linux-kernel - Re: [PATCH bpf-next v9 3/4] bpf, arm64: Implement bpf_arch_text

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Message-ID: <8489a831-1785-fa8d-183e-22fd841b65d0@nvidia.com>
Date:   Thu, 21 Jul 2022 08:29:46 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Xu Kuohai <xukuohai@...wei.com>, bpf@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Will Deacon <will@...nel.org>, KP Singh <kpsingh@...nel.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Zi Shen Lim <zlim.lnx@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Russell King <rmk+kernel@...linux.org.uk>,
        James Morse <james.morse@....com>,
        Hou Tao <houtao1@...wei.com>,
        Jason Wang <wangborong@...rlc.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH bpf-next v9 3/4] bpf, arm64: Implement
 bpf_arch_text_poke() for arm64



On 18/07/2022 16:37, Xu Kuohai wrote:
> On 7/18/2022 9:52 PM, Jon Hunter wrote:
> 
> [..]
>>
>> This change appears to be causing the build to fail ...
>>
>> /tmp/cc52xO0c.s: Assembler messages:
>> /tmp/cc52xO0c.s:8: Error: operand 1 should be an integer register --
>> `mov lr,x9'
>> /tmp/cc52xO0c.s:7: Error: undefined symbol lr used as an immediate value
>> make[2]: *** [scripts/Makefile.build:250: arch/arm64/net/bpf_jit_comp.o]
>> Error 1
>> make[1]: *** [scripts/Makefile.build:525: arch/arm64/net] Error 2
>>
>> Let me know if you have any thoughts.
>>
> 
> Sorry for this failure, but I can't reproduce it.
> 
> I guess maybe your assembler doesn't recognize "lr". Could you give a
> try to replace "lr" with "x30"?
> 
>   #if IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)
>   "      bti j\n" /* dummy_tramp is called via "br x10" */
>   #endif
> -"      mov x10, lr\n"
> -"      mov lr, x9\n"
> +"      mov x10, x30\n"
> +"      mov x30, x9\n"
>   "      ret x10\n"
>   "      .size dummy_tramp, .-dummy_tramp\n"
>   "      .popsection\n
> 
> Thanks.


Sorry for delay, this did not seem to land in my inbox. Anyway, yes this 
fixes the build issue for me!

Thanks!
Jon

-- 
nvpublic