/src/libcrun/linux.c#L3881-L3891) to avoid attacks like [CVE-2019-5736](https://nvd.nist.gov/vuln/detail/CVE-2019-5736).
+
+To ease the hurt, always place the `require` call at the start of your program:
+
+````lua
+-- entry point module for luabundler
+require "luacrun"
+
+return function(...) -- the entry point
+    print("Hello World!")
+end
+````
+
+It's not required to use the library at the moment. Since it is cached, the `require()` will not open the library again.
+
+If the entry point is at the C-side, you may use the `luaL_requiref` to open the library instead of `require()` call in Lua code.
+````c
+#include <lua.h>
+#include <lauxlib.h>
+
+extern int luaopen_luacrun(lua_State *S);
+
+int main(int argc, char *argv[]) {
+    lua_State *S = luaL_newstate();
+    // Open the library before any actual logic,
+    // to make sure users will not notice the program have actually started twice
+    luaL_requiref(S, "luacrun", &luaopen_luacrun, false);
+    lua_pop(S, 1);
+    // ...your code
+}
+````
+
+The protection might cause another problem in REPL:
+````
+$ lua
+Lua 5.4.4  Copyright (C) 1994-2022 Lua.org, PUC-Rio
+> luacrun = require "luacrun"
+Lua 5.4.4  Copyright (C) 1994-2022 Lua.org, PUC-Rio
+> luacrun
+nil
+>
+````
+
+When you call `require "luacrun"` at the first time, the REPL restarted and the state have been reset.
+
+The workaround is `require "luacrun"` again and you get the library this time. The protection will not apply again if it's already applied.
+````
+$ lua
+Lua 5.4.4  Copyright (C) 1994-2022 Lua.org, PUC-Rio
+> luacrun = require "luacrun"
+Lua 5.4.4  Copyright (C) 1994-2022 Lua.org, PUC-Rio
+> luacrun
+nil
+> luacrun = require "luacrun"
+> luacrun
+table: 0x561edad470d0
+>
+````
+
+It's safe to use luacrun in multi-state usage, the program restarts only once.
+
+
+## Test
+
+You need [busted](https://lunarmodules.github.io/busted/) and below dependencies to run tests:
+
+- [dkjson](https://luarocks.org/modules/dhkolf/dkjson)
+- [luaposix](https://luaposix.github.io)
+
+````sh
+luarocks install busted dkjson luaposix
+````
+
+The tests assume environment variable `INIT` exists. It's the `init` program compiled in `tests`.
+
+````sh
+INIT=$(pwd)/tests/init lua_modules/bin/busted lua
+````