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Re: [Qemu-devel] qemu-user: relocating target code weakness


From: Stefano Bonifazi
Subject: Re: [Qemu-devel] qemu-user: relocating target code weakness
Date: Mon, 24 Jan 2011 23:24:02 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.13) Gecko/20101208 Thunderbird/3.1.7


how can the ldso possibly prevent clashes ?  it has no idea what
addresses an app will ask for at runtime.

plus, if the kernel is employing ASLR (which isnt uncommon nowadays),
the load addresses could be anywhere.
-mike
Well not alone, in my mind ld.so asks the memory manager through calling mmap where it can map the shared modules inside the process address space.. the memory manager should know what addresses are free and which are taken .. then when the process code requires dynamic memory allocation, it does it again through the memory manager (i.e. malloc) avoiding of allocating memory where shared modules have been loaded into.. Again with ASLR I think the mmu should be aware of all used memory slots, avoiding conflicts.. Well your view of random possible clashes maybe is what happens or happened in Windows systems :D But Linux is supposed to be different, isn't it?
Best regards,
Stefano B.




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