Re: [PATCH] net/tap: fix build issue with ARM32

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Wed, 31 Jan 2018 09:59:45 +0000
> From: Ophir Munk <ophirmu@mellanox.com>
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>, "dev@dpdk.org"
>  <dev@dpdk.org>
> CC: Thomas Monjalon <thomas@monjalon.net>, Pascal Mazon
>  <pascal.mazon@6wind.com>, Jan Viktorin <viktorin@rehivetech.com>, Jianbo
>  Liu <jianbo.liu@arm.com>
> Subject: RE: [dpdk-dev]  [PATCH] net/tap: fix build issue with ARM32
> 
> Hi,
> Please see comments inline
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jerin Jacob
> > Sent: Wednesday, January 31, 2018 7:14 AM
> > To: dev@dpdk.org
> > Cc: Thomas Monjalon <thomas@monjalon.net>; Jerin Jacob
> > <jerin.jacob@caviumnetworks.com>; Pascal Mazon
> > <pascal.mazon@6wind.com>; Jan Viktorin <viktorin@rehivetech.com>;
> > Jianbo Liu <jianbo.liu@arm.com>
> > Subject: [dpdk-dev] [PATCH] net/tap: fix build issue with ARM32
> > 
> > arm32 Linux does not support eBPF interface.
> > Since tap PMD driver has a dependency on eBPF(the symbol __NR_bpf),
> > disabling it armv7 config.
> > 
> > compilation error log:
> > In file included from /tmp/dpdk/drivers/net/tap/tap_bpf_api.c:15:0:
> > /tmp/dpdk/drivers/net/tap/tap_bpf.h:103:4: error: #error __NR_bpf not
> > defined  #  error __NR_bpf not defined
> >     ^
> 
> arm architecture is missing is file drivers/tap/tap_bpf.h
> I suggest adding it, for example
> 
> # elif defined(__arm__)
> #  define __NR_bpf 386

By looking at Linux source code
http://elixir.free-electrons.com/linux/v4.15/source/tools/build/feature/test-bpf.c#L6
I am not sure, Is eBPF support available for arm32 support?

> 
> It should work for you. Can you please try it?

I don't have access to an arm32 board. I was facing cross compilation
build issue with arm32.

> If it doesn't work for you, please have a look in this link:
>  https://sourceforge.net/p/predef/wiki/Architectures/
> where you can see more arm architecture definitions.
> You should find the one suitable for you.

I guess, it is not just matter of enabling the build for arm32. It should work
at runtime too, If some can confirm following addition in the drivers/net/tap/tap_bpf.h
works then we can add it.

# elif defined(__arm__)
#  define __NR_bpf 386

> 
> > /tmp/dpdk/drivers/net/tap/tap_bpf_api.c: In function ‘sys_bpf’:
> > /tmp/dpdk/drivers/net/tap/tap_bpf_api.c:92:17: error: ‘__NR_bpf’
> > undeclared (first use in this function)
> >   return syscall(__NR_bpf, cmd, attr, size);
> >                  ^
> > /tmp/dpdk/drivers/net/tap/tap_bpf_api.c:92:17: note: each undeclared
> > identifier is reported only once for each function it appears in
> > /tmp/dpdk/drivers/net/tap/tap_bpf_api.c:93:1: error: control reaches end of
> > non-void function [-Werror=return-type]  }  ^
> > cc1: all warnings being treated as errors
> > 
> > Fixes: b02d85e1 ("net/tap: add eBPF API")
> > 
> > Cc: Pascal Mazon <pascal.mazon@6wind.com>
> > Cc: Jan Viktorin <viktorin@rehivetech.com>
> > Cc: Jianbo Liu <jianbo.liu@arm.com>
> > 
> > Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > ---
> >  config/defconfig_arm-armv7a-linuxapp-gcc | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/config/defconfig_arm-armv7a-linuxapp-gcc
> > b/config/defconfig_arm-armv7a-linuxapp-gcc
> > index a20b7a85f..4a55bb397 100644
> > --- a/config/defconfig_arm-armv7a-linuxapp-gcc
> > +++ b/config/defconfig_arm-armv7a-linuxapp-gcc
> > @@ -80,3 +80,4 @@ CONFIG_RTE_LIBRTE_BNX2X_PMD=n
> > CONFIG_RTE_LIBRTE_QEDE_PMD=n  CONFIG_RTE_LIBRTE_SFC_EFX_PMD=n
> > CONFIG_RTE_LIBRTE_AVP_PMD=n
> > +CONFIG_RTE_LIBRTE_PMD_TAP=n
> > --
> 
> I suggest fixing the compilation issue by adding the missing architecture system call number
> (as suggested above) instead of disabling TAP compilation by default
> 
> > 2.16.1
>