[Crash-utility] RFC: string search for crash

Here is a patch to add string search to crash-5.1.1. It requires the my previous patch for the parse_line routine. It searches for the specified strings, and for half or more of the string appearing at the start and end of search blocks (usually pages) in case the string spans a page boundary. It is currently invoked with the -c option to search, as in: crash-5.1.1str> search -k -e 0xffffc90000000000 -c "getty[3895]" ffff880123b54810: :46 getty[3895]: /dev/ttyS1: No such file or dir or crash-5.1.1str> search -k -c -e 0xffffc90000000000 "getty[3895]" ffff880123b54810: :46 getty[3895]: /dev/ttyS1: No such file or dir It reports the found string in 48 chars of context (except at the end of pages), and it reports aligned addresses, so the found string doesn't always appear at the beginning of the context (as in the example above). It could optionally use strncasecmp to do case-insensitive searches. I simplified it :-) by combining the main and tail searches into one loop and added a 10-15% performance degradation somewhere. Here it searches the dump for bugs and danger :-) crash-5.1.1str> search -k -c -e 0xffffc90000000000 "bugs" "danger" ffff8801254c0ff8: ug:Debug ffff880125cd4ff8: ebian/bu ffff880125ec8870: efb: danger danger! Oopsen imminent!..<6>Mode (% ffff880125ec8878: ger danger! Oopsen imminent!..<6>Mode (%dx%d) la ffff880125eee518: ofb: danger danger! Oopsen imminent!..<3>neofb: ffff880125eee520: ger danger! Oopsen imminent!..<3>neofb: neo2200 ffff880125f72000: ger_event....................................... ffff880125fc3560: ice bugs (default = 0, 128kB max transfer = 0x1, The first two hits come because half or more of "bugs" occurred at the end of a page. The next to the last hit is found because the last half of "danger" appears at the beginning of a page. Bob Montgomery