AIX Version 4.3 Differences Guide

2.4.1 Dump Support
You can now use the dump interface, through a dump table, to dump specified
memory using a real address without requiring the real address to have virtual
address mapping.
To support dumping real memory using a real address, a new data structure, and
a new magic number, DMP_MAGIC_REAL, has been defined. The following are
modified to check for the magic number and handle the new table format:
• savecore.c
• copydump.c
savecore() and copycore() check for both DMP_MAGIC and DMP_MAGIC_REAL
and are able to process either of the dump table formats.
When displaying the data for a dump table, crash and dmpfmt use an address
format that distinguishes real addresses from virtual addresses. A real address
can be entered on a crash subcommand as r:address. For example:
> od r:10012
2.4.2 Programming Interface
When dump is initialized, it allocates one page from the pinned heap. It also gets
the real address for this page. When dumping memory referenced by a virtual
address, dump will do the following for each page (or page segment) to be
copied:
1. Turn data translation off
2. Copy the data to the buffer at the real address
3. Turn data translation back on
4. Dump the data
This retrieves the data in real mode while calling the device driver code in virtual
mode.
Note: Only one page will be dumped at a time.
The external dump interfaces are found in /usr/include/sys/dump.h, and new
structures have been defined in this file. In the dumpinfo structure, dm_hostip
becomes __ulong32_t. The structures dump_read and dumpio_stat are defined
for the kernel and extensions only.
2.5 Bad Block Relocation during System Dump (4.3.1)
In previous versions of AIX, if the LVM detected a bad block and received an I/O
error while processing a system dump, the dump was aborted if no secondary
dump device was available. In AIX Version 4.3.1, the LVM will now try to relocate
the bad block so that processing of the system dump can continue and
information is not lost.
2.6 Kernel Protection
Memory overlays are extremely destructive and, in certain cases, can destroy the
kernel's ability to respond to interrupts, making it impossible to obtain a dump. A
AIX Kernel Enhancements 17