Q: "Execution Protection (NX) What does execution protection do?" A: http://www.microsoft.com/technet/prodtechnol/winxppro/maintain/winxpsp2.mspx#XSLTsection130121120120 Alempana muutamia lainauksia jotka aukottomasti osoittavat että Intelin IA32e 64-bit laajennos IA32 32-bit -arkkitehtuuriin ei tule ainakaan näillä näkymin ja lähiaikoina tukemaan ns. NX-muistilohkoja. Prescott-ydin ei sitä tue, joten vaaditaan vähintään uusi Pentium IV / Xeon -versio. Ja jo olemassaolevan Prescott-version markkinoille tulo tuntuu kangertelevan kalliin hinnan ja vähäisen tarjonnan parissa. (maaliskuu-2004) NX-muistilohkotuki on arkipäivää "big iron"-palvelimissa, jotka käyttävät esim. Sun SPARC -prosessoria. Myös Intel Itanium -prosessoreissa NX-tuki on. Samoin 64-bittisissä AMD-prosessoreissa. NX-tuen käyttöönotto edellyttää vastaavaa tukea myös käyttöjärjestelmältä, tällä hetkellä 32-bit Windows (Windows Server 2003, Windows XP/2000/NT) ei sitä tue, Windows XP Service Pack 2 tukee sitä Itanium- ja AMD64-prosessoreilla. "NX (No-Execute) bit: Initial implementation will not support the NX bit." -- http://www.ussg.iu.edu/hypermail/linux/kernel/0402.3/0276.html "Even though there are some differences between Intel’s and AMD’s 64-bit extended processors’ capabilities, such as NX (non execute) bit featured in AMD64" -- http://www.xbitlabs.com/news/cpu/display/20040325151223.html "Both Intel and Advanced Micro Devices (AMD) have defined and shipped Windows-compatible architectures for execution protection. Windows supports execution protection on the AMD64 platform and Intel Itanium Processor Family (IPF) processors. The 32-bit version of Windows (beginning with Service Pack 2 for Windows XP) utilizes the no-execute page-protection (NX) processor feature as defined by AMD." "It is hoped that future 32-bit and 64-bit processors will provide execution protection." -- http://www.microsoft.com/technet/prodtechnol/winxppro/maintain/winxpsp2.mspx#XSLTsection130121120120 Intel 64-bit Extension Technology http://www.intel.com/technology/64bitextensions/faq.htm http://www.intel.com/technology/64bitextensions/index.htm?iid=techtrends+spotlight_64bit ftp://download.intel.com/technology/64bitextensions/ AMD64 Architecture Tech Docs http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_739_7044,00.html Intel introduces processor numbers: http://www.intel.com/products/processor_number/index.htm?iid=HPAGE+low_news_040323a& " || 1. No NX bit in page descriptors. || - Looks like Intel is missing something important here. | | They probably forgot to add that to the doc. No. If you look at the cpuid feature-bit description in the IA32e pdf, it says function 80000001-edx bits 28-21 are reserved, and bits 19-12 are reserved, with no mention at all of bit 20 (the NX feature bit). Looks like it was in the doc, and pulled out later on. " -- http://www.sandpile.org/post/msgs/20005079.htm Even though there are some differences between Intel’s and AMD’s 64-bit extended processors’ capabilities, such as NX (non execute) bit featured in AMD64, generally speaking IA32e – now called Extended Memory 64 Technology – and AMD64 – also known as x86-64 – are compatible and are capable of running similar specially written 64-bit code. http://www.xbitlabs.com/news/cpu/display/20040310223922.html NX (non execute) bit featured in AMD64 http://www.xbitlabs.com/news/cpu/display/20040225144527.html Analyst: Intel Reverse-Engineered AMD64 April 5, 2004 By Mark Hachman http://www.extremetech.com/article2/0,1558,1562294,00.asp "The core of AMD’s Enhanced Virus Protection is the so-called NX bit in the page-translation tables that specifies whether instructions can be executed from the page. The capability is also available on Intel’s Itanium and Itanium 2 microprocessors, but is not present in IA32e chips, such as Intel Pentium 4 E also known as Prescott, unlike suggested by certain sources last year." http://www.xbitlabs.com/news/cpu/display/20040225144527.html AMD64 vs. IA32e - differences http://www.techspot.com/vb/showthread/t-11135.html http://www.aceshardware.com/forum?read=115062421 http://www.ussg.iu.edu/hypermail/linux/kernel/0402.3/0276.html HP reckons that the Opteron and Intel's EM64T - that is Chipzilla servers which use the iAMD64 Intel's EM64T has 64-bit wide general purpose registers, 48-bit of virtual addressing, and up to 40 bits of physical addressing. But Intel Noconas will only address 40-bits and Potomac will do the same. -- http://www.theinquirer.net/?article=15219 Intel Xeon with Intel Extended Memory 64 Technology (EM64T) Intel's 64-bit extension technology previously code-named Yamhill, then CT, will now be known as "Intel Extended Memory 64 Technology", or Intel EM64T. Ace's HW forum posts: Prescott, like Nocona, includes support for AMD64 (minus NX bit support and a couple of other things). It's currently not enabled, and there's no guarantee that it