File size: 12,308 Bytes
3ce1a40 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 | #include "wasm.h"
#include <cstring>
namespace unify::wasm {
Value Value::f32(float v) { uint32_t b; std::memcpy(&b, &v, 4); return {ValType::F32, b}; }
Value Value::f64(double v) { uint64_t b; std::memcpy(&b, &v, 8); return {ValType::F64, b}; }
float Value::as_f32() const { uint32_t b = uint32_t(bits); float v; std::memcpy(&v, &b, 4); return v; }
double Value::as_f64() const { double v; std::memcpy(&v, &bits, 8); return v; }
void write_uleb(std::vector<uint8_t>& out, uint64_t v) {
do { uint8_t b = v & 0x7F; v >>= 7; if (v) b |= 0x80; out.push_back(b); } while (v);
}
void write_sleb(std::vector<uint8_t>& out, int64_t v) {
bool more = true;
while (more) {
uint8_t b = v & 0x7F;
v >>= 7;
if ((v == 0 && !(b & 0x40)) || (v == -1 && (b & 0x40))) more = false; else b |= 0x80;
out.push_back(b);
}
}
namespace {
struct Reader {
const uint8_t* p;
const uint8_t* end;
std::string err;
bool ok() const { return err.empty(); }
bool need(size_t n) { if (size_t(end - p) < n) { if (err.empty()) err = "unexpected end of module"; return false; } return true; }
uint8_t u8() { return need(1) ? *p++ : 0; }
uint64_t uleb(int max_bits = 32) {
uint64_t r = 0; int shift = 0;
for (;;) {
if (!need(1)) return 0;
uint8_t b = *p++;
r |= uint64_t(b & 0x7F) << shift;
shift += 7;
if (!(b & 0x80)) break;
if (shift >= max_bits + 7) { err = "LEB128 too long"; return 0; }
}
return r;
}
int64_t sleb(int bits) {
int64_t r = 0; int shift = 0; uint8_t b;
do {
if (!need(1)) return 0;
b = *p++;
r |= int64_t(b & 0x7F) << shift;
shift += 7;
if (shift > bits + 7) { err = "LEB128 too long"; return 0; }
} while (b & 0x80);
if (shift < 64 && (b & 0x40)) r |= -(int64_t(1) << shift);
return r;
}
std::string name() { uint64_t n = uleb(); if (!need(n)) return {}; std::string s(reinterpret_cast<const char*>(p), n); p += n; return s; }
ValType valtype() {
uint8_t t = u8();
if (t != 0x7F && t != 0x7E && t != 0x7D && t != 0x7C) { err = "unsupported value type"; return ValType::I32; }
return ValType(t);
}
};
// Evaluates a constant initializer expression (i32/i64/f32/f64.const ... end).
Value const_expr(Reader& r) {
Value v;
uint8_t op = r.u8();
switch (op) {
case 0x41: v = Value::i32(int32_t(r.sleb(32))); break;
case 0x42: v = Value::i64(r.sleb(64)); break;
case 0x43: { if (r.need(4)) { float f; std::memcpy(&f, r.p, 4); r.p += 4; v = Value::f32(f); } break; }
case 0x44: { if (r.need(8)) { double d; std::memcpy(&d, r.p, 8); r.p += 8; v = Value::f64(d); } break; }
default: r.err = "unsupported constant expression";
}
if (r.u8() != 0x0B) r.err = "constant expression not terminated";
return v;
}
// Skips one instruction's immediates. Returns false for unknown opcodes.
