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link: use Wasm.string_table offsets for Wasm.undefs keys

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This avoids having dangling pointers into `InternPool.string_bytes`.
This commit is contained in:
Jacob Young
2023-06-11 03:10:54 -04:00
committed by Andrew Kelley
parent 7e5dea6366
commit 7507a76879
1 changed files with 37 additions and 23 deletions
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60
src/link/Wasm.zig
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@@ -149,7 +149,8 @@ discarded: std.AutoHashMapUnmanaged(SymbolLoc, SymbolLoc) = .{},
/// into the final binary.
resolved_symbols: std.AutoArrayHashMapUnmanaged(SymbolLoc, void) = .{},
/// Symbols that remain undefined after symbol resolution.
undefs: std.StringArrayHashMapUnmanaged(SymbolLoc) = .{},
/// Note: The key represents an offset into the string table, rather than the actual string.
undefs: std.AutoArrayHashMapUnmanaged(u32, SymbolLoc) = .{},
/// Maps a symbol's location to an atom. This can be used to find meta
/// data of a symbol, such as its size, or its offset to perform a relocation.
/// Undefined (and synthetic) symbols do not have an Atom and therefore cannot be mapped.
@@ -514,6 +515,10 @@ pub fn createEmpty(gpa: Allocator, options: link.Options) !*Wasm {
/// Leaves index undefined and the default flags (0).
fn createSyntheticSymbol(wasm: *Wasm, name: []const u8, tag: Symbol.Tag) !SymbolLoc {
const name_offset = try wasm.string_table.put(wasm.base.allocator, name);
return wasm.createSyntheticSymbolOffset(name_offset, tag);
}
fn createSyntheticSymbolOffset(wasm: *Wasm, name_offset: u32, tag: Symbol.Tag) !SymbolLoc {
const sym_index = @intCast(u32, wasm.symbols.items.len);
const loc: SymbolLoc = .{ .index = sym_index, .file = null };
try wasm.symbols.append(wasm.base.allocator, .{
@@ -691,7 +696,7 @@ fn resolveSymbolsInObject(wasm: *Wasm, object_index: u16) !void {
try wasm.resolved_symbols.putNoClobber(wasm.base.allocator, location, {});
if (symbol.isUndefined()) {
try wasm.undefs.putNoClobber(wasm.base.allocator, sym_name, location);
try wasm.undefs.putNoClobber(wasm.base.allocator, sym_name_index, location);
}
continue;
}
@@ -801,7 +806,7 @@ fn resolveSymbolsInObject(wasm: *Wasm, object_index: u16) !void {
try wasm.resolved_symbols.put(wasm.base.allocator, location, {});
assert(wasm.resolved_symbols.swapRemove(existing_loc));
if (existing_sym.isUndefined()) {
_ = wasm.undefs.swapRemove(sym_name);
_ = wasm.undefs.swapRemove(sym_name_index);
}
}
}
@@ -812,15 +817,16 @@ fn resolveSymbolsInArchives(wasm: *Wasm) !void {
log.debug("Resolving symbols in archives", .{});
var index: u32 = 0;
undef_loop: while (index < wasm.undefs.count()) {
const sym_name = wasm.undefs.keys()[index];
const sym_name_index = wasm.undefs.keys()[index];
for (wasm.archives.items) |archive| {
const sym_name = wasm.string_table.get(sym_name_index);
log.debug("Detected symbol '{s}' in archive '{s}', parsing objects..", .{ sym_name, archive.name });
const offset = archive.toc.get(sym_name) orelse {
// symbol does not exist in this archive
continue;
};
log.debug("Detected symbol '{s}' in archive '{s}', parsing objects..", .{ sym_name, archive.name });
// Symbol is found in unparsed object file within current archive.
// Parse object and and resolve symbols again before we check remaining
// undefined symbols.
