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

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

[Frank Hunleth]

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.

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
---
 package/qemu/qemu.mk | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
index 093ae64..bd6f555 100644
--- a/package/qemu/qemu.mk
+++ b/package/qemu/qemu.mk
@@ -74,6 +74,24 @@ define HOST_QEMU_CONFIGURE_CMDS
 	)
 endef
 
+define HOST_QEMU_LINUX_VERSION_CHECK
+	host_version_parts=`uname -r | sed 's/\-.*//g' | sed 's/\./ /g'` ;\
+	host_version_code=0 ;\
+	multiplier=65536 ;\
+	for host_version_part in $$host_version_parts; do \
+		host_version_code=`echo "$$host_version_code + $$host_version_part * $$multiplier" | bc` ;\
+		multiplier=`echo "$$multiplier / 256" | bc` ;\
+	done ;\
+	target_version_code=`grep LINUX_VERSION_CODE $(STAGING_DIR)/usr/include/linux/version.h | awk '{print $$3}'` ;\
+	if test $$host_version_code -lt $$target_version_code ; then \
+		echo "Refusing to install qemu-user since the target Linux version is newer" ;\
+		echo "than the host's. Missing system calls will fail." ;\
+		exit 1 ;\
+	fi
+endef
+
+HOST_QEMU_POST_BUILD_HOOKS += HOST_QEMU_LINUX_VERSION_CHECK
+
 $(eval $(host-autotools-package))
 
 # variable used by other packages
-- 
1.8.3.2

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

[Arnout Vandecappelle]

On 02/08/14 22:54, Frank Hunleth 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.
> 
> Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>

 Thanks Frank!

> ---
>  package/qemu/qemu.mk | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
> index 093ae64..bd6f555 100644
> --- a/package/qemu/qemu.mk
> +++ b/package/qemu/qemu.mk
> @@ -74,6 +74,24 @@ define HOST_QEMU_CONFIGURE_CMDS
>  	)
>  endef
>  
> +define HOST_QEMU_LINUX_VERSION_CHECK

 Just to be sure, I'd start with a

	test `uname -s` = Linux

(some people try to run buildroot on *BSDs, with varying degrees of success).

> +	host_version_parts=`uname -r | sed 's/\-.*//g' | sed 's/\./ /g'` ;\
> +	host_version_code=0 ;\
> +	multiplier=65536 ;\
> +	for host_version_part in $$host_version_parts; do \
> +		host_version_code=`echo "$$host_version_code + $$host_version_part * $$multiplier" | bc` ;\
> +		multiplier=`echo "$$multiplier / 256" | bc` ;\

 Even though we do put bc in our dependencies, I'd prefer to avoid
relying on it - not many people know it. Instead, I'd use either bash's
let builtin, or POSIX-compliant expr.

> +	done ;\
> +	target_version_code=`grep LINUX_VERSION_CODE $(STAGING_DIR)/usr/include/linux/version.h | awk '{print $$3}'` ;\

 You can do the grep inside the awk:

awk '/LINUX_VERSION_CODE/ {print $$3}' .../version.h



 Since it is possible to build host-qemu without building anything for
the target, you can't rely on version.h being present already. To make
sure it is there, add toolchain to the HOST_QEMU_DEPENDENCIES.

> +	if test $$host_version_code -lt $$target_version_code ; then \
> +		echo "Refusing to install qemu-user since the target Linux version is newer" ;\
> +		echo "than the host's. Missing system calls will fail." ;\
> +		exit 1 ;\
> +	fi
> +endef
> +
> +HOST_QEMU_POST_BUILD_HOOKS += HOST_QEMU_LINUX_VERSION_CHECK

 I think a pre-configure hook is more appropriate.


 Regards,
 Arnout

> +
>  $(eval $(host-autotools-package))
>  
>  # variable used by other packages
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F

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

[Yann E. MORIN]

Arnout, Frank, All,

On 2014-02-10 18:06 +0100, Arnout Vandecappelle spake thusly:
> On 02/08/14 22:54, Frank Hunleth wrote:
[--SNIP--]
> > +	host_version_parts=`uname -r | sed 's/\-.*//g' | sed 's/\./ /g'` ;\
> > +	host_version_code=0 ;\
> > +	multiplier=65536 ;\
> > +	for host_version_part in $$host_version_parts; do \
> > +		host_version_code=`echo "$$host_version_code + $$host_version_part * $$multiplier" | bc` ;\
> > +		multiplier=`echo "$$multiplier / 256" | bc` ;\
> 
>  Even though we do put bc in our dependencies, I'd prefer to avoid
> relying on it - not many people know it. Instead, I'd use either bash's
> let builtin, or POSIX-compliant expr.

POSIX defines (basic) mathematical expressions, eg:
  multiplier=$((multiplier/256))

See: The Open Group Base Specifications Issue 7, Shell Command Language:
    http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04

> > +	if test $$host_version_code -lt $$target_version_code ; then \
> > +		echo "Refusing to install qemu-user since the target Linux version is newer" ;\
> > +		echo "than the host's. Missing system calls will fail." ;\
> > +		exit 1 ;\
> > +	fi
> > +endef
> > +
> > +HOST_QEMU_POST_BUILD_HOOKS += HOST_QEMU_LINUX_VERSION_CHECK
> 
>  I think a pre-configure hook is more appropriate.

Indeed.

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
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'------------------------------^-------^------------------^--------------------'

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

[Frank Hunleth]

On Mon, Feb 10, 2014 at 3:46 PM, Yann E. MORIN <yann.morin.1998@free.fr> wrote:
> Arnout, Frank, All,
>
> On 2014-02-10 18:06 +0100, Arnout Vandecappelle spake thusly:
>> On 02/08/14 22:54, Frank Hunleth wrote:
> [--SNIP--]
>> > +   host_version_parts=`uname -r | sed 's/\-.*//g' | sed 's/\./ /g'` ;\
>> > +   host_version_code=0 ;\
>> > +   multiplier=65536 ;\
>> > +   for host_version_part in $$host_version_parts; do \
>> > +           host_version_code=`echo "$$host_version_code + $$host_version_part * $$multiplier" | bc` ;\
>> > +           multiplier=`echo "$$multiplier / 256" | bc` ;\
>>
>>  Even though we do put bc in our dependencies, I'd prefer to avoid
>> relying on it - not many people know it. Instead, I'd use either bash's
>> let builtin, or POSIX-compliant expr.
>
> POSIX defines (basic) mathematical expressions, eg:
>   multiplier=$((multiplier/256))
>
> See: The Open Group Base Specifications Issue 7, Shell Command Language:
>     http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04

Thanks Arnout and Yann - I always learn something when I submit a
patch to this project.

Revised patch coming shortly...

>
>> > +   if test $$host_version_code -lt $$target_version_code ; then \
>> > +           echo "Refusing to install qemu-user since the target Linux version is newer" ;\
>> > +           echo "than the host's. Missing system calls will fail." ;\
>> > +           exit 1 ;\
>> > +   fi
>> > +endef
>> > +
>> > +HOST_QEMU_POST_BUILD_HOOKS += HOST_QEMU_LINUX_VERSION_CHECK
>>
>>  I think a pre-configure hook is more appropriate.
>
> Indeed.
>
> Regards,
> Yann E. MORIN.
>
> --
> .-----------------.--------------------.------------------.--------------------.
> |  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
> | +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
> | +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
> | http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
> '------------------------------^-------^------------------^--------------------'



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