bool skip_immediates(Reader& r, uint8_t op) {
switch (op) {
case 0x02: case 0x03: case 0x04: { // blocktype: 0x40, valtype, or s33 type index
uint8_t b = *r.p;
if (b == 0x40 || b == 0x7F || b == 0x7E || b == 0x7D || b == 0x7C) r.p++; else r.sleb(33);
return true;
}
case 0x0C: case 0x0D: case 0x10: case 0x20: case 0x21: case 0x22: case 0x23: case 0x24: r.uleb(); return true;
case 0x0E: { uint64_t n = r.uleb(); for (uint64_t i = 0; i <= n; i++) r.uleb(); return true; }
case 0x11: r.uleb(); r.uleb(); return true;
case 0x3F: case 0x40: r.u8(); return true;
case 0x41: r.sleb(32); return true;
case 0x42: r.sleb(64); return true;
case 0x43: r.need(4); r.p += 4; return true;
case 0x44: r.need(8); r.p += 8; return true;
default:
if (op >= 0x28 && op <= 0x3E) { r.uleb(); r.uleb(); return true; } // memarg
if (op == 0x00 || op == 0x01 || op == 0x05 || op == 0x0B || op == 0x0F || op == 0x1A || op == 0x1B) return true;
if (op >= 0x45 && op <= 0xC4) return true; // numeric, no immediates
if (op == 0xFC) { r.uleb(); return true; } // saturating truncation prefix
return false;
}
}
// Builds block -> end / if -> else maps so branches jump in O(log n) without rescanning.
bool index_blocks(Function& f, std::string& err) {
Reader r{f.code.data(), f.code.data() + f.code.size(), {}};
std::vector<uint32_t> open;
while (r.p < r.end && r.ok()) {
uint32_t at = uint32_t(r.p - f.code.data());
uint8_t op = r.u8();
if (op == 0x02 || op == 0x03 || op == 0x04) open.push_back(at);
if (op == 0x05) {
if (open.empty()) { err = "else without if"; return false; }
f.else_of[open.back()] = at;
}
if (op == 0x0B) {
if (open.empty()) {
if (r.p != r.end) { err = "code after function end"; return false; }
return true;
}
f.end_of[open.back()] = at;
open.pop_back();
}
if (!skip_immediates(r, op)) { err = "unsupported opcode 0x" + std::to_string(op); return false; }
}
if (!r.ok()) { err = r.err; return false; }
err = "function body missing end";
return false;
}
} // namespace
bool decode(const std::vector<uint8_t>& bytes, Module& m, std::string& error) {
m = Module{};
Reader r{bytes.data(), bytes.data() + bytes.size(), {}};
static const uint8_t magic[8] = {0x00, 'a', 's', 'm', 0x01, 0x00, 0x00, 0x00};
if (bytes.size() < 8 || std::memcmp(bytes.data(), magic, 8)) { error = "not a WASM v1 module"; return false; }
r.p += 8;
std::vector<uint32_t> func_types;
uint8_t last_id = 0;
while (r.p < r.end && r.ok()) {
uint8_t id = r.u8();
uint64_t size = r.uleb();
if (!r.need(size)) break;
Reader s{r.p, r.p + size, {}};
r.p += size;
if (id != 0) {
if (id < last_id) { error = "sections out of order"; return false; }
last_id = id;
}
switch (id) {
case 0: break; // custom
case 1: { // type
uint64_t n = s.uleb();
for (uint64_t i = 0; i < n && s.ok(); i++) {
if (s.u8() != 0x60) { s.err = "expected func type"; break; }
FuncType t;
uint64_t np = s.uleb(); for (uint64_t k = 0; k < np; k++) t.params.push_back(s.valtype());
uint64_t nr = s.uleb(); for (uint64_t k = 0; k < nr; k++) t.results.push_back(s.valtype());
if (t.results.size() > 1) { s.err = "multi-value results unsupported"; break; }
m.types.push_back(t);
}
break;
}
case 2: { // import
uint64_t n = s.uleb();
for (uint64_t i = 0; i < n && s.ok(); i++) {
Import im;
im.module = s.name(); im.name = s.name(); im.kind = s.u8();
if (im.kind == 0) { im.type_index = uint32_t(s.uleb()); m.imported_funcs++; }
else if (im.kind == 2) {
uint8_t flags = s.u8();
