IBM AIX Continuous Availability Features - IBM Redbooks

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Example 3-19 shows the SMIT menu for the current storage key setting. Example 3-19 SMIT menu to check current storage key setting 80 IBM AIX Continuous Availability Features Change/Show Kernel Storage Protection Keys State Move cursor to desired item and press Enter. Show Kernel Storage Protection Keys State Change Next Boot Kernel Storage Protection Keys State F1=Help F2=Refresh F3=Cancel F8=Image F9=Shell F10=Exit Enter=Do The current storage key setting for our test system is shown in Example 3-20. Example 3-20 Current storage key setting COMMAND STATUS Command: OK stdout: yes stderr: no Before command completion, additional instructions may appear below. Current Kernel Storage Protection Keys State is enabled. Next Boot Kernel Storage Protection Keys State is default. F1=Help F2=Refresh F3=Cancel F6=Command F8=Image F9=Shell F10=Exit /=Find n=Find Next You can change the next boot storage key setting by using the second option of the SMIT menu shown in Example 3-19. Note: Although you may be able to use the command line for checking and altering storage key settings, this is not supported for direct use. Only SMIT menus are supported. 3.7.3 Kernel mode protection keys Kernel keys provide a Reliability function by limiting the damage that a software component can do to other parts of the system. The keys will prevent kernel extensions from damaging core kernel components, and provide isolation between kernel extension classes. Kernel keys will also help provide a significant Availability function by helping to prevent error propagation.
Note: Kernel and kernel extensions are not necessarily protected from other kernel extensions. Kernel and kernel extensions are only protected (to the extent possible) from key-safe extensions. For details about protection degrees, refer to 3.7.4, “Degrees of storage key protection and porting considerations” on page 84, which describes key-safe and key-unsafe kernel extensions. Furthermore, key-unsafe extensions’ access rights are also somewhat limited. In particular, certain kernel parts appear only as read-only to the key-unsafe kernel extensions. Serviceability is enhanced by detecting memory addressing errors closer to their origin. Kernel keys allow many random overlays to be detected when the error occurs, rather than when the corrupted memory is used. With kernel key support, the AIX kernel introduces kernel domains and private memory access. Kernel domains are component data groups that are created to segregate sections of the kernel and kernel extensions from each other. Hardware protection of kernel memory domains is provided and enforced. Also, global storage heaps are separated and protected. This keeps heap corruption errors within kernel domains. There are also private memory keys that allow memory objects to be accessed only by authorized components. In addition to RAS benefits, private memory keys are a tool to enforce data encapsulation. There is a static kernel key-to-storage key mapping function set by the kernel at boot time. This mapping function is dependent on the number of storage keys that are present in the system. Note: Kernel keys are not intended to provide a security function. There is no infrastructure provided to authorize access to memory. The goal is to detect and prevent accidental memory overlays. The data protection kernel keys provide can be circumvented, but this is by design. Kernel code, with the appropriate protection gate, can still access any memory for compatibility reasons. Analogy To understand the concept of kernel storage keys, consider a simple analogy. Assume there is a large house (the kernel) with many rooms (components and device drivers) and many members (kernel processes and kernel execution path), and each member has keys only for a few other selected rooms in addition to its own room (keyset). Therefore, members having a key for a room are considered safe to be allowed inside. Every time a member wants to enter a room, the member needs to see whether its keyset contains a key for that room. If the member does not have the corresponding key, it can either create a key which will permit the member to enter the room (which means it will add the key to its keyset). Or the member can try to enter without a key. If the member tries to enter without a key, an alarm will trip (cause a DSI/Kernel crash) and everything will come to a halt because one member (a component or kernel execution path) tried to intrude into an unauthorized room. Kernel keys The kernel's data is classified into kernel keys according to intended use. A kernel key is a software key that allows the kernel to create data protection classes, regardless of the number of hardware keys available. A kernel keyset is a representation of a collection of kernel keys and the desired read or write access to them. Remember, several kernel keys Chapter 3. AIX advanced continuous availability tools and features 81
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Front cover IBM AIX Continuous Avai
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Note: Before using this information
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2.3.7 Minidump . . . . . . . . . .
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vi IBM AIX Continuous Availability
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Trademarks The following terms are
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Engineering degree in Computer Scie
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Find out more about the residency p
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1.1 Overview In May 2007, IBM intro
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1.5 Continuous operations Continuou
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1.6.2 Availability 1.6.3 Serviceabi
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IBM has tried to enhance FFDC featu
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10 IBM AIX Continuous Availability
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2.1 System availability AIX is buil
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On AIX 5.3, the only way to persist
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When used on a standalone server (s
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mirrored volume group on the client
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2.2.1 Error checking Run-Time Error
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The PowerPC hardware gives software
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System dumps can also be user-initi
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Live dumps are small dumps that do
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Trace is a valuable tool for observ
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Page 48 and 49: Logging can be added to many of the
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Page 56 and 57: operations) without affecting produ
Page 58 and 59: Quorum A quorum is a vote of the nu
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Page 64 and 65: display its output in a format suit
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Page 82 and 83: .vmker | YES | ON/3 | OFF/3 .vmpool
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Page 86 and 87: Table 3-3 Concurrent update termino
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Page 90 and 91: Setting efix state to: STABLE +----
Page 92 and 93: mode, storage keys are called user
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Page 132 and 133: 3. Interval probe manager The inter
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Non-fragments 00000066 Promotions 0
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immediately after the returned stor
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This option should be used with car
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3.9.6 KDB commands for XMDBG ► xm
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Name AIX version Hardware required
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Online resources These Web sites ar
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sysdumpdev 27 tprof 28 trace 28 trc
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subsequent reboot 71, 133 SUE 18 Sy
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