Displaying and Changing Registers

Displaying and Changing Registers

symmon(1) provides commands that allow you to display and alter the processor and coprocessor general-purpose registers. To identify a general-purpose register (there are 32 registers, numbered 0 through 31), you can use names such as "r0" or "r31," or you can use the compiler usage names (in some cases, you may need to prepend a "$"). The compiler names and the associated "r" names are listed in Table 10-1.

Processor and Coprocessor General-purpose Registers
Compiler Processor Usage
zero r0 Wired zero
at r1 Assembler temporary
v0 r2 Function value registers
v1 r3
a0 r4 Argument registers
a1 r5
a2 r6
a3 r7
t0 r8 Caller saved registers
t1 r9
t2 r10
t3 r11
t4 r12
t5 r13
t6 r14
t7 r15
s0 r16 Callee saved
s1 r17
s2 r18
s3 r19
s4 r20
s5 r21
s6 r22
s7 r23
t8 r24 Caller saved
t9 r25
k0 r26 Kernel temporary
k1 r27
gp r28 Global pointer
sp r29 Stack pointer
fp/s8 r30 Callee saved
ra r31 Return address

Processor and Coprocessor General-purpose Registers
Compiler	Processor	Usage
zero	r0	Wired zero
at	r1	Assembler temporary
v0	r2	Function value registers
v1	r3
a0	r4	Argument registers
a1	r5
a2	r6
a3	r7
t0	r8	Caller saved registers
t1	r9
t2	r10
t3	r11
t4	r12
t5	r13
t6	r14
t7	r15
s0	r16	Callee saved
s1	r17
s2	r18
s3	r19
s4	r20
s5	r21
s6	r22
s7	r23
t8	r24	Caller saved
t9	r25
k0	r26	Kernel temporary
k1	r27
gp	r28	Global pointer
sp	r29	Stack pointer
fp/s8	r30	Callee saved
ra	r31	Return address

You can refer to special R2000/3000/4000/8000 registers and system coprocessor registers by using the names listed in Table 10-2, Table 10-3, and Table 10-4.

R2000-R4000 Processor and Coprocessor Special Registers
Name R2000/3000/4000 Register
mdlo Mul/div register lower word
mdhi Mul/div register higher word
pc epc Exception PC
sr Status register
cause Cause register
tlbhi entryhi TLB entry hi register
tlblo entrylo TLB entry lo register
badvaddr Bad virtual address
index inx TLB index register
context ctxt Context register
random Random register

R2000-R4000 Processor and Coprocessor Special Registers
Name	R2000/3000/4000 Register
mdlo	Mul/div register lower word
mdhi	Mul/div register higher word
pc epc	Exception PC
sr	Status register
cause	Cause register
tlbhi entryhi	TLB entry hi register
tlblo entrylo	TLB entry lo register
badvaddr	Bad virtual address
index inx	TLB index register
context ctxt	Context register
random	Random register

R4000-only System Coprocessor Registers
Name R4000Series System Coprocessor Register
tlblo0 TLB entrylo0 register
tlblo1 TLB entrylo1 register
pagemask TLB pagemask register
wired TLB wired register
count Timer count register
compare Timer compare register
watchlo WatchLo register
watchhi WatchHi register
ecc Ecc register
cacherr Cache error and status register
errepc Cache ErrorEpc register
taglo Cache tag register
config Configuration register

R4000-only System Coprocessor Registers
Name	R4000Series System Coprocessor Register
tlblo0	TLB entrylo0 register
tlblo1	TLB entrylo1 register
pagemask	TLB pagemask register
wired	TLB wired register
count	Timer count register
compare	Timer compare register
watchlo	WatchLo register
watchhi	WatchHi register
ecc	Ecc register
cacherr	Cache error and status register
errepc	Cache ErrorEpc register
taglo	Cache tag register
config	Configuration register

R8000-only Special Registers
Name R8000 Series Special Register
tlbset TLBset register
(index into a TLB entry's set)
trapbase Trapbase register
(base address of trap vectors)
ubase UBase register
pbase PBase register
gbase GBase register
shiftamt ShiftAmt register
wired Wired register
badpaddr BadPAddr register

R8000-only Special Registers
Name	R8000 Series Special Register
tlbset	TLBset register (index into a TLB entry's set)
trapbase	Trapbase register (base address of trap vectors)
ubase	UBase register
pbase	PBase register
gbase	GBase register
shiftamt	ShiftAmt register
wired	Wired register
badpaddr	BadPAddr register