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From: David Mosberger <davidm@napali.hpl.hp.com>
To: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
	William Lee Irwin III <wli@holomorphy.com>,
	Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>,
	Jens Axboe <axboe@suse.de>
Subject: Re: [PATCH][2.6] WARN_ON_STACK_VAR aka fighting variable lifetime bugs
Date: Mon, 11 Aug 2003 11:43:08 -0700	[thread overview]
Message-ID: <16183.58300.408086.272654@napali.hpl.hp.com> (raw)
In-Reply-To: <Pine.LNX.4.53.0308091430410.32166@montezuma.mastecende.com>

>>>>> On Sat, 9 Aug 2003 15:29:41 -0400 (EDT), Zwane Mwaikambo <zwane@arm.linux.org.uk> said:

  Zwane> --- linux-2.6.0-test2-irq/include/asm-ia64/bug.h	30 Jul 2003 00:06:30 -0000	1.1.1.1
  Zwane> +++ linux-2.6.0-test2-irq/include/asm-ia64/bug.h	9 Aug 2003 19:14:09 -0000
  Zwane> +#define WARN_ON_STACK_VAR(ptr) do { \
  Zwane> +	unsigned long __ti = (unsigned long)current_thread_info(); \
  Zwane> +	WARN_ON((__ti & (unsigned long)(ptr)) == __ti); \
  Zwane> +} while (0)

Note that on ia64 we don't use bit-masking to calculate the
task-pointer.  Instead, thread-info follows the task structure.  This
is done such that the task-structure, thread-info, and kernel stack
can be mapped by a single (pinned) TLB entry.

The correct check for a variable being on the stack of the current
task would be something like this:

	((unsigned long)(ptr) - (unsigned long) current) < IA64_STK_OFFSET

(IA64_STK_OFFSET is declared by <asm/ptrace.h>).

Thanks,

	--david

  parent reply	other threads:[~2003-08-11 18:46 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-08-09 19:29 Zwane Mwaikambo
2003-08-09 19:33 ` Zwane Mwaikambo
2003-08-11 18:43 ` David Mosberger [this message]
2003-08-11 18:41   ` Zwane Mwaikambo

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