VM_PROT_EXEC on the stack

Ed Schouten ed at 80386.nl
Sat Jun 14 17:48:12 UTC 2008

Hello everyone,

I'm not a real guru when it comes to low level x86 hardware stuff, but
some time ago I read somewhere that the NX bit on AMD64 CPU's could be
used to mark the stack as non-executable, making it impossible to
execute code on the stack (through buffer overflows).

When I look at procstat -v's output on FreeBSD/amd64, I see the stack
has VM_PROT_EXEC. Is there a specific reason for this?

 Ed Schouten <ed at 80386.nl>
 WWW: http://80386.nl/
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