Re: [PATCH -tip] x86: acpi/sleep.c saved_magic fix overflow

Sam Ravnborg
2009-04-10T19:27:46Z

On Sat, Apr 11, 2009 at 12:46:56AM +0530, Jaswinder Singh Rajput wrote:
> On Fri, 2009-04-10 at 21:13 +0200, Sam Ravnborg wrote:
> > On Fri, Apr 10, 2009 at 07:55:45PM +0200, Pavel Machek wrote:
> > > On Fri 2009-04-10 23:06:55, Jaswinder Singh Rajput wrote:
> > > > Impact: fix overflow
> > >
> > > > Constant 0x123456789abcdef0 is so big for a long.
> > > > So using saved_magic 0x12345678 for both 32 and 64 bit.
> > >
> > > Have you tested the patch? I have feeling that this is tested from
> > > assembly... Plus it is only set to long constant on 64-bit, so I don't
> > > think you are fixing anything. And if your code is correct the
> > > variable is write only...
> >
> > $ git grep saved_magic
> > kernel/acpi/sleep.c: saved_magic = 0x12345678;
> > kernel/acpi/sleep.c: saved_magic = 0x123456789abcdef0;
> > kernel/acpi/sleep.h:extern long saved_magic;
> > kernel/acpi/wakeup_32.S: movl %cs:saved_magic, %eax
> > kernel/acpi/wakeup_32.S:ENTRY(saved_magic) .long 0
> > kernel/acpi/wakeup_64.S: movq saved_magic, %rax
> > kernel/acpi/wakeup_64.S:ENTRY(saved_magic) .quad 0
> >
> >
> > wakeup_32.S:
> > movl %cs:saved_magic, %eax
> > cmpl $0x12345678, %eax
> >
> > wakeup_64.S:
> > movq saved_magic, %rax
> > movq $0x123456789abcdef0, %rdx
> >
> > So patch is obviously bogus.
> >
>
> Sorry, I was confused by this sparse warning on 64 bit box:
>
> CHECK arch/x86/kernel/acpi/sleep.c
> arch/x86/kernel/acpi/sleep.c:107:16: warning: constant 0x123456789abcdef0 is so big it is long
>
> atleast I found problem in sparse ;-)

Sparse tells you that the constant is so big it is long - correct.
So rather than being implicit appending an L would make sparse happy.

So please use the constant 0x123456789abcdef0L and I think sparse is silenced.
And code/functionality is the same.

Sam