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Merged
merged 1 commit into from
Sep 11, 2021
Merged

Support new dylink.0 custom section format #15019

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108 changes: 76 additions & 32 deletions src/library_dylink.js
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Original file line number Diff line number Diff line change
Expand Up @@ -256,60 +256,104 @@ var LibraryDylink = {
// returns the side module metadata as an object
// { memorySize, memoryAlign, tableSize, tableAlign, neededDynlibs}
$getDylinkMetadata: function(binary) {
var next = 0;
var offset = 0;
var end = 0;

function getU8() {
return binary[offset++];
}

function getLEB() {
var ret = 0;
var mul = 1;
while (1) {
var byte = binary[next++];
var byte = binary[offset++];
ret += ((byte & 0x7f) * mul);
mul *= 0x80;
if (!(byte & 0x80)) break;
}
return ret;
}

function getString() {
var len = getLEB();
offset += len;
return UTF8ArrayToString(binary, offset - len, len);
}

var name = 'dylink.0';
if (binary instanceof WebAssembly.Module) {
var dylinkSection = WebAssembly.Module.customSections(binary, "dylink");
var dylinkSection = WebAssembly.Module.customSections(binary, name);
if (dylinkSection.length === 0) {
name = 'dylink'
dylinkSection = WebAssembly.Module.customSections(binary, name);
}
assert(dylinkSection.length != 0, 'need dylink section');
binary = new Uint8Array(dylinkSection[0]);
end = binary.length
} else {
var int32View = new Uint32Array(new Uint8Array(binary.subarray(0, 24)).buffer);
assert(int32View[0] == 0x6d736100, 'need to see wasm magic number'); // \0asm
// we should see the dylink section right after the magic number and wasm version
// we should see the dylink custom section right after the magic number and wasm version
assert(binary[8] === 0, 'need the dylink section to be first')
next = 9;
getLEB(); //section size
assert(binary[next] === 6); next++; // size of "dylink" string
assert(binary[next] === 'd'.charCodeAt(0)); next++;
assert(binary[next] === 'y'.charCodeAt(0)); next++;
assert(binary[next] === 'l'.charCodeAt(0)); next++;
assert(binary[next] === 'i'.charCodeAt(0)); next++;
assert(binary[next] === 'n'.charCodeAt(0)); next++;
assert(binary[next] === 'k'.charCodeAt(0)); next++;
}

var customSection = {};
customSection.memorySize = getLEB();
customSection.memoryAlign = getLEB();
customSection.tableSize = getLEB();
customSection.tableAlign = getLEB();
offset = 9;
var section_size = getLEB(); //section size
end = offset + section_size;
name = getString();
}

var customSection = { neededDynlibs: [] };
if (name == 'dylink') {
customSection.memorySize = getLEB();
customSection.memoryAlign = getLEB();
customSection.tableSize = getLEB();
customSection.tableAlign = getLEB();
// shared libraries this module needs. We need to load them first, so that
// current module could resolve its imports. (see tools/shared.py
// WebAssembly.make_shared_library() for "dylink" section extension format)
var neededDynlibsCount = getLEB();
for (var i = 0; i < neededDynlibsCount; ++i) {
var name = getString();
customSection.neededDynlibs.push(name);
}
} else {
assert(name === 'dylink.0');
var WASM_DYLINK_MEM_INFO = 0x1;
var WASM_DYLINK_NEEDED = 0x2;
while (offset < end) {
var subsectionType = getU8();
var subsectionSize = getLEB();
if (subsectionType === WASM_DYLINK_MEM_INFO) {
customSection.memorySize = getLEB();
customSection.memoryAlign = getLEB();
customSection.tableSize = getLEB();
customSection.tableAlign = getLEB();
} else if (subsectionType === WASM_DYLINK_NEEDED) {
var neededDynlibsCount = getLEB();
for (var i = 0; i < neededDynlibsCount; ++i) {
var name = getString();
customSection.neededDynlibs.push(name);
}
} else {
#if ASSERTIONS
err('unknown dylink.0 subsection: ' + subsectionType)
#endif
// unknown subsection
offset += subsectionSize;
}
}
}

