j trap_entry
handle_reset:
- la t0, trap_entry
+ // If misa doesn't exist (or is following an old spec where it has a
+ // different number), skip the next block.
+ la t0, 3f
csrw mtvec, t0
csrwi mstatus, 0
+
+ // make sure these registers exist by seeing if either S or U bits
+ // are set before attempting to zero them out.
+ csrr t1, misa
+ addi t2, x0, 1
+ slli t2, t2, 20 // U_EXTENSION
+ and t2, t1, t2
+ bne x0, t2, 1f
+ addi t2, x0, 1
+ slli t2, t2, 18 // S_EXTENSION
+ and t2, t1, t2
+ bne x0, t2, 1f
+ j 2f
+1:
csrwi mideleg, 0
csrwi medeleg, 0
+2:
csrwi mie, 0
+3:
+ la t0, trap_entry
+ csrw mtvec, t0
+ csrwi mstatus, 0
# initialize global pointer
.option push
addi sp, sp, 32*REGBYTES
mret
+loop_forever:
+ j loop_forever
+
// Fill the stack with data so we can see if it was overrun.
.align 4
stack_bottom:
.fill STACK_SIZE/4, 4, 0x22446688
stack_top:
+ // Prevent stack_top from being identical to next symbol, which may cause gdb
+ // to report we're halted at stack_top which happens to be the same address
+ // as main.
+ .word 0
#endif