From: Jiri Slaby <jslaby@suse.cz>
To: David Miller <davem@davemloft.net>
Cc: alexei.starovoitov@gmail.com, mingo@kernel.org, mingo@redhat.com,
tglx@linutronix.de, hpa@zytor.com, x86@kernel.org,
jpoimboe@redhat.com, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, daniel@iogearbox.net,
edumazet@google.com
Subject: Re: [PATCH v3 07/29] x86: bpf_jit, use ENTRY+ENDPROC
Date: Tue, 25 Apr 2017 16:41:48 +0200 [thread overview]
Message-ID: <bd853573-04d3-20a2-c124-7114f7684477@suse.cz> (raw)
In-Reply-To: <20170424.142420.290668473718207530.davem@davemloft.net>
On 04/24/2017, 08:24 PM, David Miller wrote:
> From: Jiri Slaby <jslaby@suse.cz>
> Date: Mon, 24 Apr 2017 19:51:54 +0200
>
>> For example what's the point of making the sk_load_word_positive_offset
>> label a global, callable function? Note that this is exactly the reason
>> why this particular two hunks look weird to you even though the
>> annotations only mechanically paraphrase what is in the current code.
>
> So that it can be referenced by the eBPF JIT, because these are
> helpers for eBPF JIT generated code. Every architecture implementing
> an eBPF JIT has this "mess".
I completely understand the needs for this, but I am complaining about
the way it is written. That is not the best -- unbalanced annotations, C
macros in lowercase (apart from that, C macros in .S need semicolons &
backslashes), FUNC macro, etc.
> You can't even put a tracepoint or kprobe on these things and expect
> to see "arguments" or "return PC" values in the usual spots. This
> code has special calling conventions and register usage as Alexei
> explained.
Yes, I can see that.
> I would suggest that you read and understand how this assembler is
> designed, how it is called from the generated JIT code, and what it's
> semantics and register usage are, before trying to annotating it.
Of course I studied the code. I only missed macro CHOOSE_LOAD_FUNC which
I see now. So that answers why sk_load_word_positive_offset & similar
are marked as .globl.
But the original question I asked still remains: why do you mind calling
them BPF_FUNC_START & *_END, given:
1) the functions are marked by "FUNC" already:
$ git grep FUNC linus/master arch/x86/net/bpf_jit.S
linus/master:arch/x86/net/bpf_jit.S:#define FUNC(name) \
linus/master:arch/x86/net/bpf_jit.S:FUNC(sk_load_word)
linus/master:arch/x86/net/bpf_jit.S:FUNC(sk_load_word_positive_offset)
linus/master:arch/x86/net/bpf_jit.S:FUNC(sk_load_half)
linus/master:arch/x86/net/bpf_jit.S:FUNC(sk_load_half_positive_offset)
linus/master:arch/x86/net/bpf_jit.S:FUNC(sk_load_byte)
linus/master:arch/x86/net/bpf_jit.S:FUNC(sk_load_byte_positive_offset)
linus/master:arch/x86/net/bpf_jit.S:FUNC(sk_load_word_negative_offset)
linus/master:arch/x86/net/bpf_jit.S:FUNC(sk_load_half_negative_offset)
linus/master:arch/x86/net/bpf_jit.S:FUNC(sk_load_byte_negative_offset)
2) they _are_ all callable from within the JIT code:
EMIT1_off32(0xE8, jmp_offset);
Yes, I fucked up the ENDs. They should be on different locations. But
the pieces are still functions from my POV and should be annotated
accordingly.
thanks,
--
js
suse labs
next prev parent reply other threads:[~2017-04-25 14:41 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-21 14:12 [PATCH v3 01/29] x86: boot/copy, remove unused functions Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 02/29] x86_32: boot, extract efi_pe_entry from startup_32 Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 03/29] x86_64: boot, extract efi_pe_entry from startup_64 Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 04/29] x86: assembly, use ENDPROC for functions Jiri Slaby
2017-04-26 1:42 ` Josh Poimboeuf
2017-05-12 7:53 ` Jiri Slaby
2017-05-12 22:15 ` Josh Poimboeuf
2017-05-17 13:23 ` Jiri Slaby
2017-05-19 9:17 ` Jiri Slaby
2017-05-19 19:50 ` Josh Poimboeuf
2017-04-21 14:12 ` [PATCH v3 05/29] x86: assembly, add ENDPROC to functions Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 06/29] x86: assembly, annotate functions by ENTRY, not GLOBAL Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 07/29] x86: bpf_jit, use ENTRY+ENDPROC Jiri Slaby
2017-04-21 19:32 ` Alexei Starovoitov
2017-04-24 6:45 ` Jiri Slaby
2017-04-24 14:41 ` David Miller
2017-04-24 14:52 ` Jiri Slaby
2017-04-24 15:08 ` David Miller
2017-04-24 15:41 ` Jiri Slaby
2017-04-24 15:51 ` David Miller
2017-04-24 15:53 ` Jiri Slaby
2017-04-24 15:55 ` Ingo Molnar
2017-04-24 16:02 ` Jiri Slaby
2017-04-24 16:40 ` Ingo Molnar
2017-04-24 16:47 ` Alexei Starovoitov
2017-04-24 17:51 ` Jiri Slaby
2017-04-24 18:24 ` David Miller
2017-04-25 14:41 ` Jiri Slaby [this message]
2017-04-21 14:12 ` [PATCH v3 08/29] linkage: new macros for assembler symbols Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 09/29] x86: assembly, use DATA_SIMPLE for data Jiri Slaby
2017-04-27 11:53 ` Pavel Machek
2017-04-27 12:30 ` Jiri Slaby
2017-04-27 12:43 ` Pavel Machek
2017-04-21 14:12 ` [PATCH v3 10/29] x86: assembly, annotate relocate_kernel Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 11/29] x86: entry, annotate THUNKs Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 12/29] x86: assembly, annotate local functions Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 13/29] x86: crypto, " Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 14/29] x86: boot, " Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 15/29] x86: assembly, annotate aliases Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 16/29] x86: entry, annotate interrupt symbols properly Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 17/29] x86: head, annotate data appropriatelly Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 18/29] x86: boot, " Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 19/29] x86: um, " Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 20/29] x86: xen-pvh, " Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 21/29] x86: purgatory, start using annotations Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 22/29] x86: assembly, use SYM_FUNC_INNER_LABEL instead of GLOBAL Jiri Slaby
2017-04-21 14:12 ` [PATCH v3 23/29] x86: realmode, use SYM_DATA_* " Jiri Slaby
2017-04-21 14:13 ` [PATCH v3 24/29] x86: assembly, remove GLOBAL macro Jiri Slaby
2017-04-21 14:13 ` [PATCH v3 25/29] x86: assembly, make some functions local Jiri Slaby
2017-04-21 14:13 ` [PATCH v3 26/29] x86_64: assembly, change all ENTRY to SYM_FUNC_START Jiri Slaby
2017-04-21 14:13 ` [PATCH v3 27/29] x86_32: " Jiri Slaby
2017-04-21 14:13 ` [PATCH v3 28/29] x86_32: lguest, use SYM_ENTRY Jiri Slaby
2017-04-21 14:13 ` [PATCH v3 29/29] x86: assembly, replace WEAK uses Jiri Slaby
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