From d3abeb667aae0269f668758e048b13f913c6aa14 Mon Sep 17 00:00:00 2001
From: Seth Jennings <sjenning@redhat.com>
Date: Wed, 1 Oct 2014 13:57:53 -0500
Subject: [PATCH] Allow user to skip gcc version check

Right now, unless the entire gcc version string, including build date
and package version, matches the distro kernel exactly, kpatch-build
won't proceed.

For some distros, it is very difficult to rollback to a previous
version of gcc and keep that version pinned on the system so that the
package manager doesn't update it.

For these user, add a --skip-gcc-check flag to kpatch-build to allow the
version check to be skipped.  If the user does this, it is assumed they
know what they are doing.  This flag is documented as "not recommended".

Signed-off-by: Seth Jennings <sjenning@redhat.com>
---
 kpatch-build/kpatch-build | 17 +++++++++++++++--
 man/kpatch-build.1        |  9 +++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/kpatch-build/kpatch-build b/kpatch-build/kpatch-build
index f0747cf..b560fbd 100755
--- a/kpatch-build/kpatch-build
+++ b/kpatch-build/kpatch-build
@@ -48,6 +48,7 @@ VERSIONFILE="$CACHEDIR/version"
 TEMPDIR=
 APPLIEDPATCHFILE="kpatch.patch"
 DEBUG=0
+SKIPGCCCHECK=0
 
 warn() {
 	echo "ERROR: $1" >&2
@@ -110,6 +111,10 @@ gcc_version_check() {
 	local kgccver=$(readelf -p .comment $VMLINUX |grep GCC: | tr -s ' ' | cut -d ' ' -f6-)
 	if [[ $gccver != $kgccver ]]; then
 		warn "gcc/kernel version mismatch"
+		echo "gcc version:    $gccver"
+		echo "kernel version: $kgccver"
+		echo "Install the matching gcc version (recommended) or use --skip-gcc-check"
+		echo "to skip the version matching enforcement (not recommended)"
 		return 1
 	fi
 
@@ -192,9 +197,11 @@ usage() {
 	echo "		-v, --vmlinux	Specify original vmlinux" >&2
 	echo "		-t, --target	Specify custom kernel build targets" >&2
 	echo "		-d, --debug	Keep scratch files in /tmp" >&2
+	echo "		--skip-gcc-check   Skip gcc version matching check" >&2
+	echo "		                   (not recommended)" >&2
 }
 
-options=$(getopt -o hr:s:c:v:t:d -l "help,sourcerpm:,sourcedir:,config:,vmlinux:,target:,debug" -- "$@") || die "getopt failed"
+options=$(getopt -o hr:s:c:v:t:d -l "help,sourcerpm:,sourcedir:,config:,vmlinux:,target:,debug,skip-gcc-check" -- "$@") || die "getopt failed"
 
 eval set -- "$options"
 
@@ -236,6 +243,10 @@ while [[ $# -gt 0 ]]; do
 		DEBUG=1
 		set -o xtrace
 		;;
+	--skip-gcc-check)
+		echo "WARNING: Skipping gcc version matching check (not recommended)"
+		SKIPGCCCHECK=1
+		;;
 	--)
 		if [[ -z "$2" ]]; then
 			warn "no patch file specified"
@@ -309,7 +320,9 @@ elif [[ $DISTRO = ubuntu ]] || [[ $DISTRO = debian ]]; then
 	export PATH=/usr/lib/ccache:$PATH
 fi
 
-gcc_version_check || die
+if [[ $SKIPGCCCHECK -eq 0 ]]; then
+	gcc_version_check || die
+fi
 
 if [[ -n "$USERSRCDIR" ]]; then
 	echo "Using source directory at $USERSRCDIR"
diff --git a/man/kpatch-build.1 b/man/kpatch-build.1
index 03556c3..e9fb893 100644
--- a/man/kpatch-build.1
+++ b/man/kpatch-build.1
@@ -37,6 +37,15 @@ to work on other distros.
 -d|--debug
    Keep scratch files in /tmp
 
+--skip-gcc-check
+   Skips check that ensures that the system gcc version and
+   the gcc version that built the kernel match.  Skipping this
+   check is not recommended, but is useful if the exact gcc
+   version is not available or is not easily installed. Use
+   only when confident that the two versions of gcc output
+   identical objects for a given target.  Otherwise, use of
+   this option might result in unexpected changed objects
+   being detected.
 
 .SH SEE ALSO
 kpatch(1)