netdev - Re: "A call to built-in function '__stack_chk_fail' is not supported." when building BPF samples/tools

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Message-ID: <072e1637-f08a-4653-3cbd-bff33d0548a0@iogearbox.net>
Date:   Tue, 5 Mar 2019 00:31:59 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Hazrael <hazrael@...tonmail.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: "A call to built-in function '__stack_chk_fail' is not
 supported." when building BPF samples/tools

On 03/05/2019 12:18 AM, Hazrael wrote:
> Hello,
> 
> I guess I'm taking risks by asking this here, as the problem
> I have is definitely more likely to come from my setup, but
> after many research I don't know where to seek help.

No worries, completely fine to ask.

> So here it goes : when I try building samples/bpf or
> tools/testing/selftests/bpf/, I always end up with the following
> error (here when compiling samples):
> 
>  CLANG-bpf  <path_to>/samples/bpf/sockex1_kern.o
>  error: <unknown>:0:0: in function bpf_prog1 i32 (%struct.__sk_buff*):
>  A call to built-in function '__stack_chk_fail' is not supported.

Hm, looks like your toolchain might have stack protector enabled by
default. Could you try with setting CFLAGS with -fno-stack-protector
as in the below:

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 65e667b..ebfb3d1 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -213,6 +213,7 @@ BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \
                          readelf -S ./llvm_btf_verify.o | grep BTF; \
                          /bin/rm -f ./llvm_btf_verify.o)

+EXTRA_CFLAGS += -fno-stack-protector
 ifneq ($(BTF_LLVM_PROBE),)
        EXTRA_CFLAGS += -g
 else

> - I'm running Archlinux (up-to-date) / 4.20.13-arch1-1-ARCH
> - clang  7.0.1 / gcc 8.2.1 /
> - It happens on *_kern.c programs only
> - I tried following steps from Cilium BPF doc, right after a fresh
> Archlinux install
> (https://cilium.readthedocs.io/en/v1.3/bpf/#compiling-the-kernel)
> - My kernel config matches what is required by Cilium guide.
> - All in all, I tried with
>   - archlinux "stock" kernel
>   - many 'custom' kernels I compiled and installed (still on arch)
>   - the net and net-next trees just as in Cilium guide (still on arch,
>   fresh install)
> - It worked fine on my Slackware with 4.20.0 kernel and a random Fedora...
> 
> So... guess that comes from my llvm/clang, but found nothing useful
> online yet. I'm in the process of building llvm from scratch,even
> if build parameters in llvm archlinux package don't seem odd compared
> to what Cilium (once again :P) recommends.
> 
> 
> I'm not asking for a full debug of course but if someone's here uses
> Archlinux for BPF development and has some pointers, that would be nice !
> 
> 
> And again, if that was totally the wrong place for such question, I'm
> deeply sorry :/
> 
> Nicolas C.
> 
>