[PATCH] [RESEND] mtd: only use __xipram annotation when XIP_KERNEL is set

[PATCH] [RESEND] mtd: only use __xipram annotation when XIP_KERNEL is set

[Arnd Bergmann]

When XIP_KERNEL is enabled, some functions are defined in the .data
ELF section because we require them to be in RAM whenever we communicate
with the flash chip. However this causes problems when FTRACE is
enabled and gcc emits calls to __gnu_mcount_nc in the function
prolog:

drivers/built-in.o: In function `cfi_chip_setup':
:(.data+0x272fc): relocation truncated to fit: R_ARM_CALL against symbol `__gnu_mcount_nc' defined in .text section in arch/arm/kernel/built-in.o
drivers/built-in.o: In function `cfi_probe_chip':
:(.data+0x27de8): relocation truncated to fit: R_ARM_CALL against symbol `__gnu_mcount_nc' defined in .text section in arch/arm/kernel/built-in.o
/tmp/ccY172rP.s: Assembler messages:
/tmp/ccY172rP.s:70: Warning: ignoring changed section attributes for .data
/tmp/ccY172rP.s: Error: 1 warning, treating warnings as errors
make[5]: *** [drivers/mtd/chips/cfi_probe.o] Error 1
/tmp/ccK4rjeO.s: Assembler messages:
/tmp/ccK4rjeO.s:421: Warning: ignoring changed section attributes for .data
/tmp/ccK4rjeO.s: Error: 1 warning, treating warnings as errors
make[5]: *** [drivers/mtd/chips/cfi_util.o] Error 1
/tmp/ccUvhCYR.s: Assembler messages:
/tmp/ccUvhCYR.s:1895: Warning: ignoring changed section attributes for .data
/tmp/ccUvhCYR.s: Error: 1 warning, treating warnings as errors

Specifically, this does not work because the .data section is not
marked executable, which leads LD to not generate trampolines for
long calls.

This moves the __xipram functions into their own .xiptext section instead.
The section is still placed next to .data and located in RAM but is marked
executable, which avoids the build errors.

Also, we only need to place the XIP functions into a separate section
if both CONFIG_XIP_KERNEL and CONFIG_MTD_XIP are set: When only MTD_XIP
is used, the whole kernel is still in RAM and we do not need to worry
about pulling out the rug under it. When only XIP_KERNEL but not MTD_XIP
is set, the kernel is in some form of ROM, but we never write to it.

Note that MTD_XIP has been broken on ARM since around 2011 or 2012. I
have sent another patch[2] to fix compilation, which I plan to merge
through arm-soc unless there are objections. The obvious alternative
to that would be to completely rip out the MTD_XIP support from the
kernel, since obviously nobody has been using it in a long while.

Link: [1] https://patchwork.kernel.org/patch/8109771/
Link: [2] https://patchwork.kernel.org/patch/9855225/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 include/asm-generic/vmlinux.lds.h |  1 +
 include/linux/mtd/xip.h           | 10 ++++++----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index da0be9a8d1de..ff507c178327 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -203,6 +203,7 @@
  * pull in .data..stuff which has its own requirements. Same for bss.
  */
 #define DATA_DATA							\
+	*(.xiptext)							\
 	*(.data .data.[0-9a-zA-Z_]*)					\
 	*(.ref.data)							\
 	*(.data..shared_aligned) /* percpu related */			\
diff --git a/include/linux/mtd/xip.h b/include/linux/mtd/xip.h
index abed4dec5c2f..e373690cce0a 100644
--- a/include/linux/mtd/xip.h
+++ b/include/linux/mtd/xip.h
@@ -30,7 +30,9 @@
  * obviously not be running from flash.  The __xipram is therefore marking
  * those functions so they get relocated to ram.
  */
-#define __xipram noinline __attribute__ ((__section__ (".data")))
+#ifdef CONFIG_XIP_KERNEL
+#define __xipram noinline __attribute__ ((__section__ (".xiptext")))
+#endif
 
 /*
  * Each architecture has to provide the following macros.  They must access
@@ -90,10 +92,10 @@
 #define xip_cpu_idle()  do { } while (0)
 #endif
 
-#else
+#endif /* CONFIG_MTD_XIP */
 
+#ifndef __xipram
 #define __xipram
-
-#endif /* CONFIG_MTD_XIP */
+#endif
 
 #endif /* __LINUX_MTD_XIP_H__ */
-- 
2.9.0

Re: [PATCH] [RESEND] mtd: only use __xipram annotation when XIP_KERNEL is set

[Boris Brezillon]

