From 1acc701fdbcefba6ff1aea833001b6301ad8673e Mon Sep 17 00:00:00 2001
From: Matthew Bauer <mjbauer95@gmail.com>
Date: Wed, 17 Jul 2019 17:00:46 -0400
Subject: [PATCH] nixos/binfmt: handle wasm binaries
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This adds handling for WASM binaries to binfmt’s emulatedSystems. To
enable, add this to your configuration:

  boot.binfmt.emulatedSystems = [ "wasm32-wasi" ];

After rebuilding with nixos-rebuild switch, you can run wasm binaries
directly.
---
 nixos/modules/system/boot/binfmt.nix | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/nixos/modules/system/boot/binfmt.nix b/nixos/modules/system/boot/binfmt.nix
index d6c0f0504868..eff258945776 100644
--- a/nixos/modules/system/boot/binfmt.nix
+++ b/nixos/modules/system/boot/binfmt.nix
@@ -115,6 +115,14 @@ let
       magicOrExtension = ''\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xf3\x00'';
       mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
     };
+    wasm32-wasi = {
+      magicOrExtension = ''\x00asm'';
+      mask = ''\xff\xff\xff\xff'';
+    };
+    wasm64-wasi = {
+      magicOrExtension = ''\x00asm'';
+      mask = ''\xff\xff\xff\xff'';
+    };
     x86_64-windows = {
       magicOrExtension = ".exe";
       recognitionType = "extension";