im.min_pages = uint32_t(s.uleb());
if (flags & 1) { im.max_pages = uint32_t(s.uleb()); im.has_max = true; }
m.has_memory = m.memory_imported = true;
m.memory_min = im.min_pages; m.memory_max = im.max_pages; m.memory_has_max = im.has_max;
} else { s.err = "only function and memory imports are supported"; }
m.imports.push_back(im);
}
break;
}
case 3: { uint64_t n = s.uleb(); for (uint64_t i = 0; i < n; i++) func_types.push_back(uint32_t(s.uleb())); break; }
case 4: { // table
uint64_t n = s.uleb();
for (uint64_t i = 0; i < n; i++) { s.u8(); uint8_t f = s.u8(); s.uleb(); if (f & 1) s.uleb(); }
break;
}
case 5: { // memory
if (s.uleb() != 1) { s.err = "exactly one memory supported"; break; }
uint8_t flags = s.u8();
m.memory_min = uint32_t(s.uleb());
if (flags & 1) { m.memory_max = uint32_t(s.uleb()); m.memory_has_max = true; }
m.has_memory = true;
break;
}
case 6: { // global
uint64_t n = s.uleb();
for (uint64_t i = 0; i < n && s.ok(); i++) { Global g; g.type = s.valtype(); g.mut = s.u8() != 0; g.init = const_expr(s); m.globals.push_back(g); }
break;
}
case 7: { // export
uint64_t n = s.uleb();
for (uint64_t i = 0; i < n; i++) { Export e; e.name = s.name(); e.kind = s.u8(); e.index = uint32_t(s.uleb()); m.exports.push_back(e); }
break;
}
case 8: s.uleb(); break; // start (ignored: kernels have none)
case 9: { // elem (active, table 0, funcref indices)
uint64_t n = s.uleb();
for (uint64_t i = 0; i < n && s.ok(); i++) {
if (s.uleb() != 0) { s.err = "unsupported element segment"; break; }
Value off = const_expr(s);
uint64_t k = s.uleb();
uint32_t base = uint32_t(off.as_i32());
if (m.table.size() < base + k) m.table.resize(base + k, 0xFFFFFFFFu);
for (uint64_t j = 0; j < k; j++) m.table[base + j] = uint32_t(s.uleb());
}
break;
}
case 10: { // code
uint64_t n = s.uleb();
if (n != func_types.size()) { s.err = "function/code count mismatch"; break; }
for (uint64_t i = 0; i < n && s.ok(); i++) {
uint64_t body_size = s.uleb();
if (!s.need(body_size)) break;
Reader b{s.p, s.p + body_size, {}};
s.p += body_size;
Function f;
f.type_index = func_types[i];
uint64_t groups = b.uleb();
for (uint64_t g = 0; g < groups && b.ok(); g++) {
uint64_t count = b.uleb();
if (count > 50000) { b.err = "too many locals"; break; }
ValType t = b.valtype();
for (uint64_t k = 0; k < count; k++) f.locals.push_back(t);
}
if (!b.ok()) { s.err = b.err; break; }
f.code.assign(b.p, b.end);
std::string e;
if (!index_blocks(f, e)) { s.err = "function " + std::to_string(i) + ": " + e; break; }
m.functions.push_back(std::move(f));
}
break;
}
case 11: { // data (active, memory 0)
uint64_t n = s.uleb();
for (uint64_t i = 0; i < n && s.ok(); i++) {
if (s.uleb() != 0) { s.err = "unsupported data segment"; break; }
DataSegment d;
d.offset = uint32_t(const_expr(s).as_i32());
uint64_t len = s.uleb();
if (!s.need(len)) break;
d.bytes.assign(s.p, s.p + len);
s.p += len;
m.data.push_back(std::move(d));
}
break;
}
case 12: s.uleb(); break; // data count
default: error = "unknown section " + std::to_string(id); return false;
}
if (!s.ok()) { error = s.err; return false; }
}
if (!r.ok()) { error = r.err; return false; }
for (auto& f : m.functions) if (f.type_index >= m.types.size()) { error = "function type index out of range"; return false; }
for (auto& im : m.imports) if (im.kind == 0 && im.type_index >= m.types.size()) { error = "import type index out of range"; return false; }
return true;
}
} // namespace unify::wasm
|