Found this problem while enabling queued rwlock on SPARC.
The parameter CONFIG_CPU_BIG_ENDIAN is used to clear the
specific byte in qrwlock structure. Without this parameter,
we clear the wrong byte.
Here is the code in include/asm-generic/qrwlock.h
static inline u8 *__qrwlock_write_byte(struct qrwlock *lock)
{
return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);
}
Also found few more references of this parameter in
drivers/of/base.c
drivers/of/fdt.c
drivers/tty/serial/earlycon.c
drivers/tty/serial/serial_core.c
Here is our previous discussion.
https://lkml.org/lkml/2017/5/24/620
Based on the discussion, it was decided to add CONFIG_CPU_BIG_ENDIAN
for all the fixed big endian architecture(frv, h8300, m68k, openrisc,
parisc and sparc). And warn if there are inconsistencies in this definition.
v1 -> v2:
Updated the commit messages and acks.
Babu Moger (2):
arch: Define CPU_BIG_ENDIAN for all fixed big endian archs
include: warn for inconsistent endian config definition
arch/frv/Kconfig | 3 +++
arch/h8300/Kconfig | 3 +++
arch/m68k/Kconfig | 3 +++
arch/openrisc/Kconfig | 3 +++
arch/parisc/Kconfig | 3 +++
arch/sparc/Kconfig | 3 +++
include/linux/byteorder/big_endian.h | 4 ++++
include/linux/byteorder/little_endian.h | 4 ++++
8 files changed, 26 insertions(+), 0 deletions(-)
While working on enabling queued rwlock on SPARC, found
this following code in include/asm-generic/qrwlock.h
which uses CONFIG_CPU_BIG_ENDIAN to clear a byte.
static inline u8 *__qrwlock_write_byte(struct qrwlock *lock)
{
return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);
}
Problem is many of the fixed big endian architectures don't define
CPU_BIG_ENDIAN and clears the wrong byte.
Define CPU_BIG_ENDIAN for all the fixed big endian architecture to fix it.
Also found few more references of this config parameter in
drivers/of/base.c
drivers/of/fdt.c
drivers/tty/serial/earlycon.c
drivers/tty/serial/serial_core.c
Be aware that this may cause regressions if someone has worked-around
problems in the above code already. Remove the work-around.
Here is our original discussion
https://lkml.org/lkml/2017/5/24/620
Signed-off-by: Babu Moger <[email protected]>
Suggested-by: Arnd Bergmann <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>
Acked-by: David S. Miller <[email protected]>
---
arch/frv/Kconfig | 3 +++
arch/h8300/Kconfig | 3 +++
arch/m68k/Kconfig | 3 +++
arch/openrisc/Kconfig | 3 +++
arch/parisc/Kconfig | 3 +++
arch/sparc/Kconfig | 3 +++
6 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/arch/frv/Kconfig b/arch/frv/Kconfig
index eefd9a4..1cce824 100644
--- a/arch/frv/Kconfig
+++ b/arch/frv/Kconfig
@@ -17,6 +17,9 @@ config FRV
select HAVE_DEBUG_STACKOVERFLOW
select ARCH_NO_COHERENT_DMA_MMAP
+config CPU_BIG_ENDIAN
+ def_bool y
+
config ZONE_DMA
bool
default y
diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig
index 3ae8525..5380ac8 100644
--- a/arch/h8300/Kconfig
+++ b/arch/h8300/Kconfig
@@ -23,6 +23,9 @@ config H8300
select HAVE_ARCH_HASH
select CPU_NO_EFFICIENT_FFS
+config CPU_BIG_ENDIAN
+ def_bool y
+
config RWSEM_GENERIC_SPINLOCK
def_bool y
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index d140206..029a58b 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -23,6 +23,9 @@ config M68K
select OLD_SIGSUSPEND3
select OLD_SIGACTION
+config CPU_BIG_ENDIAN
+ def_bool y
+
config RWSEM_GENERIC_SPINLOCK
bool
default y
diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index 1e95920..a0f2e4a 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -29,6 +29,9 @@ config OPENRISC
select CPU_NO_EFFICIENT_FFS if !OPENRISC_HAVE_INST_FF1
select NO_BOOTMEM
+config CPU_BIG_ENDIAN
+ def_bool y
+
config MMU
def_bool y
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 531da9e..dda1f55 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -47,6 +47,9 @@ config PARISC
and later HP3000 series). The PA-RISC Linux project home page is
at <http://www.parisc-linux.org/>.
+config CPU_BIG_ENDIAN
+ def_bool y
+
config MMU
def_bool y
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 58243b0..eb213b5 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -92,6 +92,9 @@ config ARCH_DEFCONFIG
config ARCH_PROC_KCORE_TEXT
def_bool y
+config CPU_BIG_ENDIAN
+ def_bool y
+
config ARCH_ATU
bool
default y if SPARC64
--
1.7.1
We have seen some generic code use config parameter CONFIG_CPU_BIG_ENDIAN
to decide the endianness.
Here are the few examples.
include/asm-generic/qrwlock.h
drivers/of/base.c
drivers/of/fdt.c
drivers/tty/serial/earlycon.c
drivers/tty/serial/serial_core.c
Display warning if CPU_BIG_ENDIAN is not defined on big endian
architecture and also warn if it defined on little endian architectures.
