Always exit after machine code page protection change fails.

Reported by Sergey Kaplun.

(cherry picked from commit c50232e)

src/lj_mcode.c

@@ -180,14 +180,15 @@ static void mcode_protect(jit_State *J, int prot)
 #define MCPROT_RUN	MCPROT_RX
 
 /* Protection twiddling failed. Probably due to kernel security. */
-static LJ_NOINLINE void mcode_protfail(jit_State *J)
+static LJ_NORET LJ_NOINLINE void mcode_protfail(jit_State *J)
 {
   lua_CFunction panic = J2G(J)->panic;
   if (panic) {
     lua_State *L = J->L;
     setstrV(L, L->top++, lj_err_str(L, LJ_ERR_JITPROT));
     panic(L);
   }
+  exit(EXIT_FAILURE);
 }
 
 /* Change protection of MCode area. */

test/tarantool-tests/CMakeLists.txt

@@ -65,6 +65,7 @@ add_subdirectory(gh-6189-cur_L)
 add_subdirectory(lj-416-xor-before-jcc)
 add_subdirectory(lj-601-fix-gc-finderrfunc)
 add_subdirectory(lj-727-lightuserdata-itern)
+add_subdirectory(lj-802-panic-at-mcode-protfail)
 add_subdirectory(lj-flush-on-trace)
 
 # The part of the memory profiler toolchain is located in tools

test/tarantool-tests/lj-802-panic-at-mcode-protfail.test.lua

@@ -0,0 +1,26 @@
+local tap = require('tap')
+local test = tap.test('lj-flush-on-trace'):skipcond({
+  ['Test requires JIT enabled'] = not jit.status(),
+  ['Disabled on *BSD due to #4819'] = jit.os == 'BSD',
+  ['mprotect overriding can break Tarantool'] = _TARANTOOL,
+})
+
+test:plan(3)
+
+-- <makecmd> runs %testname%/script.lua by <LUAJIT_TEST_BINARY>
+-- with the given environment, launch options and CLI arguments.
+local script = require('utils').exec.makecmd(arg, {
+  env = { LD_PRELOAD = 'mymprotect.so' },
+  redirect = '2>&1',
+})
+
+local poison = 'runtime code generation succeed'
+local output = script(poison)
+test:like(output, 'runtime code generation failed, restricted kernel%?',
+          'Panic occurred as a result of <mprotect> failure')
+test:unlike(output, 'Segmentation fault',
+            'LuaJIT exited as a result of the panic (error check)')
+test:unlike(output, poison,
+            'LuaJIT exited as a result of the panic (poison check)')
+
+test:done(true)

test/tarantool-tests/lj-802-panic-at-mcode-protfail/CMakeLists.txt

@@ -0,0 +1 @@
+BuildTestCLib(mymprotect mymprotect.c)

test/tarantool-tests/lj-802-panic-at-mcode-protfail/mymprotect.c

@@ -0,0 +1,6 @@
+#include <sys/mman.h>
+
+int mprotect(void *addr, size_t len, int prot)
+{
+	return -1;
+}

test/tarantool-tests/lj-802-panic-at-mcode-protfail/script.lua

@@ -0,0 +1,11 @@
+jit.opt.start('hotloop=1')
+
+-- XXX: 
+local a = 0
+for i = 1, 3 do
+  a = a + i
+end
+
+-- XXX: Just a simple contract in case if panic at <mprotect>
+-- failure didn't occur.
+io.write(arg[1])