Merge pull request #15405 from Luukdegram/wasm

wasm: implement more runtime safety checks

1 files changed, 43 insertions, 0 deletions

diff --git a/src/link/Wasm.zig b/src/link/Wasm.zig
index 2125a8faaa..0fe9ec5e3b 100644
--- a/src/link/Wasm.zig
+++ b/src/link/Wasm.zig
@@ -1209,6 +1209,11 @@ fn resolveLazySymbols(wasm: *Wasm) !void {
             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);
+    }
 }
 
 // Tries to find a global symbol by its name. Returns null when not found,
@@ -2185,6 +2190,43 @@ fn setupInitFunctions(wasm: *Wasm) !void {
     std.sort.sort(InitFuncLoc, wasm.init_funcs.items, {}, InitFuncLoc.lessThan);
 }
 
+/// Generates an atom containing the global error set' size.
+/// This will only be generated if the symbol exists.
+fn setupErrorsLen(wasm: *Wasm) !void {
+    const loc = wasm.findGlobalSymbol("__zig_errors_len") orelse return;
+
+    const errors_len = wasm.base.options.module.?.global_error_set.count();
+    // overwrite existing atom if it already exists (maybe the error set has increased)
+    // if not, allcoate a new atom.
+    const atom_index = if (wasm.symbol_atom.get(loc)) |index| blk: {
+        const atom = wasm.getAtomPtr(index);
+        if (atom.next) |next_atom_index| {
+            const next_atom = wasm.getAtomPtr(next_atom_index);
+            next_atom.prev = atom.prev;
+            atom.next = null;
+        }
+        if (atom.prev) |prev_index| {
+            const prev_atom = wasm.getAtomPtr(prev_index);
+            prev_atom.next = atom.next;
+            atom.prev = null;
+        }
+        atom.deinit(wasm);
+        break :blk index;
+    } else new_atom: {
+        const atom_index = @intCast(Atom.Index, wasm.managed_atoms.items.len);
+        try wasm.symbol_atom.put(wasm.base.allocator, loc, atom_index);
+        try wasm.managed_atoms.append(wasm.base.allocator, undefined);
+        break :new_atom atom_index;
+    };
+    const atom = wasm.getAtomPtr(atom_index);
+    atom.* = Atom.empty;
+    atom.sym_index = loc.index;
+    atom.size = 2;
+    try atom.code.writer(wasm.base.allocator).writeIntLittle(u16, @intCast(u16, errors_len));
+
+    try wasm.parseAtom(atom_index, .{ .data = .read_only });
+}
+
 /// Creates a function body for the `__wasm_call_ctors` symbol.
 /// Loops over all constructors found in `init_funcs` and calls them
 /// respectively based on their priority which was sorted by `setupInitFunctions`.
@@ -3317,6 +3359,7 @@ pub fn flushModule(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Nod
     // So we can rebuild the binary file on each incremental update
     defer wasm.resetState();
     try wasm.setupInitFunctions();
+    try wasm.setupErrorsLen();
     try wasm.setupStart();
     try wasm.setupImports();
     if (wasm.base.options.module) |mod| {