https://github.com/python/cpython/commit/581c4434de62d9d36392f10e65866c081fb... commit: 581c4434de62d9d36392f10e65866c081fb18d71 branch: main author: Christian Heimes <christian@python.org> committer: miss-islington <31488909+miss-islington@users.noreply.github.com> date: 2022-03-30T12:28:33-07:00 summary: bpo-47162: Add call trampoline to mitigate bad fpcasts on Emscripten (GH-32189) files: A Misc/NEWS.d/next/Core and Builtins/2022-03-30-13-13-25.bpo-47162.yDJMUm.rst M Include/internal/pycore_object.h M Objects/call.c M Objects/descrobject.c M Objects/methodobject.c M Python/import.c M Python/importdl.c M Python/importdl.h diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h index 06671b5057afa..177b06e2dd4f7 100644 --- a/Include/internal/pycore_object.h +++ b/Include/internal/pycore_object.h @@ -242,6 +242,33 @@ extern PyObject* _PyType_GetSubclasses(PyTypeObject *); PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, PyObject *); +/* C function call trampolines to mitigate bad function pointer casts. + * + * Typical native ABIs ignore additional arguments or fill in missing + * values with 0/NULL in function pointer cast. Compilers do not show + * warnings when a function pointer is explicitly casted to an + * incompatible type. + * + * Bad fpcasts are an issue in WebAssembly. WASM's indirect_call has strict + * function signature checks. Argument count, types, and return type must + * match. + * + * Third party code unintentionally rely on problematic fpcasts. The call + * trampoline mitigates common occurences of bad fpcasts on Emscripten. + */ +#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE) +#define _PyCFunction_TrampolineCall(meth, self, args) \ + _PyCFunctionWithKeywords_TrampolineCall( \ + (*(PyCFunctionWithKeywords)(void(*)(void))meth), self, args, NULL) +extern PyObject* _PyCFunctionWithKeywords_TrampolineCall( + PyCFunctionWithKeywords meth, PyObject *, PyObject *, PyObject *); +#else +#define _PyCFunction_TrampolineCall(meth, self, args) \ + (meth)((self), (args)) +#define _PyCFunctionWithKeywords_TrampolineCall(meth, self, args, kw) \ + (meth)((self), (args), (kw)) +#endif // __EMSCRIPTEN__ && PY_CALL_TRAMPOLINE + #ifdef __cplusplus } #endif diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-03-30-13-13-25.bpo-47162.yDJMUm.rst b/Misc/NEWS.d/next/Core and Builtins/2022-03-30-13-13-25.bpo-47162.yDJMUm.rst new file mode 100644 index 0000000000000..7ecbfb37cd17b --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2022-03-30-13-13-25.bpo-47162.yDJMUm.rst @@ -0,0 +1,4 @@ +WebAssembly cannot deal with bad function pointer casts (different count +or types of arguments). Python can now use call trampolines to mitigate +the problem. Define :c:macro:`PY_CALL_TRAMPOLINE` to enable call +trampolines. diff --git a/Objects/call.c b/Objects/call.c index cf8fa1eeffe1c..448476223adc0 100644 --- a/Objects/call.c +++ b/Objects/call.c @@ -211,7 +211,8 @@ _PyObject_MakeTpCall(PyThreadState *tstate, PyObject *callable, PyObject *result = NULL; if (_Py_EnterRecursiveCall(tstate, " while calling a Python object") == 0) { - result = call(callable, argstuple, kwdict); + result = _PyCFunctionWithKeywords_TrampolineCall( + (PyCFunctionWithKeywords)call, callable, argstuple, kwdict); _Py_LeaveRecursiveCall(tstate); } diff --git a/Objects/descrobject.c b/Objects/descrobject.c index e255d4ae5f86f..7cbfe8d9c1940 100644 --- a/Objects/descrobject.c +++ b/Objects/descrobject.c @@ -13,6 +13,25 @@ class property "propertyobject *" "&PyProperty_Type" [clinic start generated code]*/ /*[clinic end generated code: output=da39a3ee5e6b4b0d input=556352653fd4c02e]*/ +// see pycore_object.h +#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE) +#include <emscripten.h> +EM_JS(PyObject*, descr_set_trampoline_call, (setter set, PyObject *obj, PyObject *value, void *closure), { + return wasmTable.get(set)(obj, value, closure); +}); + +EM_JS(PyObject*, descr_get_trampoline_call, (getter get, PyObject *obj, void *closure), { + return wasmTable.get(get)(obj, closure); +}); +#else +#define descr_set_trampoline_call(set, obj, value, closure) \ + (set)((obj), (value), (closure)) + +#define descr_get_trampoline_call(get, obj, closure) \ + (get)((obj), (closure)) + +#endif // __EMSCRIPTEN__ && PY_CALL_TRAMPOLINE + static void descr_dealloc(PyDescrObject *descr) { @@ -180,7 +199,8 @@ getset_get(PyGetSetDescrObject *descr, PyObject *obj, PyObject *type) return NULL; } if (descr->d_getset->get != NULL) - return descr->d_getset->get(obj, descr->d_getset->closure); + return descr_get_trampoline_call( + descr->d_getset->get, obj, descr->d_getset->closure); PyErr_Format(PyExc_AttributeError, "attribute '%V' of '%.100s' objects is not readable", descr_name((PyDescrObject *)descr), "?", @@ -232,8 +252,9 @@ getset_set(PyGetSetDescrObject *descr, PyObject *obj, PyObject *value) return -1; } if (descr->d_getset->set != NULL) { - return descr->d_getset->set(obj, value, - descr->d_getset->closure); + return descr_set_trampoline_call( + descr->d_getset->set, obj, value, + descr->d_getset->closure); } PyErr_Format(PyExc_AttributeError, "attribute '%V' of '%.100s' objects is not writable", @@ -306,7 +327,8 @@ method_vectorcall_VARARGS( Py_DECREF(argstuple); return NULL; } - PyObject *result = meth(args[0], argstuple); + PyObject *result = _PyCFunction_TrampolineCall( + meth, args[0], argstuple); Py_DECREF(argstuple); _Py_LeaveRecursiveCall(tstate); return result; @@ -339,7 +361,8 @@ method_vectorcall_VARARGS_KEYWORDS( if (meth == NULL) { goto exit; } - result = meth(args[0], argstuple, kwdict); + result = _PyCFunctionWithKeywords_TrampolineCall( + meth, args[0], argstuple, kwdict); _Py_LeaveRecursiveCall(tstate); exit: Py_DECREF(argstuple); @@ -427,7 +450,7 @@ method_vectorcall_NOARGS( if (meth == NULL) { return NULL; } - PyObject *result = meth(args[0], NULL); + PyObject *result = _PyCFunction_TrampolineCall(meth, args[0], NULL); _Py_LeaveRecursiveCall(tstate); return result; } @@ -455,7 +478,7 @@ method_vectorcall_O( if (meth == NULL) { return NULL; } - PyObject *result = meth(args[0], args[1]); + PyObject *result = _PyCFunction_TrampolineCall(meth, args[0], args[1]); _Py_LeaveRecursiveCall(tstate); return result; } diff --git a/Objects/methodobject.c b/Objects/methodobject.c index 93fac22ec437c..8bcb1e0fadb8c 100644 --- a/Objects/methodobject.c +++ b/Objects/methodobject.c @@ -483,7 +483,8 @@ cfunction_vectorcall_NOARGS( if (meth == NULL) { return NULL; } - PyObject *result = meth(PyCFunction_GET_SELF(func), NULL); + PyObject *result = _PyCFunction_TrampolineCall( + meth, PyCFunction_GET_SELF(func), NULL); _Py_LeaveRecursiveCall(tstate); return result; } @@ -510,7 +511,8 @@ cfunction_vectorcall_O( if (meth == NULL) { return NULL; } - PyObject *result = meth(PyCFunction_GET_SELF(func), args[0]); + PyObject *result = _PyCFunction_TrampolineCall( + meth, PyCFunction_GET_SELF(func), args[0]); _Py_LeaveRecursiveCall(tstate); return result; } @@ -537,7 +539,9 @@ cfunction_call(PyObject *func, PyObject *args, PyObject *kwargs) PyObject *result; if (flags & METH_KEYWORDS) { - result = (*(PyCFunctionWithKeywords)(void(*)(void))meth)(self, args, kwargs); + result = _PyCFunctionWithKeywords_TrampolineCall( + (*(PyCFunctionWithKeywords)(void(*)(void))meth), + self, args, kwargs); } else { if (kwargs != NULL && PyDict_GET_SIZE(kwargs) != 0) { @@ -546,7 +550,15 @@ cfunction_call(PyObject *func, PyObject *args, PyObject *kwargs) ((PyCFunctionObject*)func)->m_ml->ml_name); return NULL; } - result = meth(self, args); + result = _PyCFunction_TrampolineCall(meth, self, args); } return _Py_CheckFunctionResult(tstate, func, result, NULL); } + +#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE) +#include <emscripten.h> + +EM_JS(PyObject*, _PyCFunctionWithKeywords_TrampolineCall, (PyCFunctionWithKeywords func, PyObject *self, PyObject *args, PyObject *kw), { + return wasmTable.get(func)(self, args, kw); +}); +#endif diff --git a/Python/import.c b/Python/import.c index 982ec8cfe631a..4b6d6d16821a9 100644 --- a/Python/import.c +++ b/Python/import.c @@ -527,7 +527,7 @@ import_find_extension(PyThreadState *tstate, PyObject *name, else { if (def->m_base.m_init == NULL) return NULL; - mod = def->m_base.m_init(); + mod = _PyImport_InitFunc_TrampolineCall(def->m_base.m_init); if (mod == NULL) return NULL; if (PyObject_SetItem(modules, name, mod) == -1) { @@ -958,6 +958,13 @@ PyImport_GetImporter(PyObject *path) return get_path_importer(tstate, path_importer_cache, path_hooks, path); } +#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE) +#include <emscripten.h> +EM_JS(PyObject*, _PyImport_InitFunc_TrampolineCall, (PyModInitFunction func), { + return wasmTable.get(func)(); +}); +#endif // __EMSCRIPTEN__ && PY_CALL_TRAMPOLINE + static PyObject* create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec) { @@ -973,8 +980,7 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec) /* Cannot re-init internal module ("sys" or "builtins") */ return PyImport_AddModuleObject(name); } - - mod = (*p->initfunc)(); + mod = _PyImport_InitFunc_TrampolineCall(*p->initfunc); if (mod == NULL) { return NULL; } diff --git a/Python/importdl.c b/Python/importdl.c index f66c6013d2c98..870ae2730071b 100644 --- a/Python/importdl.c +++ b/Python/importdl.c @@ -102,7 +102,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp) const char *oldcontext; dl_funcptr exportfunc; PyModuleDef *def; - PyObject *(*p0)(void); + PyModInitFunction p0; name_unicode = PyObject_GetAttrString(spec, "name"); if (name_unicode == NULL) { @@ -157,7 +157,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp) goto error; } - p0 = (PyObject *(*)(void))exportfunc; + p0 = (PyModInitFunction)exportfunc; /* Package context is needed for single-phase init */ oldcontext = _Py_PackageContext; @@ -166,7 +166,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp) _Py_PackageContext = oldcontext; goto error; } - m = p0(); + m = _PyImport_InitFunc_TrampolineCall(p0); _Py_PackageContext = oldcontext; if (m == NULL) { diff --git a/Python/importdl.h b/Python/importdl.h index 9847652b1f1b3..26d18b626df05 100644 --- a/Python/importdl.h +++ b/Python/importdl.h @@ -10,6 +10,14 @@ extern const char *_PyImport_DynLoadFiletab[]; extern PyObject *_PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *); +typedef PyObject *(*PyModInitFunction)(void); + +#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE) +extern PyObject *_PyImport_InitFunc_TrampolineCall(PyModInitFunction func); +#else +#define _PyImport_InitFunc_TrampolineCall(func) (func)() +#endif + /* Max length of module suffix searched for -- accommodates "module.slb" */ #define MAXSUFFIXSIZE 12