On Fri, 21 Jul 2017 22:26:25 +0200
Arnd Bergmann <arnd@arndb.de> wrote:

> When XIP_KERNEL is enabled, some functions are defined in the .data
> ELF section because we require them to be in RAM whenever we communicate
> with the flash chip. However this causes problems when FTRACE is
> enabled and gcc emits calls to __gnu_mcount_nc in the function
> prolog:
> 
> drivers/built-in.o: In function `cfi_chip_setup':
> :(.data+0x272fc): relocation truncated to fit: R_ARM_CALL against symbol `__gnu_mcount_nc' defined in .text section in arch/arm/kernel/built-in.o
> drivers/built-in.o: In function `cfi_probe_chip':
> :(.data+0x27de8): relocation truncated to fit: R_ARM_CALL against symbol `__gnu_mcount_nc' defined in .text section in arch/arm/kernel/built-in.o
> /tmp/ccY172rP.s: Assembler messages:
> /tmp/ccY172rP.s:70: Warning: ignoring changed section attributes for .data
> /tmp/ccY172rP.s: Error: 1 warning, treating warnings as errors
> make[5]: *** [drivers/mtd/chips/cfi_probe.o] Error 1
> /tmp/ccK4rjeO.s: Assembler messages:
> /tmp/ccK4rjeO.s:421: Warning: ignoring changed section attributes for .data
> /tmp/ccK4rjeO.s: Error: 1 warning, treating warnings as errors
> make[5]: *** [drivers/mtd/chips/cfi_util.o] Error 1
> /tmp/ccUvhCYR.s: Assembler messages:
> /tmp/ccUvhCYR.s:1895: Warning: ignoring changed section attributes for .data
> /tmp/ccUvhCYR.s: Error: 1 warning, treating warnings as errors
> 
> Specifically, this does not work because the .data section is not
> marked executable, which leads LD to not generate trampolines for
> long calls.
> 
> This moves the __xipram functions into their own .xiptext section instead.
> The section is still placed next to .data and located in RAM but is marked
> executable, which avoids the build errors.
> 
> Also, we only need to place the XIP functions into a separate section
> if both CONFIG_XIP_KERNEL and CONFIG_MTD_XIP are set: When only MTD_XIP
> is used, the whole kernel is still in RAM and we do not need to worry
> about pulling out the rug under it. When only XIP_KERNEL but not MTD_XIP
> is set, the kernel is in some form of ROM, but we never write to it.
> 
> Note that MTD_XIP has been broken on ARM since around 2011 or 2012. I
> have sent another patch[2] to fix compilation, which I plan to merge
> through arm-soc unless there are objections. The obvious alternative
> to that would be to completely rip out the MTD_XIP support from the
> kernel, since obviously nobody has been using it in a long while.
> 
> Link: [1] https://patchwork.kernel.org/patch/8109771/
> Link: [2] https://patchwork.kernel.org/patch/9855225/
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  include/asm-generic/vmlinux.lds.h |  1 +
>  include/linux/mtd/xip.h           | 10 ++++++----

For the MTD part,

Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>

>  2 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index da0be9a8d1de..ff507c178327 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -203,6 +203,7 @@
>   * pull in .data..stuff which has its own requirements. Same for bss.
>   */
>  #define DATA_DATA							\
> +	*(.xiptext)							\
>  	*(.data .data.[0-9a-zA-Z_]*)					\
>  	*(.ref.data)							\
>  	*(.data..shared_aligned) /* percpu related */			\
> diff --git a/include/linux/mtd/xip.h b/include/linux/mtd/xip.h
> index abed4dec5c2f..e373690cce0a 100644
> --- a/include/linux/mtd/xip.h
> +++ b/include/linux/mtd/xip.h
> @@ -30,7 +30,9 @@
>   * obviously not be running from flash.  The __xipram is therefore marking
>   * those functions so they get relocated to ram.
>   */
> -#define __xipram noinline __attribute__ ((__section__ (".data")))
> +#ifdef CONFIG_XIP_KERNEL
> +#define __xipram noinline __attribute__ ((__section__ (".xiptext")))
> +#endif
>  
>  /*
>   * Each architecture has to provide the following macros.  They must access
> @@ -90,10 +92,10 @@
>  #define xip_cpu_idle()  do { } while (0)
>  #endif
>  
> -#else
> +#endif /* CONFIG_MTD_XIP */
>  
> +#ifndef __xipram
>  #define __xipram
> -
> -#endif /* CONFIG_MTD_XIP */
> +#endif
>  
>  #endif /* __LINUX_MTD_XIP_H__ */

