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From: "Kawai, Hidehiro" <hidehiro.kawai.ez@hitachi.com>
To: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@osdl.org>,
	kernel list <linux-kernel@vger.kernel.org>,
	Pavel Machek <pavel@ucw.cz>, Robin Holt <holt@sgi.com>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>,
	Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
	sugita <yumiko.sugita.yf@hitachi.com>,
	Satoshi OSHIMA <soshima@redhat.com>,
	"Hideo AOKI@redhat" <haoki@redhat.com>
Subject: Re: [PATCH 3/4] coredump: ELF-FDPIC: enable to omit anonymous shared memory
Date: Tue, 20 Feb 2007 18:45:15 +0900	[thread overview]
Message-ID: <45DAC32B.4030603@hitachi.com> (raw)
In-Reply-To: <20368.1171638335@redhat.com>

Hi,

Thank you for your comments.

David Howells wrote:

>> static int elf_fdpic_dump_segments(struct file *file, struct mm_struct *mm,
>>-				   size_t *size, unsigned long *limit)
>>+				   size_t *size, unsigned long *limit,
>>+				   unsigned int omit_anon_shared)
> 
> Why are you passing it as an extra argument when you could just use
> mm->coredump_omit_anon_shared here:
> 
>>+		if (!maydump(vma, omit_anon_shared))

> I wouldn't worry, were I you, about the setting changing whilst it's being
> used.  If you are worried about that, you can probably do some locking against
> that.

Core dumping is separated two phases, one is the phase of writing
headers, the other is the phase of writing memory segments.  If the
coredump_omit_anon_shared setting is changed between these two phases,
a corrupted core file will be generated because the offsets written
in headers don't match their bodies.  So we need to use the same
setting in both phases.

I think that locking makes codes complex and generates overhead.
So I wouldn't like to use lock as far as possible.  I think passing
the flag as an extra argument is the simplest implementation to
avoid the core file corruption.

Thanks,
-- 
Hidehiro Kawai
Hitachi, Ltd., Systems Development Laboratory


  parent reply	other threads:[~2007-02-20  9:45 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-16 13:34 [PATCH 0/4] coredump: core dump masking support v3 Kawai, Hidehiro
2007-02-16 13:39 ` [PATCH 1/4] coredump: add an interface to control the core dump routine Kawai, Hidehiro
2007-02-16 13:40 ` [PATCH 2/4] coredump: ELF: enable to omit anonymous shared memory Kawai, Hidehiro
2007-02-16 13:41 ` [PATCH 3/4] coredump: ELF-FDPIC: " Kawai, Hidehiro
2007-02-16 13:42 ` [PATCH 4/4] coredump: documentation for proc entry Kawai, Hidehiro
2007-02-16 15:05 ` [PATCH 3/4] coredump: ELF-FDPIC: enable to omit anonymous shared memory David Howells
2007-02-16 16:50   ` Robin Holt
2007-02-16 20:09   ` David Howells
2007-03-02 16:55     ` Hugh Dickins
2007-03-03 14:10     ` David Howells
2007-03-05 19:04       ` Hugh Dickins
2007-03-06 18:13       ` David Howells
2007-03-09 14:12       ` Move to unshared VMAs in NOMMU mode? David Howells
2007-03-12 20:50         ` Robin Getz
2007-03-13 10:14         ` David Howells
2007-03-15 21:20         ` Hugh Dickins
2007-03-15 22:47         ` David Howells
2007-03-19 19:23           ` Eric W. Biederman
2007-03-20 11:06           ` David Howells
2007-03-20 16:48             ` Eric W. Biederman
2007-03-20 19:12             ` David Howells
2007-03-20 19:51             ` David Howells
2007-03-21 16:11             ` David Howells
2007-03-03 14:25     ` [PATCH] NOMMU: Hide vm_mm in NOMMU mode David Howells
2007-02-20  9:45   ` Kawai, Hidehiro [this message]
2007-02-20 10:58   ` [PATCH 3/4] coredump: ELF-FDPIC: enable to omit anonymous shared memory David Howells
2007-02-20 12:56     ` Robin Holt
2007-02-21 10:00     ` Kawai, Hidehiro
2007-02-21 11:33     ` David Howells
2007-02-21 11:54       ` Robin Holt
2007-02-22  5:33         ` Kawai, Hidehiro
2007-02-22 11:47         ` David Howells
2007-02-16 15:08 ` [PATCH 0/4] coredump: core dump masking support v3 David Howells
2007-02-20  9:48   ` Kawai, Hidehiro
2007-02-24  3:32 ` Markus Gutschke
2007-02-24 11:39   ` Pavel Machek
2007-03-01 12:35   ` Kawai, Hidehiro
2007-03-01 18:16     ` Markus Gutschke
2007-02-24 10:02 ` David Howells
2007-02-24 20:01   ` Markus Gutschke
2007-02-26 11:49   ` David Howells
2007-02-26 12:01     ` Pavel Machek
2007-02-26 12:42     ` David Howells
2007-03-02  4:41 [PATCH 0/4] coredump: core dump masking support v4 Kawai, Hidehiro
2007-03-02  4:50 ` [PATCH 3/4] coredump: ELF-FDPIC: enable to omit anonymous shared memory Kawai, Hidehiro

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