mr subcommand

The mr subcommand modifies general purpose, segment, special, or floating point registers.

Format

mr [gp | sr | sp | fp | reg_name]

Parameters

Item	Description
gp	Modifies general purpose registers.
sr	Modifies segment registers.
sp	Modifies special purpose registers.
fp	Modifies floating point registers.
reg_name	Modifies a specific register by name.

Individual registers can also be selected for modification by register name. The current thread context is used to locate the register values to be modified. Use the sw subcommand to change the context to other threads. When the register being modified is in the mst subcommand context, the KDB kernel debugger alters the Machine Save State Area. When the register being modified is a special register, the register is altered immediately. Symbolic expressions are allowed as input.

If the gp, sr, sp, or fp options are used, modification of all of the registers in the group is allowed. The current value for a single register is shown and modification is allowed. Then, the value for the next register is displayed for modification. Entry of an invalid character, such as a period (.), ends modification of the registers. If the value for a register is to be left unmodified, press Enter to continue to the next register for modification.

Other

No aliases.

Examples

The following is an example of how to use the mr subcommand:

   KDB(0)> dc @iar  //print current instruction
   .open+000000    mflr    r0
   KDB(0)> mr iar  //modify current instruction address
   iar : 001C5BA0 = @iar+4
   KDB(0)> dc @iar  //print current instruction
   .open+000004     stw    r31,FFFFFFFC(stkp)
   KDB(0)> mr iar  //restore current instruction address
   iar : 001C5BA4 = @iar-4
   KDB(0)> dc @iar  //print current instruction
   .open+000000    mflr    r0
   KDB(0)> mr sr  //modify first invalid segment register
   s0  : 00000000 = <CR/LF>
   s1  : 60000323 = <CR/LF>
   s2  : 20001E1E = <CR/LF>
   s3  : 007FFFFF = 0
   s4  : 007FFFFF = .  //end of input
   KDB(0)> dr s3  //print segment register 3
   s3  : 00000000
   KDB(0)> mr s3  //restore segment register 3
   s3  : 00000000 = 007FFFFF
   KDB(0)> mr f29  //modify floating point register f29
   f29 : 0000000000000000 = 000333335999999A
   KDB(1)> mr vr0 //modify vector register vr0
   vr0 : 00000000000000000000000000000000 = 1122334455667788 <CR/LF>
    = 99aabbccddeeff00
   KDB(0)> dr f29
   f29 : 000333335999999A
   KDB(1)> dr vr0 //dump vector register vr0
   vr0 : 112233445566778899AABBCCDDEEFF00
   KDB(0)> u
   Uthread [2FF3B400]:
      save@......2FF3B400   fpr@.......2FF3B550
   ...
   KDB(0)> dd 2FF3B550 20
   __ublock+000150: C027C28F5C28F5C3 000333335999999A  .'..\(....33Y...
   __ublock+000160: 3FE3333333333333 3FC9999999999999  ?.333333?.......
   __ublock+000170: 7FF0000000000000 00100000C0000000  ................
   __ublock+000180: 4000000000000000 000000009A068000  @...............
   __ublock+000190: 7FF8000000000000 00000000BA411000  .............A..
   __ublock+0001A0: 0000000000000000 0000000000000000  ................
   __ublock+0001B0: 0000000000000000 0000000000000000  ................
   __ublock+0001C0: 0000000000000000 0000000000000000  ................
   __ublock+0001D0: 0000000000000000 0000000000000000  ................
   __ublock+0001E0: 0000000000000000 0000000000000000  ................
   __ublock+0001F0: 0000000000000000 0000000000000000  ................
   __ublock+000200: 0000000000000000 0000000000000000  ................
   __ublock+000210: 0000000000000000 0000000000000000  ................
   __ublock+000220: 0000000000000000 0000000000000000  ................
   __ublock+000230: 0000000000000000 000333335999999A  ..........33Y...
   __ublock+000240: 0000000000000000 0000000000000000  ................
   KDB(0)>

Note: The vr0 register modifies the current vector register contents. The vector register state of the current thread is not modified unless the thread is the current owner of the vector unit. The 16-byte vector input is entered as 8 bytes followed by a carriage return and then followed by 8 bytes.