netdev - [suricata PATCH 2/3] suricata/ebpf: compile with clang -target bpf

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Date:   Wed, 07 Feb 2018 23:21:19 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     eric@...it.org
Cc:     victor@...iniac.net, netdev@...r.kernel.org,
        Jesper Dangaard Brouer <brouer@...hat.com>, yhs@...com,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: [suricata PATCH 2/3] suricata/ebpf: compile with clang -target bpf

From: Jesper Dangaard Brouer <netoptimizer@...uer.com>

Enable compiling eBPF programs with clang -target bpf.

This is mostly to workaround a bug in libbpf, where clang > ver 4.0.0
generates some ELF sections (.eh_frame) when -target bpf is NOT specified,
and libbpf fails loading such files.

Notice libbpf is provided by the kernel, and in kernel v4.16 the library
will contain the needed function for attatching to the XDP hook.

Kernel commit 949abbe88436 ("libbpf: add function to setup XDP")
 https://git.kernel.org/torvalds/c/949abbe88436

As it looks now, the library fix will not get into kernel v4.16. Thus, we
need this workaround for Suricata.  In-order to recommend people installing
the library libbpf from kernel v4.16.

Signed-off-by: Jesper Dangaard Brouer <netoptimizer@...uer.com>
---
 ebpf/Makefile.am |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ebpf/Makefile.am b/ebpf/Makefile.am
index 66db35f80c7e..d0ee44ae668e 100644
--- a/ebpf/Makefile.am
+++ b/ebpf/Makefile.am
@@ -6,7 +6,7 @@ BPF_CFLAGS = -Iinclude
 all: lb.bpf filter.bpf bypass_filter.bpf xdp_filter.bpf vlan_filter.bpf

 %.bpf: %.c
-	${CC} -Wall $(BPF_CFLAGS) -O2 -D__KERNEL__ -D__ASM_SYSREG_H -emit-llvm -c $< -o - | ${LLC} -march=bpf -filetype=obj -o $@
+	${CC} -Wall $(BPF_CFLAGS) -O2 -D__KERNEL__ -D__ASM_SYSREG_H -target bpf -emit-llvm -c $< -o - | ${LLC} -march=bpf -filetype=obj -o $@

 CLEANFILES = *.bpf