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| author | Thomas Weißschuh <linux@weissschuh.net> | 2022-11-03 16:24:07 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-11-10 19:07:31 +0100 |
| commit | d3d76fbde1c456a6d19991baa99ea8c2d6e6696f (patch) | |
| tree | 1d8439184733609465b51d19a761613b91f2fe84 /kernel/ksysfs.c | |
| parent | 52c4d11f1dce60453ab2a75fd7103118cedb2b58 (diff) | |
| download | linux-d3d76fbde1c456a6d19991baa99ea8c2d6e6696f.tar.gz linux-d3d76fbde1c456a6d19991baa99ea8c2d6e6696f.tar.bz2 linux-d3d76fbde1c456a6d19991baa99ea8c2d6e6696f.zip | |
kernel/ksysfs.c: export kernel cpu byteorder
Certain files in procfs are formatted in byteorder-dependent formats.
For example the IP addresses in /proc/net/udp.
When using emulation like qemu-user, applications are not guaranteed to
be using the same byteorder as the kernel.
Therefore the kernel needs to provide a way for applications to discover
the byteorder used in API-filesystems.
Using systemcalls is not enough because these are intercepted and
translated by the emulation.
Also this makes it easier for non-compiled applications like
shellscripts to discover the byteorder.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20221103152407.3348-1-linux@weissschuh.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/ksysfs.c')
| -rw-r--r-- | kernel/ksysfs.c | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c index 65dba9076f31..2df00b789b90 100644 --- a/kernel/ksysfs.c +++ b/kernel/ksysfs.c @@ -6,6 +6,7 @@ * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.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 CPU_BYTEORDER_STRING "little" +#elif defined(__BIG_ENDIAN) +#define CPU_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); +/* cpu byteorder */ +static ssize_t cpu_byteorder_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%s\n", CPU_BYTEORDER_STRING); +} +KERNEL_ATTR_RO(cpu_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, + &cpu_byteorder_attr.attr, #ifdef CONFIG_UEVENT_HELPER &uevent_helper_attr.attr, #endif |