Re: [Valgrind-users] At which address is valgrind loaded?

[Nicholas N. <nj...@cs...>]

On Thu, 24 May 2007, Julian Seward wrote:

>> 1) Why 0x38000000? It just seems such a weird number to me.
>
> It seems arbitrary but in fact it is a good compromise given the
> constraints.  In most cases Linux allows processes to access the
> lowest 3GB of memory, but sometimes this is limited to 2 or even
> 1 GB.  So 0x38000000 is (7/8) * 1 GB, so V will work even on a
> system with only 1GB for user space.  However, 0x38000000 is
> almost always far away from the default load address of executables
> (which is usually much lower) and so it pretty much guarantees that
> V will not conflict with the client executable's load address.

If you run "cat /proc/self/maps" you'll see how the address space normally 
is laid out, and "valgrind cat /proc/self/maps" how Valgrind changes this.

Only the tool+core binary gets loaded at 0x38000000, and it's something like 
2.5MB, ie. small.  All the other memory dynamically allocated by the tool 
and core can go anywhere.

Nick