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74fb3e1c3e
Most of the time, Valgrind masks async signals, and polls for such signals at regular interval. There is a very narrow range of code (around client syscall logic) where such signals are unmasked (as they must be able to interrupt syscalls). This is the only range of code where Valgrind is expecting to receive such a signal. When gdbserver is ptraced invoked, Valgrind is artificially made to jump out of this code portion. Signals are not masked. When ptraceing valgrind, vgdb will get these signals but cannot transmit them immediately, otherwise they arrive in range of code where they are not expected (causing internal error in syscall logic) and/or causing gdbserver syscalls to be interrupted. 3 solutions to solve that were looked at: 1. have the gdbserver code masking signals "as quickly as possible". Easy to implement, but this leaves still a small window of code where signals are not masked and would cause a problem. 2. have vgdb setting the SIGMASK of valgrind before invoking gdbserver. This would be easy to implement, but changing the SIGMASK of the ptrace-d process is only available on very recent kernels. 3. have vgdb queuing signals, and only transmitting them once gdbserver invocation is finished. This 3rd solution has been implemented. git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13896
Release notes for Valgrind
~~~~~~~~~~~~~~~~~~~~~~~~~~
If you are building a binary package of Valgrind for distribution,
please read README_PACKAGERS. It contains some important information.
If you are developing Valgrind, please read README_DEVELOPERS. It contains
some useful information.
For instructions on how to build/install, see the end of this file.
If you have problems, consult the FAQ to see if there are workarounds.
Executive Summary
~~~~~~~~~~~~~~~~~
Valgrind is a framework for building dynamic analysis tools. There are
Valgrind tools that can automatically detect many memory management
and threading bugs, and profile your programs in detail. You can also
use Valgrind to build new tools.
The Valgrind distribution currently includes six production-quality
tools: a memory error detector, two thread error detectors, a cache
and branch-prediction profiler, a call-graph generating cache abd
branch-prediction profiler, and a heap profiler. It also includes
three experimental tools: a heap/stack/global array overrun detector,
a different kind of heap profiler, and a SimPoint basic block vector
generator.
Valgrind is closely tied to details of the CPU, operating system and to
a lesser extent, compiler and basic C libraries. This makes it difficult
to make it portable. Nonetheless, it is available for the following
platforms:
- X86/Linux
- AMD64/Linux
- PPC32/Linux
- PPC64/Linux
- ARM/Linux
- x86/MacOSX
- AMD64/MacOSX
- S390X/Linux
- MIPS32/Linux
- MIPS64/Linux
Note that AMD64 is just another name for x86_64, and Valgrind runs fine
on Intel processors. Also note that the core of MacOSX is called
"Darwin" and this name is used sometimes.
Valgrind is licensed under the GNU General Public License, version 2.
Read the file COPYING in the source distribution for details.
However: if you contribute code, you need to make it available as GPL
version 2 or later, and not 2-only.
Documentation
~~~~~~~~~~~~~
A comprehensive user guide is supplied. Point your browser at
$PREFIX/share/doc/valgrind/manual.html, where $PREFIX is whatever you
specified with --prefix= when building.
Building and installing it
~~~~~~~~~~~~~~~~~~~~~~~~~~
To install from the Subversion repository :
0. Check out the code from SVN, following the instructions at
http://www.valgrind.org/downloads/repository.html.
1. cd into the source directory.
2. Run ./autogen.sh to setup the environment (you need the standard
autoconf tools to do so).
3. Continue with the following instructions...
To install from a tar.bz2 distribution:
4. Run ./configure, with some options if you wish. The only interesting
one is the usual --prefix=/where/you/want/it/installed.
5. Run "make".
6. Run "make install", possibly as root if the destination permissions
require that.
7. See if it works. Try "valgrind ls -l". Either this works, or it
bombs out with some complaint. In that case, please let us know
(see www.valgrind.org).
Important! Do not move the valgrind installation into a place
different from that specified by --prefix at build time. This will
cause things to break in subtle ways, mostly when Valgrind handles
fork/exec calls.
The Valgrind Developers