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From: Puranjay Mohan <puranjay@kernel.org>
To: Leon Hwang <hffilwlqm@gmail.com>, bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
	maciej.fijalkowski@intel.com, jakub@cloudflare.com,
	pulehui@huawei.com, hffilwlqm@gmail.com,
	kernel-patches-bot@fb.com, puranjay12@gmail.com
Subject: Re: [PATCH v5 bpf-next 2/3] bpf, arm64: Fix tailcall hierarchy
Date: Wed, 26 Jun 2024 12:05:47 +0000	[thread overview]
Message-ID: <mb61pwmmbykmc.fsf@kernel.org> (raw)
In-Reply-To: <20240623161528.68946-3-hffilwlqm@gmail.com>

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Leon Hwang <hffilwlqm@gmail.com> writes:

> This patch fixes a tailcall issue caused by abusing the tailcall in
> bpf2bpf feature on arm64 like the way of "bpf, x64: Fix tailcall
> hierarchy".
>
> On arm64, when a tail call happens, it uses tail_call_cnt_ptr to
> increment tail_call_cnt, too.
>
> At the prologue of main prog, it has to initialize tail_call_cnt and
> prepare tail_call_cnt_ptr.
>
> At the prologue of subprog, it pushes x26 register twice, and does not
> initialize tail_call_cnt.
>
> At the epilogue, it pops x26 twice, no matter whether it is main prog or
> subprog.
>
> Fixes: d4609a5d8c70 ("bpf, arm64: Keep tail call count across bpf2bpf calls")
> Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>

Acked-by: Puranjay Mohan <puranjay@kernel.org>

Thanks,
Puranjay

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  reply	other threads:[~2024-06-26 12:06 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-06-23 16:15 [PATCH v5 bpf-next 0/3] bpf: Fix tailcall hierarchy Leon Hwang
2024-06-23 16:15 ` [PATCH v5 bpf-next 1/3] bpf, x64: " Leon Hwang
2024-07-11  0:15   ` Eduard Zingerman
2024-07-11  2:02     ` Leon Hwang
2024-06-23 16:15 ` [PATCH v5 bpf-next 2/3] bpf, arm64: " Leon Hwang
2024-06-26 12:05   ` Puranjay Mohan [this message]
2024-06-23 16:15 ` [PATCH v5 bpf-next 3/3] selftests/bpf: Add testcases for tailcall hierarchy fixing Leon Hwang
2024-07-11  2:01   ` Eduard Zingerman
2024-07-11 14:36     ` Leon Hwang

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