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SubjectRe: Re:Re: [PATCH] powerpc: Fix a bug in div64 32 if divisor is zero
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>> Yet, I have noticed that there is no checking of 'base' in these functions.
>> But I am not sure how to check is better.As we know that the result is
>> undefined when divisor is zero. It maybe good to print error and dump stack.
>> Let the process to know that the divisor is zero by sending SIGFPE.

> That is now what the PowerPC integer divide insns do: they just leave
> the result undefined (and they can set the overflow flag then, but no
> one uses that).

OK ,So just keep the patch as below. If this patch looks good for you, please
help to review. I will send the new patch later.

Thanks for your reply.

diff --git a/arch/powerpc/boot/div64.S b/arch/powerpc/boot/div64.S
index 4354928ed62e..1d3561cf16fa 100644
--- a/arch/powerpc/boot/div64.S
+++ b/arch/powerpc/boot/div64.S
@@ -13,8 +13,10 @@

.globl __div64_32
.globl __div64_32
__div64_32:
+ cmplwi r4,0 # check if divisor r4 is zero
lwz r5,0(r3) # get the dividend into r5/r6
lwz r6,4(r3)
+ beq 5f # jump to label 5 if r4(divisor) is zero
cmplw r5,r4
li r7,0
li r8,0
@@ -52,7 +54,7 @@ __div64_32:
4: stw r7,0(r3) # return the quotient in *r3
stw r8,4(r3)
mr r3,r6 # return the remainder in r3
- blr
+5: blr # return if divisor r4 is zero

/*
* Extended precision shifts.
diff --git a/arch/powerpc/lib/div64.S b/arch/powerpc/lib/div64.S
index 3d5426e7dcc4..570774d9782d 100644
--- a/arch/powerpc/lib/div64.S
+++ b/arch/powerpc/lib/div64.S
@@ -13,8 +13,10 @@
#include <asm/processor.h>

_GLOBAL(__div64_32)
+ cmplwi r4,0 # check if divisor r4 is zero
lwz r5,0(r3) # get the dividend into r5/r6
lwz r6,4(r3)
+ beq 5f # jump to label 5 if r4(divisor) is zero
cmplw r5,r4
li r7,0
li r8,0
@@ -52,4 +54,4 @@ _GLOBAL(__div64_32)
4: stw r7,0(r3) # return the quotient in *r3
stw r8,4(r3)
mr r3,r6 # return the remainder in r3
- blr
+5: blr # return if divisor r4 is zero
Guohua

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