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Re: [Qemu-devel] [PATCH] ivshmem-server: Detect and use if there is requ


From: Markus Armbruster
Subject: Re: [Qemu-devel] [PATCH] ivshmem-server: Detect and use if there is required -lrt linking
Date: Mon, 22 May 2017 08:28:14 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux)

Kamil Rytarowski <address@hidden> writes:

> Hello,
>
> Excuse me for delay, I missed this mail.

No problem.

> Please see in-line.
>
> On 17.05.2017 09:28, Markus Armbruster wrote:
>> Kamil Rytarowski <address@hidden> writes:
>> 
>>> ivshmem-server makes use of the POSIX shared memory object interfaces.
>>> This library is provided on NetBSD in -lrt (POSIX Real-time Library).
>>> Add ./configure check if there is needed -lrt linking for shm_open()
>>> and if so use it. Introduce new configure generated variable LIBS_SHMLIB.
>>>
>>> This fixes build issue on NetBSD.
>>>
>>> Signed-off-by: Kamil Rytarowski <address@hidden>
>>> ---
>>>  Makefile  |  1 +
>>>  configure | 20 ++++++++++++++++++++
>>>  2 files changed, 21 insertions(+)
>>>
>>> diff --git a/Makefile b/Makefile
>>> index 31d41a7eae..3248cb53d7 100644
>>> --- a/Makefile
>>> +++ b/Makefile
>>> @@ -473,6 +473,7 @@ ivshmem-client$(EXESUF): $(ivshmem-client-obj-y) 
>>> $(COMMON_LDADDS)
>>>     $(call LINK, $^)
>>>  ivshmem-server$(EXESUF): $(ivshmem-server-obj-y) $(COMMON_LDADDS)
>>>     $(call LINK, $^)
>>> +ivshmem-server$(EXESUF): LIBS += $(LIBS_SHMLIB)
>>>  
>>>  module_block.h: $(SRC_PATH)/scripts/modules/module_block.py config-host.mak
>>>     $(call quiet-command,$(PYTHON) $< $@ \
>>> diff --git a/configure b/configure
>>> index 7c020c076b..50c3aee746 100755
>>> --- a/configure
>>> +++ b/configure
>>> @@ -179,6 +179,7 @@ audio_pt_int=""
>>>  audio_win_int=""
>>>  cc_i386=i386-pc-linux-gnu-gcc
>>>  libs_qga=""
>>> +libs_shmlib=""
>>>  debug_info="yes"
>>>  stack_protector=""
>>>  
>>> @@ -4133,6 +4134,24 @@ elif compile_prog "" "$pthread_lib -lrt" ; then
>>>    libs_qga="$libs_qga -lrt"
>>>  fi
>>>  
>>> +##########################################
>>> +# Do we need librt for shm_open()
>>> +cat > $TMPC <<EOF
>>> +#include <sys/mman.h>
>>> +#include <sys/stat.h>
>>> +#include <fcntl.h>
>>> +#include <stddef.h>
>>> +int main(void) {
>>> +  return shm_open(NULL, O_RDWR, 0644);
>>> +}
>>> +EOF
>>> +
>>> +if compile_prog "" "" ; then
>>> +  :
>>> +elif compile_prog "" "-lrt" ; then
>>> +  libs_shmlib="$libs_shmlib -lrt"
>>> +fi
>>> +
>>>  if test "$darwin" != "yes" -a "$mingw32" != "yes" -a "$solaris" != yes -a \
>>>          "$aix" != "yes" -a "$haiku" != "yes" ; then
>>>      libs_softmmu="-lutil $libs_softmmu"
>>> @@ -5949,6 +5968,7 @@ echo "EXESUF=$EXESUF" >> $config_host_mak
>>>  echo "DSOSUF=$DSOSUF" >> $config_host_mak
>>>  echo "LDFLAGS_SHARED=$LDFLAGS_SHARED" >> $config_host_mak
>>>  echo "LIBS_QGA+=$libs_qga" >> $config_host_mak
>>> +echo "LIBS_SHMLIB+=$libs_shmlib" >> $config_host_mak
>>>  echo "TASN1_LIBS=$tasn1_libs" >> $config_host_mak
>>>  echo "TASN1_CFLAGS=$tasn1_cflags" >> $config_host_mak
>>>  echo "POD2MAN=$POD2MAN" >> $config_host_mak
>> 
>> We already have a test for -lrt.
>
> Correct.
>
>>  It looks for timer_create() and
>> clock_gettime().
>
>
> timer_create(2) and clock_settime(2) are in libc on NetBSD.
>
>>  If we need -lrt,
>
> We need it just for shm_open(3).
>
>> we add it to LIBS and to LIBS_QGA.
>> The latter because we don't use LIBS for qemu-ga:
>> 
>>     qemu-ga$(EXESUF): LIBS = $(LIBS_QGA)
>> 
>> This patch adds a second test for -lrt, to look for shm_open().  It adds
>> -lrt to new variable LIBS_SHMLIB, which gets used only for
>> ivshmem-server:
>> 
>>     ivshmem-server$(EXESUF): LIBS += $(LIBS_SHMLIB)
>> 
>> Note that ivshmem-server already uses LIBS.
>> 
>> Shouldn't we instead widen the existing test for -lrt to cover
>> shm_open()?
>> 
>
> I will prepare patch in the requested way. I don't have preference.
>
>> Can you confirm that the existing test does not add -lrt to LIBS on
>> NetBSD?
>> 
>
> config-host.mak:LIBS+=-lm -L/usr/pkg/lib -lgthread-2.0 -pthread
> -Wl,-R/usr/pkg/lib -lglib-2.0 -lintl   -lz
> config-host.mak:LIBS_QGA+=-lm -L/usr/pkg/lib -lgthread-2.0 -pthread
> -Wl,-R/usr/pkg/lib -lglib-2.0 -lintl
>
>> tests/ivshmem-test.c also calls shm_open().  Does it work on NetBSD?
>> 
>
> Currently it's disabled, as it requires eventfd() (Linux API).

You're right.

So is the ivshmem device.  Hmm.  Why would anyone want ivshmem-server on
NetBSD?  Its purpose is connecting ivshmem-doorbell devices.  Could we
simply add the obvious CONFIG_IVSHMEM dependence to
contrib/ivshmem-*/Makefile.objs?



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