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Replace error with PANIC for callbacks from JIT-compiled code.

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This commit is contained in:
Mike Pall 2012-10-21 19:15:03 +02:00
parent f6536c6696
commit 1d5c2ce4e2
2 changed files with 23 additions and 3 deletions
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16
doc/ext_ffi_semantics.html
View File

@ -934,6 +934,22 @@ advisable in general. Do this only if you know the C function, that
called the callback, copes with the forced stack unwinding and doesn't
leak resources.
</p>
<p>
One thing that's not allowed, is to let an FFI call into a C&nbsp;function
get JIT-compiled, which in turn calls a callback, calling into Lua again.
Usually this attempt is caught by the interpreter first and the
C&nbsp;function is blacklisted for compilation.
</p>
<p>
However, this heuristic may fail under specific circumstances: e.g. a
message polling function might not run Lua callbacks right away and the call
gets JIT-compiled. If it later happens to call back into Lua, you'll get a
VM PANIC with the message <tt>"bad callback"</tt>. Then you'll need to
manually turn off JIT-compilation with
<a href="ext_jit.html#jit_onoff_func"><tt>jit.off()</tt></a> for the
surrounding Lua function that invokes such a message polling function (or
similar).
</p>
<h3 id="callback_resources">Callback resource handling</h3>
<p>

10
src/lj_ccallback.c
View File

@ -527,10 +527,14 @@ static void callback_conv_result(CTState *cts, lua_State *L, TValue *o)
lua_State * LJ_FASTCALL lj_ccallback_enter(CTState *cts, void *cf)
{
lua_State *L = cts->L;
global_State *g = cts->g;
lua_assert(L != NULL);
if (gcref(cts->g->jit_L))
lj_err_caller(gco2th(gcref(cts->g->jit_L)), LJ_ERR_FFI_BADCBACK);
lj_trace_abort(cts->g); /* Never record across callback. */
if (gcref(g->jit_L)) {
setstrV(L, L->top++, lj_err_str(L, LJ_ERR_FFI_BADCBACK));
if (g->panic) g->panic(L);
exit(EXIT_FAILURE);
}
lj_trace_abort(g); /* Never record across callback. */
/* Setup C frame. */
cframe_prev(cf) = L->cframe;
setcframe_L(cf, L);