will be possible to enable it with software / a new BIOS later. But the transistors are there. http://www.aceshardware.com/forum?read=115069447 The transistors are certainly there, but it is unknown if they are working properly yet. Until shown that this technology works, say on any number of other working 64 bit OS's, it simply could be a botched design that's waiting for a redesign to get it working. Given that Intel is only promising to implement this when Longhorn is released next year, I'd say that it probably isn't fully functional yet. http://www.aceshardware.com/forum?read=115069759 What Is An EM64T? ... In the meantime, they've come up with a clever and snappy new name for the chip: Intel Extended Memory 64 Technology, or EM64T. ... http://www.informationweek.com/story/showArticle.jhtml?articleID=18311555 Ace's Hardware General Message Board ... What is em64t? Intel needs to stop making up new codes. ... Has anyone confirmed there is no hidden EM64T mode in Prescott > by actually trying to use it? ... www.aceshardware.com/forum?read=115069344 - 56k - 6 Apr 2004 EM64T is strongly based on and compatible with AMD's AMD64 instruction set extension. http://en.wikipedia.org/wiki/EM64T Differences between AMD64 and Intel 64-bit Extension Technology " 1. SYSCALL/SYSRET and SYSENTER/SYSEXIT in the compatibility mode In the compatibility mode of the long mode of AMD64, we can use only SYSCALL/SYSRET. In the compatibility mode of the IA-32e mode of Intel 64-bit Extension Technology, we can use only SYSENTER/SYSEXIT. AMD64 Intel64 mode Legacy Long IA-32e Legacy sub-mode 64-bit Compatibility Compatibility 64-bit SYSCALL/SYSRET Yes Yes Yes No Yes No SYSENTER/SYSEXITYes No No Yes Yes Yes In the long mode of AMD64, we can use only SYSCALL/SYSRET, regardless of sub-modes (both of the 64-bit mode and the compatibility mode). In AMD64, we can use SYSENTER/SYSEXIT only in the legacy mode (see page 184 of AMD64 Architecture Programmer's Manual, Volume 2: System Programming, Chapter 6: System-Management Instructions). On the other hand, in the IA-32e mode of Intel 64-bit Extension Technology, we can use SYSENTER/SYSEXIT, regardress of sub-modes (both of the 64-bit mode and the compatibility mode). In addition, we can use SYSCALL/SYSRET only in the 64-bit mode (see page 1-6 of Intel 64-Bit Extension Technology Software Developer's Guide Volume 1 of 2: Chapter 1 Introduction). 2. No Execute (NX) Bit in page tables In AMD64, the MSB of PML4E/PDPE/PDE/PTE is NX bit that represents that pages are non-executable. On the other hand, in Intel 64-bit Extension Technology, the MSB of PML4E/PDPE/PDE/PTE is just reserved. ... to be continued. Toshiyuki Maeda " -- http://user.ecc.u-tokyo.ac.jp/~rr27109/amdvsintel/ "Intel will almost completely switch over to Prescotts by Q3, he said. Intel's version of NX, a security feature that can help prevent viral attack, is called XD and will be switched on in summer." -- 20040514 http://www.theinquirer.net/?article=15915 VIA C5J "Esther" -prosessori sisältää NX-bit-tuen. -- 20040519 http://www.theinquirer.net/?article=16008 ", and x86 64-bit capability (called Extended Memory 64 Technology or "EM64T") was announced earlier this year and will be shipping in upcoming Xeon (Nocona) processors in the next few months." "Otellini did not give specific dates for the Vanderpool and Silvervale virtualization technologies, or LaGrande security features, though we believe LaGrande is implemented in all current Prescott-family processors." "Otellini said that Intel cannot guarantee that EM64T features in existing Prescott chips would be fully compatible with future Prescott processors that formally support EM64T. " " The "thermal wall" as Otellini described it, is the major reason for the recent cancellation of the Prescott follow-on processor codenamed Tejas, and the Xeon (Nocona) follow-on codenamed Jayhawk, both which would have been shipped in 2005" "Intel will be enabling a few new features in Prescott-based processors in 2004, the first being XD, which relates to security, and is similar to AMD's NX (no-execute) bit technology (called "Enhanced Virus Protection") in its 64-bit x86 instruction set. " -- 20040521 http://www.extremetech.com/article2/0,1558,1595421,00.asp (May 14, 2004) http://www.xbitlabs.com/news/cpu/display/20040602110858.html --klip-- A "Product Change Notification #104101-00" state [...] The new capabilities Intel plans to include are the so-called AAC technology that adjusts performance depending on load in order to maintain low heat dissipation and quiet operation of personal computers as well as XD technology - aka Execute Disable Bit (NX bit) [...] --klip-- NX-bit, WinXP SP2: http://www.xbitlabs.com/news/cpu/display/20040225144527.html -- 20040606 -- 20040331,20040428,20040515,20040519,20040521,20040606 Jussi Heino juhehe@utu.fi jh@iki.fi http://users.utu.fi/juhehe/jutut/NX-bit.txt