From: Peter Zijlstra <peterz@infradead.org>
To: Song Liu <song@kernel.org>
Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
ast@kernel.org, daniel@iogearbox.net, mcgrof@kernel.org,
torvalds@linux-foundation.org, rick.p.edgecombe@intel.com,
kernel-team@fb.com
Subject: Re: [PATCH bpf-next 2/5] x86/alternative: introduce text_poke_set
Date: Wed, 18 May 2022 19:09:34 +0200 [thread overview]
Message-ID: <20220518170934.GG10117@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20220516054051.114490-3-song@kernel.org>
On Sun, May 15, 2022 at 10:40:48PM -0700, Song Liu wrote:
> Introduce a memset like API for text_poke. This will be used to fill the
> unused RX memory with illegal instructions.
FWIW, you're going to use it to set INT3 (0xCC), that's not an illegal
instruction. INTO (0xCE) would be an illegal instruction (in 64bit
mode).
> + return addr;
> +}
> +
> +/**
> + * text_poke_set - memset into (an unused part of) RX memory
> + * @addr: address to modify
> + * @c: the byte to fill the area with
> + * @len: length to copy, could be more than 2x PAGE_SIZE
> + *
> + * Not safe against concurrent execution; useful for JITs to dump
> + * new code blocks into unused regions of RX memory. Can be used in
> + * conjunction with synchronize_rcu_tasks() to wait for existing
> + * execution to quiesce after having made sure no existing functions
> + * pointers are live.
That comment suffers from copy-pasta and needs an update because it
clearly isn't correct.
> + */
Other than that, seems fine.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
next prev parent reply other threads:[~2022-05-18 17:10 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-16 5:40 [PATCH bpf-next 0/5] bpf_prog_pack followup Song Liu
2022-05-16 5:40 ` [PATCH bpf-next 1/5] bpf: fill new bpf_prog_pack with illegal instructions Song Liu
2022-05-16 5:40 ` [PATCH bpf-next 2/5] x86/alternative: introduce text_poke_set Song Liu
2022-05-17 19:16 ` Edgecombe, Rick P
2022-05-17 21:09 ` Song Liu
2022-05-18 6:58 ` Song Liu
2022-05-18 7:45 ` Peter Zijlstra
2022-05-18 15:32 ` Song Liu
2022-05-18 17:09 ` Peter Zijlstra [this message]
2022-05-18 18:34 ` Song Liu
2022-05-19 7:38 ` Peter Zijlstra
2022-05-16 5:40 ` [PATCH bpf-next 3/5] bpf: introduce bpf_arch_text_invalidate for bpf_prog_pack Song Liu
2022-05-16 5:40 ` [PATCH bpf-next 5/5] bpf: use module_alloc_huge " Song Liu
2022-05-17 19:15 ` Edgecombe, Rick P
2022-05-17 21:08 ` Song Liu
2022-05-17 23:58 ` Edgecombe, Rick P
2022-05-18 6:25 ` Song Liu
2022-05-18 6:34 ` Song Liu
2022-05-18 16:49 ` Edgecombe, Rick P
2022-05-18 18:31 ` Song Liu
2022-05-19 6:42 ` Song Liu
2022-05-19 16:56 ` Edgecombe, Rick P
2022-05-19 18:25 ` Song Liu
[not found] ` <20220516054051.114490-5-song@kernel.org>
2022-05-18 6:28 ` [PATCH bpf-next 4/5] module: introduce module_alloc_huge Song Liu
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