Re: [RESEND PATCH] MIPS: head: Reorder instructions missing a delay slot

[James Hogan]

On Tue, Jun 27, 2017 at 07:22:16PM +0000, Karl Beldan wrote:
> In this sequence the 'move' is assumed in the delay slot of the 'beq',
> but head.S is in reorder mode and the former gets pushed one 'nop'
> farther by the assembler.
> 
> The corrected behavior made booting with an UHI supplied dtb erratic.
> 
> Fixes: 15f37e158892 ("MIPS: store the appended dtb address in a variable")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> Cc: Jonas Gorski <jogo@xxxxxxxxxxx>
> Signed-off-by: Karl Beldan <karl.beldan+oss@xxxxxxxxx>

Ouch, nice catch.

Reviewed-by: James Hogan <james.hogan@xxxxxxxxxx>

Cheers
James

> ---
>  arch/mips/kernel/head.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/mips/kernel/head.S b/arch/mips/kernel/head.S
> index cf05220..d1bb506 100644
> --- a/arch/mips/kernel/head.S
> +++ b/arch/mips/kernel/head.S
> @@ -106,8 +106,8 @@ NESTED(kernel_entry, 16, sp)			# kernel entry point
>  	beq		t0, t1, dtb_found
>  #endif
>  	li		t1, -2
> -	beq		a0, t1, dtb_found
>  	move		t2, a1
> +	beq		a0, t1, dtb_found
>  
>  	li		t2, 0
>  dtb_found:
> -- 
> 2.10.1
> 
>

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