473,683 Members | 2,643 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

Problem with reading procfs

Hi, I'm developing an application that access the procfs and then
read/write /proc/<PID>/mem of a process to change the content of a
file
owned by that process.

The sequential steps performed by the application are the followings:

1) catch, by using ptrace, of the "read" system call
2) read the file content directly on /proc/PID/mem
3) modify this content
4) write back the modified content on /proc/PD/mem

The problem is that it returns "Error 22 Invalid argument" every time
it tries to read (or write) on procfs.
(I've already patched the kernel to allow read/write operation on
/proc/<pid>/mem and I've tried the pread/pwrite functions, but they
have the same behavior).

This is an extract of my code:
....
int eax_reg, ecx_reg, ret;
char * buffer;
char orig_buf[eax_reg+1];
char proc_path[MAX_FILE_NAME+1];

// traced_proc is the pid_t of the traced process
// get number of bytes to read
eax_reg = ptrace(PTRACE_P EEKUSER, traced_proc, 4*EAX, NULL);
// get traced process space buffer
ecx_reg = ptrace(PTRACE_P EEKUSER, traced_proc, 4*ECX, NULL);

buffer = malloc(sizeof(c har)*eax_reg);
memset(orig_buf ,0,eax_reg+1);
memset(proc_pat h, 0, sizeof(proc_pat h));

sprintf(proc_pa th, "/proc/%d/mem", traced_proc);
fd_proc = open(proc_path, O_RDWR);

lseek(fd_proc, ecx_reg, SEEK_SET);
int ret = read(fd_proc, buffer, eax_reg);
if (ret < 0) {
perror("read");
fprintf(stderr, "Failed to read: %d - %s\n", errno, strerror(errno) );
}
....
if I run the application with strace, the output for the code shown
above is:

open("/proc/13271/mem", O_RDWR) = 3
lseek(3, 3086368768, SEEK_SET) = 3086368768
read(3, 0xbfca0940, 280) = -1 EINVAL (Invalid argument)

Can someone tell me where I'm wrong?
Thanks in advance for any help...
Dec 11 '07 #1
2 3258
In article <9f************ *************** *******@s19g200 0prg.googlegrou ps.com>,
Simone <si************ ***@gmail.comwr ote:
>Hi, I'm developing an application that access the procfs and then
read/write /proc/<PID>/mem of a process to change the content of a
file
owned by that process.
Everything you describe is operating system dependant, and so should
be addressed to a newsgroup that is specific to your OS.

Even different OSs that support procfs have differences in how to
use them properly.
--
"I will speculate that [...] applications [...] could actually see a
performance boost for most users by going dual-core [...] because it
is running the adware and spyware that [...] are otherwise slowing
down the single CPU that user has today" -- Herb Sutter
Dec 11 '07 #2
Simone wrote, On 11/12/07 21:29:
Hi, I'm developing an application that access the procfs and then
read/write /proc/<PID>/mem of a process to change the content of a
<snip>
open("/proc/13271/mem", O_RDWR) = 3
lseek(3, 3086368768, SEEK_SET) = 3086368768
read(3, 0xbfca0940, 280) = -1 EINVAL (Invalid argument)

Can someone tell me where I'm wrong?
Thanks in advance for any help...
This is all very Linux specific (not even Posix I believe) so you should
ask in one of the Linux groups after checking the relevant FAQs/charters
and a weeks worth of postings to see what goes on.

Note that just because someone once posted about a topic on a group that
does not mean the post was topical, and it might be that the responses
(if any) were just pointing out that it was not topical, so you need to
read posts not just look at subject lines.

For more information about what a lot of regulars consider to be topical
and why see http://clc-wiki.net/wiki/Introduction_to_comp.lang.c
--
Flash Gordon
Dec 11 '07 #3

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

1
2574
by: Magnus Lycka | last post by:
I'm trying to read standard out in a process started with popen2 in a non-blocking way. (Other good ways of doing this than the one I tried are appreciated.) I've tried to dumb down my code to see what happens, and socket.poll seems to behave very strangely. I've tried to use the .poll method for the poll object with and without a timeout, but in either case, the output randomly switches between on of the versions below. It runs fast,...
7
5437
by: Thomas Sourmail | last post by:
Hi, I hope I am missing something simple, but.. here is my problem: I need my program to check the last column of a file, as in : a b c d target ref 0 0 0 0 1 a 1 0 0 0 1.5 b 2 0 0 0 2 c
0
3935
by: Lokkju | last post by:
I am pretty much lost here - I am trying to create a managed c++ wrapper for this dll, so that I can use it from c#/vb.net, however, it does not conform to any standard style of coding I have seen. It is almost like it is trying to implement it's own COM interfaces... below is the header, and a link to the dll+code: Zip file with header, example, and DLL:...
5
8939
by: Scott M. Lyon | last post by:
I've just discovered a bug in some code I wrote a little while ago, and I need you guys' help to fix it. My program imports data from a standard Excel Spreadsheet (just with specific column headers). I used ODBC in my VB.NET program to read that spreadsheet into a dataset, to make it easy to manipulate. The code I use to read it is as the bottom of this posting.
7
2212
by: DBMS_Plumber | last post by:
Having a hard time with a UDF. Wonder if folk might care to take a look and tell me what's up. All of this kicked off from trying to build a set of C++ iostream derived classes that can make DB2's gimped BLOB API (sqludf_append() etc) look--to the extent that this is possible--like something C++ libraries can use to serialize stuff to (via iostream::read(), iostream::write() and what-not).
11
1927
by: aljaber | last post by:
hi, i am facing a problem with my program output here is the program /*********************************************\ * CD Database * * * \*********************************************/
5
14984
blazedaces
by: blazedaces | last post by:
Ok, so you know my problem, java is running out of memory reading with SAX, the event-based xml parser intended more-so than DOM for extremely large files. I'll try to explain what I've been doing and why I have to do it. Hopefully someone has a suggestion... Alright, so I'm using a gps-simulation program that outputs gps data, like longitude, lattitude, altitude, etc. (hundreds of terms, these are just the well known ones). In the newer...
6
3525
by: efrenba | last post by:
Hi, I came from delphi world and now I'm doing my first steps in C++. I'm using C++builder because its ide is like delphi although I'm trying to avoid the vcl. I need to insert new features to an old program that I wrote in delphi and it's a good opportunity to start with c++.
10
2194
by: oktayarslan | last post by:
Hi all; I have a problem when inserting an element to a vector. All I want is reading some data from a file and putting them into a vector. But the program is crashing after pushing a data which has string value. I really do not understand why push_back() function is trying to remove previously inserted data. Thanks for any help
0
8504
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it. First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
0
9042
Oralloy
by: Oralloy | last post by:
Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed. This is as boiled down as I can make it. Here is my compilation command: g++-12 -std=c++20 -Wnarrowing bit_field.cpp Here is the code in...
0
8771
tracyyun
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
0
7581
agi2029
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own.... Now, this would greatly impact the work of software developers. The idea...
0
5789
by: conductexam | last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one. At the time of converting from word file to html my equations which are in the word document file was convert into image. Globals.ThisAddIn.Application.ActiveDocument.Select();...
0
4299
by: TSSRALBI | last post by:
Hello I'm a network technician in training and I need your help. I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs. The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols. I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
0
4519
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
1
2934
by: 6302768590 | last post by:
Hai team i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
2
2195
muto222
by: muto222 | last post by:
How can i add a mobile payment intergratation into php mysql website.

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.