From: "Török Edwin" <edwintorok@gmail.com>
To: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: /proc/pid/maps containg anonymous maps that have PROT_NONE
Date: Wed, 05 Nov 2008 13:14:24 +0200 [thread overview]
Message-ID: <49118010.20202@gmail.com> (raw)
Hi,
I noticed that there are (quite large) entries in /proc/pid/maps that
have PROT_NONE, right after an existing mapping:
7fffe4000000-7fffe406a000 rw-p 7fffe4000000 00:00 0
7fffe406a000-7fffe8000000 ---p 7fffe406a000 00:00 0
7ffff76d1000-7ffff76e0000 r-xp 00000000 09:03 260750
/lib/libbz2.so.1.0.4
7ffff76e0000-7ffff78df000 ---p 0000f000 09:03 260750
/lib/libbz2.so.1.0.4
I don't mind that 2Mb map, but what is 7fffe406a000-7fffe8000000 ---p ?
(63M)
Is it coming from glibc mapping memory as PROT_NONE, and using
mprotect/madvise to make it writable, and then
caching the mappings for future use, rather than freeing them?
/proc/pid/smaps shows:
7fffe406a000-7fffe8000000 ---p 7fffe406a000 00:00 0
Size: 65112 kB
Rss: 0 kB
Pss: 0 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 0 kB
Swap: 0 kB
I straced the program creating these, and I couldn't find anything with
7fffe406a000, but only before that address:
[pid 31928] mprotect(0x7fffe4000000, 135168, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4021000, 131072, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4041000, 32768, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4049000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe404a000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe404b000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe404c000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe404d000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe404e000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe404f000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4050000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4051000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4052000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4053000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4054000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4055000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4056000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4057000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4058000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe4059000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe405a000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe405b000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe405c000, 4096, PROT_READ|PROT_WRITE) = 0
[pid 31928] mprotect(0x7fffe405d000, 53248, PROT_READ|PROT_WRITE) = 0
[pid 31928] madvise(0x7fffe4069000, 4096, 0x4 /* MADV_??? */) = 0
[pid 31928] madvise(0x7fffe4021000, 294912, 0x4 /* MADV_??? */) = 0
[pid 31928] madvise(0x7fffe4021000, 4096, 0x4 /* MADV_??? */) = 0
There is an mprotect and madvise that end at 0x7fffe406a000.
Those mprotects and madvise are coming from glibc. Its strange that I
don't see the mmap only the mprotect, but I used strace -f.
This happens on:
Linux debian 2.6.26-1-amd64 #1 SMP Thu Oct 9 14:16:53 UTC 2008 x86_64
GNU/Linux
strace is here:
http://edwintorok.googlepages.com/log2.bz2
Best regards,
--Edwin
next reply other threads:[~2008-11-05 11:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-05 11:14 Török Edwin [this message]
2008-11-05 16:12 ` /proc/pid/maps containg anonymous maps that have PROT_NONE Hugh Dickins
2008-11-05 17:56 ` Török Edwin
2008-11-05 18:47 ` Török Edwin
2008-11-06 1:15 ` KOSAKI Motohiro
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=49118010.20202@gmail.com \
--to=edwintorok@gmail.com \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.