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[PATCH v2 0/2] Define CPU_BIG_ENDIAN or warn for inconsistencies

Started byBabu Moger <babu.moger@oracle.com>
First post2017-06-09 21:50 +0200
Last post2017-06-09 22:00 +0200
Articles 4 — 2 participants

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  [PATCH v2 0/2] Define CPU_BIG_ENDIAN or warn for inconsistencies Babu Moger <babu.moger@oracle.com> - 2017-06-09 21:50 +0200
    [PATCH v2 1/2] arch: Define CPU_BIG_ENDIAN for all fixed big endian archs Babu Moger <babu.moger@oracle.com> - 2017-06-09 22:00 +0200
      Re: [PATCH v2 1/2] arch: Define CPU_BIG_ENDIAN for all fixed big  endian archs Stafford Horne <shorne@gmail.com> - 2017-06-10 10:30 +0200
    [PATCH v2 2/2] include: warn for inconsistent endian config definition Babu Moger <babu.moger@oracle.com> - 2017-06-09 22:00 +0200

#1662712 — [PATCH v2 0/2] Define CPU_BIG_ENDIAN or warn for inconsistencies

FromBabu Moger <babu.moger@oracle.com>
Date2017-06-09 21:50 +0200
Subject[PATCH v2 0/2] Define CPU_BIG_ENDIAN or warn for inconsistencies
Message-ID<tQy4W-5Fa-11@gated-at.bofh.it>
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(-)

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#1662715 — [PATCH v2 1/2] arch: Define CPU_BIG_ENDIAN for all fixed big endian archs

FromBabu Moger <babu.moger@oracle.com>
Date2017-06-09 22:00 +0200
Subject[PATCH v2 1/2] arch: Define CPU_BIG_ENDIAN for all fixed big endian archs
Message-ID<tQyeB-5Jz-9@gated-at.bofh.it>
In reply to#1662712
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 <babu.moger@oracle.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: David S. Miller <davem@davemloft.net>
---
 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

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#1662902 — Re: [PATCH v2 1/2] arch: Define CPU_BIG_ENDIAN for all fixed big endian archs

FromStafford Horne <shorne@gmail.com>
Date2017-06-10 10:30 +0200
SubjectRe: [PATCH v2 1/2] arch: Define CPU_BIG_ENDIAN for all fixed big endian archs
Message-ID<tQJWq-4Hc-5@gated-at.bofh.it>
In reply to#1662715
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 <babu.moger@oracle.com>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Acked-by: David S. Miller <davem@davemloft.net>
> ---
>  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 <shorne@gmail.com>

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
>

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#1662716 — [PATCH v2 2/2] include: warn for inconsistent endian config definition

FromBabu Moger <babu.moger@oracle.com>
Date2017-06-09 22:00 +0200
Subject[PATCH v2 2/2] include: warn for inconsistent endian config definition
Message-ID<tQyeB-5Jz-11@gated-at.bofh.it>
In reply to#1662712
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 <babu.moger@oracle.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 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

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