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wasm-linker: ensure custom sections are parsed

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Not all custom sections are represented by a symbol, which means the
section will not be parsed by the lazy parsing and therefore get garbage-
collected. This is problematic as it may contain debug information that
should not be garbage-collected. To resolve this, we manually create
local symbols for those sections and also ensure they do not get garbage-
collected.
This commit is contained in:
Luuk de Gram 2024-01-08 16:15:28 +01:00
parent 63de8a5989
commit 2b3e6f680c
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GPG Key ID: A8CFE58E4DC7D664
2 changed files with 26 additions and 10 deletions
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12
src/link/Wasm.zig
View File

@ -3260,7 +3260,7 @@ pub fn getMatchingSegment(wasm: *Wasm, object_index: u16, symbol_index: u32) !u3
break :blk index;
};
} else if (mem.eql(u8, section_name, ".debug_ranges")) {
return wasm.debug_line_index orelse blk: {
return wasm.debug_ranges_index orelse blk: {
wasm.debug_ranges_index = index;
try wasm.appendDummySegment();
break :blk index;
@ -5301,14 +5301,8 @@ fn markReferences(wasm: *Wasm) !void {
const object = &wasm.objects.items[file];
const atom_index = try Object.parseSymbolIntoAtom(object, file, sym_loc.index, wasm);
const atom = wasm.getAtom(atom_index);
for (atom.relocs.items) |reloc| {
const target_loc: SymbolLoc = .{ .index = reloc.index, .file = atom.file };
const target_sym = target_loc.getSymbol(wasm);
if (target_sym.isAlive() or !do_garbage_collect) {
sym.mark();
continue; // Skip all other relocations as this debug atom is already marked now
}
}
const atom_sym = atom.symbolLoc().getSymbol(wasm);
atom_sym.mark();
}
}
}

24
src/link/Wasm/Object.zig
View File

@ -80,6 +80,9 @@ const RelocatableData = struct {
offset: u32,
/// Represents the index of the section it belongs to
section_index: u32,
/// Whether the relocatable section is represented by a symbol or not.
/// Can only be `true` for custom sections.
represented: bool = false,
const Tag = enum { data, code, custom };
@ -753,6 +756,24 @@ fn Parser(comptime ReaderType: type) type {
log.debug("Found legacy indirect function table. Created symbol", .{});
}
// Not all debug sections may be represented by a symbol, for those sections
// we manually create a symbol.
if (parser.object.relocatable_data.get(.custom)) |custom_sections| {
for (custom_sections) |*data| {
if (!data.represented) {
try symbols.append(.{
.name = data.index,
.flags = @intFromEnum(Symbol.Flag.WASM_SYM_BINDING_LOCAL),
.tag = .section,
.virtual_address = 0,
.index = data.section_index,
});
data.represented = true;
log.debug("Created synthetic custom section symbol for '{s}'", .{parser.object.string_table.get(data.index)});
}
}
}
parser.object.symtable = try symbols.toOwnedSlice();
},
}
@ -791,9 +812,10 @@ fn Parser(comptime ReaderType: type) type {
.section => {
symbol.index = try leb.readULEB128(u32, reader);
const section_data = parser.object.relocatable_data.get(.custom).?;
for (section_data) |data| {
for (section_data) |*data| {
if (data.section_index == symbol.index) {
symbol.name = data.index;
data.represented = true;
break;
}
}