linux-kernel - Re: [PATCH] sysfs: add BIN_ATTR

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Message-ID: <7546990b-8060-9451-129a-19aaa856d2e1@linux.vnet.ibm.com>
Date:   Tue, 1 Oct 2019 14:08:53 -0400
From:   Nayna <nayna@...ux.vnet.ibm.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-efi@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Eric Ricther <erichte@...ux.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>, linux-kernel@...r.kernel.org,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Claudio Carvalho <cclaudio@...ux.ibm.com>,
        Matthew Garret <matthew.garret@...ula.com>,
        linuxppc-dev@...abs.org, Paul Mackerras <paulus@...ba.org>,
        Jeremy Kerr <jk@...abs.org>,
        Elaine Palmer <erpalmer@...ibm.com>,
        "Oliver O'Halloran" <oohall@...il.com>,
        linux-integrity@...r.kernel.org,
        George Wilson <gcwilson@...ux.ibm.com>
Subject: Re: [PATCH] sysfs: add BIN_ATTR_WO() macro

Hi Greg,


On 08/26/2019 11:01 AM, Greg Kroah-Hartman wrote:
> This variant was missing from sysfs.h, I guess no one noticed it before.
>
> Turns out the powerpc secure variable code can use it, so add it to the
> tree for it, and potentially others to take advantage of, instead of
> open-coding it.
>
> Reported-by: Nayna Jain <nayna@...ux.ibm.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>
> I'll queue this up to my tree for 5.4-rc1, but if you want to take this
> in your tree earlier, feel free to do so.
>
>   include/linux/sysfs.h | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
> index 965236795750..5420817ed317 100644
> --- a/include/linux/sysfs.h
> +++ b/include/linux/sysfs.h
> @@ -196,6 +196,12 @@ struct bin_attribute {
>   	.size	= _size,						\
>   }
>   
> +#define __BIN_ATTR_WO(_name) {						\
> +	.attr	= { .name = __stringify(_name), .mode = 0200 },		\
> +	.store	= _name##_store,					\
> +	.size	= _size,						\
> +}
> +
>   #define __BIN_ATTR_RW(_name, _size)					\
>   	__BIN_ATTR(_name, 0644, _name##_read, _name##_write, _size)
>   
> @@ -208,6 +214,9 @@ struct bin_attribute bin_attr_##_name = __BIN_ATTR(_name, _mode, _read,	\
>   #define BIN_ATTR_RO(_name, _size)					\
>   struct bin_attribute bin_attr_##_name = __BIN_ATTR_RO(_name, _size)
>   
> +#define BIN_ATTR_WO(_name, _size)					\
> +struct bin_attribute bin_attr_##_name = __BIN_ATTR_WO(_name, _size)
> +
>   #define BIN_ATTR_RW(_name, _size)					\
>   struct bin_attribute bin_attr_##_name = __BIN_ATTR_RW(_name, _size)
>   

I am sorry. I didn't notice it via inspection but there is a bug in this 
macro. When I actually try using it, compilation fails. Here's a likely 
patch:

diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 5420817ed317..fa7ee503fb76 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -196,9 +196,9 @@ struct bin_attribute {
         .size   = _size,                                                \
  }
  
-#define __BIN_ATTR_WO(_name) {                                         \
+#define __BIN_ATTR_WO(_name, _size) {                                  \
         .attr   = { .name = __stringify(_name), .mode = 0200 },         \
-       .store  = _name##_store,                                        \
+       .write  = _name##_write,                                        \
         .size   = _size,                                                \
  }


Thanks & Regards,
     - Nayna