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From: Steven Rostedt <rostedt@goodmis.org>
To: Alexei Starovoitov <ast@fb.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	"David S. Miller" <davem@davemloft.net>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	netdev <netdev@vger.kernel.org>, kernel-team <kernel-team@fb.com>,
	linux-api <linux-api@vger.kernel.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH v7 bpf-next 06/10] tracepoint: compute num_args at build time
Date: Wed, 28 Mar 2018 13:38:30 -0400	[thread overview]
Message-ID: <20180328133830.3d5d74d3@gandalf.local.home> (raw)
In-Reply-To: <fdcb0bf0-f896-ffb3-b9de-0b17f5f70fc6@fb.com>

On Wed, 28 Mar 2018 10:10:34 -0700
Alexei Starovoitov <ast@fb.com> wrote:


> > and have:
> >
> > 	u64 tp_offset = (u64)tp - (u64)_sdata;
> >
> > 	if (WARN_ON(tp_offset > UINT_MAX)
> > 		return -EINVAL;
> >
> > 	 btp->tp_offset = (u32)tp_offset;  
> 
> above math has to be build time constant, so warn_on likely
> won't work.

Right, it would require a BUILD_BUG_ON.

> imo the whole thing is too fragile and obscure.
> I suggest to compress this 8 bytes * num_of_tracepoints later.
> Especially would be good to do it in one way for
> bpf_raw_event_map, ftrace and other places.

Fair enough. We can defer this shrinkage to another time. I only
suggested it here over your concern for the added bloat.

-- Steve

  reply	other threads:[~2018-03-28 17:38 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-28  2:10 [PATCH v7 bpf-next 00/10] bpf, tracing: introduce bpf raw tracepoints Alexei Starovoitov
2018-03-28  2:10 ` Alexei Starovoitov
2018-03-28  2:10 ` [PATCH v7 bpf-next 01/10] treewide: remove large struct-pass-by-value from tracepoint arguments Alexei Starovoitov
2018-03-28  2:10   ` Alexei Starovoitov
2018-03-28  2:10 ` [PATCH v7 bpf-next 02/10] net/mediatek: disambiguate mt76 vs mt7601u trace events Alexei Starovoitov
2018-03-28  2:10   ` Alexei Starovoitov
2018-03-28  2:10 ` [PATCH v7 bpf-next 03/10] net/mac802154: disambiguate mac80215 vs mac802154 " Alexei Starovoitov
2018-03-28  2:10   ` Alexei Starovoitov
2018-03-28  2:10 ` [PATCH v7 bpf-next 04/10] net/wireless/iwlwifi: fix iwlwifi_dev_ucode_error tracepoint Alexei Starovoitov
2018-03-28  2:10   ` Alexei Starovoitov
2018-03-28  2:11 ` [PATCH v7 bpf-next 05/10] macro: introduce COUNT_ARGS() macro Alexei Starovoitov
2018-03-28  2:11   ` Alexei Starovoitov
2018-03-28  2:11 ` [PATCH v7 bpf-next 06/10] tracepoint: compute num_args at build time Alexei Starovoitov
2018-03-28  2:11   ` Alexei Starovoitov
2018-03-28 13:49   ` Mathieu Desnoyers
2018-03-28 16:43     ` Alexei Starovoitov
2018-03-28 17:04       ` Steven Rostedt
2018-03-28 17:10         ` Alexei Starovoitov
2018-03-28 17:38           ` Steven Rostedt [this message]
2018-03-28 18:03             ` Alexei Starovoitov
2018-03-28 18:10               ` Steven Rostedt
2018-03-28 18:19                 ` Alexei Starovoitov
2018-03-28 18:54                   ` Steven Rostedt
2018-03-28 19:22                     ` Mathieu Desnoyers
2018-03-28 19:25                       ` Alexei Starovoitov
2018-03-28 19:32                       ` Steven Rostedt
2018-03-28 19:38                         ` Steven Rostedt
2018-03-28 19:47                           ` Mathieu Desnoyers
2018-03-28 17:14       ` Mathieu Desnoyers
2018-03-28  2:11 ` [PATCH v7 bpf-next 07/10] bpf: introduce BPF_RAW_TRACEPOINT Alexei Starovoitov
2018-03-28  2:11   ` Alexei Starovoitov
2018-03-28 17:41   ` Steven Rostedt
2018-03-28 17:41     ` Steven Rostedt
2018-03-28  2:11 ` [PATCH v7 bpf-next 08/10] libbpf: add bpf_raw_tracepoint_open helper Alexei Starovoitov
2018-03-28  2:11   ` Alexei Starovoitov
2018-03-28  2:11 ` [PATCH v7 bpf-next 09/10] samples/bpf: raw tracepoint test Alexei Starovoitov
2018-03-28  2:11   ` Alexei Starovoitov
2018-03-28  2:11 ` [PATCH v7 bpf-next 10/10] selftests/bpf: test for bpf_get_stackid() from raw tracepoints Alexei Starovoitov
2018-03-28  2:11   ` Alexei Starovoitov

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