From e1a1d8f94ff63b4aa690887dbfe0f208911bc7b4 Mon Sep 17 00:00:00 2001
From: Pavel Roskin <proski@gnu.org>
Date: Tue, 4 Feb 2014 17:34:05 -0500
Subject: [PATCH] Port elements of the build system from ndiswrapper

This eliminates compilation to find the kernel version. The new Makefile
provides more sanity checks and more verbose reporting.
---
 Makefile.inc    | 75 +++++++++++++++++++++++++------------------------
 kernelversion.c | 21 --------------
 2 files changed, 39 insertions(+), 57 deletions(-)
 delete mode 100644 kernelversion.c

diff --git a/Makefile.inc b/Makefile.inc
index 0749410..9741cce 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -49,47 +49,50 @@ endif
 # DESTDIR is used as path prefix during installation.
 DESTDIR ?=
 
-# KERNELPATH is the path to the Linux kernel build tree.  Unless a
-# separate build directory was used for the kernel build, it's the same
-# as the kernel source tree.  KERNELPATH is used to access the kernel
-# configuration, include files and the build system.  To build for
-# another kernel, set KERNELPATH manually, for example with:
-# make KERNELPATH=/path/to/kernel/source
-
-# The default KERNELPATH points to the directory where the currently
-# running kernel was compiled.  Note that the configuration and the
-# version of the kernel tree might have changed since then.
-ifeq ($(wildcard $(KERNELPATH)),)
-KERNELPATH = /lib/modules/$(shell uname -r)/build
-# sanity check: does KERNELPATH exist?
-ifeq ($(shell cd $(KERNELPATH) && pwd),)
-$(error $(KERNELPATH) is missing, please set KERNELPATH)
-endif
-export KERNELPATH
-endif
-
-# KERNELRELEASE is the target kernel's version.  It's always taken from
-# the kernel build tree.  Kernel Makefile doesn't always know the exact
-# kernel version (especially for vendor stock kernels), so we get it
-# from <linux/version.h> instead. But simply grepping it from version.h
-# doesn't work, since some distributions have multiple UTS_RELEASE
-# in that file.
-# This trick has been inspired by the lm_sensors project.
-ifndef KERNELRELEASE
-KERNELRELEASE := $(shell $(CC) -I $(KERNELPATH)/include -E $(TOP)/kernelversion.c | grep uts_release | cut -f2 -d'"')
-ifeq (,$(KERNELRELEASE))
-$(error Cannot detect kernel version - please check compiler and KERNELPATH)
+# By default, we try to compile the modules for the currently running
+# kernel.  But it's the first approximation, as we will re-read the
+# version from the kernel sources.
+KVERS_UNAME ?= $(shell uname -r)
+
+# KERNELPATH is the path to the Linux kernel build tree.  It is usually the
+# same as the kernel source tree, except when the kernel was compiled in
+# a separate directory.
+KERNELPATH ?= $(shell readlink -f /lib/modules/$(KVERS_UNAME)/build)
+
+ifeq (,$(KERNELPATH))
+$(error Kernel build tree not found - please set KERNELPATH to configured kernel)
 endif
+
+KERNELCONF := $(KERNELPATH)/.config
+ifeq (,$(wildcard $(KERNELCONF)))
+$(error No .config found in $(KERNELPATH), please set KERNELPATH to configured kernel)
 endif
 
-# KERNELCONF is the name of the file that holds the configuration
-# of the target kernel.
-KERNELCONF ?=	$(KERNELPATH)/.config
+ifneq (,$(wildcard $(KERNELPATH)/include/linux/version.h))
+ifneq (,$(wildcard $(KERNELPATH)/include/generated/uapi/linux/version.h))
+$(error Multiple copies of version.h found, please clean your build tree)
+endif
+endif
 
-# sanity check: does KERNELCONF exist?
-ifeq ($(wildcard $(KERNELCONF)),)
-$(error KERNELCONF: $(KERNELCONF) does not exist.)
+# Kernel Makefile doesn't always know the exact kernel version, so we
+# get it from the kernel headers instead and pass it to make.
+VERSION_H := $(KERNELPATH)/include/generated/utsrelease.h
+ifeq (,$(wildcard $(VERSION_H)))
+VERSION_H := $(KERNELPATH)/include/linux/utsrelease.h
+endif
+ifeq (,$(wildcard $(VERSION_H)))
+VERSION_H := $(KERNELPATH)/include/linux/version.h
 endif
+ifeq (,$(wildcard $(VERSION_H)))
+$(error Please run 'make modules_prepare' in $(KERNELPATH))
+endif
+
+KERNELRELEASE := $(shell sed -ne 's/"//g;s/^\#define UTS_RELEASE //p' $(VERSION_H))
+
+ifeq (,$(KERNELRELEASE))
+$(error Cannot find UTS_RELEASE in $(VERSION_H), please report)
+endif
+
 include $(KERNELCONF)
 
 # KMODPATH nominates the directory where the modules will be
diff --git a/kernelversion.c b/kernelversion.c
deleted file mode 100644
index 9a6845d..0000000
--- a/kernelversion.c
+++ /dev/null
@@ -1,21 +0,0 @@
-/* This file is used for a trick to determine the version of the kernel
- * build tree. Simply grepping <linux/version.h> doesn't work, since
- * some distributions have multiple UTS_RELEASE definitions in that
- * file.
- * Taken from the lm_sensors project.
- *
- * $Id$
- */
-#include <linux/version.h>
-
-#ifndef UTS_RELEASE
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,33)
-/* Linux 2.6.33+ uses <generated/utsrelease.h> */
-#include <generated/utsrelease.h>
-#else
-/* Linux 2.6.18 - 2.6.32 uses <linux/utsrelease.h> */
-#include <linux/utsrelease.h>
-#endif
-#endif
-
-char *uts_release = UTS_RELEASE;
-- 
2.35.1