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Topic: Protected mode

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	"Working in the Protected Mode Environment"
		Protected mode on the 386 offers the programmer better protection and more memory than on the 286.
		In V86 mode, the 386 operates in protected mode but allows some programs it is running to use a simulated real-mode environment.
		Although the processor is in V86 mode, the interrupt handling still occurs in protected mode.
	members.tripod.com /protected_mode/prashant/protmode.html (6054 words)

	Protected Mode Basics (Site not responding. Last check: 2007-11-05)
		In protected mode, memory segmentation is defined by a set of tables (called descriptor tables) and the segment registers contain pointers into these tables.
		Protected mode differs from real mode in this respect each time the CPU loads a segment register, it fully loads the descriptor cache register, no previous values are honored.
		All that remains in order to enter protected mode is changing the CPU state to protected mode and jumping to clear the prefetch queue (not necessary on the Pentium).
	www.x86.org /articles/pmbasics/tspec_a1_doc.htm (4153 words)

	Protected mode - Wikipedia, the free encyclopedia
		Protected mode is an operational mode of x86-compatible CPUs of the 80286 series or later.
		Protected mode has a number of new features designed to enhance multitasking and system stability, such as memory protection, and hardware support for virtual memory as well as task switching.
		In other words, protected mode was less compatible with DOS applications than real mode applications would be and so there was a need for virtual 8086 mode, which came with the 386.
	en.wikipedia.org /wiki/Protected_mode (1069 words)

	386 Protected Mode
		In protected mode segment registers are pointers to data structures that define segmentation limits and addresses.
		Segment registers are called "selectors" when operating in protected mode, to distinguish their operation from that of real mode.
		Every protected mode program must include a table of "descriptors", which are 8 byte data structures that define the start and end of a segment.
	www.ganssle.com /articles/aprot1.htm (2395 words)

	protected mode (Site not responding. Last check: 2007-11-05)
		In real mode, addresses are generated by adding an address offset to the value of a segment register shifted left four bits.
		Which segment register is used depends on the instruction, on the addressing mode and of an optional instruction prefix which selects the segment register explicitly.
		A solution which is portable to protected mode with almost the same efficiency would involve using a table of segments instead of calculating new segment register values ad hoc.
	burks.bton.ac.uk /burks/foldoc/2/94.htm (595 words)

	A CRASH COURSE IN PROTECTED MODE
		In protected mode this SEGMENT value is interpreted completely different than in real mode and Virtual 86 mode.
		All you need to know to program in protected mode is what descriptors are available to you and what are the selector values of these descriptors.
		This was only meant to be a rough introduction to the protected mode segmentation mechanism of the 80386+.
	www.geocities.com /SiliconValley/2151/pmode.html (908 words)

	DPMI 0.9: General Notes for Protected Mode Programs
		Protected mode programs should use the virtual interrupt state services to determine the current interrupt flag state (see section 17.1).
		Protected mode hardware interrupt handlers will always be called even for interrupts that occur in real mode.
		Protected mode hardware interrupt handlers that need to call software running in real mode must either be sure that the real mode software that they are calling will not modify segment registers or they must use the state save service (see section 11.6) to save and restore the real mode segment registers.
	www.tenberry.com /web/dpmi/02.htm (1743 words)

	About PMODE/W (Site not responding. Last check: 2007-11-05)
		Any IRQs that occur in protected mode and have not been hooked by a protected mode handler will be sent on to their real mode handlers.
		The protected mode handler may chain to the real mode handler for that IRQ by calling the previous protected mode handler for that IRQ.
		Whenever you make a call to real mode, or a callback or IRQ is passed from real mode to its routine in protected mode, a nested stack is used.
	www.tmt.com /helphtml/pmodew_about.htm (2176 words)

