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The following crash functions are related to STREAMS.
The following example illustrates the debugging of a line printer. Knowledge of the data structures of the driver is needed for debugging. The example starts with the following data structure of the line printer driver.
struct lp { short lp_flags; queue_t *lp_qptr; /* back pointer to write queue */ }; extern struct lp lp_lp[];The first command,
nm lp_lp
, prints
the value and type for the line printer
driver data structure.
The second command, rd 40275750 20
,
prints 20 values starting from the location
40275750 (note that the rd command
is an alias of od).
The third command, size queue
,
gives the size of the queue structure.
The next two functions again give
the 20 values starting at the specified
locations in the hexadecimal format.
The command rd -c 4032bf40 32
gives
the character representation of the
value in the given location.
The option -x gives a value
in the hexadecimal representation and
the option -a produces the
same in the ASCII format.
/usr/sbin/crash dumpfile - /dev/mem, namelist = /stand/unix, outfile = crash.out> nm lp_lp lp_lp 40275750 bss
> rd 40275750 20 40275750: 00000000 00000000 00000000 40262f60 40275760: 00000000 00000000 00000000 00000000 40275770: 00000000 00000000 00000000 00000000 40275780: 00000000 00000000 00000000 00000000 40275790: 00000000 00000000 00000000 00000000
> size queue 36
> rd 40262f60 20 40262f60: 4017315c 402624a4 4026257c 00000000 40262f70: 00000000 40275758 0200002e 00000200 40262f80: 02000100 00000000 00000000 00000000 40262f90: 00000000 00000000 00000000 00000000 40262fa0: 00000000 00000000 00000000 00000000
> rd 402624a4 20 402624a4: 40262624 00000000 00000000 4032bf40 402624b4: 4032bf5f 40236884 4026233c 00000000 402624c4: 00000000 40331fd9 40331fd9 00000000 402624d4: 00000000 00000000 00000000 4032bf80 402623e4: 4032bf80 40236894 40262564 00000000
> rd -c 4032bf40 32 4032bf40: l i t t l e r e d l i g h t 4042bf50: o n t h e h i g h w a y \n
> rd -x 40262624 20 40252624: 40262594 402624a4 00000000 4032bd40 40262634: 4032bd5f 40236804 00000000 00000000 40262644: 00000000 4030c800 4030c800 402319e4 40262654: 00000000 00000000 00000000 4032be40 40262664: 4032be40 40236844 4026239c 00000000
> rd -a 4032bd40 31 little red light on the highway