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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: ast@kernel.org, john.fastabend@gmail.com, netdev@vger.kernel.org,
	bpf@vger.kernel.org
Subject: Re: [PATCH rfc bpf-next 7/8] bpf, x86: emit patchable direct jump as tail call
Date: Thu, 14 Nov 2019 19:23:46 -0800	[thread overview]
Message-ID: <20191115032345.loei6qqgyo4tdbuq@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <78a8cbc4887d00b3dc4705347f05572630650cbf.1573779287.git.daniel@iogearbox.net>

On Fri, Nov 15, 2019 at 02:04:01AM +0100, Daniel Borkmann wrote:
> for later modifications. In ii) fixup_bpf_tail_call_direct() walks
> over the progs poke_tab, locks the tail call maps poke_mutex to
> prevent from parallel updates and patches in the right locations via
...
> @@ -1610,6 +1671,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>  		prog->bpf_func = (void *)image;
>  		prog->jited = 1;
>  		prog->jited_len = proglen;
> +		fixup_bpf_tail_call_direct(prog);

Why not to move fixup_bpf_tail_call_direct() just before
bpf_jit_binary_lock_ro() and use simple memcpy instead of text_poke ?

imo this logic in patch 7:
case BPF_JMP | BPF_TAIL_CALL:
+   if (imm32)
+            emit_bpf_tail_call_direct(&bpf_prog->aux->poke_tab[imm32 - 1],
would have been easier to understand if patch 7 and 8 were swapped.


  reply	other threads:[~2019-11-15  3:23 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-15  1:03 [PATCH rfc bpf-next 0/8] Optimize BPF tail calls for direct jumps Daniel Borkmann
2019-11-15  1:03 ` [PATCH rfc bpf-next 1/8] bpf, x86: generalize and extend bpf_arch_text_poke " Daniel Borkmann
2019-11-15 23:22   ` Andrii Nakryiko
2019-11-15 23:42     ` Daniel Borkmann
2019-11-16  0:01       ` Andrii Nakryiko
2019-11-15  1:03 ` [PATCH rfc bpf-next 2/8] bpf: add bpf_prog_under_eviction helper Daniel Borkmann
2019-11-15  1:03 ` [PATCH rfc bpf-next 3/8] bpf: move bpf_free_used_maps into sleepable section Daniel Borkmann
2019-11-15 23:32   ` Andrii Nakryiko
2019-11-15  1:03 ` [PATCH rfc bpf-next 4/8] bpf: move owner type,jited info into array auxillary data Daniel Borkmann
2019-11-15 23:19   ` Andrii Nakryiko
2019-11-15  1:03 ` [PATCH rfc bpf-next 5/8] bpf: add jit poke descriptor mock-up for jit images Daniel Borkmann
2019-11-18 18:17   ` Andrii Nakryiko
2019-11-18 18:43     ` Daniel Borkmann
2019-11-15  1:04 ` [PATCH rfc bpf-next 6/8] bpf: add poke dependency tracking for prog array maps Daniel Borkmann
2019-11-18 17:39   ` Andrii Nakryiko
2019-11-18 18:39     ` Daniel Borkmann
2019-11-18 18:46       ` Andrii Nakryiko
2019-11-18 21:35         ` Daniel Borkmann
2019-11-15  1:04 ` [PATCH rfc bpf-next 7/8] bpf, x86: emit patchable direct jump as tail call Daniel Borkmann
2019-11-15  3:23   ` Alexei Starovoitov [this message]
2019-11-15  7:27     ` Daniel Borkmann
2019-11-15  1:04 ` [PATCH rfc bpf-next 8/8] bpf: constant map key tracking for prog array pokes Daniel Borkmann
2019-11-15  4:29   ` Alexei Starovoitov
2019-11-15  7:13     ` Daniel Borkmann
2019-11-15 16:33       ` Alexei Starovoitov
2019-11-15 16:49         ` Daniel Borkmann
2019-11-18 18:11   ` Andrii Nakryiko
2019-11-18 21:45     ` Daniel Borkmann

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