Notes

macOS Shim Files for Linux Kernel Build

· 1min
Tags:linux,kernel,macos,shim

macOS does not have several headers the Linux kernel’s host tools depend on. The stubs below fill those gaps so the build can run. The approach originated in Building Linux Kernel on macOS Natively by Seiya, and is walked through in How I Compiled and Ran a Linux Kernel for RISC-V on My Apple Silicon Mac.

scripts/macos-include/elf.h

Proxies macOS to libelf and adds missing relocation constants from Linux’s elf.h.

#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

scripts/macos-include/byteswap.h

Maps Linux’s bswap_* macros to clang builtins.

#pragma once
#define bswap_16 __builtin_bswap16
#define bswap_32 __builtin_bswap32
#define bswap_64 __builtin_bswap64

scripts/macos-include/gethostuuid.h

Empty stub. Prevents macOS’s <gethostuuid.h> from referencing the suppressed uuid_t typedef.

#pragma once

scripts/macos-include/fcntl.h

Defines Linux-only O_LARGEFILE as a no-op.

#pragma once
#include_next <fcntl.h>
#define O_LARGEFILE 0

scripts/macos-include/unistd.h

Stubs copy_file_range so callers fall back to plain read/write.

#pragma once
#include_next <unistd.h>
#include <sys/types.h>
static inline ssize_t copy_file_range(int a, void *b, int c, void *d, size_t e, unsigned int f) { return -1; }

HOSTCFLAGS

Pass to gmake so the kernel build picks up the shims:

HOSTCFLAGS="-Iscripts/macos-include -I$(brew --prefix libelf)/include -Wno-incompatible-pointer-types -D_UUID_T"

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