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openrisc: head: Init r0 to 0 on start

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Originally openrisc spec 0 specified that r0 would be wired to ground.
This is no longer the case.  r0 is not guaranteed to be 0 at init, so we
need to initialize it to 0 before using it.

Also, if we are clearing r0 we cant use r0 to clear itself. Change the
the CLEAR_GPR macro to use movhi for clearing.

Reported-by: Jakob Viketoft <jakob.viketoft@aacmicrotec.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>
This commit is contained in:
Stafford Horne 2017-02-05 18:55:40 +09:00
parent a0eba4f7eb
commit a4d4426635
1 changed files with 4 additions and 1 deletions
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5
arch/openrisc/kernel/head.S
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@ -35,7 +35,7 @@
l.add rd,rd,rs
#define CLEAR_GPR(gpr) \
l.or gpr,r0,r0
l.movhi gpr,0x0
#define LOAD_SYMBOL_2_GPR(gpr,symbol) \
l.movhi gpr,hi(symbol) ;\
@ -443,6 +443,9 @@ _dispatch_do_ipage_fault:
__HEAD
.global _start
_start:
/* Init r0 to zero as per spec */
CLEAR_GPR(r0)
/* save kernel parameters */
l.or r25,r0,r3 /* pointer to fdt */