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Message-Id: <20221101130401.1841-1-linux@weissschuh.net>
Date: Tue, 1 Nov 2022 14:04:01 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: linux-fsdevel@...r.kernel.org
Cc: Thomas Weißschuh <linux@...ssschuh.net>,
linux-kernel@...r.kernel.org, Karel Zak <kzak@...hat.com>,
Masatake YAMATO <yamato@...hat.com>, linux-api@...r.kernel.org,
Greg KH <gregkh@...uxfoundation.org>
Subject: [PATCH v2] proc: add byteorder file
Certain files in procfs are formatted in byteorder dependent ways. For
example the IP addresses in /proc/net/udp.
Assuming the byteorder of the userspace program is not guaranteed to be
correct in the face of emulation as for example with qemu-user.
Also this makes it easier for non-compiled applications like
shellscripts to discover the byteorder.
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
Development of userspace part: https://github.com/util-linux/util-linux/pull/1872
v1: https://lore.kernel.org/lkml/20221101005043.1791-1-linux@weissschuh.net/
v1->v2:
* Move file to /sys/kernel/byteorder
---
.../ABI/testing/sysfs-kernel-byteorder | 12 ++++++++++++
kernel/ksysfs.c | 18 ++++++++++++++++++
2 files changed, 30 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-byteorder
diff --git a/Documentation/ABI/testing/sysfs-kernel-byteorder b/Documentation/ABI/testing/sysfs-kernel-byteorder
new file mode 100644
index 000000000000..4c45016d78ae
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-byteorder
@@ -0,0 +1,12 @@
+What: /sys/kernel/byteorder
+Date: February 2023
+KernelVersion: 6.2
+Contact: linux-fsdevel@...r.kernel.org
+Description:
+ The current endianness of the running kernel.
+
+ Access: Read
+
+ Valid values:
+ "little", "big"
+Users: util-linux
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index 65dba9076f31..7c7cb2c96ac0 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -6,6 +6,7 @@
* Copyright (C) 2004 Kay Sievers <kay.sievers@...y.org>
*/
+#include <asm/byteorder.h>
#include <linux/kobject.h>
#include <linux/string.h>
#include <linux/sysfs.h>
@@ -20,6 +21,14 @@
#include <linux/rcupdate.h> /* rcu_expedited and rcu_normal */
+#if defined(__LITTLE_ENDIAN)
+#define BYTEORDER_STRING "little"
+#elif defined(__BIG_ENDIAN)
+#define BYTEORDER_STRING "big"
+#else
+#error Unknown byteorder
+#endif
+
#define KERNEL_ATTR_RO(_name) \
static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
@@ -34,6 +43,14 @@ static ssize_t uevent_seqnum_show(struct kobject *kobj,
}
KERNEL_ATTR_RO(uevent_seqnum);
+/* kernel byteorder */
+static ssize_t byteorder_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%s\n", BYTEORDER_STRING);
+}
+KERNEL_ATTR_RO(byteorder);
+
#ifdef CONFIG_UEVENT_HELPER
/* uevent helper program, used during early boot */
static ssize_t uevent_helper_show(struct kobject *kobj,
@@ -215,6 +232,7 @@ EXPORT_SYMBOL_GPL(kernel_kobj);
static struct attribute * kernel_attrs[] = {
&fscaps_attr.attr,
&uevent_seqnum_attr.attr,
+ &byteorder_attr.attr,
#ifdef CONFIG_UEVENT_HELPER
&uevent_helper_attr.attr,
#endif
base-commit: 5aaef24b5c6d4246b2cac1be949869fa36577737
--
2.38.1
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