Re: [PATCH] [RESEND] mtd: only use __xipram annotation when XIP_KERNEL is set

[Arnd Bergmann]

On Fri, Aug 4, 2017 at 9:35 AM, Boris Brezillon
<boris.brezillon@free-electrons.com> wrote:
> On Fri, 21 Jul 2017 22:26:25 +0200
> Arnd Bergmann <arnd@arndb.de> wrote:

>> Note that MTD_XIP has been broken on ARM since around 2011 or 2012. I
>> have sent another patch[2] to fix compilation, which I plan to merge
>> through arm-soc unless there are objections. The obvious alternative
>> to that would be to completely rip out the MTD_XIP support from the
>> kernel, since obviously nobody has been using it in a long while.
>>
>> Link: [1] https://patchwork.kernel.org/patch/8109771/
>> Link: [2] https://patchwork.kernel.org/patch/9855225/
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> ---
>>  include/asm-generic/vmlinux.lds.h |  1 +
>>  include/linux/mtd/xip.h           | 10 ++++++----
>
> For the MTD part,
>
> Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>

Thanks. If you don't mind, could you just apply the patch to the mtd tree?

      Arnd

Re: [PATCH] [RESEND] mtd: only use __xipram annotation when XIP_KERNEL is set

[Boris Brezillon]

On Fri, 4 Aug 2017 11:00:05 +0200
Arnd Bergmann <arnd@arndb.de> wrote:

> On Fri, Aug 4, 2017 at 9:35 AM, Boris Brezillon
> <boris.brezillon@free-electrons.com> wrote:
> > On Fri, 21 Jul 2017 22:26:25 +0200
> > Arnd Bergmann <arnd@arndb.de> wrote:  
> 
> >> Note that MTD_XIP has been broken on ARM since around 2011 or 2012. I
> >> have sent another patch[2] to fix compilation, which I plan to merge
> >> through arm-soc unless there are objections. The obvious alternative
> >> to that would be to completely rip out the MTD_XIP support from the
> >> kernel, since obviously nobody has been using it in a long while.
> >>
> >> Link: [1] https://patchwork.kernel.org/patch/8109771/
> >> Link: [2] https://patchwork.kernel.org/patch/9855225/
> >> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> >> ---
> >>  include/asm-generic/vmlinux.lds.h |  1 +
> >>  include/linux/mtd/xip.h           | 10 ++++++----  
> >
> > For the MTD part,
> >
> > Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>  
> 
> Thanks. If you don't mind, could you just apply the patch to the mtd tree?

Sure. I'll let Brian apply it.

Re: [PATCH] [RESEND] mtd: only use __xipram annotation when XIP_KERNEL is set

[Boris Brezillon]

Le Fri, 4 Aug 2017 11:00:05 +0200,
Arnd Bergmann <arnd@arndb.de> a écrit :

> On Fri, Aug 4, 2017 at 9:35 AM, Boris Brezillon
> <boris.brezillon@free-electrons.com> wrote:
> > On Fri, 21 Jul 2017 22:26:25 +0200
> > Arnd Bergmann <arnd@arndb.de> wrote:  
> 
> >> Note that MTD_XIP has been broken on ARM since around 2011 or 2012. I
> >> have sent another patch[2] to fix compilation, which I plan to merge
> >> through arm-soc unless there are objections. The obvious alternative
> >> to that would be to completely rip out the MTD_XIP support from the
> >> kernel, since obviously nobody has been using it in a long while.
> >>
> >> Link: [1] https://patchwork.kernel.org/patch/8109771/
> >> Link: [2] https://patchwork.kernel.org/patch/9855225/
> >> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> >> ---
> >>  include/asm-generic/vmlinux.lds.h |  1 +
> >>  include/linux/mtd/xip.h           | 10 ++++++----  
> >
> > For the MTD part,
> >
> > Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>  
> 
> Thanks. If you don't mind, could you just apply the patch to the mtd tree?

Applied to l2-mtd/master.

Thanks,

Boris

> 
>       Arnd