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[5.0] improve exception handling #24

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Oct 2, 2024
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[5.0] improve exception handling #24

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59 changes: 37 additions & 22 deletions include/eosio/vm/backend.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -58,14 +58,38 @@ namespace eosio { namespace vm {
static constexpr bool is_jit = false;
};

template <typename T>
struct maybe_unique_ptr {
maybe_unique_ptr(T* ptr = nullptr, bool owns = true) : ptr(ptr), owns(owns) {}
maybe_unique_ptr(const maybe_unique_ptr&) = delete;
maybe_unique_ptr& operator=(const maybe_unique_ptr&) = delete;
~maybe_unique_ptr() {
if (ptr && owns)
delete ptr;
}
T& operator*() const { return *ptr; }
T* operator->() const { return ptr; }
T* get() const { return ptr; }
void reset(T* new_ptr, bool new_owns = true) {
if (ptr && owns)
delete ptr;
this->ptr = new_ptr;
this->owns = new_owns;
}
private:
T* ptr;
public:
bool owns;
};

template <typename HostFunctions = std::nullptr_t, typename Impl = interpreter, typename Options = default_options, typename DebugInfo = null_debug_info>
class backend {
using host_t = detail::host_type_t<HostFunctions>;
using context_t = typename Impl::template context<HostFunctions>;
using parser_t = typename Impl::template parser<HostFunctions, Options, DebugInfo>;
void construct(host_t* host=nullptr) {
mod->finalize();
if (exec_ctx_created_by_backend) {
if (ctx.owns) {
ctx->set_wasm_allocator(memory_alloc);
}
// Now data required by JIT is finalized; create JIT module
Expand All @@ -76,13 +100,13 @@ namespace eosio { namespace vm {
// Important. Release the memory used by parsing.
mod->allocator.release_base_memory();
}
if (exec_ctx_created_by_backend) {
if (ctx.owns) {
ctx->initialize_globals();
}
if constexpr (!std::is_same_v<HostFunctions, std::nullptr_t>)
HostFunctions::resolve(*mod);
// FIXME: should not hard code knowledge of null_backend here
if (exec_ctx_created_by_backend) {
if (ctx.owns) {
if constexpr (!std::is_same_v<Impl, null_backend>)
initialize(host);
}
Expand Down Expand Up @@ -118,27 +142,19 @@ namespace eosio { namespace vm {
// * Contract validation only needs single parsing as the instantiated module is not cached.
// * JIT execution needs single parsing only.
// * Interpreter execution requires two-passes parsing to prevent memory mappings exhaustion
// * Leap reuses execution context per thread; is_exec_ctx_created_by_backend is set
// * Leap reuses execution context per thread; ctx.owns is set
// to false when a backend is constructued
backend(wasm_code_ptr& ptr, size_t sz, wasm_allocator* alloc, const Options& options = Options{}, bool single_parsing = true, bool exec_ctx_by_backend = true)
: memory_alloc(alloc), mod(std::make_shared<module>()), exec_ctx_created_by_backend(exec_ctx_by_backend), mod_sharable{true}, initial_max_call_depth(detail::get_max_call_depth(options)), initial_max_pages(detail::get_max_pages(options)) {
if (exec_ctx_created_by_backend) {
ctx = new context_t{parse_module2(ptr, sz, options, single_parsing), initial_max_call_depth};
: memory_alloc(alloc), mod(std::make_shared<module>()), ctx(nullptr, exec_ctx_by_backend), mod_sharable{true}, initial_max_call_depth(detail::get_max_call_depth(options)), initial_max_pages(detail::get_max_pages(options)) {
if (ctx.owns) {
ctx.reset(new context_t{parse_module2(ptr, sz, options, single_parsing), initial_max_call_depth});
ctx->set_max_pages(initial_max_pages);
} else {
parse_module2(ptr, sz, options, single_parsing);
}
construct();
}


~backend() {
if (exec_ctx_created_by_backend && ctx) {
// delete only if the context was created by the backend
delete ctx;
}
}

module& parse_module(wasm_code& code, const Options& options) {
mod->allocator.use_default_memory();
return parser_t{ mod->allocator, options }.parse_module(code, *mod, debug);
Expand Down Expand Up @@ -176,26 +192,26 @@ namespace eosio { namespace vm {
assert(from.mod_sharable); // `from` backend's mod is sharable
assert(!mod_sharable); // `to` backend's mod must not be sharable
mod = from.mod;
exec_ctx_created_by_backend = from.exec_ctx_created_by_backend;
ctx.owns = from.ctx.owns;
initial_max_call_depth = from.initial_max_call_depth;
initial_max_pages = from.initial_max_pages;
}

void set_context(context_t* ctx_ptr) {
// ctx cannot be set if it is created by the backend
assert(!exec_ctx_created_by_backend);
ctx = ctx_ptr;
assert(!ctx.owns);
ctx.reset(ctx_ptr, false);
}

inline void reset_max_call_depth() {
// max_call_depth cannot be reset if ctx is created by the backend
assert(!exec_ctx_created_by_backend);
assert(!ctx.owns);
ctx->set_max_call_depth(initial_max_call_depth);
}

inline void reset_max_pages() {
// max_pages cannot be reset if ctx is created by the backend
assert(!exec_ctx_created_by_backend);
assert(!ctx.owns);
ctx->set_max_pages(initial_max_pages);
}

Expand Down Expand Up @@ -349,8 +365,7 @@ namespace eosio { namespace vm {
wasm_allocator* memory_alloc = nullptr; // non owning pointer
std::shared_ptr<module> mod = nullptr;
DebugInfo debug;
context_t* ctx = nullptr;
bool exec_ctx_created_by_backend = true; // true if execution context is created by backend (legacy behavior), false if provided by users (Leap uses this)
maybe_unique_ptr<context_t> ctx = nullptr;
bool mod_sharable = false; // true if mod is sharable (compiled by the backend)
uint32_t initial_max_call_depth = 0;
uint32_t initial_max_pages = 0;
Expand Down