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From: Jiong Wang <jiong.wang@netronome•com>
To: Oleksandr Natalenko <oleksandr@natalenko•name>
Cc: Jiong Wang <jiong.wang@netronome•com>,
	Jakub Kicinski <jakub.kicinski@netronome•com>,
	"David S. Miller" <davem@davemloft•net>,
	Alexei Starovoitov <ast@kernel•org>,
	Daniel Borkmann <daniel@iogearbox•net>,
	Martin KaFai Lau <kafai@fb•com>, Song Liu <songliubraving@fb•com>,
	Yonghong Song <yhs@fb•com>,
	Jesper Dangaard Brouer <hawk@kernel•org>,
	John Fastabend <john.fastabend@gmail•com>,
	netdev@vger•kernel.org, bpf@vger•kernel.org,
	oss-drivers@netronome•com, linux-kernel@vger•kernel.org,
	xdp-newbies@vger•kernel.org, valdis@vt•edu
Subject: Re: [oss-drivers] netronome/nfp/bpf/jit.c cannot be build with -O3
Date: Tue, 07 May 2019 12:31:29 +0100	[thread overview]
Message-ID: <87ef5abiwe.fsf@netronome.com> (raw)
In-Reply-To: <4414f1798ea3c0f70128b7e4caa14edc@natalenko.name>


Oleksandr Natalenko writes:

> Hi.
>
> On 07.05.2019 00:01, Jiong Wang wrote:
>> I guess it's because constant prop. Could you try the following change 
>> to
>> __emit_shift?
>> 
>> drivers/net/ethernet/netronome/nfp/bpf/jit.c
>> __emit_shift:331
>> -       if (sc == SHF_SC_L_SHF)
>> +       if (sc == SHF_SC_L_SHF && shift)
>>                 shift = 32 - shift;
>> 
>> emit_shf_indir is passing "0" as shift to __emit_shift which will
>> eventually be turned into 32 and it was OK because we truncate to 
>> 5-bit,
>> but before truncation, it will overflow the shift mask.
>
> Yup, it silences the error for me.

Thanks for the testing.

I have also reproduced this issue after switching to gcc 8.3, and confirmed
the error is triggered from "value too large for the field" check inside
__BF_FIELD_CHECK due to immediate "32" is out of range for mask 0x1f.

Will send out a fix.

Regards,
Jiong

     prev parent reply	other threads:[~2019-05-07 11:31 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-06 19:40 netronome/nfp/bpf/jit.c cannot be build with -O3 Oleksandr Natalenko
2019-05-06 21:00 ` Jakub Kicinski
2019-05-06 21:24   ` Oleksandr Natalenko
2019-05-06 21:35     ` Jakub Kicinski
2019-05-07  5:01       ` Oleksandr Natalenko
2019-05-06 22:01 ` [oss-drivers] " Jiong Wang
2019-05-07  5:05   ` Oleksandr Natalenko
2019-05-07 11:31     ` Jiong Wang [this message]

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