From: "H. Peter Anvin" <hpa@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>, gcc <gcc@gcc.gnu.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Thomas Gleixner <tglx@linutronix.de>,
David Daney <ddaney.cavm@gmail.com>,
Behan Webster <behanw@converseincode.com>
Subject: Re: [RFC] gcc feature request: Moving blocks into sections
Date: Mon, 12 Aug 2013 10:47:37 -0700 [thread overview]
Message-ID: <52091FB9.4080805@linux.intel.com> (raw)
In-Reply-To: <20130812160950.GT3008@twins.programming.kicks-ass.net>
On 08/12/2013 09:09 AM, Peter Zijlstra wrote:
>>
>> On the majority of architectures, including x86, you cannot simply copy
>> a piece of code elsewhere and have it still work.
>
> I thought we used -fPIC which would allow just that.
>
Doubly wrong. The kernel is not compiled with -fPIC, nor does -fPIC
allow this kind of movement for code that contains intramodule
references (that is *all* references in the kernel). Since we really
doesn't want to burden the kernel with a GOT and a PLT, that is life.
>> You end up doing a
>> bunch of the work that a JIT would do anyway, and would end up with
>> considerably higher complexity and worse results than a true JIT.
>
> Well, less complexity but worse result, yes. We'd only poke the specific
> static_branch sites with either NOPs or the (relative) jump target for
> each of these branches. Then copy the result.
Once again, you can't "copy the result". You end up with a full
disassembler.
-hpa
next prev parent reply other threads:[~2013-08-12 17:47 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-05 16:55 [RFC] gcc feature request: Moving blocks into sections Steven Rostedt
2013-08-05 17:02 ` H. Peter Anvin
2013-08-05 17:24 ` Steven Rostedt
2013-08-05 17:12 ` Linus Torvalds
2013-08-05 17:15 ` Linus Torvalds
2013-08-05 17:55 ` Steven Rostedt
2013-08-05 18:11 ` Steven Rostedt
2013-08-05 18:17 ` H. Peter Anvin
2013-08-05 18:23 ` Steven Rostedt
2013-08-05 18:29 ` H. Peter Anvin
2013-08-05 18:49 ` Steven Rostedt
2013-08-05 18:51 ` H. Peter Anvin
2013-08-05 19:01 ` Linus Torvalds
2013-08-05 19:54 ` Mathieu Desnoyers
2013-08-05 19:57 ` Linus Torvalds
2013-08-05 20:02 ` Steven Rostedt
2013-08-05 21:28 ` Mathieu Desnoyers
2013-08-05 21:43 ` H. Peter Anvin
2013-08-06 4:14 ` Mathieu Desnoyers
2013-08-06 4:28 ` H. Peter Anvin
2013-08-06 16:15 ` Steven Rostedt
2013-08-06 16:19 ` H. Peter Anvin
2013-08-06 16:26 ` Steven Rostedt
2013-08-06 16:29 ` H. Peter Anvin
2013-08-05 21:44 ` Steven Rostedt
2013-08-05 22:08 ` Mathieu Desnoyers
2013-08-05 19:09 ` Steven Rostedt
2013-08-05 18:20 ` Linus Torvalds
2013-08-05 18:24 ` Linus Torvalds
2013-08-05 18:34 ` Linus Torvalds
2013-08-05 18:38 ` H. Peter Anvin
2013-08-05 19:04 ` Steven Rostedt
2013-08-05 19:40 ` Marek Polacek
2013-08-05 19:56 ` Linus Torvalds
2013-08-05 19:57 ` Jason Baron
2013-08-05 20:35 ` Richard Henderson
2013-08-06 2:26 ` Jason Baron
2013-08-06 3:03 ` Steven Rostedt
2013-08-05 18:33 ` H. Peter Anvin
2013-08-05 18:39 ` Steven Rostedt
2013-08-05 18:49 ` Linus Torvalds
2013-08-05 19:39 ` Steven Rostedt
2013-08-06 14:19 ` Steven Rostedt
2013-08-06 17:48 ` Linus Torvalds
2013-08-06 17:58 ` Steven Rostedt
2013-08-06 20:33 ` Mathieu Desnoyers
2013-08-06 20:43 ` Steven Rostedt
2013-08-07 0:45 ` Steven Rostedt
2013-08-07 0:56 ` Steven Rostedt
2013-08-07 5:06 ` Ondřej Bílka
2013-08-07 15:02 ` Steven Rostedt
2013-08-07 16:03 ` Mathieu Desnoyers
2013-08-07 16:11 ` Steven Rostedt
2013-08-07 23:22 ` Mathieu Desnoyers
2013-08-05 20:06 ` Jason Baron
2013-08-05 19:04 ` Andi Kleen
2013-08-05 19:16 ` Steven Rostedt
2013-08-05 19:30 ` Xinliang David Li
2013-08-05 19:25 ` Linus Torvalds
2013-08-12 9:17 ` Peter Zijlstra
2013-08-12 14:56 ` H. Peter Anvin
2013-08-12 16:02 ` Andi Kleen
2013-08-12 16:11 ` Peter Zijlstra
2013-08-12 16:09 ` Peter Zijlstra
2013-08-12 17:47 ` H. Peter Anvin [this message]
2013-08-13 7:50 ` Peter Zijlstra
2013-08-13 14:46 ` H. Peter Anvin
2013-08-13 14:52 ` Steven Rostedt
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