netdev - Re: [suricata PATCH 1/3] suricata/ebpf: take clang -target bpf include issue of stdint.h into account

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Date:   Thu, 08 Feb 2018 00:52:09 +0100
From:   Eric Leblond <eric@...it.org>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     victor@...iniac.net, netdev@...r.kernel.org, yhs@...com,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [suricata PATCH 1/3] suricata/ebpf: take clang -target bpf
 include issue of stdint.h into account

Hi,

On Wed, 2018-02-07 at 23:21 +0100, Jesper Dangaard Brouer wrote:
> From: Jesper Dangaard Brouer <netoptimizer@...uer.com>
> 
> This patch prepares code before enabling the clang -target bpf.
> 
> The clang compiler does not like #include <stdint.h> when
> using '-target bpf' it will fail with:
> 
>  fatal error: 'gnu/stubs-32.h' file not found
...
> This can be worked around by installing the 32-bit version of
> glibc-devel.i686 on your distribution.
> 
> But the BPF programs does not really need to include stdint.h,
> if converting:
>   uint64_t -> __u64
>   uint32_t -> __u32
>   uint16_t -> __u16
>   uint8_t  -> __u8
> 
> This patch does this type syntax conversion.

There is an issue for system like Debian because they don't have a
asm/types.h in the include path if the architecture is not defined
which is the case due to target bpf. This results in:

clang-5.0 -Wall -Iinclude -O2 \
	-D__KERNEL__ -D__ASM_SYSREG_H \
	-target bpf -S -emit-llvm vlan_filter.c -o vlan_filter.ll
In file included from vlan_filter.c:19:
In file included from include/linux/bpf.h:11:
/usr/include/linux/types.h:5:10: fatal error: 'asm/types.h' file not
found
#include <asm/types.h>
         ^~~~~~~~~~~~~
1 error generated.
Makefile:523: recipe for target 'vlan_filter.bpf' failed

To go into details, the Debian package providing the 'asm/typs.h'
include is the the headers or linux-libc-dev. But this package comes
with a flavor and thus we have a prefix: 
 linux-libc-dev:amd64: /usr/include/x86_64-linux-gnu/asm/types.h

"Fun" part here is that if you build a debian package of the via make
in Linux tree then the linux-libc-dev package is correct.

So I propose the following patch that fixes the issue for me:

diff --git a/ebpf/Makefile.am b/ebpf/Makefile.am
index 89a3304e9..712b05343 100644
--- a/ebpf/Makefile.am
+++ b/ebpf/Makefile.am
@@ -16,6 +16,7 @@ all: $(BPF_TARGETS)
 $(BPF_TARGETS): %.bpf: %.c
 #      From C-code to LLVM-IR format suffix .ll (clang -S -emit-llvm)
        ${CLANG} -Wall $(BPF_CFLAGS) -O2 \
+               -I/usr/include/$(host_cpu)-$(host_os)/ \
                -D__KERNEL__ -D__ASM_SYSREG_H \
                -target bpf -S -emit-llvm $< -o ${@:.bpf=.ll}
 #      From LLVM-IR to BPF-bytecode in ELF-obj file

Let me know if it is ok for you.

Best regards,
-- 
Eric Leblond <eric@...it.org>