Re: Executing from dynamically allocated memory

From	Alex McDonald <blog@rivadpm.com>
Newsgroups	comp.compilers
Subject	Re: Executing from dynamically allocated memory
Date	2013-10-12 11:12 -0700
Organization	Compilers Central
Message-ID	<13-10-008@comp.compilers> (permalink)
References	<13-10-004@comp.compilers>

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On Saturday, 12 October 2013 01:05:39 UTC+1, news  wrote:
> 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. ...

> 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?
>
> Or might there be something even weirder going on?
> [ Sounds like the NX bit.  See http://en.wikipedia.org/wiki/NX_bit#Linux -John]

mprotect(2) - Linux man page
Name

mprotect - set protection on a region of memory
Synopsis

#include <sys/mman.h>

int mprotect(void *addr, size_t len, int prot);

Description

mprotect() changes protection for the calling process's memory page(s)
containing any part of the address range in the interval [addr,
addr+len-1]. addr must be aligned to a page boundary.

If the calling process tries to access memory in a manner that
violates the protection, then the kernel generates a SIGSEGV signal
for the process.

prot is either PROT_NONE or a bitwise-or of the other values in the
following list:

...

PROT_EXEC

The memory can be executed.

...

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Thread

Executing from dynamically allocated memory "news" <news@fx32.iad.highwinds-media.com> - 2013-10-12 00:05 +0000
  Re: Executing from dynamically allocated memory "James Harris" <james.harris.1@gmail.com> - 2013-10-12 10:10 +0100
  Re: Executing from dynamically allocated memory Sébastien Fricker <sebastien.fricker@gmail.com> - 2013-10-12 11:52 +0200
  Re: Executing from dynamically allocated memory chakaram@auth.gr - 2013-10-12 19:20 +0300
  Re: Executing from dynamically allocated memory Alex McDonald <blog@rivadpm.com> - 2013-10-12 11:12 -0700
  Re: Executing from dynamically allocated memory sandmann@cs.au.dk (Søren Sandmann) - 2013-10-12 20:58 +0200
  Re: Executing from dynamically allocated memory Jens Kallup <jkallup@web.de> - 2013-10-13 10:44 +0200

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