Quoting r. Greg KH <[email protected]>:
> Subject: Re: [PATCH] pci-sysfs: backport fix for 2.6.11.12
>
> On Tue, May 31, 2005 at 07:36:19PM +0300, Michael S. Tsirkin wrote:
> > Greg, before 2.6.12, pci_write_config in pci-sysfs.c was broken, causing
> > incorrect data being written to the configuration register,
> > which in the case of my userspace driver results in system failure.
> >
> > This has been fixed in 2.6.12-rc5:
> >
> > http://www.kernel.org/diff/diffview.cgi?file=%2Fpub%2Flinux%2Fkernel%2Fv2.6%2Ftesting%2Fpatch-2.6.12-rc5.bz2;z=2656
> >
> > Would you please consider merging the fix for 2.6.11.12 as well?
>
> Would you care to split out only the proper part for that fix? There
> are a few different patches in that link above.
Hmm. There's also a new attribute there, that shall wait for 2.6.12.
There was a general cleanup coverting *all* direct uses of char* to
first cast to u8 *, not only in pci_write_config where it triggers
an actual bug. Do you want all that cleanup in?
I can do it, just let me know.
> > Alternatively (since there were multiple other changes in pci-sysfs.c), here's
> > a small patch to fix just this issue.
>
> I don't think this fixes the problem properly. Can you verify it?
I did verify it before sending :), my patch below does fix the problem.
> Also, this is only a 64bit issue, right?
No, unsigned int is 32 bit wide on all platforms with gcc,
char is signed and 8 bit wide on all platforms with gcc.
So if you have a char value with a top bit set:
char c = 0xe0;
then the following holds:
((unsigned int)c) == 0xffffffe0
> What platform are you seeing
> this on?
I use Intel x86_64.
> And, any patch that you want to propose for the -stable releases, needs
> to be sent to the [email protected] email alias.
>
> thanks,
>
> greg k-h
>
Okay, since its small I repost here. Let me know whether you want that or
the bigger cleanup backported 2.6.12.
---
cast from (signed) char to unsigned int in pci_write_config causes the result
to be sign extended, clobbering high bits in the result. Thus:
# setpci -s 07:00.0 14.L=E4
# setpci -s 07:00.0 14.L
ffffffe4
Signed-off-by: Michael S. Tsirkin <[email protected]>
--- linux-2.6.11-openib/drivers/pci/pci-sysfs.c.bad 2005-05-30 13:45:02.000000000 +0300
+++ linux-2.6.11-openib/drivers/pci/pci-sysfs.c 2005-05-30 13:51:39.000000000 +0300
@@ -161,10 +161,10 @@ pci_write_config(struct kobject *kobj, c
}
while (size > 3) {
- unsigned int val = buf[off - init_off];
- val |= (unsigned int) buf[off - init_off + 1] << 8;
- val |= (unsigned int) buf[off - init_off + 2] << 16;
- val |= (unsigned int) buf[off - init_off + 3] << 24;
+ unsigned int val = (u8)buf[off - init_off];
+ val |= (unsigned int)(u8)buf[off - init_off + 1] << 8;
+ val |= (unsigned int)(u8)buf[off - init_off + 2] << 16;
+ val |= (unsigned int)(u8)buf[off - init_off + 3] << 24;
pci_write_config_dword(dev, off, val);
off += 4;
size -= 4;
--
MST - Michael S. Tsirkin
-
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