building-linux-on-macos.patch

From 774c044b810b044e444f2ce854eddff8608bf017 Mon Sep 17 00:00:00 2001
From: Seiya Nuta <nuta@seiya.me>
Date: Wed, 2 Jul 2025 12:55:09 +0900
Subject: [PATCH] Build Linux on macOS

Note: This patch is GPLv2 licensed.

This patch enables building Linux on macOS 15.5 (Sequoia) natively using Homebrew packages:

    brew install make llvm lld findutils gnu-sed libelf

    export PATH="$(brew --prefix findutils)/libexec/gnubin:$(brew --prefix gnu-sed)/libexec/gnubin:$(brew --prefix llvm)/bin:$PATH"
    export ARCH=riscv LLVM=1 HOSTCFLAGS="-Iscripts/macos-include -I $(brew --prefix libelf)/include"

    gmake Image -j$(nproc)

Interestingly, changes are only applied to build scripts, not kernel source code:

- Add missing byteswap.h.
- Add missing elf.h - libelf is installed via Homebrew, however, it's too old
  and needs some definitions from newer elf.h headers.
- Work around uuid_t definition issue in file2alias.c [1].

Tested with v6.12.34 and v6.1.141, riscv and arm64 allnoconfig builds.
---
 scripts/macos-include/byteswap.h |  4 ++++
 scripts/macos-include/elf.h      | 24 ++++++++++++++++++++++++
 scripts/mod/file2alias.c         |  3 +++
 3 files changed, 31 insertions(+)
 create mode 100644 scripts/macos-include/byteswap.h
 create mode 100644 scripts/macos-include/elf.h

diff --git a/scripts/macos-include/byteswap.h b/scripts/macos-include/byteswap.h
new file mode 100644
index 000000000..fd97ed5e1
--- /dev/null
+++ b/scripts/macos-include/byteswap.h
@@ -0,0 +1,4 @@
+#pragma once
+#define bswap_16 __builtin_bswap16
+#define bswap_32 __builtin_bswap32
+#define bswap_64 __builtin_bswap64
diff --git a/scripts/macos-include/elf.h b/scripts/macos-include/elf.h
new file mode 100644
index 000000000..5d42ed858
--- /dev/null
+++ b/scripts/macos-include/elf.h
@@ -0,0 +1,24 @@
+#pragma once
+#include <libelf/gelf.h>
+
+#define STT_SPARC_REGISTER 3
+#define R_386_32 1
+#define R_386_PC32 2
+#define R_MIPS_HI16 5
+#define R_MIPS_LO16 6
+#define R_MIPS_26 4
+#define R_MIPS_32 2
+#define R_ARM_ABS32 2
+#define R_ARM_REL32 3
+#define R_ARM_PC24 1
+#define R_ARM_CALL 28
+#define R_ARM_JUMP24 29
+#define R_ARM_THM_JUMP24 30
+#define R_ARM_THM_PC22 10
+#define R_ARM_MOVW_ABS_NC 43
+#define R_ARM_MOVT_ABS 44
+#define R_ARM_THM_MOVW_ABS_NC 47
+#define R_ARM_THM_MOVT_ABS 48
+#define R_ARM_THM_JUMP19 51
+#define R_AARCH64_ABS64 257
+#define R_AARCH64_PREL64 260
diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index 721e0e9f1..fd043c1e9 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -10,7 +10,10 @@
  * of the GNU General Public License, incorporated herein by reference.
  */

+#define _UUID_T
+#define uuid_t int
 #include "modpost.h"
+#undef uuid_t
 #include "devicetable-offsets.h"

 /* We use the ELF typedefs for kernel_ulong_t but bite the bullet and
--
2.46.0