4.3BSD-Reno/share/man/cat4/kadb.0

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KADB(4)                       1988			  KADB(4)



NNAAMMEE
     kdb - kernel debugging facility

SSYYNNOOPPSSIISS
     ooppttiioonnss KKAADDBB

DDEESSCCRRIIPPTTIIOONN
     _K_d_b is a debugging facility for the kernel based on _a_d_b(1).
     _K_d_b may be used to symbolically examine and modify memory
     locations, set breakpoints, and single step the system.

     Several boot time options are used in conjunction with the
     debugger.	To ``enable'' the debugger, the system must be
     booted with the RB_KDB flag (0x40) specified in the
     _b_o_o_t_h_o_w_t_o register.  When the debugger is enabled the system
     will read in and initialize the symbol table from the booted
     system.  If the RB_HALT flag (0x08) is also specified, the
     system will enter the debugger at the earliest possible time
     to allow breakpoints to be set before the system starts
     operation.  From that point on, if the RB_NOSYNC flag (0x04)
     is set, typing ``^[k'', ``^[K'', or ``^[^K'' at the console
     causes a trap into the debugger.

     _K_d_b supports most of the _a_d_b command language.  The output
     formats `f', `F', `Y', are not supported.	The address space
     maps do not exist, thus the `/m', `?m', and `$m' commands do
     not exist.  Shell escapes and command files are not sup-
     ported.  The `:r' and `:k' commands make no sense and are
     not recognized.  Finally, the signal arguments to the con-
     tinue and single step commands are ignored.

NNOOTTEESS
     _K_d_b normally runs at a priority level below the interrupt
     level of the clock and all devices; the level of the highest
     priority software interrupt.  If the debugger is entered on
     the kernel's per-process stack at an ipl below its normal
     operating level it automatically switches to the interrupt
     stack to avoid potential overflow of the kernel stack.
     Should the debugger operate on the kernel stack the message
     ``(on kernel stack)'' will be printed on entry.

     Note also that because _k_d_b use input from the console to
     force entry to the debugger it may not be possible to force
     entry if the system hangs at a priority level higher than
     the console receiver interrupt.

SSEEEE AALLSSOO
     adb(1)







Printed 7/27/90              August				1