[PATCH v2] arm: Add unwinding support for division functions

From: Laura Abbott
Date: Wed May 18 2011 - 13:34:28 EST


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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/