>>> set noexec_user_stack = 1
>
>> [...], there is a reason, why SUN does enable stack execution by
>> default, if i am correctly informed this is due to some fortran or
>> rare/old compiler issue, and might break some fortran or other alien
>> language code...
>
>It'll also break gcc's nested function support, since it's implemented
>with stack trampolines. (It doesn't *have* to be; in principle
>function pointers could be widened to carry the same information. But
>doing that would break function-pointer compatability with code
>compiled with other compilers...not to mention meaning that most
>function pointers would carry a bunch of unnecessary-for-them extra
>data around. Another possible way around it would be to cause gcc to
>keep part of the stack in the data segment, out of what the kernel
>thinks of as the stack, and have it do its trampolines there. This
>runs into big problems with setjmp and other nonlocal exits, and
>possibly with signal handlers as well.)
It's wrong to say it affects all nested functions; it only affects
nested functions passed as parameter.
In current gcc releases this has been fixed. The trampoline code
now calls "mprotect()" after putting a trampoline on the stack.
Casper
Received on May 02 2000
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