[Buildroot] [PATCH 2/2] qemu: add host/target Linux version check

Frank Hunleth fhunleth at troodon-software.com
Fri Dec 12 13:56:58 UTC 2014


Hi Thomas,

On Wed, Dec 10, 2014 at 5:11 PM, Thomas Petazzoni
<thomas.petazzoni at free-electrons.com> wrote:
>
> 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 at 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 at free-electrons.com>

Thanks for revisiting and improving the old host-qemu patch. I'm using
your new changes to qemu.mk right now and everything seems to work as
expected. So,

Tested-by: Frank Hunleth <fhunleth at troodon-software.com>

Thanks,
Frank

> ---
>  package/qemu/qemu.mk | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
>
> diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
> index 9cff5ed..6c5ddf3 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)"    \
> --
> 2.1.0
>


-- 
Frank Hunleth
Troodon Software LLC
Embedded Software Development
http://troodon-software.com/



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