From af665d822a166ae62547c1c310207f11acaded17 Mon Sep 17 00:00:00 2001
From: volth <volth@volth.com>
Date: Wed, 18 Sep 2019 22:34:41 +0000
Subject: [PATCH 1/2] add config.environment.ld-linux

Add option to install symlink to ld-linux(8) system-wide to allow running unmodified ELF binaries.
It might be useful to run games or executables distributed inside jar files as discussed
https://discourse.nixos.org/t/runtime-alternative-to-patchelf-set-interpreter/3539
https://discourse.nixos.org/t/running-binaries-without-fhs-and-patchelf/1828

It is the third concession to FHS after `/bin/sh` and `/usr/bin/env` but it is disabled by default unlike those two
---
 .../system/activation/activation-script.nix   | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/nixos/modules/system/activation/activation-script.nix b/nixos/modules/system/activation/activation-script.nix
index ddfd1af4a319..9141c8222b73 100644
--- a/nixos/modules/system/activation/activation-script.nix
+++ b/nixos/modules/system/activation/activation-script.nix
@@ -162,6 +162,16 @@ in
         <literal>/usr/bin/env</literal>.
       '';
     };
+
+    environment.ld-linux = mkOption {
+      default = false;
+      type = types.bool;
+      visible = false;
+      description = ''
+        Install symlink to ld-linux(8) system-wide to allow running unmodified ELF binaries.
+        It might be useful to run games or executables distributed inside jar files.
+      '';
+    };
   };
 
 
@@ -198,6 +208,27 @@ in
         rmdir --ignore-fail-on-non-empty /usr/bin /usr
       '';
 
+    system.activationScripts.ld-linux =
+      concatStrings (
+        mapAttrsToList
+          (target: source:
+            if config.environment.ld-linux then ''
+              mkdir -m 0755 -p $(dirname ${target})
+              ln -sfn ${escapeShellArg source} ${target}.tmp
+              mv -f ${target}.tmp ${target} # atomically replace
+            '' else ''
+              rm -f ${target}
+              rmdir --ignore-fail-on-non-empty $(dirname ${target})
+            '')
+          {
+            "i686-linux"   ."/lib/ld-linux.so.2"          = "${pkgs.glibc.out}/lib/ld-linux.so.2";
+            "x86_64-linux" ."/lib/ld-linux.so.2"          = "${pkgs.pkgsi686Linux.glibc.out}/lib/ld-linux.so.2";
+            "x86_64-linux" ."/lib64/ld-linux-x86-64.so.2" = "${pkgs.glibc.out}/lib64/ld-linux-x86-64.so.2";
+            "aarch64-linux"."/lib/ld-linux-aarch64.so.1"  = "${pkgs.glibc.out}/lib/ld-linux-aarch64.so.1";
+            "armv7l-linux" ."/lib/ld-linux-armhf.so.3"    = "${pkgs.glibc.out}/lib/ld-linux-armhf.so.3";
+          }.${pkgs.stdenv.system} or {}
+      );
+
     system.activationScripts.specialfs =
       ''
         specialMount() {

From 45db499d2de2235388212a911b8344b58ddfda36 Mon Sep 17 00:00:00 2001
From: volth <volth@volth.com>
Date: Thu, 19 Sep 2019 00:32:35 +0000
Subject: [PATCH 2/2] rmdir: avoid failing when directory did not exist

I bet nobody has `environment.usrbinenv = null`, it would fail on the second activation trying to `rmdir` inexisting `/usr/bin`
---
 nixos/modules/system/activation/activation-script.nix | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/nixos/modules/system/activation/activation-script.nix b/nixos/modules/system/activation/activation-script.nix
index 9141c8222b73..495d77dfd497 100644
--- a/nixos/modules/system/activation/activation-script.nix
+++ b/nixos/modules/system/activation/activation-script.nix
@@ -205,7 +205,7 @@ in
       ''
       else ''
         rm -f /usr/bin/env
-        rmdir --ignore-fail-on-non-empty /usr/bin /usr
+        rmdir -p /usr/bin || true
       '';
 
     system.activationScripts.ld-linux =
@@ -218,7 +218,7 @@ in
               mv -f ${target}.tmp ${target} # atomically replace
             '' else ''
               rm -f ${target}
-              rmdir --ignore-fail-on-non-empty $(dirname ${target})
+              rmdir $(dirname ${target}) || true
             '')
           {
             "i686-linux"   ."/lib/ld-linux.so.2"          = "${pkgs.glibc.out}/lib/ld-linux.so.2";