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support for single wasm interface #20

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merged 3 commits into from
Sep 8, 2023
Merged

support for single wasm interface #20

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7d184fb
support single wasm interface
linh2931 Aug 23, 2023
b79fd16
remove copy constructor from backend and use a share method instead
linh2931 Aug 26, 2023
23d897d
prevent invalid sharing of compiled mod in backend
linh2931 Sep 1, 2023
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73 changes: 44 additions & 29 deletions include/eosio/vm/backend.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -64,52 +64,53 @@ namespace eosio { namespace vm {
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();
mod->finalize();
if (exec_ctx_created_by_backend) {
ctx->set_wasm_allocator(memory_alloc);
}
// Now data required by JIT is finalized; create JIT module
// such that memory used in parsing can be released.
if constexpr (Impl::is_jit) {
mod.make_jit_module();
mod->make_jit_module();

// Important. Release the memory used by parsing.
mod.allocator.release_base_memory();
mod->allocator.release_base_memory();
}
if (exec_ctx_created_by_backend) {
ctx->initialize_globals();
}
if constexpr (!std::is_same_v<HostFunctions, std::nullptr_t>)
HostFunctions::resolve(mod);
HostFunctions::resolve(*mod);
// FIXME: should not hard code knowledge of null_backend here
if (exec_ctx_created_by_backend) {
if constexpr (!std::is_same_v<Impl, null_backend>)
initialize(host);
}
}
public:
backend() {}
backend(wasm_code&& code, host_t& host, wasm_allocator* alloc, const Options& options = Options{})
: memory_alloc(alloc), ctx(new context_t{parse_module(code, options), detail::get_max_call_depth(options)}) {
: memory_alloc(alloc), mod(std::make_shared<module>()), ctx(new context_t{parse_module(code, options), detail::get_max_call_depth(options)}), mod_sharable{true} {
ctx->set_max_pages(detail::get_max_pages(options));
construct(&host);
}
backend(wasm_code&& code, wasm_allocator* alloc, const Options& options = Options{})
: memory_alloc(alloc), ctx(new context_t{parse_module(code, options), detail::get_max_call_depth(options)}) {
: memory_alloc(alloc), mod(std::make_shared<module>()), ctx(new context_t{parse_module(code, options), detail::get_max_call_depth(options)}), mod_sharable{true} {
ctx->set_max_pages(detail::get_max_pages(options));
construct();
}
backend(wasm_code& code, host_t& host, wasm_allocator* alloc, const Options& options = Options{})
: memory_alloc(alloc), ctx(new context_t{parse_module(code, options), detail::get_max_call_depth(options)}) {
: memory_alloc(alloc), mod(std::make_shared<module>()), ctx(new context_t{parse_module(code, options), detail::get_max_call_depth(options)}), mod_sharable{true} {
ctx->set_max_pages(detail::get_max_pages(options));
construct(&host);
}
backend(wasm_code& code, wasm_allocator* alloc, const Options& options = Options{})
: memory_alloc(alloc), ctx(new context_t{(parse_module(code, options)), detail::get_max_call_depth(options)}) {
: memory_alloc(alloc), mod(std::make_shared<module>()), ctx(new context_t{(parse_module(code, options)), detail::get_max_call_depth(options)}), mod_sharable{true} {
ctx->set_max_pages(detail::get_max_pages(options));
construct();
}
backend(wasm_code_ptr& ptr, size_t sz, host_t& host, wasm_allocator* alloc, const Options& options = Options{})
: memory_alloc(alloc), ctx(new context_t{parse_module2(ptr, sz, options, true), detail::get_max_call_depth(options)}) { // single parsing. original behavior {
: memory_alloc(alloc), mod(std::make_shared<module>()), ctx(new context_t{parse_module2(ptr, sz, options, true), detail::get_max_call_depth(options)}), mod_sharable{true} { // single parsing. original behavior {
ctx->set_max_pages(detail::get_max_pages(options));
construct(&host);
}
Expand All @@ -119,8 +120,8 @@ namespace eosio { namespace vm {
// * 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
// 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 is_exec_ctx_created_by_backend = true)
: memory_alloc(alloc), exec_ctx_created_by_backend(is_exec_ctx_created_by_backend), initial_max_call_depth(detail::get_max_call_depth(options)), initial_max_pages(detail::get_max_pages(options)) {
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};
ctx->set_max_pages(initial_max_pages);
Expand All @@ -130,6 +131,7 @@ namespace eosio { namespace vm {
construct();
}


~backend() {
if (exec_ctx_created_by_backend && ctx) {
// delete only if the context was created by the backend
Expand All @@ -138,14 +140,14 @@ namespace eosio { namespace vm {
}

