[PATCH v3] MIPS: zboot: head.S clean up

[PATCH v3] MIPS: zboot: head.S clean up

[Jiaxun Yang]

.cprestore is removed as we don't expect Position Independent
zboot ELF.

.noreorder is also removed and rest instructions are massaged
to improve readability.

t9 register is used for indirect jump as MIPS ABI requirement.

start label is removed as it already defined in LEAF.

Reported-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>

--
v2: Remove start label (paul)
---
 arch/mips/boot/compressed/head.S | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/mips/boot/compressed/head.S b/arch/mips/boot/compressed/head.S
index 409cb483a9ff..070b2fbabae4 100644
--- a/arch/mips/boot/compressed/head.S
+++ b/arch/mips/boot/compressed/head.S
@@ -15,10 +15,7 @@
 #include <asm/asm.h>
 #include <asm/regdef.h>
 
-	.set noreorder
-	.cprestore
 	LEAF(start)
-start:
 	/* Save boot rom start args */
 	move	s0, a0
 	move	s1, a1
@@ -35,21 +32,20 @@ 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
-- 
2.30.0

Re: [PATCH v3] MIPS: zboot: head.S clean up

[Huacai Chen]

Reviewed-by: Huacai Chen <chenhuacai@kernel.org>

On Wed, Dec 30, 2020 at 11:49 AM Jiaxun Yang <jiaxun.yang@flygoat.com> wrote:
>
> .cprestore is removed as we don't expect Position Independent
> zboot ELF.
>
> .noreorder is also removed and rest instructions are massaged
> to improve readability.
>
> t9 register is used for indirect jump as MIPS ABI requirement.
>
> start label is removed as it already defined in LEAF.
>
> Reported-by: Paul Cercueil <paul@crapouillou.net>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
>
> --
> v2: Remove start label (paul)
> ---
>  arch/mips/boot/compressed/head.S | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
>
> diff --git a/arch/mips/boot/compressed/head.S b/arch/mips/boot/compressed/head.S
> index 409cb483a9ff..070b2fbabae4 100644
> --- a/arch/mips/boot/compressed/head.S
> +++ b/arch/mips/boot/compressed/head.S
> @@ -15,10 +15,7 @@
>  #include <asm/asm.h>
>  #include <asm/regdef.h>
>
> -       .set noreorder
> -       .cprestore
>         LEAF(start)
> -start:
>         /* Save boot rom start args */
>         move    s0, a0
>         move    s1, a1
> @@ -35,21 +32,20 @@ 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
> --
> 2.30.0
>

Re: [PATCH v3] MIPS: zboot: head.S clean up

[Thomas Bogendoerfer]

On Wed, Dec 30, 2020 at 11:47:22AM +0800, Jiaxun Yang wrote:
> .cprestore is removed as we don't expect Position Independent
> zboot ELF.
> 
> .noreorder is also removed and rest instructions are massaged
> to improve readability.
> 
> t9 register is used for indirect jump as MIPS ABI requirement.
> 
> start label is removed as it already defined in LEAF.
> 
> Reported-by: Paul Cercueil <paul@crapouillou.net>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> 
> --
> v2: Remove start label (paul)
> ---
>  arch/mips/boot/compressed/head.S | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]