Re: [PATCH v2] arm: Add unwinding support for division functions
From: Dave Martin
Date: Thu May 19 2011 - 07:10:54 EST
On Wed, May 18, 2011 at 10:33:26AM -0700, Laura Abbott wrote:
> The software division functions never had unwinding annotations
> added. Currently, when a division by zero occurs the backtrace shown
> will stop at Ldiv0 or some completely unrelated function. Add
> unwinding annotations in hopes of getting a more useful backtrace
> when a division by zero occurs.
>
> Signed-off-by: Laura Abbott <lauraa@xxxxxxxxxxxxxx>
> ---
> arch/arm/lib/lib1funcs.S | 25 ++++++++++++++++++++-----
> 1 files changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/lib/lib1funcs.S b/arch/arm/lib/lib1funcs.S
> index 6dc0648..c562f64 100644
> --- a/arch/arm/lib/lib1funcs.S
> +++ b/arch/arm/lib/lib1funcs.S
> @@ -35,7 +35,7 @@ Boston, MA 02111-1307, USA. */
>
> #include <linux/linkage.h>
> #include <asm/assembler.h>
> -
> +#include <asm/unwind.h>
>
> .macro ARM_DIV_BODY dividend, divisor, result, curbit
>
> @@ -207,6 +207,7 @@ Boston, MA 02111-1307, USA. */
>
> ENTRY(__udivsi3)
> ENTRY(__aeabi_uidiv)
> +UNWIND(.fnstart)
>
> subs r2, r1, #1
> moveq pc, lr
> @@ -230,10 +231,12 @@ ENTRY(__aeabi_uidiv)
> mov r0, r0, lsr r2
> mov pc, lr
>
> +UNWIND(.fnend)
> ENDPROC(__udivsi3)
> ENDPROC(__aeabi_uidiv)
>
> ENTRY(__umodsi3)
> +UNWIND(.fnstart)
>
> subs r2, r1, #1 @ compare divisor with 1
> bcc Ldiv0
> @@ -247,10 +250,12 @@ ENTRY(__umodsi3)
>
> mov pc, lr
>
> +UNWIND(.fnend)
> ENDPROC(__umodsi3)
>
> ENTRY(__divsi3)
> ENTRY(__aeabi_idiv)
> +UNWIND(.fnstart)
>
> cmp r1, #0
> eor ip, r0, r1 @ save the sign of the result.
> @@ -287,10 +292,12 @@ ENTRY(__aeabi_idiv)
> rsbmi r0, r0, #0
> mov pc, lr
>
> +UNWIND(.fnend)
> ENDPROC(__divsi3)
> ENDPROC(__aeabi_idiv)
>
> ENTRY(__modsi3)
> +UNWIND(.fnstart)
>
> cmp r1, #0
> beq Ldiv0
> @@ -310,11 +317,14 @@ ENTRY(__modsi3)
> rsbmi r0, r0, #0
> mov pc, lr
>
> +UNWIND(.fnend)
> ENDPROC(__modsi3)
>
> #ifdef CONFIG_AEABI
>
> ENTRY(__aeabi_uidivmod)
> +UNWIND(.fnstart)
> +UNWIND(.save {r0, r1, ip, lr} )
>
> stmfd sp!, {r0, r1, ip, lr}
> bl __aeabi_uidiv
> @@ -323,10 +333,12 @@ ENTRY(__aeabi_uidivmod)
> sub r1, r1, r3
> mov pc, lr
>
> +UNWIND(.fnend)
> ENDPROC(__aeabi_uidivmod)
>
> ENTRY(__aeabi_idivmod)
> -
> +UNWIND(.fnstart)
> +UNWIND(.save {r0, r1, ip, lr} )
> stmfd sp!, {r0, r1, ip, lr}
> bl __aeabi_idiv
> ldmfd sp!, {r1, r2, ip, lr}
> @@ -334,15 +346,18 @@ ENTRY(__aeabi_idivmod)
> sub r1, r1, r3
> mov pc, lr
>
> +UNWIND(.fnend)
> ENDPROC(__aeabi_idivmod)
>
> #endif
>
> Ldiv0:
> -
> +UNWIND(.fnstart)
> +UNWIND(.pad #4)
> +UNWIND(.save {lr})
> str lr, [sp, #-8]!
> bl __div0
> mov r0, #0 @ About as wrong as it could be.
> ldr pc, [sp], #8
> -
> -
> +UNWIND(.fnend)
> +ENDPROC(Ldiv0)
> --
> 1.7.3.3
>
OK, that looks good to me.
Tested with CONFIG_THUMB2_KERNEL on omap4.
Acked-by: Dave Martin <dave.martin@xxxxxxxxxx>
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