From 6519e3fb71d167b435fa73ff7b06c338e5ef5714 Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <slyich@gmail.com>
Date: Fri, 1 Aug 2025 21:58:28 +0100
Subject: [PATCH] linuxHeaders: fix build on 32-bit systems with 64-bit inodes

Without the change builx of `pkgsi686Linux.linuxHeaders` fails on my
`btrfs` with 64-bit inodes as:

    linux-headers> fixdep: error fstat'ing file: scripts/basic/.fixdep.d: Value too large for defined data type

Normally `Kbuild` attempts to pass correct LFS flags by extracting
them from `getconf` as:
    HOST_LFS_CFLAGS := $(shell getconf LFS_CFLAGS 2>/dev/null)

But `nixpkgs` does not provide it and the build fails.

The change hardcodes LFS flags for 32-bit systems.
---
 pkgs/os-specific/linux/kernel-headers/default.nix | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/pkgs/os-specific/linux/kernel-headers/default.nix b/pkgs/os-specific/linux/kernel-headers/default.nix
index 371eb343f74d..cd91b50d8df7 100644
--- a/pkgs/os-specific/linux/kernel-headers/default.nix
+++ b/pkgs/os-specific/linux/kernel-headers/default.nix
@@ -90,6 +90,16 @@ let
         # `$(..)` expanded by make alone
         "HOSTCC:=$(CC_FOR_BUILD)"
         "HOSTCXX:=$(CXX_FOR_BUILD)"
+        # To properly detect LFS flags 32-bit build environments like
+        # pkgsi686Linux.linuxHeaders Kbuild uses this Makefile bit:
+        #     HOST_LFS_CFLAGS := $(shell getconf LFS_CFLAGS 2>/dev/null)
+        #
+        # `getconf` is not available in early bootstrap and thus the
+        # build fails on filesystems with 64-bit inodes as:
+        #     linux-headers> fixdep: error fstat'ing file: scripts/basic/.fixdep.d: Value too large for defined data type
+        #
+        # Let's hardcode subset of the output of `getconf` for this case.
+        "HOST_LFS_CFLAGS=-D_FILE_OFFSET_BITS=64"
       ];
 
       # Skip clean on darwin, case-sensitivity issues.