Re: [PATCH] MIPS: zboot: head.S clean up

Paul Cercueil
2020-12-21T14:10:47Z

Hi Jiaxun,

Le lun. 21 déc. 2020 à 21:00, Jiaxun Yang <jiaxun.yang@flygoat.com> a
écrit :
> .cprestore is removed as we don't except Position Independent
> zboot ELF.
>
> .noreorder is also removed and rest instructions is massaged
> to improve readability.
>
> t9 register is used to indirect jump as MIPS ABI requirement.
>
> Reported-by: Paul Cercueil <paul@crapouillou.net>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
> arch/mips/boot/compressed/head.S | 17 +++++++----------
> 1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/arch/mips/boot/compressed/head.S
> b/arch/mips/boot/compressed/head.S
> index 409cb483a9ff..977218c90bc8 100644
> --- a/arch/mips/boot/compressed/head.S
> +++ b/arch/mips/boot/compressed/head.S
> @@ -15,8 +15,6 @@
> #include <asm/asm.h>
> #include <asm/regdef.h>
>
> - .set noreorder
> - .cprestore
> LEAF(start)
> start:

You can also remove the 'start' label, since it's declared inside the
LEAF() macro as well. GNU's assembler won't mind, but LLVM will choke
on that.

Cheers,
-Paul

> /* Save boot rom start args */
> @@ -35,21 +33,20 @@ start:
> PTR_LA a0, (.heap) /* heap address */
> PTR_LA sp, (.stack + 8192) /* stack address */
>
> - PTR_LA ra, 2f
> - PTR_LA k0, decompress_kernel
> - jr k0
> - nop
> + PTR_LA t9, decompress_kernel
> + jalr t9
> +
> 2:
> move a0, s0
> move a1, s1
> move a2, s2
> move a3, s3
> - PTR_LI k0, KERNEL_ENTRY
> - jr k0
> - nop
> + PTR_LI t9, KERNEL_ENTRY
> + jalr t9
> +
> 3:
> b 3b
> - nop
> +
> END(start)
>
> .comm .heap,BOOT_HEAP_SIZE,4
> --
> 2.29.2
>