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Topic: Interrupt Descriptor Table

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Maverick - The Operating System The only reason the Interrupt Descriptor Table (IDT) is used in this is because we need to have the Multitask ISR routine called each time the PIT send an interrupt signal. The Global Descriptor Table (GDT) contain generally segment and system descriptors. We don't have any handlers for CPU exceptions so these will just dump system state information on the screen, and if any of the other interrupts are called, except the Multitask ISR (IDT[50h]), the system state will also be dumped. www.maverick-os.dk /Development/FirstTest/Goal_Multitasking.html

Intel 8086 CPU Family Architecture LIDT - Load Interrupt Descriptor Table (286+ privileged) Usage: LIDT src Modifies flags: None Loads a value from an operand into the Interrupt Descriptor Table (IDT) register. LGDT - Load Global Descriptor Table (286+ privileged) Usage: LGDT src Modifies flags: None Loads a value from an operand into the Global Descriptor Table (GDT) register. LLDT - Load Local Descriptor Table (286+ privileged) Usage: LLDT src Modifies flags: None Loads a value from an operand into the Local Descriptor Table Register (LDTR). library.n0i.net /hardware/i8086opcodes

LGDT/LIDT--Load Global/Interrupt Descriptor Table Register Loads the values in the source operand into the global descriptor table register (GDTR) or the interrupt descriptor table register (IDTR). The source operand specifies a 6-byte memory location that contains the base address (a linear address) and the limit (size of table in bytes) of the global descriptor table (GDT) or the interrupt descriptor table (IDT). If operand-size attribute is 32 bits, a 16-bit limit (lower 2 bytes of the 6-byte data operand) and a 32-bit base address (upper 4 bytes of the data operand) are loaded into the register. www.cen.uiuc.edu /~cjiang/reference/vc155.htm

SGDT/SIDT--Store Global/Interrupt Descriptor Table Register Stores the contents of the global descriptor table register (GDTR) or the interrupt descriptor table register (IDTR) in the destination operand. See LGDT/LIDT--Load Global/Interrupt Descriptor Table Register in this chapter for information on loading the GDTR and IDTR. The SGDT and SIDT instructions are only useful in operating-system software; however, they can be used in application programs without causing an exception to be generated. www.cen.uiuc.edu /~cjiang/reference/vc288.htm

Linux 2.4.x Initialization for IA-32 HOWTO: Glossary IDT: Interrupt Descriptor Table, an i386-specific table that contains information used in handling interrupts LDT: Local Descriptor Table, an i386-specific memory management table that is used to describe memory for each non-kernel process GDT: Global Descriptor Table, an i386 memory management table justlinux.net /Linux-Init-HOWTO-6.html

x86 Segmentation for the 15-410 Student The segment number indexes a segment descriptor table which is much like the interrupt descriptor table. There are two tables of segment descriptors, the global descriptor table and the local descriptor table. The table indexed by the segment number depends on the table selector flag. www.cs.cmu.edu /~410/doc/segments/segments.html

Descriptor Tables The other Descriptor Table, the "Interrupt Descriptor Table" (short: IDT) is also available from all programs. The consequence is that descriptors may not be defined at a random position in memory, but only within the descriptor table (fig. All descriptors used by an application (for example descriptors for code and data segments) are administrated in tables. microlabs.cs.utt.ro /~mmarcu/books/03/p_all5.htm

Interrupts Instead, 256 interrupt descriptors are used in the interrupt descriptor table (IDT). The same interrupt assignments are made and the same sequence of operations occurs in protected mode but the interrupt table is different. The interrupt vector contents are fetched and loaded into CS and IP and execution resumes in the ISR. www.cs.umbc.edu /~plusquel/310/slides/8086_interrupts.html

INTERRUP.PRI First, the interrupt table consists of eight-byte descriptors instead of four-byte addresses, and need not be located at physical address zero, nor contain the full 256 entries (the address and size of the Interrupt Descriptor Table (IDT) may be manipulated with the LIDT and SIDT instructions). The interrupt handler has to be careful to preserve any registers that it uses which are not used to communicate results to the program that invoked the interrupt. Since a program can invoke an interrupt by number rather than by its address (as it has to in calling subroutines), interrupts are a convenient way of providing services without having to recompile a program whenever the address of the code providing the service changes. www.oopweb.com /Assembly/Documents/InterList/Volume/INTERRUP.PRI   (1053 words)

Interrupts Instead, 256 interrupt descriptors are used in the interrupt descriptor table (IDT). The same interrupt assignments are made and the same sequence of operations occurs in protected mode but the interrupt table is different. Fully nested mode allows the highest-priority interrupt request from a slave to be recognized by the master while it is processing another interrupt from a slave. www.cs.umbc.edu /~plusquel/310/slides/8086_interrupts.html   (875 words)

Body The IDTR points to the interrupt descriptor table which contains the addresses of the interrupt service routines that are indexed by interrupt type numbers. d) On the Pentium processor hardware interrupts can be disabled and enabled by manipulating the interrupt flag using the "cli" and "sti" assembly-language instructions. f) On the Pentium nonmaskable interrupts cannot be disabled by clearing the interrupt flag using cli. www.cs.uni.edu /~fienup/cs142f04/lectures/lec25_11-30-04.htm   (246 words)

Computer Abbreviation IDT Interface Design Tool + Interrupt Descriptor Table abbreviations.virtualsplat.com /category/computer-abbreviation-i.asp   (246 words)

