From: Daniel Borkmann <daniel@iogearbox.net>
To: David Daney <david.daney@cavium.com>,
Alexei Starovoitov <ast@kernel.org>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mips@linux-mips.org, ralf@linux-mips.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RFC 2/3] samples/bpf: Add define __EMITTING_BPF__ when building BPF
Date: Fri, 16 Jun 2017 12:24:06 +0200 [thread overview]
Message-ID: <5943B1C6.7040809@iogearbox.net> (raw)
In-Reply-To: <20170615223543.22867-3-david.daney@cavium.com>
On 06/16/2017 12:35 AM, David Daney wrote:
> ... this allows gating of inline assembly code that causes llvm to
> fail when emitting BPF.
>
> Signed-off-by: David Daney <david.daney@cavium.com>
I don't have a better idea at the moment, perhaps there could be
a clang rewrite plugin that would ignore all inline assembly code
since this is never used from BPF progs. Hmm. Really ugly that
we have to add this __EMITTING_BPF__ into arch asm files, but I
don't have a better idea for an immediate workaround right now ...
I would really prefer if we could avoid just for the sake of the
kernel samples going down the road of adding a !defined(__EMITTING_BPF__)
into a uapi asm header for mips, though. Is this coming from
networking sample code or rather tracing?
> ---
> samples/bpf/Makefile | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index a0561dc762fe..4979e6b56662 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -193,12 +193,12 @@ $(src)/*.c: verify_target_bpf
>
> $(obj)/tracex5_kern.o: $(obj)/syscall_nrs.h
>
> -# asm/sysreg.h - inline assembly used by it is incompatible with llvm.
> -# But, there is no easy way to fix it, so just exclude it since it is
> -# useless for BPF samples.
> +# __EMITTING_BPF__ used to exclude inline assembly, which cannot be
> +# emitted in BPF code.
> $(obj)/%.o: $(src)/%.c
> $(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \
> - -D__KERNEL__ -D__ASM_SYSREG_H -Wno-unused-value -Wno-pointer-sign \
> + -D__KERNEL__ -D__EMITTING_BPF__ \
> + -Wno-unused-value -Wno-pointer-sign \
> -Wno-compare-distinct-pointer-types \
> -Wno-gnu-variable-sized-type-not-at-end \
> -Wno-address-of-packed-member -Wno-tautological-compare \
>
next prev parent reply other threads:[~2017-06-16 10:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-15 22:35 [PATCH RFC 0/3] bpf/arm64/mips: Avoid inline asm in BPF David Daney
2017-06-15 22:35 ` [PATCH RFC 1/3] arm64: Gate inclusion of asm/sysreg.h by __EMITTING_BPF__ David Daney
2017-06-15 22:35 ` [PATCH RFC 2/3] samples/bpf: Add define __EMITTING_BPF__ when building BPF David Daney
2017-06-16 10:24 ` Daniel Borkmann [this message]
2017-06-16 16:14 ` David Miller
2017-06-19 14:37 ` Andy Gospodarek
2017-06-15 22:35 ` [PATCH RFC 3/3] MIPS: Include file changes to enable building BPF code with llvm David Daney
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