@@ -1191,28 +1197,36 @@ fn validateFeatures(
/// if one or multiple undefined references exist. When none exist, the symbol will
/// not be created, ensuring we don't unneccesarily emit unreferenced symbols.
fn resolveLazySymbols(wasm: *Wasm) !void {
if (wasm.undefs.fetchSwapRemove("__heap_base")) |kv| {
const loc = try wasm.createSyntheticSymbol("__heap_base", .data);
try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc);
_ = wasm.resolved_symbols.swapRemove(loc); // we don't want to emit this symbol, only use it for relocations.
if (wasm.string_table.getOffset("__heap_base")) |name_offset| {
if (wasm.undefs.fetchSwapRemove(name_offset)) |kv| {
const loc = try wasm.createSyntheticSymbolOffset(name_offset, .data);
try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc);
_ = wasm.resolved_symbols.swapRemove(loc); // we don't want to emit this symbol, only use it for relocations.
}
}
if (wasm.undefs.fetchSwapRemove("__heap_end")) |kv| {
const loc = try wasm.createSyntheticSymbol("__heap_end", .data);
try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc);
_ = wasm.resolved_symbols.swapRemove(loc);
if (wasm.string_table.getOffset("__heap_end")) |name_offset| {
if (wasm.undefs.fetchSwapRemove(name_offset)) |kv| {
const loc = try wasm.createSyntheticSymbolOffset(name_offset, .data);
try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc);
_ = wasm.resolved_symbols.swapRemove(loc);
}
}
if (!wasm.base.options.shared_memory) {
if (wasm.undefs.fetchSwapRemove("__tls_base")) |kv| {
const loc = try wasm.createSyntheticSymbol("__tls_base", .global);
try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc);
if (wasm.string_table.getOffset("__tls_base")) |name_offset| {
if (wasm.undefs.fetchSwapRemove(name_offset)) |kv| {
const loc = try wasm.createSyntheticSymbolOffset(name_offset, .global);
try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc);
}
}
}
if (wasm.undefs.fetchSwapRemove("__zig_errors_len")) |kv| {
const loc = try wasm.createSyntheticSymbol("__zig_errors_len", .data);
try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc);
_ = wasm.resolved_symbols.swapRemove(kv.value);
if (wasm.string_table.getOffset("__zig_errors_len")) |name_offset| {
if (wasm.undefs.fetchSwapRemove(name_offset)) |kv| {
const loc = try wasm.createSyntheticSymbolOffset(name_offset, .data);
try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc);
_ = wasm.resolved_symbols.swapRemove(kv.value);
}
}
}
@@ -1611,7 +1625,7 @@ pub fn getGlobalSymbol(wasm: *Wasm, name: []const u8, lib_name: ?[]const u8) !u3
wasm.symbols.items[sym_index] = symbol;
gop.value_ptr.* = .{ .index = sym_index, .file = null };
try wasm.resolved_symbols.put(wasm.base.allocator, gop.value_ptr.*, {});
try wasm.undefs.putNoClobber(wasm.base.allocator, name, gop.value_ptr.*);
try wasm.undefs.putNoClobber(wasm.base.allocator, name_index, gop.value_ptr.*);
return sym_index;
}
@@ -1769,7 +1783,7 @@ pub fn updateDeclExports(
// if the symbol was previously undefined, remove it as an import
_ = wasm.imports.remove(sym_loc);
_ = wasm.undefs.swapRemove(mod.intern_pool.stringToSlice(exp.name));
_ = wasm.undefs.swapRemove(export_name);
}
}
@@ -1885,7 +1899,7 @@ pub fn addOrUpdateImport(
const loc: SymbolLoc = .{ .file = null, .index = symbol_index };
global_gop.value_ptr.* = loc;
try wasm.resolved_symbols.put(wasm.base.allocator, loc, {});
try wasm.undefs.putNoClobber(wasm.base.allocator, full_name, loc);
try wasm.undefs.putNoClobber(wasm.base.allocator, decl_name_index, loc);
}
if (type_index) |ty_index| {