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qemu: add host/target Linux version check

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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
<fhunleth@troodon-software.com>, 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 <thomas.petazzoni@free-electrons.com>
Tested-by: Frank Hunleth <fhunleth@troodon-software.com>
This commit is contained in:
Thomas Petazzoni 2014-12-10 23:11:59 +01:00
parent b268df55c1
commit f7add51c39
1 changed files with 28 additions and 0 deletions
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28
package/qemu/qemu.mk
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@ -59,6 +59,34 @@ HOST_QEMU_ARCH = ppc
endif endif
HOST_QEMU_TARGETS = $(HOST_QEMU_ARCH)-linux-user 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 define HOST_QEMU_CONFIGURE_CMDS
cd $(@D); $(HOST_CONFIGURE_OPTS) ./configure \ cd $(@D); $(HOST_CONFIGURE_OPTS) ./configure \
--target-list="$(HOST_QEMU_TARGETS)" \ --target-list="$(HOST_QEMU_TARGETS)" \