May '98 Feature - Advanced Embedded X86 Programming: Protection and Segmentation LDTs, like the GDT and the interrupt descriptor table (IDT), are built by the OS, not by the task. Whenever a hardware interrupt is raised or a valid software interrupt is encountered, the related descriptor of the IDT is analyzed and the CPL set to the descriptor’s DPL (as seen in Figure 5). For an interrupt gate, execution starts in the address found in the descriptor (typically an interrupt handler in the OS) with the interrupts disabled; when the handler terminates, extra protection checks occur to ensure a proper return to the caller. www.embedded.com /98/9805fe2.htm   (4682 words)

Protected Mode Basics In protected mode, memory segmentation is defined by a set of tables (called descriptor tables) and the segment registers contain pointers into these tables. In protected mode, the information pushed on the stack can vary, as can the base address of the interrupt vector table and the size of the interrupt table. 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. www.x86.org /articles/pmbasics/tspec_a1_doc.htm   (4153 words)

i386.info-1 The contents of the i386 Interrupt Descriptor Table are discussed in Intel's i386 User's Manual. The initialization code is responsible for initializing the Global Descriptor Table such that the i386 is in the thirty-two bit flat memory model with paging disabled. The i386 must be placed in protected mode and the segment registers and associated selectors must be initialized before the initialize_executive directive is invoked. www.rtems.com /onlinedocs/rtems-doc-20030417/info/i386.info-1   (4153 words)

Kernel Mode Linux In the original Linux kernel, interrupts are handled by interrupt handling routines specified as gates in the Interrupt Descriptor Table (IDT). The kernel code segment is used for the kernel itself, and its privilege level is kernel mode. Thus, the kernel is protected by CPUs, because programs executed in user mode cannot access memory that belongs to programs executed in kernel mode. www.linuxjournal.com /node/6516/print   (2341 words)

Multics Glossary The 645 and 6180 process-switching instruction, which directs the appending unit to the base (or page table) of the descriptor segment. The 645 and 6180 instruction instruction that stores an eight-word encoding of the processor state (other than register contents and the state of the EIS unit on the 6180) at the time of an interrupt or fault. Joke from that time: GE executives had a big meeting in Florida to decide how to become number two in the computer business (this was in the days when it was "IBM and the seven dwarfs"). www.mit.edu /afs/net/user/srz/www/multics-glossary.html   (18881 words)

Protected mode and operating systems Basic pmode, unreal mode, interrupts and exceptions, multitasking with TSSes and without, Ring 0 versus Ring 3, etc. This was a by-product of my attempt to write an operating system, so it's missing Local Descriptor Tables (LDTs), Virtual 8086 mode, DPMI, etc. Make process creates disassembly and symbol table files Realtime clock code now works with BCD or binary modes, and uses interrupt instead of polling to wait for end of update my.execpc.com /CE/AC/geezer/os   (838 words)

Anti-Virus Research - Dealing with Metamorphism A higher action is a phrase used to describe the purpose of a related group of instructions, and can, for example, be anything from locating the Interrupt Descriptor Table (a single instruction, SIDT), to hooking an API (usually a small series of instructions), or even decryption (variable, but often a large number of instructions). Win32.Metaphor's metamorphism works by disassembling its own code into a custom pseudo-code, which is a meta-language for describing the actions of the code of the virus without any reference to the actual code. All of those lines of code are testament to the power of Win32.Metaphor's metamorphic engine, as they could be replaced by the equivalent five lines of code on the right side. www3.ca.com /securityadvisor/newsinfo/collateral.aspx?cid=48051   (838 words)

Global Descriptor Table - Wikipedia, the free encyclopedia Apart from the machine instructions which allow one to set/get the position of the GDT (and of the Interrupt Descriptor Table) in memory, every machine instruction referencing memory has an implicit Segment Register, occasionally two. The Global Descriptor Table or GDT is a data structure used by Intel x86-family processors starting with the 80286 in order to define the characteristics of the various memory areas used during program execution, for example the base address, the size and access privileges like executability and writability. The LDT is supposed to contain memory segments which are private to a specific program, while the GDT is supposed to contain global segments. en.wikipedia.org /wiki/GDT   (402 words)

A Crash Course on theDepths of Win32 Structured Exception Handling, MSJ January 1997 The handler is defined by the interrupt descriptor table entry that corresponds to an exception. This magic is accomplished through data in tables that you don't normally see. Since the handler for a particular exception may not be at the head of the list, there needs to be an orderly way of removing all exception handlers in the list that are ahead of the handler that actually deals with the exception. www.microsoft.com /msj/0197/exception/exception.aspx   (8025 words)

Linux Kernel 2.4 Internals: Process and Interrupt Management The other versions of UNIX separated the task state information into one part which should be kept memory-resident at all times (called 'proc structure' which includes process state, scheduling information etc.) and another part which is only needed when the process is running (called 'u area' which includes file descriptor table, disk quota information etc.). This means that when this task is sleeping on a wait queue with many other tasks, it will be woken up alone instead of causing "thundering herd" problem by waking up all the waiters. This task queue is exported to modules but shouldn't be used except for the special purposes which it was designed for. jamesthornton.com /linux/lki/lki-2.html   (6810 words)

triplefault.txt Load the interrupt descriptor table register (IDTR) with a value whose limit=0. Triple- faulting the CPU to trigger a SHUTDOWN cycle was the brain-child of Intel. Triple faulting the CPU is about 1/3 faster than using the keyboard controller method (your mileage may vary depending on how and where you drive). www.x86.org /ftp/productivity/triplefault.txt   (719 words)

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