#if ASSERTIONS
var tableAlign = Math.pow(2, customSection.tableAlign);
assert(tableAlign === 1, 'invalid tableAlign ' + tableAlign);
#endif
// shared libraries this module needs. We need to load them first, so that
// current module could resolve its imports. (see tools/shared.py
// WebAssembly.make_shared_library() for "dylink" section extension format)
var neededDynlibsCount = getLEB();
customSection.neededDynlibs = [];
for (var i = 0; i < neededDynlibsCount; ++i) {
var nameLen = getLEB();
var nameUTF8 = binary.subarray(next, next + nameLen);
next += nameLen;
var name = UTF8ArrayToString(nameUTF8, 0);
customSection.neededDynlibs.push(name);
}

#if DYLINK_DEBUG
err('dylink needed:' + customSection.neededDynlibs);
#endif

assert(offset == end);
return customSection;
},

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2 changes: 1 addition & 1 deletion tools/building.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1266,7 +1266,7 @@ def is_wasm_dylib(filename):
section = next(module.sections())
if section.type == webassembly.SecType.CUSTOM:
module.seek(section.offset)
if module.readString() == 'dylink':
if module.readString() in ('dylink', 'dylink.0'):
return True
return False

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60 changes: 48 additions & 12 deletions tools/webassembly.py
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Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,11 @@ class ExternType(IntEnum):
EVENT = 4


class DylinkType(IntEnum):
MEM_INFO = 1
NEEDED = 2


Section = namedtuple('Section', ['type', 'size', 'offset'])
Limits = namedtuple('Limits', ['flags', 'initial', 'maximum'])
Import = namedtuple('Import', ['kind', 'module', 'field'])
Expand Down Expand Up @@ -178,7 +183,13 @@ def readLimits(self):
return Limits(flags, initial, maximum)

def seek(self, offset):
self.buf.seek(offset)
return self.buf.seek(offset)

def tell(self):
return self.buf.tell()

def skip(self, count):
self.buf.seek(count, os.SEEK_CUR)

def sections(self):
"""Generator that lazily returns sections from the wasm file."""
Expand All @@ -200,18 +211,43 @@ def parse_dylink_section(wasm_file):
module.seek(dylink_section.offset)
# section name
section_name = module.readString()
assert section_name == 'dylink'
mem_size = module.readULEB()
mem_align = module.readULEB()
table_size = module.readULEB()
table_align = module.readULEB()

needed = []
needed_count = module.readULEB()
while needed_count:
libname = module.readString()
needed.append(libname)
needed_count -= 1

if section_name == 'dylink':
mem_size = module.readULEB()
mem_align = module.readULEB()
table_size = module.readULEB()
table_align = module.readULEB()

needed_count = module.readULEB()
while needed_count:
libname = module.readString()
needed.append(libname)
needed_count -= 1
elif section_name == 'dylink.0':
section_end = dylink_section.offset + dylink_section.size
while module.tell() < section_end:
subsection_type = module.readULEB()
subsection_size = module.readULEB()
end = module.tell() + subsection_size
if subsection_type == DylinkType.MEM_INFO:
mem_size = module.readULEB()
mem_align = module.readULEB()
table_size = module.readULEB()
table_align = module.readULEB()
elif subsection_type == DylinkType.NEEDED:
needed_count = module.readULEB()
while needed_count:
libname = module.readString()
needed.append(libname)
needed_count -= 1
else:
print(f'unknown subsection: {subsection_type}')
# ignore unknown subsections
module.skip(subsection_size)
assert(module.tell() == end)
else:
utils.exit_with_error('error parsing shared library')

return Dylink(mem_size, mem_align, table_size, table_align, needed)

Expand Down