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@(#)kdump.1 8.1 (Berkeley) 6/6/93
$FreeBSD: head/usr.bin/kdump/kdump.1 140933 2005-01-28 12:17:33Z gnn $
.Dd January 28, 2005 .Dt KDUMP 1 .Os .Sh NAME .Nm kdump .Nd display kernel trace data .Sh SYNOPSIS .Nm .Op Fl dEnlRT .Op Fl f Ar trfile .Op Fl m Ar maxdata .Op Fl p Ar pid .Op Fl t Op cnisuw .Sh DESCRIPTION The .Nm command displays the kernel trace files produced with .Xr ktrace 1 in human readable format. By default, the file
a ktrace.out in the current directory is displayed.
p The options are as follows: l -tag -width Fl t Fl d Display all numbers in decimal. t Fl E Display elapsed timestamps (time since beginning of trace). t Fl f Ar trfile Display the specified file instead of
a ktrace.out . t Fl l Loop reading the trace file, once the end-of-file is reached, waiting for more data. t Fl m Ar maxdata Display at most .Ar maxdata bytes when decoding .Tn I/O . t Fl n Suppress ad hoc translations. Normally .Nm tries to decode many system calls into a more human readable format. For example, .Xr ioctl 2 values are replaced with the macro name and .Va errno values are replaced with the .Xr strerror 3 string. Suppressing this feature yields a more consistent output format and is easily amenable to further processing. t Fl p Ar pid Display only trace events that correspond to the process .Ar pid . This may be useful when there are multiple processes recorded in the same trace file. t Fl R Display relative timestamps (time since previous entry). t Fl T Display absolute timestamps for each entry (seconds since epoch). t Fl t Ar cnisuw See the .Fl t option of .Xr ktrace 1 . .El
p The output format of .Nm is line oriented with several fields. The example below shows a section of a kdump generated by the following commands: d -literal -offset indent ?> ktrace echo "ktrace" ?> kdump 85045 echo CALL writev(0x1,0x804b030,0x2) 85045 echo GIO fd 1 wrote 7 bytes "ktrace " 85045 echo RET writev 7 .Ed
p The first field is the PID of the process being traced. The second field is the name of the program being traced. The third field is the operation that the kernel performed on behalf of the process.
p In the first line above, the kernel executes the .Xr writev 2 system call on behalf of the process so this is a .Li CALL operation. The fourth field shows the system call that was executed, including its arguments. The .Xr writev 2 system call takes a file descriptor, in this case 1, or standard output, then a pointer to the iovector to write, and the number of iovectors that are to be written. In the second line we see the operation was .Li GIO , for general I/O, and that file descriptor 1 had seven bytes written to it. This is followed by the seven bytes that were written, the string .Qq Li ktrace with a carriage return and line feed. The last line is the .Li RET operation, showing a return from the kernel, what system call we are returning from, and the return value that the process received. Seven bytes were written by the .Xr writev 2 system call, so 7 is the return value.
p The possible operations are: l -column -offset indent ".Li GENIO" ".No data from user process" t Sy Name Ta Sy Operation Ta Sy Fourth field t Li CALL Ta enter syscall Ta syscall name and arguments t Li RET Ta return from syscall Ta syscall name and return value t Li NAMI Ta file name lookup Ta path to file t Li GENIO Ta general I/O Ta fd, read/write, number of bytes t Li SIG Ta signal Ta signal name, handler, mask, code t Li CSW Ta context switch Ta stop/resume user/kernel t Li USER Ta data from user process Ta the data .El .Sh SEE ALSO .Xr ktrace 1 .Sh HISTORY The .Nm command appeared in x 4.4 .