b subcommand

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The b subcommand sets a permanent global breakpoint in the code. KDB kernel debugger checks whether a valid instruction is trapped.

Note: This subcommand is only available within the KDB kernel debugger. It is not included in the kdb command.

Format

b [-p | -v] [ address]

Parameters

Item	Description
-p	Indicates that the breakpoint address is a physical or real address.
-v	Indicates that the breakpoint address is a effective or virtual address.
address	Specifies the address of the breakpoint. This may either be a physical address or a virtual address. Symbols, hexadecimal values, or hexadecimal expressions can be used to specify the address.

If an invalid instruction is detected, a warning message is displayed. If the warning message is displayed, the breakpoint should be removed; otherwise, memory can be corrupted.

Other

brk

Examples

The following example is before VMM setup:

   KDB(0)> b vsi  //set break point on vsi()
   .vsi+000000 (real address:002AA5A4) permanent & global
   KDB(0)> e  //exit debugger
   ...
   Breakpoint
   .vsi+000000     stmw    r29,FFFFFFF4(stkp)  <.mainstk+001EFC> 
   r29=isync_sc1+000040,FFFFFFF4(stkp)=.mainstk+001EFC

The following example is after VMM setup:

   KDB(0)> b  //display current active break points
   No breakpoints are set.
   KDB(0)> b 0  //set break point at address 0
   WARNING: break point at 00000000 on invalid instruction (00000000)
   00000000 (sid:00000000) permanent & global
   KDB(0)> c 0  //remove break point at address 0
   KDB(0)> b vmvcs  //set break point on vmvcs()
   .vmvcs+000000 (sid:00000000) permanent & global
   KDB(0)> b i_disable  //set break point on i_disable()
   .i_disable+000000 (sid:00000000) permanent & global
   KDB(0)> e  //exit debugger
   ...
   Breakpoint
   .i_disable+000000   mfmsr    r7                  <start+001008> r7=DEADBEEF
   KDB(0)> b  //display current active break points
   0:      .vmvcs+000000 (sid:00000000)  permanent & global
   1:      .i_disable+000000 (sid:00000000)  permanent & global
   KDB(0)> c 1  //remove break point slot 1
   KDB(0)> b  //display current active break points
   0:      .vmvcs+000000 (sid:00000000)  permanent & global
   KDB(0)> e  //exit debugger
   ...
   Breakpoint
   .vmvcs+000000    mflr    r10                 <.initcom+000120>
   KDB(0)> ca  //remove all break points