Re: is the xen toolstack backwards compatible ?

[Christoph Egger <Christoph.Egger@amd.com>]

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On Wednesday 09 December 2009 08:22:14 Keir Fraser wrote:
> On 09/12/2009 00:23, "Sander Eikelenboom" <linux@eikelenboom.it> wrote:
> > So if it was no coincidence but desirable, at the moment xend and xentop
> > from unstable don't seem to work on 3.4.2 hypervisor anymore.
>
> There's no compatibility guarantee across different major Xen releases. But
> Christoph Egger did a lot of work to allow multiple toolstacks to be
> installed side by side. I think you should just need to specify a
> PREFIX=/path/to value when building the tools. Is that right, Christoph?

Yes, this is right.
*Before* you start xend, you need to set two environment variables
LD_LIBRARY_PATH and PYTHONPATH.

Here is an example for PREFIX="/usr/local" and compiled with python 2.5:

export LD_LIBRARY_PATH="/usr/local/lib"
export PYTHONPATH="/usr/local/lib/python2.5/site-packages"

If these are not set correct, python tells you it can't find its modules or
the dynamic linker tells you it can't find the shared libs built from 
tools/libxc.

You should use the same python version you compiled with.
If you are on a machine where 'python' does not exist as a symbolic link to
the installed python version (like me on NetBSD) you need the attached patch
or all python programs installed with "INSTALL_PYTHON_PROG"
end up with '#!' in the first line instead of '#!/path/to/python2.5'
which is stupid.

I already submitted attached patch earlier but Ian Jackson objected it because
he wants a way to have tools working with a different python version than it
has been compiled with. This sounds obscure to me when looking at the path 
python modules get installed to.

Keir: Please take attached patch. This is better than the current situation
regardless Ian likes it or not. In the latter case taking the patch should 
motivate him to come up with a patch finally. :)

Again:
Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>

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diff -r bc3aca17cb88 tools/misc/Makefile
--- a/tools/misc/Makefile	Thu Jul 23 09:01:30 2009 +0100
+++ b/tools/misc/Makefile	Thu Jul 23 15:45:48 2009 +0200
@@ -25,8 +25,7 @@ INSTALL_BIN := $(INSTALL_BIN-y)
 INSTALL_SBIN-y := xm xen-bugtool xen-python-path xend xenperf xsview xenpm xen-tmem-list-parse gtraceview gtracestat
 INSTALL_SBIN := $(INSTALL_SBIN-y)
 
-DEFAULT_PYTHON_PATH := $(shell $(XEN_ROOT)/tools/python/get-path)
-PYTHON_PATH ?= $(DEFAULT_PYTHON_PATH)
+PYTHON_PATH := $(shell which $(PYTHON))
 INSTALL_PYTHON_PROG = $(XEN_ROOT)/tools/python/install-wrap \
 "$(PYTHON_PATH)" $(INSTALL_PROG)
 
diff -r bc3aca17cb88 tools/python/get-path
--- a/tools/python/get-path	Thu Jul 23 09:01:30 2009 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,22 +0,0 @@
-#! /usr/bin/env bash
-set -e
-
-check () {
-	set +e
-	p=`type -p python$v`
-	r=$?
-	set -e
-	if [ $r = 0 ]; then
-		echo >&2 "${0##*/}: will use #!$p for python programs"
-		printf "%s\n" "$p"
-		exit 0
-	fi
-}
-
-v="$(python -V 2>&1)"
-v="${v#* }"
-check
-v="${v%.*}"
-check
-echo >&2 'python version not determined, will use env to find python at runtime'
-printf "/usr/bin/env python\n"
diff -r bc3aca17cb88 tools/python/install-wrap
--- a/tools/python/install-wrap	Thu Jul 23 09:01:30 2009 +0100
+++ b/tools/python/install-wrap	Thu Jul 23 15:45:48 2009 +0200
@@ -1,44 +1,60 @@
-#! /usr/bin/env bash
+#!/bin/sh
 # usage:
 #  .../install-wrap $(PYTHON_PATH) install <options-to-install> <src>... <dest>
 # where
 #  PYTHON_PATH is what to put after #! and may be `/usr/bin/env python'
 #
-# Used via $(INSTALL_PYTHON_PROG) in Rules.mk; PYTHON_PATH comes from
-# .../get-path alongside this script
+# Used via $(INSTALL_PYTHON_PROG) in Rules.mk; PYTHON_PATH comes from $(PYTHON)
 
 set -e
-if [ $# -lt 2 ]; then echo >&2 "${0##*/}: too few arguments"; exit 1; fi
-pythonpath="$1"; shift
+if test $# -lt 2; then
+	echo >&2 "${0##*/}: too few arguments"
+	exit 1
+fi
 
-install=("$1"); shift
-srcs=()
+pythonpath="$1"
+shift
+
+install="$1"
+shift
+srcs=""
 
 while [ $# != 0 ]; do
 	case "$1" in
-	-|--)	install=("${install[@]}" "$1"); shift; break ;;
-	-*)	install=("${install[@]}" "$1"); shift ;;
-	*)	break ;;
+	-|--)	install=`echo "${install} $1"`
+		shift
+		break
+		;;
+	-*)	install=`echo "${install} $1"`
+		shift
+		;;
+	*)	break
+		;;
 	esac
 done
-while [ $# -gt 1 ]; do
-	srcs=("${srcs[@]}" "$1"); shift
+
+while test $# -gt 1; do
+	srcs=`echo "${srcs} $1"`
+	shift
 done
-dest="$1"; shift
+
+dest="$1"
+shift
 
 destf="$dest"
-for srcf in "${srcs[@]}"; do
+for srcf in ${srcs}; do
 	if test -d "$dest"; then
-		destf="$dest/${srcf%%*/}";
+		destf="$dest/${srcf%%*/}"
 	fi
 	org="$(sed -n '2q; /^#! *\/usr\/bin\/env python *$/p' $srcf)"
-	if [ "x$org" = x ]; then
-		"${install[@]}" "$srcf" "$destf"
+	if test "x$org" = x; then
+		eval "${install} $srcf $destf"
 		continue
 	fi
 	tmpf="$destf.tmp"
-	"${install[@]}" "$srcf" "$tmpf"
+	eval "${install} $srcf $tmpf"
 	printf >"$tmpf" "#!%s\n" "$pythonpath"
 	sed -e 1d "$srcf" >>"$tmpf"
 	mv -f "$tmpf" "$destf"
 done
+exit 0

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