Re: Executing from dynamically allocated memory

"news" <news@fx32.iad.highwinds-media.com> wrote in message
> In the past, I've malloc'd memory, written machine instructions into it,
> and called the function I built there.
>
> All this on a 32-bit intel instruction set, on a Debian system.
>
> This appears no longer too work. My program gives a segmentation fault.
> The debugger tells me that the segmentation fault occurs on the first
> instruction of the called function, a
> push %ebp
> residing in malloced memory.
>
> Now it was a year or three ago that this worked. Has Linux changed in
> this respect? Is there something new I have to do to allocate executable
> writable memory for this purpose?


Possibly. As John says, this could be caused by current Linux setting the NX
bit for malloced pages. The dump may/should show if that is the case, if you
can decipher the dump.


Instead of malloc you may need to use mmap. It allows permissions to be
specified.


James

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