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From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	Rabin Vincent <rabin@rab.in>,
	linux-arm-kernel@lists.infradead.org,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] tracing/syscalls: ignore numbers outside NR_syscalls' range
Date: Thu, 30 Oct 2014 11:35:23 +0000	[thread overview]
Message-ID: <20141030113523.GQ27405@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <20141030073028.284c468c@gandalf.local.home>

On Thu, Oct 30, 2014 at 07:30:28AM -0400, Steven Rostedt wrote:
> On Thu, 30 Oct 2014 11:14:41 +0000
> Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:
> 
> 
> > We have always had syscall number range of 0x900000 or so.  The tracing
> > design does not expect that.  Therefore, the tracing design did not take
> > account of ARM when it was created.  Therefore, it's up to the tracing
> > people to decide how to properly fit their ill-designed subsystem into
> > one of the popular and well-established kernel architectures - or at
> > least suggest a way to work around this issue.
> > 
> 
> 
> Fine, lets define a MAX_SYSCALL_NR that is by default NR_syscalls, but
> an architecture can override it.
> 
> In trace_syscalls.c, where the checks are done, have this:
> 
> #ifndef MAX_SYSCALL_NR
> # define MAX_SYSCALL_NR NR_syscalls
> #endif
> 
> change all the checks to test against MAX_SYSCALL_NR instead of
> NR_syscalls.
> 
> Then in arch/arm/include/asm/syscall.h have:
> 
> #define MAX_SYSCALL_NR 0xa00000
> 
> or whatever would be the highest syscall number for ARM.

Or do we just ignore the high "special" ARM syscalls and treat them (from
the tracing point of view) as non-syscalls, avoiding the allocation of
something around 1.2MB for the syscall bitmap.  I really don't know, I
don't use any of this tracing stuff, so it isn't something I care about.

Maybe those who do use the facility should have an input here?

-- 
FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
according to speedtest.net.

  reply	other threads:[~2014-10-30 11:35 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-29 22:06 [PATCH] tracing/syscalls: ignore numbers outside NR_syscalls' range Rabin Vincent
2014-10-30  8:26 ` Christoph Hellwig
2014-10-30 10:18   ` Russell King - ARM Linux
2014-10-30 11:10     ` Steven Rostedt
2014-10-30 11:14       ` Russell King - ARM Linux
2014-10-30 11:30         ` Steven Rostedt
2014-10-30 11:35           ` Russell King - ARM Linux [this message]
2014-11-03 17:08             ` Nathan Lynch
2014-11-03 17:58               ` Steven Rostedt
2014-10-30 11:52       ` Steven Rostedt
2014-10-30 11:55         ` Steven Rostedt
2014-10-31 10:01     ` Ingo Molnar

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