From: Leon Hwang <leon.hwang@linux.dev>
To: Xu Kuohai <xukuohai@huaweicloud.com>
Cc: a.s.protopopov@gmail.com, alexis.lothore@bootlin.com,
andrii@kernel.org, ast@kernel.org, bjorn@kernel.org,
bpf@vger.kernel.org, chleroy@kernel.org, daniel@iogearbox.net,
davem@davemloft.net, eddyz87@gmail.com, gor@linux.ibm.com,
hbathini@linux.ibm.com, hca@linux.ibm.com, hengqi.chen@gmail.com,
iii@linux.ibm.com, johan.almbladh@anyfinetworks.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux@armlinux.org.uk,
list+bpf@vahedi.org, luke.r.nels@gmail.com, martin.lau@linux.dev,
naveen@kernel.org, paulburton@kernel.org, pulehui@huawei.com,
puranjay@kernel.org, udknight@gmail.com, xi.wang@gmail.com,
yangtiezhu@loongson.cn, yonghong.song@linux.dev
Subject: Re: [PATCH bpf-next v9 4/5] bpf, x86: Emit ENDBR for indirect jump targets
Date: Sat, 14 Mar 2026 21:35:10 +0800 [thread overview]
Message-ID: <9ddae3d2-173d-460d-b283-12c983164a69@linux.dev> (raw)
In-Reply-To: <f384599a-75b8-4387-80db-b20429a0bafd@huaweicloud.com>
On 2026/3/14 14:48, Xu Kuohai wrote:
> On 3/13/2026 6:15 PM, Leon Hwang wrote:
>>> +#ifdef CONFIG_X86_KERNEL_IBT
>>> + if (bpf_insn_is_indirect_target(env, bpf_prog, i - 1))
>>> + EMIT_ENDBR();
>>> +#endif
>> NIT: is this CONFIG check necessary?
>>
>> EMIT_ENDBR already checks it.
>>
>> #ifdef CONFIG_X86_KERNEL_IBT
>> #define EMIT_ENDBR() EMIT(gen_endbr(), 4)
>> #define EMIT_ENDBR_POISON() EMIT(gen_endbr_poison(), 4)
>> #else
>> #define EMIT_ENDBR()
>> #define EMIT_ENDBR_POISON()
>> #endif
>
> Well, the code was originally written exactly without the #ifdef, but it
> triggered
> -Wempty-body warning: https://lore.kernel.org/bpf/202603051414.AAMjmOHv-
> lkp@intel.com/.
>
Let's update the macros instead, which can avoid the build warning and
get rid of the CONFIG check as well.
#define EMIT_ENDBR() do { } while (0)
#define EMIT_ENDBR_POISON() do { } while (0)
The way of "do { } while (0)" is commonly used in kernel.
Thanks,
Leon
next prev parent reply other threads:[~2026-03-14 13:35 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-12 17:02 [-next v9 0/5] emit ENDBR/BTI instructions for indirect jump targets Xu Kuohai
2026-03-12 17:02 ` [PATCH bpf-next v9 1/5] bpf: Move constants blinding out of arch-specific JITs Xu Kuohai
2026-03-12 17:50 ` bot+bpf-ci
2026-03-13 2:32 ` Xu Kuohai
2026-03-13 9:18 ` Hari Bathini
2026-03-13 9:55 ` Pu Lehui
2026-03-14 1:29 ` Eduard Zingerman
2026-03-14 4:21 ` Xu Kuohai
2026-03-15 6:05 ` kernel test robot
2026-03-12 17:02 ` [PATCH bpf-next v9 2/5] bpf: Pass bpf_verifier_env to JIT Xu Kuohai
2026-03-12 17:02 ` [PATCH bpf-next v9 3/5] bpf: Add helper to detect indirect jump targets Xu Kuohai
2026-03-12 17:02 ` [PATCH bpf-next v9 4/5] bpf, x86: Emit ENDBR for " Xu Kuohai
2026-03-13 10:15 ` Leon Hwang
2026-03-14 6:48 ` Xu Kuohai
2026-03-14 13:35 ` Leon Hwang [this message]
2026-03-23 13:39 ` Xu Kuohai
2026-03-12 17:02 ` [PATCH bpf-next v9 5/5] bpf, arm64: Emit BTI for indirect jump target Xu Kuohai
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