[TOOL] Valgrind, an Open-Source Memory Debugger for x86-GNU/Linux
From: SecuriTeam (support_at_securiteam.com)
Date: 10/22/03
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To: list@securiteam.com Date: 22 Oct 2003 19:09:50 +0200
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Valgrind, an Open-Source Memory Debugger for x86-GNU/Linux
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DETAILS
Valgrind is a GPL'd tool to help you find memory-management problems in
your programs. When a program is run under Valgrind's supervision, all
reads and writes of memory are checked, and calls to
malloc/new/free/delete are intercepted. As a result, Valgrind can detect
problems such as:
* Use of uninitialised memory
* Reading/writing memory after it has been free'd
* Reading/writing off the end of malloc'd blocks
* Reading/writing inappropriate areas on the stack
* Memory leaks -- where pointers to malloc'd blocks are lost forever
* Passing of uninitialised and/or unaddressible memory to system calls
* Mismatched use of malloc/new/new [] vs free/delete/delete []
* Some misuses of the POSIX pthreads API
Valgrind tracks each byte of memory in the original program with nine
status bits, one of which tracks addressability of that byte, while the
other eight track the validity of the byte. As a result, it can detect the
use of single uninitialised bits, and does not report spurious errors on
bitfield operations.
You can use it to debug more or less any dynamically linked ELF x86
executable, without modification, recompilation, or anything. If you want,
Valgrind can start GDB and attach it to your program at the point(s) where
errors are detected, so that you can poke around and figure out what was
going on at the time.
Valgrind works well enough to debug many large x86-linux applications. To
give you some idea of the scale of programs it can run: most of KDE3,
Gnome stuff, Mozilla, OpenOffice, MySQL, Opera, KOffice-1.2beta1,
emacs-21.2, xemacs-21.5(--pdump), Netscape-4.78, Gcc, AbiWord, etc, etc.
KDE3 was extensively valgrinded in the two months prior to the KDE 3.0
release. Valgrind is primarily a debugging tool for large, complex
programs. It is not a toy or a research vehicle.
Valgrind contains built-in support for doing very detailed cache
profiling. Since we already intercept every read and write, and have all
the debugging information for your program close to hand, it's not too
hard to also do a detailed simulation of your CPU's L1-D, L1-I and unified
L2 caches. The supplied vg_annotate program will show your source code
with these counts attached to every line. The cache arrangement of your
CPU is auto-detected using the CPUID instruction. If that does not work or
you want to override it, you can specify custom cache parameters on the
command line. The manual contains full documentation of this new feature.
The cache profiling aspects (and much, much else) are due to the excellent
hacking of Nick Nethercote. Please do try it out -- you just need to put
valgrind --skin=cachegrind in front of your program invocations, rather
than valgrind. We hope it will be a useful performance-analysis tool.
ADDITIONAL INFORMATION
The tool can be downloaded from: <http://developer.kde.org/~sewardj/>
http://developer.kde.org/~sewardj/.
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