	Introduction to the Protected Mode API (Windows IETechCol) (Site not responding. Last check: 2007-11-05)
		Protected Mode helps reduce the severity of threats to Windows Internet Explorer 7 and its extensions by eliminating the silent installation of malicious code through software vulnerabilities.
		Protected Mode accomplishes this goal using the integrity mechanisms of Microsoft Windows Vista which restrict access to processes, files, and registry keys with higher integrity levels.
		The Protected Mode API enables software vendors to develop extensions and add-ons for Microsoft Internet Explorer that can interact with the file system and registry from a low-integrity process, such as Protected Mode Internet Explorer.
	msdn.microsoft.com /workshop/security/protmode/overviews/pmie_intro.asp (542 words)

	Bona Fide OS Development - Protected Mode
		Protected mode allows programs to access more than 1 megabyte of physical memory, and protects against misuse of memory (i.e.
		In protected mode, besides the segment base address, we also need the segment size (limit) and some flags indicating what the segment is used for.
		This is a fourth mode of operation found on the 386 CPU, with addressing similar to real mode but some of the protection mechanisms of protected mode.
	www.osdever.net /tutorials/pm.php?the_id=16 (1663 words)

	Introduction to Protected-Mode
		A 32-bit address bus replaced the old 24-bit bus of the 80286 giving the user a total of 4GB physical address space, a third operating mode dubbed Virtual-Mode was implemented to support execution of old 8086 code while still running in a protected-mode environment, and, last but not least, Paging support was added.
		Protection checks are made before any memory cycle is started; A protection violation terminates the offending memory cycle and generates an exception.
		When the processor is running in virtual-mode, it behaves as if it were an 8086 equipped with protection, multitasking and paging support.
	www.internals.com /articles/protmode/introduction.htm (1391 words)

	protected mode - Glossary - CNET.com (Site not responding. Last check: 2007-11-05)
		In protected mode, different parts of memory are assigned to different programs.
		This way, memory is "protected" in the sense that only the assigned program can access it.
		Windows and OS/2 run primarily in protected mode, but can switch between the use of protected-mode and real-mode applications.
	www.cnet.com /Resources/Info/Glossary/Terms/protected.html (78 words)

	What is protected mode? - A Word Definition From the Webopedia Computer Dictionary
		Although the DOS operating system is not designed to take advantage of these features, some DOS programs can run in protected mode using special drivers.
		Provides a lengthy and detailed explanation of protected mode and how the CPU handles it internally, the role of memory management, and how to enter and exit protected mode.
		This page notes both the impact protected mode has on performance, and what influences the performance of protected mode programs.
	www.webopedia.com /TERM/P/protected_mode.html (287 words)

	Introduction to Protected Mode Programming
		This mode requires that the machine be dropped into protected mode, the segment limits set to 4 gigabytes, and then the machine is popped back to real-mode without a CPU reset.
		Borland Pascal 7.0 is a 16-bit protected mode compiler and it allows programmers to use up to 16 MB of memory.
		In Protected Mode, however, each selector has a flag that designates read/write or read-only, and code selectors are always flagged as read-only.
	www.monstersoft.com /tutorial1/PM_intro.html (1510 words)

	IEBlog : More details on Protected Mode IE in Windows Vista
		User Account Protection is enabled in the Windows Vista CTP build, but Protected Mode work is not done yet and hence users are unable to install ActiveX controls in the default configuration.
		Protected Mode also includes compatibility features which allow most add-ons to continue running unaffected and which provides impacted add-ons with feasible implementation options.
		But yes, Protected mode is explicitly designed to be a defense-in-depth measure that would mitigate exploit of a vulnerability even if a patch was not available.
	blogs.msdn.com /ie/archive/2005/09/20/471975.aspx (1803 words)

	Guide: What does protected mode mean? (Site not responding. Last check: 2007-11-05)
		Real mode is when the CPU is running in 8086 compatible mode.
		Protected mode is when the CPU is running in, well, the not quite as compatible mode.
		The purpose of protected mode is not to protect your program.
	www.delorie.com /djgpp/doc/ug/basics/protected.html (288 words)

	Protected Mode
		The use of protected mode didn't become popular until the rise in dominance of the Microsoft Windows operating system.
		Protected mode is now currently the way that most people use their PCs.
		Protected mode is also sometimes called 386 Enhanced Mode, since it became mainstream with that family of processors.
	www.pcguide.com /ref/cpu/arch/int/modesProtected-c.html (445 words)

