From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-2.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM, MAILING_LIST_MULTI autolearn=unavailable autolearn_force=no version=3.4.4 X-Google-Thread: 103376,b1f4420d01b2c4eb X-Google-Attributes: gid103376,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news3.google.com!proxad.net!feeder1-2.proxad.net!cleanfeed3-a.proxad.net!nnrp14-2.free.fr!not-for-mail Return-Path: X-Virus-Scanned: amavisd-new at ada-france.org From: Duncan Sands To: comp.lang.ada@ada-france.org Subject: Re: LLVM--Low Level Virtual Machine--and Ada Date: Mon, 23 Jul 2007 09:47:51 +0200 User-Agent: KMail/1.9.7 References: <1184730995.862147.208590@g12g2000prg.googlegroups.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Cc: Robert A Duff X-BeenThere: comp.lang.ada@ada-france.org X-Mailman-Version: 2.1.9rc1 Precedence: list List-Id: "Gateway to the comp.lang.ada Usenet newsgroup" List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.ada Message-ID: X-Leafnode-NNTP-Posting-Host: 88.191.17.134 Organization: Guest of ProXad - France NNTP-Posting-Date: 23 Jul 2007 09:50:03 MEST NNTP-Posting-Host: 88.191.14.223 X-Trace: 1185177003 news-2.free.fr 28468 88.191.14.223:35015 X-Complaints-To: abuse@proxad.net Xref: g2news1.google.com comp.lang.ada:16543 Date: 2007-07-23T09:50:03+02:00 Hi Bob, thanks for your informative reply. > Another problem is that some modern machines use DEP (which I think > stands for "data execution prevention" or something like that). DEP > means the operating system prevents writeable data from being executed > as code. The purpose is to prevent certain kinds of security holes > that are common in languages that don't do array-bounds checking. > But DEP prevents trampolines from working, so users have to turn > it off in order to run some Ada programs (such as the compiler). > It's a pain because users get some mysterious error message > when trampolines are used. I'm not sure that this is a problem anymore: gcc uses a bunch of tricks (eg: setting a flag on the program that notes it runs code on the stack) to inform the operating system that the trampoline is kosher IIRC. That said, I haven't tried to implement any of this in LLVM yet, which is also why I'm vague on the details. > Another problem (I've heard) is that there's at least one machine > supported by gcc where trampolines don't work. I don't remember which > machine, and I don't even know for sure that this is true. All architectures currently supported by LLVM support trampolines in gcc. Ciao, Duncan.