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insn_impl_eh.h
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insn_impl_eh.h
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/*
* https://github.com/WebAssembly/exception-handling
*
* Implementation notes:
*
* - Because we don't have GC, we implement exnref as a copy-able type,
* rather than a reference to an object.
* cf. https://github.com/WebAssembly/exception-handling/issues/287
*
* Because of this approach, we have a fixed size limit on
* exception parameters. (TOYWASM_EXCEPTION_MAX_CELLS)
* It also means that we can't accept exnref as a parameter for exceptions.
*
* Note that this approach is incompatible with configurations with
* fixed-sized values because one value (exnref) needs to contain
* another. (eg. i32) For now, we just require TOYWASM_USE_SMALL_CELLS.
*
* - We don't have embedder APIs to deal with exceptions.
* cf.
* https://github.com/WebAssembly/exception-handling/blob/main/proposals/exception-handling/Exceptions.md#js-api
*/
INSN_IMPL(try_table)
{
int ret;
struct mem_context *mctx = NULL;
struct resulttype *rt_parameter = NULL;
struct resulttype *rt_result = NULL;
#if defined(__GNUC__) && !defined(__clang__)
ret = 0; /* suppress maybe-uninitialized warning */
#endif
LOAD_PC;
READ_LEB_S33(blocktype);
READ_LEB_U32(vec_count);
if (VALIDATING) {
struct validation_context *vctx = VCTX;
struct module *m = vctx->module;
mctx = validation_mctx(vctx);
ret = get_functype_for_blocktype(mctx, m, blocktype,
&rt_parameter, &rt_result);
if (ret != 0) {
goto fail;
}
ret = pop_valtypes(rt_parameter, vctx);
if (ret != 0) {
goto fail;
}
uint32_t i;
for (i = 0; i < vec_count; i++) {
uint32_t tagidx;
const struct tagtype *tt;
const struct functype *ft;
const struct resulttype *tag_rt = NULL;
bool with_exnref = false;
READ_U8(catch_op);
switch (catch_op) {
case CATCH_REF:
with_exnref = true;
/* fallthrough */
case CATCH:
READ_LEB_U32_TO(tagidx);
CHECK(tagidx < m->nimportedtags + m->ntags);
tt = module_tagtype(m, tagidx);
ft = module_tagtype_functype(m, tt);
tag_rt = &ft->parameter;
break;
case CATCH_ALL_REF:
with_exnref = true;
/* fallthrough */
case CATCH_ALL:
break;
default:
return validation_failure(
vctx, "unknown catch op %u", catch_op);
}
READ_LEB_U32(labelidx);
const struct resulttype *label_rt;
ret = target_label_types(vctx, labelidx, &label_rt);
if (ret != 0) {
goto fail;
}
uint32_t saved_height = vctx->valtypes.lsize;
if (tag_rt != NULL) {
ret = push_valtypes(tag_rt, vctx);
if (ret != 0) {
goto fail;
}
}
if (with_exnref) {
ret = push_valtype(TYPE_exnref, vctx);
if (ret != 0) {
goto fail;
}
}
if (vctx->valtypes.lsize - saved_height !=
label_rt->ntypes) {
ret = EINVAL;
goto fail;
}
ret = pop_valtypes(label_rt, vctx);
if (ret != 0) {
goto fail;
}
assert(vctx->valtypes.lsize == saved_height);
}
/*
* Note: we should push our control frame _after_
* validating catch labels. ("catch 0" points to the
* surrounding block, not the try_table block itself.)
*
* cf.
* https://github.com/WebAssembly/exception-handling/issues/286
*/
uint32_t pc = ptr2pc(m, ORIG_PC - 1);
ret = push_ctrlframe(pc, FRAME_OP_TRY_TABLE, 0, rt_parameter,
rt_result, vctx);
if (ret != 0) {
goto fail;
}
rt_parameter = NULL;
rt_result = NULL;
} else {
/*
* skip and ignore catch clauses.
* we will process them when an exception is
* actually thrown. (find_catch)
*/
uint32_t i;
for (i = 0; i < vec_count; i++) {
uint32_t tagidx;
READ_U8(catch_op);
switch (catch_op) {
case CATCH_REF:
case CATCH:
READ_LEB_U32_TO(tagidx);
break;
case CATCH_ALL_REF:
case CATCH_ALL:
break;
default:
assert(false);
}
READ_LEB_U32(labelidx);
}
if (EXECUTING) {
/*
* now it's same as block.
*/
push_label(ORIG_PC, STACK, ECTX);
}
}
SAVE_PC;
INSN_SUCCESS;
fail:
if (mctx != NULL) {
resulttype_free(mctx, rt_parameter);
resulttype_free(mctx, rt_result);
}
INSN_FAIL;
}
INSN_IMPL(throw)
{
int ret;
LOAD_PC;
READ_LEB_U32(tagidx);
if (EXECUTING || VALIDATING) {
const struct module *m = MODULE;
CHECK(tagidx < m->nimportedtags + m->ntags);
const struct tagtype *tt = module_tagtype(m, tagidx);
const struct functype *ft = module_tagtype_functype(m, tt);
const struct resulttype *rt = &ft->parameter;
if (EXECUTING) {
struct exec_context *ectx = ECTX;
/*
* pop the exception parameters, create an exception,
* and push exnref.
*/
SAVE_STACK_PTR;
push_exception(ectx, tagidx, rt);
LOAD_STACK_PTR;
/*
* now it's same as throw_ref.
*/
schedule_exception(ectx);
} else {
struct validation_context *vctx = VCTX;
ret = pop_valtypes(rt, vctx);
if (ret != 0) {
goto fail;
}
/*
* ensure to allocate enough stack for push_exception
*/
ret = push_valtype(TYPE_exnref, vctx);
if (ret != 0) {
goto fail;
}
mark_unreachable(vctx);
}
}
SAVE_PC;
INSN_SUCCESS_RETURN;
fail:
INSN_FAIL;
}
INSN_IMPL(throw_ref)
{
int ret;
LOAD_PC;
if (EXECUTING) {
schedule_exception(ECTX);
} else if (VALIDATING) {
struct validation_context *vctx = VCTX;
enum valtype t;
ret = pop_valtype(TYPE_exnref, &t, vctx);
if (ret != 0) {
goto fail;
}
mark_unreachable(vctx);
}
SAVE_PC;
INSN_SUCCESS_RETURN;
fail:
INSN_FAIL;
}