Re: [Qemu-devel] Questions about gcc linker errors in crypto sub-directory

["Daniel P. Berrange" <berrange@redhat.com>]

On Mon, Sep 26, 2016 at 09:19:36AM +0000, Gonglei (Arei) wrote:
> 
> 
> 
> 
> 
> > -----Original Message-----
> > From: Daniel P. Berrange [mailto:berrange@redhat.com]
> > Sent: Monday, September 26, 2016 5:14 PM
> > To: Gonglei (Arei)
> > Cc: qemu-devel@nongnu.org
> > Subject: Re: Questions about gcc linker errors in crypto sub-directory
> > 
> > On Mon, Sep 26, 2016 at 09:03:45AM +0000, Gonglei (Arei) wrote:
> > > Hi Daniel,
> > >
> > > I'm coding cryptodev-vhost-user.c as a new cryptodev backend,
> > > but the gcc report some linker errors:
> > >
> > > crypto/cryptodev-vhost-user.o: In function
> > `qcrypto_cryptodev_vhost_crypto_cleanup':
> > > /mnt/sdb/gonglei/qemu.git/qemu/crypto/cryptodev-vhost-user.c:87:
> > undefined reference to `vhost_dev_cleanup'
> > > crypto/cryptodev-vhost-user.o: In function
> > `qcrypto_cryptodev_vhost_crypto_init':
> > > /mnt/sdb/gonglei/qemu.git/qemu/crypto/cryptodev-vhost-user.c:126:
> > undefined reference to `vhost_dev_init'
> > > crypto/cryptodev-vhost-user.o: In function
> > `qcrypto_cryptodev_vhost_user_opened':
> > > /mnt/sdb/gonglei/qemu.git/qemu/crypto/cryptodev-vhost-user.c:187:
> > undefined reference to `qemu_chr_find'
> > > /mnt/sdb/gonglei/qemu.git/qemu/crypto/cryptodev-vhost-user.c:194:
> > undefined reference to `qemu_chr_fe_claim_no_fail'
> > > crypto/cryptodev-vhost-user.o: In function
> > `qcrypto_cryptodev_vhost_user_event':
> > > /mnt/sdb/gonglei/qemu.git/qemu/crypto/cryptodev-vhost-user.c:213:
> > undefined reference to `qemu_chr_set_reconnect_time'
> > > crypto/cryptodev-vhost-user.o: In function
> > `qcrypto_cryptodev_vhost_user_init':
> > > /mnt/sdb/gonglei/qemu.git/qemu/crypto/cryptodev-vhost-user.c:257:
> > undefined reference to `qemu_chr_add_handlers'
> > > crypto/cryptodev-vhost-user.o: In function
> > `qcrypto_cryptodev_vhost_user_finalize':
> > > /mnt/sdb/gonglei/qemu.git/qemu/crypto/cryptodev-vhost-user.c:353:
> > undefined reference to `qemu_chr_add_handlers'
> > > /mnt/sdb/gonglei/qemu.git/qemu/crypto/cryptodev-vhost-user.c:354:
> > undefined reference to `qemu_chr_fe_release'
> > > collect2: ld returned 1 exit status
> > > make: *** [qemu-nbd] Error 1
> > >
> > > Currently I only change the crypto/Makefile.objs:
> > >
> > > diff --git a/crypto/Makefile.objs b/crypto/Makefile.objs
> > > index b9ad26a..575f64e 100644
> > > --- a/crypto/Makefile.objs
> > > +++ b/crypto/Makefile.objs
> > > @@ -28,6 +28,7 @@ crypto-obj-y += block-qcow.o
> > >  crypto-obj-y += block-luks.o
> > >  crypto-obj-y += cryptodev.o
> > >  crypto-obj-y += cryptodev-builtin.o
> > > +crypto-obj-y += cryptodev-vhost-user.o
> > 
> > The $(crypto-obj-y) variable is intended to only contain general purpose
> > crypto code, since it needs to be linked to all QEMU programs. Your
> > cryptodev file is specific to system emulators, so must only be linked
> > to the system emulator targets. Thus, it should not be added to the
> > crypto-obj-y variable.
> > 
> > It probably needs to be added to either common-obj-y or obj-y - I can't
> > remember which is "best"
> > 
> common-obj-y is fine! So all cryptodev stuff should be use 
> $( crypto-obj-y) variable, right? I'll change them in the next version.

Looking at this again, it actually makes me think that your
cryptodev stuff would be better in the backends/ directory.

That would mean the crypto/ directory is kept as the place for
generic crypto infrastructure, and avoiding system emulator
specific device backend code. The backends/Makefile.objs is
already setup to use common-obj-y and builds various other
device backend models.

Regards,
Daniel
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