linux-kernel - Re: [GIT PULL] hash addresses printed with %p

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Date:   Tue, 5 Dec 2017 17:32:57 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     David Laight <David.Laight@...LAB.COM>,
        'Ard Biesheuvel' <ard.biesheuvel@...aro.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Tobin C. Harding" <me@...in.cc>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>
Subject: Re: [GIT PULL] hash addresses printed with %p

On 12/05/17 at 09:52am, Greg Kroah-Hartman wrote:
> On Tue, Dec 05, 2017 at 04:45:37PM +0800, Dave Young wrote:
> > On 12/05/17 at 09:09am, Greg Kroah-Hartman wrote:
> > > On Tue, Dec 05, 2017 at 01:14:34PM +0800, Dave Young wrote:
> > > > On 12/04/17 at 03:00pm, Greg Kroah-Hartman wrote:
> > > > > On Mon, Dec 04, 2017 at 12:51:13PM +0000, David Laight wrote:
> > > > > > From: Ard Biesheuvel
> > > > > > > Sent: 04 December 2017 10:03
> > > > > > ...
> > > > > > > and uses __ATTR_RO() to emit initializers for it. __ATTR() initializes
> > > > > > > the .store member as well, which does not exists, and so it cannot be
> > > > > > > used directly.
> > > > > > > 
> > > > > > > So we should either add a .store member that is always NULL, or we
> > > > > > > should add our own
> > > > > > > 
> > > > > > > #define __ATTR_0400(_name) { \
> > > > > > > .attr = { .name = __stringify(_name), .mode = 0400 }, \
> > > > > > > .show = _name##_show, \
> > > > > > > }
> > > > > > 
> > > > > > What about an __ATTR_RO_MODE(name, mode) that doesn't set the .store member.
> > > > > > Even if the mode allowed write, writes wouldn't happen.
> > > > > 
> > > > > Ah, that might work, could you convert the other users of __ATTR() in
> > > > > the efi code to use it as well?
> > > > 
> > > > $ grep __ATTR * -RI
> > > > efi.c:			__ATTR(systab, 0400, systab_show, NULL);
> > > > efi.c:static struct kobj_attribute efi_attr_fw_vendor = __ATTR_RO(fw_vendor);
> > > > efi.c:static struct kobj_attribute efi_attr_runtime = __ATTR_RO(runtime);
> > > > efi.c:static struct kobj_attribute efi_attr_config_table = __ATTR_RO(config_table);
> > > > efi.c:	__ATTR_RO(fw_platform_size);
> > > > esrt.c:static struct esre_attribute esre_fw_class = __ATTR(fw_class, 0400,
> > > > esrt.c:static struct esre_attribute esre_##name = __ATTR(name, 0400, \
> > > > esrt.c:static struct kobj_attribute esrt_##name = __ATTR(name, 0400, \
> > > > runtime-map.c:static struct map_attribute map_type_attr = __ATTR_RO(type);
> > > > runtime-map.c:static struct map_attribute map_phys_addr_attr   = __ATTR_RO(phys_addr);
> > > > runtime-map.c:static struct map_attribute map_virt_addr_attr  = __ATTR_RO(virt_addr);
> > > > runtime-map.c:static struct map_attribute map_num_pages_attr  = __ATTR_RO(num_pages);
> > > > runtime-map.c:static struct map_attribute map_attribute_attr  = __ATTR_RO(attribute);
> > > > 
> > > > Above is all the __ATTR users for drivers/firmware/efi/*, it makes sense
> > > > to update all __ATTR_RO to __ATTR_RO_MODE, so efi.c, runtime-map.c, and
> > > > drivers/firmware/dmi-sysfs.c can be updated.  But esrt.c __ATTR seems
> > > > not necessary.
> > > > 
> > > > And if so __ATTR_RO_MODE(name, mode) still needs go to sysfs.h.
> > > > 
> > > > I can do it but need confirm, Is this what you prefer?
> > > 
> > > Yes, how about the patch below, it builds for me, haven't done anything
> > > other than that to test it :)
> > 
> > Thanks! Let me do a kexec test and a boot test for esrt.
> > 
> > > 
> > > Also, what's with the multi-line sysfs file systab?  That's really not
> > > allowed, can you please remove it?  Also the first check for !kobj and
> > > !buf is funny, that can never happen.
> > 
> > I thought to do that, but later worried about it will break things:
> > http://lists.infradead.org/pipermail/kexec/2013-December/010759.html
> 
> Heh, I guess I complained about this in the past :)
> 
> So what userspace tool uses it?
> 
> Are these values all exported through sysfs already?  If not, do that
> first.

kexec-tools uses it, ie. SMBIOS/ACPI/ACPI20 which was exported before.
Later we added files out of systab though.

Since there are also other fields like MPS/BOOTINFO/UGA etc I'm not sure
if something else has been using it as well..

> 
> > I also thought to add code comment to avoid future expanding of this
> > file. Maybe we can do this now.
> 
> Please do, but it should be a separate patch.

Ok, will send it and cc you.

> 
> thanks,
> 
> greg k-h

Thanks
Dave