Here is our original discussion
https://lkml.org/lkml/2017/5/24/620
Signed-off-by: Babu Moger <[email protected]>
Suggested-by: Arnd Bergmann <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>
---
include/linux/byteorder/big_endian.h | 4 ++++
include/linux/byteorder/little_endian.h | 4 ++++
2 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/include/linux/byteorder/big_endian.h b/include/linux/byteorder/big_endian.h
index 3920414..ffd2159 100644
--- a/include/linux/byteorder/big_endian.h
+++ b/include/linux/byteorder/big_endian.h
@@ -3,5 +3,9 @@
#include <uapi/linux/byteorder/big_endian.h>
+#ifndef CONFIG_CPU_BIG_ENDIAN
+#warning inconsistent configuration, needs CONFIG_CPU_BIG_ENDIAN
+#endif
+
#include <linux/byteorder/generic.h>
#endif /* _LINUX_BYTEORDER_BIG_ENDIAN_H */
diff --git a/include/linux/byteorder/little_endian.h b/include/linux/byteorder/little_endian.h
index 0805737..ba910bb 100644
--- a/include/linux/byteorder/little_endian.h
+++ b/include/linux/byteorder/little_endian.h
@@ -3,5 +3,9 @@
#include <uapi/linux/byteorder/little_endian.h>
+#ifdef CONFIG_CPU_BIG_ENDIAN
+#warning inconsistent configuration, CONFIG_CPU_BIG_ENDIAN is set
+#endif
+
#include <linux/byteorder/generic.h>
#endif /* _LINUX_BYTEORDER_LITTLE_ENDIAN_H */
--
1.7.1
On Fri, Jun 09, 2017 at 12:48:06PM -0700, Babu Moger wrote:
> While working on enabling queued rwlock on SPARC, found
> this following code in include/asm-generic/qrwlock.h
> which uses CONFIG_CPU_BIG_ENDIAN to clear a byte.
>
> static inline u8 *__qrwlock_write_byte(struct qrwlock *lock)
> {
> return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);
> }
>
> Problem is many of the fixed big endian architectures don't define
> CPU_BIG_ENDIAN and clears the wrong byte.
>
> Define CPU_BIG_ENDIAN for all the fixed big endian architecture to fix it.
>
> Also found few more references of this config parameter in
> drivers/of/base.c
> drivers/of/fdt.c
> drivers/tty/serial/earlycon.c
> drivers/tty/serial/serial_core.c
> Be aware that this may cause regressions if someone has worked-around
> problems in the above code already. Remove the work-around.
>
> Here is our original discussion
> https://lkml.org/lkml/2017/5/24/620
>
> Signed-off-by: Babu Moger <[email protected]>
> Suggested-by: Arnd Bergmann <[email protected]>
> Acked-by: Geert Uytterhoeven <[email protected]>
> Acked-by: David S. Miller <[email protected]>
> ---
> arch/frv/Kconfig | 3 +++
> arch/h8300/Kconfig | 3 +++
> arch/m68k/Kconfig | 3 +++
> arch/openrisc/Kconfig | 3 +++
> arch/parisc/Kconfig | 3 +++
> arch/sparc/Kconfig | 3 +++
> 6 files changed, 18 insertions(+), 0 deletions(-)
>
> diff --git a/arch/frv/Kconfig b/arch/frv/Kconfig
> index eefd9a4..1cce824 100644
> --- a/arch/frv/Kconfig
> +++ b/arch/frv/Kconfig
> @@ -17,6 +17,9 @@ config FRV
> select HAVE_DEBUG_STACKOVERFLOW
> select ARCH_NO_COHERENT_DMA_MMAP
>
> +config CPU_BIG_ENDIAN
> + def_bool y
> +
> config ZONE_DMA
> bool
> default y
> diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig
> index 3ae8525..5380ac8 100644
> --- a/arch/h8300/Kconfig
> +++ b/arch/h8300/Kconfig
> @@ -23,6 +23,9 @@ config H8300
> select HAVE_ARCH_HASH
> select CPU_NO_EFFICIENT_FFS
>
> +config CPU_BIG_ENDIAN
> + def_bool y
> +
> config RWSEM_GENERIC_SPINLOCK
> def_bool y
>
> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> index d140206..029a58b 100644
> --- a/arch/m68k/Kconfig
> +++ b/arch/m68k/Kconfig
> @@ -23,6 +23,9 @@ config M68K
> select OLD_SIGSUSPEND3
> select OLD_SIGACTION
>
> +config CPU_BIG_ENDIAN
> + def_bool y
> +
> config RWSEM_GENERIC_SPINLOCK
> bool
> default y
> diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
> index 1e95920..a0f2e4a 100644
> --- a/arch/openrisc/Kconfig
> +++ b/arch/openrisc/Kconfig
> @@ -29,6 +29,9 @@ config OPENRISC
> select CPU_NO_EFFICIENT_FFS if !OPENRISC_HAVE_INST_FF1
> select NO_BOOTMEM
>
> +config CPU_BIG_ENDIAN
> + def_bool y
> +
Acked-by: Stafford Horne <[email protected]>
I actually have this patch in my SMP branch [0] I am working on. It would
be good to get this in, I have heard verious complaints about bugs with
endianness and mmio with OpenRISC but have not been able to look into it.
This might be related as well.
[0] https://github.com/stffrdhrn/linux/commit/2cc4b90eca865c54b87b8f59e523c131f30fc9ac
> config MMU
> def_bool y
>
> diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
> index 531da9e..dda1f55 100644
> --- a/arch/parisc/Kconfig
> +++ b/arch/parisc/Kconfig
> @@ -47,6 +47,9 @@ config PARISC
> and later HP3000 series). The PA-RISC Linux project home page is
> at <http://www.parisc-linux.org/>.
>
> +config CPU_BIG_ENDIAN
> + def_bool y
> +
> config MMU
> def_bool y
>
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 58243b0..eb213b5 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -92,6 +92,9 @@ config ARCH_DEFCONFIG
> config ARCH_PROC_KCORE_TEXT
> def_bool y
>
> +config CPU_BIG_ENDIAN
> + def_bool y
> +
> config ARCH_ATU
> bool
> default y if SPARC64
> --
> 1.7.1
>