systemd-boot: Patch for firmwares that fail to load large files

nixos/tests/systemd-boot-ovmf-broken-fat-driver.patch

@@ -0,0 +1,25 @@
+From d87a7513c6f2f2824203032ef27caeb84892ed7e Mon Sep 17 00:00:00 2001
+From: Will Fancher <elvishjerricco@gmail.com>
+Date: Tue, 30 May 2023 16:53:20 -0400
+Subject: [PATCH] Intentionally break the fat driver
+
+---
+ FatPkg/EnhancedFatDxe/ReadWrite.c | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/FatPkg/EnhancedFatDxe/ReadWrite.c b/FatPkg/EnhancedFatDxe/ReadWrite.c
+index 8f525044d1f1..32c62ff7817b 100644
+--- a/FatPkg/EnhancedFatDxe/ReadWrite.c
++++ b/FatPkg/EnhancedFatDxe/ReadWrite.c
+@@ -216,6 +216,11 @@ FatIFileAccess (
+   Volume = OFile->Volume;
+   Task   = NULL;
+ 
++  if (*BufferSize > (10U * 1024U * 1024U)) {
++    IFile->Position += 10U * 1024U * 1024U;
++    return EFI_BAD_BUFFER_SIZE;
++  }
++
+   //
+   // Write to a directory is unsupported
+   //

nixos/tests/systemd-boot.nix

@@ -251,4 +251,29 @@ in
           machine.succeed("test -e /boot/efi/nixos/.extra-files/efi/netbootxyz/netboot.xyz.efi")
     '';
   };
+
+  # See: [Firmware file size bug] in systemd/default.nix
+  uefiLargeFileWorkaround = makeTest {
+    name = "uefi-large-file-workaround";
+
+    nodes.machine = { pkgs, ... }: {
+      imports = [common];
+      virtualisation.efi.OVMF = pkgs.OVMF.overrideAttrs (old: {
+        # This patch deliberately breaks the FAT driver in EDK2 to
+        # exhibit (part of) the firmware bug that we are testing
+        # for. Files greater than 10MiB will fail to be read in a
+        # single Read() call, so systemd-boot will fail to load the
+        # initrd without a workaround. The number 10MiB was chosen
+        # because if it were smaller than the kernel size, even the
+        # LoadImage call would fail, which is not the failure mode
+        # we're testing for. It needs to be between the kernel size
+        # and the initrd size.
+        patches = old.patches or [] ++ [ ./systemd-boot-ovmf-broken-fat-driver.patch ];
+      });
+    };
+
+    testScript = ''
+      machine.wait_for_unit("multi-user.target")
+    '';
+  };
 }

pkgs/os-specific/linux/systemd/default.nix

@@ -190,6 +190,16 @@ stdenv.mkDerivation (finalAttrs: {
     ./0017-inherit-systemd-environment-when-calling-generators.patch
     ./0018-core-don-t-taint-on-unmerged-usr.patch
     ./0019-tpm2_context_init-fix-driver-name-checking.patch
+
+    (fetchpatch {
+      # https://github.com/systemd/systemd/pull/25948
+      #
+      # [Firmware file size bug]: Some UEFI firmwares fail on large
+      # reads. Now that systemd-boot loads initrd itself, systems with
+      # such firmware won't boot without this fix
+      url = "https://github.com/systemd/systemd/commit/3ed1d966f00b002ed822ca9de116252bd91fe6c3.patch";
+      hash = "sha256-pwXrLTScqgnvfddlzUBZpwsoMrvRLcZPp6e4whMcyL4=";
+    })
   ] ++ lib.optional stdenv.hostPlatform.isMusl (
     let
       oe-core = fetchzip {