From f7add51c3933e16f2b747637af82e5ebcc906f8f Mon Sep 17 00:00:00 2001 From: Thomas Petazzoni Date: Wed, 10 Dec 2014 23:11:59 +0100 Subject: [PATCH] qemu: add host/target Linux version check Raise an error if the host is using an older kernel than the target. Since qemu-user passes emulated system calls to the host kernel, this prevents usage of qemu-user in situations where those system calls will fail. This is based on an original patch from Frank Hunleth , but completely rewritten in a different way: * Instead of using shell based testing, we use pure make tests, which allows to detect the problem not when host-qemu starts to build, but at the very beginning of the entire Buildroot build. * Instead of looking at $(STAGING_DIR)/usr/include/linux/version.h (which requires having a dependency on the 'toolchain' package, which is a bit unusual for a host package), we use the BR2_TOOLCHAIN_HEADERS_AT_LEAST Config.in option which tells us the version of the kernel headers used in the toolchain. Signed-off-by: Thomas Petazzoni Tested-by: Frank Hunleth --- package/qemu/qemu.mk | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk index 9cff5ede95..6c5ddf3357 100644 --- a/package/qemu/qemu.mk +++ b/package/qemu/qemu.mk @@ -59,6 +59,34 @@ HOST_QEMU_ARCH = ppc endif HOST_QEMU_TARGETS = $(HOST_QEMU_ARCH)-linux-user +ifeq ($(BR2_PACKAGE_HOST_QEMU),y) +HOST_QEMU_HOST_SYSTEM_TYPE = $(shell uname -s) +ifneq ($(HOST_QEMU_HOST_SYSTEM_TYPE),Linux) +$(error "qemu-user can only be used on Linux hosts") +endif + +HOST_QEMU_HOST_SYSTEM_VERSION_MAJOR = $(shell uname -r | cut -f1 -d'.') +HOST_QEMU_HOST_SYSTEM_VERSION_MINOR = $(shell uname -r | cut -f2 -d'.') +HOST_QEMU_TARGET_SYSTEM_VERSION_MAJOR = $(shell echo $(BR2_TOOLCHAIN_HEADERS_AT_LEAST) | cut -f1 -d'.') +HOST_QEMU_TARGET_SYSTEM_VERSION_MINOR = $(shell echo $(BR2_TOOLCHAIN_HEADERS_AT_LEAST) | cut -f2 -d'.') +HOST_QEMU_COMPARE_VERSION_MAJOR = $(shell test $(HOST_QEMU_HOST_SYSTEM_VERSION_MAJOR) -ge $(HOST_QEMU_TARGET_SYSTEM_VERSION_MAJOR) && echo OK) +HOST_QEMU_COMPARE_VERSION_MINOR = $(shell test $(HOST_QEMU_HOST_SYSTEM_VERSION_MINOR) -ge $(HOST_QEMU_TARGET_SYSTEM_VERSION_MINOR) && echo OK) + +# +# The principle of qemu-user is that it emulates the instructions of +# the target architecture when running the binary, and then when this +# binary does a system call, it converts this system call into a +# system call on the host machine. This mechanism makes an assumption: +# that the target binary will not do system calls that do not exist on +# the host. This basically requires that the target binary should be +# built with kernel headers that are older or the same as the kernel +# version running on the host machine. +# +ifneq ($(HOST_QEMU_COMPARE_VERSION_MAJOR)$(HOST_QEMU_COMPARE_VERSION_MINOR),OKOK) +$(error "Refusing to build qemu-user: target Linux version newer than host's.") +endif +endif + define HOST_QEMU_CONFIGURE_CMDS cd $(@D); $(HOST_CONFIGURE_OPTS) ./configure \ --target-list="$(HOST_QEMU_TARGETS)" \ -- 2.30.2