	Virtual 8086 Mode
		Firstly it was officially impossible to switch from protected back to real mode (although a clever IBM hack made this possible); secondly, protected mode was also incompatible with the vast amount of real-mode code around at the time.
		We can see from this that V86 mode is more similar in some ways (address formation) to real mode, and in others (protection) to protected mode.
		It may seem a bit of a hack on top of normal protected mode, but it was designed to be easy and non-disruptive to add to an existing kernel.
	osdev.berlios.de /v86.html (2692 words)

	"VIRUS BULLETIN", August 1997
		In the same year, viruses Evolution.2761 and Evolution.2770 succeeded in tapping part of the power of the protected mode, but only when the processor was in the real mode.
		Using the VCPI tools, the virus toggles the processor to protected mode with the highest privilege level, known as the supervisor.
		PM.Wanderer is the first virus to utilize i386 the protected mode and not conflict with the domimamt Microsoft operating systems, which also use that mode.
	old.antivir.ru /english/lib/wanderer.htm (2456 words)

	ProtectedMode overview [deinmeister.de]
		In Real Mode, the memory was addressed by a segment register containing a start address and an index register which points to the address relatively to the address contained in the segment register.
		In Protected Mode index registers are used in the same way, but the role of the segment register has completely changed: It does no longer point to a physical address.
		The main difference between 286 and 386 in Protected Mode is that memory blocks can be bigger than on the 286 and that the starting address can be bigger than 16MB.
	www.deinmeister.de /x86modes.htm (1255 words)

	protected mode environment - EXE loader, DOS extender replacement for x86 embedded systems
		It is usually a DOS-style, real-mode exe, unless it is being bootloaded, in which case it is a binary file or unless it is being run from ROM, in which case it is a binary image.
		This function is for use during initialization, such as to initialize a display controller to a particular graphics mode.
		Also, while in virtual 86 mode, hardware interrupts cannot be processed by protected mode interrupt service routines.
	www.smxinfo.com /rtos/kernel/pmeasy.htm (1575 words)

	The quest for ring 0
		System Management mode is one of the four modes of operation of most x86 processors (Intel Xeon, Intel Pentium, or AMD Athlon for instance).
		In protected mode, 4 different processor privilege levels (also called rings) are available, ring 0 being the most privileged one and ring 3 the least privileged one.
		Protected mode security mechanisms (paging, segmentation, rings,...) are not enforced while in System Management Mode.
	www.securityfocus.com /columnists/402 (1121 words)

	IEBlog : Protected Mode in Vista IE7
		The idea behind Protected Mode IE is that even if an attacker somehow defeated every defense mechanism and gained control of the IE process and got it to run some arbitrary code, that code would be severely limited in what it could do.
		Protected Mode provides a “compatibility layer” that consists of a set of shims that intercept certain system API calls.
		Protected Mode is only available on Windows Vista because it depends on the new privilege restrictions in Windows Vista called Mandatory Integrity Control.
	blogs.msdn.com /ie/archive/2006/02/09/528963.aspx (3890 words)

	Protected-Mode Memory Management
		It is used by the protection mechanism built into the processor to restrict access to the segment.
		When this bit is clear, a segment-not-present exception is generated whenever a selector for the descriptor is loaded into one of the segment registers.
		This is used to notify the operating system of any attempt to access a segment which has been swapped to disk (virtual memory support) or which was not previously allocated (a protection violation).
	www.internals.com /articles/protmode/protmode.htm (2289 words)

	Method for providing protected mode services for device drivers and other resident software (US5459869)
		A further method enabling such protected mode programs in an Intel x86 environment to transition between host environments is provided.
		In a preferred embodiment, a method for allowing for protected mode programs running in a DOS environment which can then transition and continue to function in a Windows environment.
		means for protecting high order registers of said protected mode code by maintaining values of said high order registers in memory and restoring said registers at a completion of an interrupt procedure; and
	www.delphion.com /details?pn10=US05459869 (489 words)

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