Breakpoints

In kadb(1M), breakpoints can be set. When reached, the kernel will automatically drop back into kadb. The standard form of a breakpoint command is:

    [module_name#] addr [, count]:b [command]

addr is the address at which the program will be stopped and the debugger will receive control, count is the number of times that the breakpoint address occurs before stopping, and command is almost any adb(1) command.

The optional module_name specifies deferred breakpoints that are set when the module is loaded. module_name identifies a particular module that contains addr. If the module has been loaded, kadb will try to set a regular breakpoint; if the module is not loaded, kadb will set a deferred breakpoint. When the module is loaded, kadb will try to resolve the location of the breakpoint and convert the breakpoint to a regular breakpoint.

Other breakpoint commands are:

The following example sets a breakpoint in scsi_transport(9F), a commonly used routine. Upon reaching the breakpoint, '$c' is used to print a stack trace. The top of the stack is displayed first. Note that kadb does not know how many arguments were passed to each function.

stopped at      edd000d8:       ta      %icc,%g0 + 125
kadb[0]: scsi_transport:b
kadb[0]: :c
test console login: root
breakpoint at:
scsi_transport: save    %sp, -0x60, %sp
kadb[0]: $c
scsi_transport(702bb578,1000,1,10000,0,702bb7fe)
sdstrategy(1019c8c0,702bb61c,0,0,702bb578,70cad7b8) + 704
bdev_strategy(1042a808,70cad7b8,705f3efc,40,10597900,2000) + 98
ufs_getpage_miss(70cad7b8,0,10597900,0,0,4023ba8c) + 2b0
ufs_getpage(0,0,0,0,2000,4023ba8c) + 7c0
segvn_fault(4023ba8c,2000,ff3b0000,0,0,0) + 7c8
as_fault(1,ff3b0000,70d98030,2000,0,ff3b0000) + 49c
pagefault(0,0,70df8048,705c7450,0,ff3b0000) + 4c
trap(10080,10000,ff3c4ea4,70df8048,ff3b0000,1) + db4
kadb[0]: $b
breakpoints
count   bkpt            type      len   command
1       scsi_transport  :b instr  4
kadb[0]: scsi_transport:d
kadb[0]: :c