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);
mod->allocator.use_default_memory();
return parser_t{ mod->allocator, options }.parse_module(code, *mod, debug);
}

module& parse_module2(wasm_code_ptr& ptr, size_t sz, const Options& options, bool single_parsing) {
if (single_parsing) {
mod.allocator.use_default_memory();
return parser_t{ mod.allocator, options }.parse_module2(ptr, sz, mod, debug);
mod->allocator.use_default_memory();
return parser_t{ mod->allocator, options }.parse_module2(ptr, sz, *mod, debug);
} else {
// To prevent large number of memory mappings used, two-passes of
// parsing are performed.
Expand All @@ -163,23 +165,36 @@ namespace eosio { namespace vm {
}

// Second pass: uses actual required memory for final parsing
mod.allocator.use_fixed_memory(largest_size);
return parser_t{ mod.allocator, options }.parse_module2(orig_ptr, sz, mod, debug);
mod->allocator.use_fixed_memory(largest_size);
return parser_t{ mod->allocator, options }.parse_module2(orig_ptr, sz, *mod, debug);
}
}

// Shares compiled module with another backend which never compiles
// module itself.
void share(const backend& from) {
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;
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This doesn't seem right. Nothing is changing ctx here, so exec_ctx_created_by_backend shouldn't change either.

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Thank you Steve @swatanabe for reviewing this!

The "empty" backend's exec_ctx_created_by_backend is constructed to have the default value true (to support legacy uses). It needs to be set to the actual value from the instantiated module when used the first time.

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This means that share can only be used in a very specific way. Any other combination will result in leaks or double deletes. This is really dangerous to begin with and it's not even documented or checked.

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Thanks. I added checks to prevent invalid sharing and added comments about the method.

initial_max_call_depth = from.initial_max_call_depth;
initial_max_pages = from.initial_max_pages;
}

void set_context(context_t* ctx_ptr) {
// execution context can be only set when it is not already created by the backend
// ctx cannot be set if it is created by the backend
assert(!exec_ctx_created_by_backend);
ctx = ctx_ptr;
}

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);
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);
ctx->set_max_pages(initial_max_pages);
}
Expand Down Expand Up @@ -277,13 +292,13 @@ namespace eosio { namespace vm {
std::atomic<bool> _timed_out = false;
auto reenable_code = scope_guard{[&](){
if (_timed_out) {
mod.allocator.enable_code(Impl::is_jit);
mod->allocator.enable_code(Impl::is_jit);
}
}};
try {
auto wd_guard = wd.scoped_run([this,&_timed_out]() {
_timed_out = true;
mod.allocator.disable_code();
mod->allocator.disable_code();
});
static_cast<F&&>(f)();
} catch(wasm_memory_exception&) {
Expand All @@ -298,9 +313,9 @@ namespace eosio { namespace vm {
template <typename Watchdog>
inline void execute_all(Watchdog&& wd, host_t& host) {
timed_run(static_cast<Watchdog&&>(wd), [&]() {
for (int i = 0; i < mod.exports.size(); i++) {
if (mod.exports[i].kind == external_kind::Function) {
std::string s{ (const char*)mod.exports[i].field_str.raw(), mod.exports[i].field_str.size() };
for (int i = 0; i < mod->exports.size(); i++) {
if (mod->exports[i].kind == external_kind::Function) {
std::string s{ (const char*)mod->exports[i].field_str.raw(), mod->exports[i].field_str.size() };
ctx->execute(host, interpret_visitor(*ctx), s);
}
}
Expand All @@ -310,9 +325,9 @@ namespace eosio { namespace vm {
template <typename Watchdog>
inline void execute_all(Watchdog&& wd) {
timed_run(static_cast<Watchdog&&>(wd), [&]() {
for (int i = 0; i < mod.exports.size(); i++) {
if (mod.exports[i].kind == external_kind::Function) {
std::string s{ (const char*)mod.exports[i].field_str.raw(), mod.exports[i].field_str.size() };
for (int i = 0; i < mod->exports.size(); i++) {
if (mod->exports[i].kind == external_kind::Function) {
std::string s{ (const char*)mod->exports[i].field_str.raw(), mod->exports[i].field_str.size() };
ctx->execute(nullptr, interpret_visitor(*ctx), s);
}
}
Expand All @@ -324,19 +339,19 @@ namespace eosio { namespace vm {
ctx->set_wasm_allocator(memory_alloc);
}

inline wasm_allocator* get_wasm_allocator() { return memory_alloc; }
inline module& get_module() { return mod; }
inline module& get_module() { return *mod; }
inline void exit(const std::error_code& ec) { ctx->exit(ec); }
inline auto& get_context() { return *ctx; }

const DebugInfo& get_debug() const { return debug; }

private:
wasm_allocator* memory_alloc = nullptr; // non owning pointer
module mod;
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)
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