* arch/s390/lib/uaccess_pt.c: Missing breaks: ?
@ 2013-04-14 6:06 Joe Perches
2013-04-15 5:48 ` Heiko Carstens
0 siblings, 1 reply; 5+ messages in thread
From: Joe Perches @ 2013-04-14 6:06 UTC (permalink / raw)
To: Heiko Carstens; +Cc: Martin Schwidefsky, linux-s390, LKML
Hello Heiko.
Commit ea81531d ("s390/uaccess: fix page table walk")
added this code. It looks like it should have break;
for each case.
------------
static unsigned long follow_table(struct mm_struct *mm,
unsigned long address, int write)
{
unsigned long *table = (unsigned long *)__pa(mm->pgd);
switch (mm->context.asce_bits & _ASCE_TYPE_MASK) {
case _ASCE_TYPE_REGION1:
table = table + ((address >> 53) & 0x7ff);
if (unlikely(*table & _REGION_ENTRY_INV))
return -0x39UL;
table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
case _ASCE_TYPE_REGION2:
table = table + ((address >> 42) & 0x7ff);
if (unlikely(*table & _REGION_ENTRY_INV))
return -0x3aUL;
table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
case _ASCE_TYPE_REGION3:
table = table + ((address >> 31) & 0x7ff);
if (unlikely(*table & _REGION_ENTRY_INV))
return -0x3bUL;
table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
case _ASCE_TYPE_SEGMENT:
table = table + ((address >> 20) & 0x7ff);
if (unlikely(*table & _SEGMENT_ENTRY_INV))
return -0x10UL;
if (unlikely(*table & _SEGMENT_ENTRY_LARGE)) {
if (write && (*table & _SEGMENT_ENTRY_RO))
return -0x04UL;
return (*table & _SEGMENT_ENTRY_ORIGIN_LARGE) +
(address & ~_SEGMENT_ENTRY_ORIGIN_LARGE);
}
table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN);
}
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: arch/s390/lib/uaccess_pt.c: Missing breaks: ?
2013-04-14 6:06 arch/s390/lib/uaccess_pt.c: Missing breaks: ? Joe Perches
@ 2013-04-15 5:48 ` Heiko Carstens
2013-04-15 5:53 ` Joe Perches
0 siblings, 1 reply; 5+ messages in thread
From: Heiko Carstens @ 2013-04-15 5:48 UTC (permalink / raw)
To: Joe Perches; +Cc: Martin Schwidefsky, linux-s390, LKML
On Sat, Apr 13, 2013 at 11:06:14PM -0700, Joe Perches wrote:
> Hello Heiko.
>
> Commit ea81531d ("s390/uaccess: fix page table walk")
> added this code. It looks like it should have break;
> for each case.
Hi Joe,
no, the fallthrough is on purpose for each case statement.
> static unsigned long follow_table(struct mm_struct *mm,
> unsigned long address, int write)
> {
> unsigned long *table = (unsigned long *)__pa(mm->pgd);
>
> switch (mm->context.asce_bits & _ASCE_TYPE_MASK) {
> case _ASCE_TYPE_REGION1:
> table = table + ((address >> 53) & 0x7ff);
> if (unlikely(*table & _REGION_ENTRY_INV))
> return -0x39UL;
> table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
> case _ASCE_TYPE_REGION2:
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: arch/s390/lib/uaccess_pt.c: Missing breaks: ?
2013-04-15 5:48 ` Heiko Carstens
@ 2013-04-15 5:53 ` Joe Perches
2013-04-15 5:58 ` Heiko Carstens
0 siblings, 1 reply; 5+ messages in thread
From: Joe Perches @ 2013-04-15 5:53 UTC (permalink / raw)
To: Heiko Carstens; +Cc: Martin Schwidefsky, linux-s390, LKML
On Mon, 2013-04-15 at 07:48 +0200, Heiko Carstens wrote:
> On Sat, Apr 13, 2013 at 11:06:14PM -0700, Joe Perches wrote:
> > Commit ea81531d ("s390/uaccess: fix page table walk")
> > added this code. It looks like it should have break;
> > for each case.
> no, the fallthrough is on purpose for each case statement.
Hi again. It might be useful to add /* fallthrough */
or some other comment showing it's intentional.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: arch/s390/lib/uaccess_pt.c: Missing breaks: ?
2013-04-15 5:53 ` Joe Perches
@ 2013-04-15 5:58 ` Heiko Carstens
2013-04-15 6:15 ` Joe Perches
0 siblings, 1 reply; 5+ messages in thread
From: Heiko Carstens @ 2013-04-15 5:58 UTC (permalink / raw)
To: Joe Perches; +Cc: Martin Schwidefsky, linux-s390, LKML
On Sun, Apr 14, 2013 at 10:53:27PM -0700, Joe Perches wrote:
> On Mon, 2013-04-15 at 07:48 +0200, Heiko Carstens wrote:
> > On Sat, Apr 13, 2013 at 11:06:14PM -0700, Joe Perches wrote:
> > > Commit ea81531d ("s390/uaccess: fix page table walk")
> > > added this code. It looks like it should have break;
> > > for each case.
> > no, the fallthrough is on purpose for each case statement.
>
> Hi again. It might be useful to add /* fallthrough */
> or some other comment showing it's intentional.
I might add some comment above the function, since for everybody
*knowing* the architecture it's obvious ;) that these must be
fallthroughs.
How did you stuble across this?
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: arch/s390/lib/uaccess_pt.c: Missing breaks: ?
2013-04-15 5:58 ` Heiko Carstens
@ 2013-04-15 6:15 ` Joe Perches
0 siblings, 0 replies; 5+ messages in thread
From: Joe Perches @ 2013-04-15 6:15 UTC (permalink / raw)
To: Heiko Carstens; +Cc: Martin Schwidefsky, linux-s390, LKML
On Mon, 2013-04-15 at 07:58 +0200, Heiko Carstens wrote:
> On Sun, Apr 14, 2013 at 10:53:27PM -0700, Joe Perches wrote:
> > On Mon, 2013-04-15 at 07:48 +0200, Heiko Carstens wrote:
> > > On Sat, Apr 13, 2013 at 11:06:14PM -0700, Joe Perches wrote:
> > > > Commit ea81531d ("s390/uaccess: fix page table walk")
> > > > added this code. It looks like it should have break;
> > > > for each case.
> > > no, the fallthrough is on purpose for each case statement.
> >
> > Hi again. It might be useful to add /* fallthrough */
> > or some other comment showing it's intentional.
>
> I might add some comment above the function, since for everybody
> *knowing* the architecture it's obvious ;) that these must be
> fallthroughs.
> How did you stuble across this?
Tony Prisk sent an patch about a duplicated set of
a variable in a switch/case without a break and I
generalized it and found this and another one in
arch/arm. (the arm one was a real defect)
This one looked like it could be intentional (or not),
but I thought I'd ask.
$ grep-2.5.4 -rP --include=*.[ch] "\b(\w+)\s*=[^;]+;\s*(?:case\s+\w+:|default:)\s*\1\s*=" *
^ permalink raw reply [flat|nested] 5+ messages in thread
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2013-04-14 6:06 arch/s390/lib/uaccess_pt.c: Missing breaks: ? Joe Perches
2013-04-15 5:48 ` Heiko Carstens
2013-04-15 5:53 ` Joe Perches
2013-04-15 5:58 ` Heiko Carstens
2013-04-15 6:15 ` Joe Perches
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