comp.os.linux.development.system Google Group

Re: mmap returning MAP_FAILED

pac...@kosh.dhis.org (Alan Curry) — Sun, 08 Nov 2009 22:29:31 UT

In article <1br5s9osd7....@snowball.wb.pf eifferfamily.net>,
Also, MAP_SHARED is the only way to get changes written back into a
memory-mapped file, so sometimes you need MAP_SHARED with PROT_WRITE
even if you don't want shared memory (simultaneously accessible by
multiple processes). It's kind of a misleading name.

Re: C/C++: Determine [My] Module's Load Address

tauno.voi...@notused.fi.invalid (Tauno Voipio) — Sun, 08 Nov 2009 20:35:52 UT

Befor you proceed too far, please think that you're
running on a demand-paged virtual-memory system.
You did not say it, but I guess that the relevant
processor architecture is Intel 386+.
The run executables are loaded at the same virtual
address, but the real physical addresses will be
determined dynamically at run-time. For different

Re: mmap returning MAP_FAILED

pfeif...@cs.nmsu.edu (Joe Pfeiffer) — Sun, 08 Nov 2009 17:09:56 UT

That would do terrible things to the utility of shared memory -- no,
MAP_SHARED and PROT_WRITE are compatible. Maybe you're thinking of
MAP_SHARED and MAP_ANONYMOUS (which didn't used to be compatible, but is
since 2.4).

Re: mmap returning MAP_FAILED

shanka...@gmail.com (Shankar) — Sun, 08 Nov 2009 09:03:23 UT

prot=3 => would mean PROT_READ|PROT_WRITE
MAP_SHARED I think is a invalid mode if you are trying to map it that
way, Probably you may want to remove PROT_WRITE and see whats
happening.
Thanks
Shankar Easwaran

Re: C/C++: Determine [My] Module's Load Address

noloa...@gmail.com (Jeffrey Walton) — Sun, 08 Nov 2009 04:36:31 UT

Lots of objdump and readelf seemed to the trick. You're right about
LOAD - and I also needed flags = PF_R|PF_X to separate the code from
the data segment.
With LOAD and PF_R|PF_X, I can find it every time.
Thanks for your help. I know I have a couple more questions for
tomorrow :)
Jeff

Re: C/C++: Determine [My] Module's Load Address

pac...@kosh.dhis.org (Alan Curry) — Sun, 08 Nov 2009 02:59:33 UT

In article <d9c7a43a-46aa-45cd-98f4-059f5 bd6c...@m35g2000vbi.googlegrou ps.com>,
I'm not sure what the definition of "module" is where you come from so I
can't translate it. It seems to include "main executable" and "shared
library" as subcases.
Oh you found a nice function to do the query after all.

Re: C/C++: Determine [My] Module's Load Address

noloa...@gmail.com (Jeffrey Walton) — Sun, 08 Nov 2009 01:08:33 UT

Hi Alan,
My bad. Would 'image' be a better term in the Linux world?
Agreed.
FIPS integrity checks. Locating a particular section in memory is an
early smoke test.
Agreed.
I thought I found the load address in struct r_debug::r_ldbase (from
elf.h). But when I iterated the array of r_debugs, I found the base

Re: C/C++: Determine [My] Module's Load Address

pac...@kosh.dhis.org (Alan Curry) — Sat, 07 Nov 2009 22:44:08 UT

In article <e5661e7b-0927-4cda-b1e9-65227 4633...@t18g2000vbj.googlegrou ps.com>,
That's because you're using the word "module" in a foreign way. We don't use
it that way. Here, "module" means kernel module 99.44% of the time.
You can probably get what you want by parsing /proc/self/maps. The lack of a

Re: How do I make files and folders inaccessible to the public on a webserver?

arag...@chatfactory.invalid (Aragorn) — Sat, 07 Nov 2009 17:06:48 UT

On Saturday 07 November 2009 15:12 in comp.os.linux.security, somebody
identifying as Peter Olcott wrote...
(1) Make sure Apache - I am assuming Apache as the webserver; substitute
by whatever webserver you are running - is not running with root
privileges and that it does not have read access to the files.

Re: How do I make files and folders inaccessible to the public on a webserver?

unruh-s...@physics.ubc.ca (Unruh) — Sat, 07 Nov 2009 16:49:48 UT

By installing passwords?
By installing a firewall which allows port 80 access only to the desired
webservice?
Execute?

Re: strange thing after moving a directory

see_signat...@localhost.localdomain.invalid (Robert Nichols) — Sat, 07 Nov 2009 16:24:11 UT

The shell does not know that its current working directory has been
renamed. The shell keeps its notion of the current directory in its
internal PWD variable. What you run when you just type "pwd" is a shell
builtin that just reports the value of $PWD. You would have to run
"/bin/pwd" explicitly to see the current name of your working directory.

Re: How do I make files and folders inaccessible to the public on a webserver?

pfeif...@cs.nmsu.edu (Joe Pfeiffer) — Sat, 07 Nov 2009 15:53:03 UT

All access? Don't put the files on the server.
If you want limited access, look up .htaccess
There are many possibilities in between.

C/C++: Determine [My] Module's Load Address

noloa...@gmail.com (Jeffrey Walton) — Sat, 07 Nov 2009 15:00:27 UT

Hi All,
I'm trying to determine my module's load address at runtime. By
'module's load address', I mean byte[0] of the in-memory image (ie,
the first byte of the Elf32_Ehdr). I believe I want information from
the struct module in kernel/modules.c. I did find sys_query_module,
but it has been depricated.

How do I make files and folders inaccessible to the public on a webserver?

nos...@seescreen.com (Peter Olcott) — Sat, 07 Nov 2009 14:12:43 UT

How do I make files and folders inaccessible to the public
on a webserver?
I want to allow execute access to a specific webservice, but
deny all other access to everything else.

Re: mmap returning MAP_FAILED

dav...@webmaster.com (David Schwartz) — Sat, 07 Nov 2009 03:52:37 UT

What exactly do you think mapping a zero-length file would do?
DS