[Buildroot] [PATCH] arch: remove support for BR2_ARC_PAGE_SIZE_4K

[Buildroot] [PATCH] arch: remove support for BR2_ARC_PAGE_SIZE_4K

[Thomas Petazzoni via buildroot]

BR2_ARC_PAGE_SIZE_4K=y is broken with both glibc and uClibc. The link
of the C library fails with:

ld: common page size (0x2000) > maximum page size (0x1000)

This is due to BR2_ARC_PAGE_SIZE_4K=y settings
-Wl,-z,max-page-size=4096, but binutils apparently defaulting to
common-page-size=8192.

While this could potentially be fixed by passing
-Wl,-z,common-page-size=4096, these failures indicates that nobody has
tested 4KB page sizes on ARC in the context of Buildroot, so it is
more sensible to drop support for this feature. Should anybody need
this, and have the ability to ensure that it works, we would certainly
be able to re-introduce the feature.

Fixes:

  http://autobuild.buildroot.net/results/c8b2f331c98453670cd982558144c4fd84674a3d/ (uclibc)
  http://autobuild.buildroot.net/results/3a22f7aac38145b26c549254b819f87329e7a77e/ (glibc)

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
---
 Config.in.legacy   | 7 +++++++
 arch/Config.in.arc | 5 -----
 arch/arch.mk.arc   | 4 +---
 linux/linux.mk     | 4 ----
 4 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/Config.in.legacy b/Config.in.legacy
index 956da10a9f..1590a9fa25 100644
--- a/Config.in.legacy
+++ b/Config.in.legacy
@@ -146,6 +146,13 @@ endif
 
 comment "Legacy options removed in 2022.08"
 
+config BR2_ARC_PAGE_SIZE_4K
+	bool "Support for 4KB pages on ARC removed"
+	select BR2_LEGACY
+	help
+	  The support to use 4KB pages on the ARC architecture has
+	  been removed, as it was broken with both glibc and uClibc.
+
 config BR2_PACKAGE_PHP_EXT_WDDX
 	bool "php wddx removed"
 	select BR2_LEGACY
diff --git a/arch/Config.in.arc b/arch/Config.in.arc
index 388d3496bc..58103ad171 100644
--- a/arch/Config.in.arc
+++ b/arch/Config.in.arc
@@ -103,10 +103,6 @@ choice
 	  size matching the hardware configuration. Otherwise
 	  user-space applications will fail at runtime.
 
-config BR2_ARC_PAGE_SIZE_4K
-	bool "4KB"
-	depends on !BR2_arc750d
-
 config BR2_ARC_PAGE_SIZE_8K
 	bool "8KB"
 	help
@@ -121,7 +117,6 @@ endchoice
 
 config BR2_ARC_PAGE_SIZE
 	string
-	default "4K" if BR2_ARC_PAGE_SIZE_4K
 	default "8K" if BR2_ARC_PAGE_SIZE_8K
 	default "16K" if BR2_ARC_PAGE_SIZE_16K
 
diff --git a/arch/arch.mk.arc b/arch/arch.mk.arc
index 32b818b0e0..697c0ff524 100644
--- a/arch/arch.mk.arc
+++ b/arch/arch.mk.arc
@@ -6,9 +6,7 @@ ARCH_TOOLCHAIN_WRAPPER_OPTS = -matomic
 endif
 
 # Explicitly set LD's "max-page-size" instead of relying on some defaults
-ifeq ($(BR2_ARC_PAGE_SIZE_4K),y)
-ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=4096
-else ifeq ($(BR2_ARC_PAGE_SIZE_8K),y)
+ifeq ($(BR2_ARC_PAGE_SIZE_8K),y)
 ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=8192
 else ifeq ($(BR2_ARC_PAGE_SIZE_16K),y)
 ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=16384
diff --git a/linux/linux.mk b/linux/linux.mk
index 322ccabbd9..f012689a9e 100644
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -362,10 +362,6 @@ define LINUX_KCONFIG_FIXUP_CMDS
 		$(call KCONFIG_ENABLE_OPT,CONFIG_AEABI))
 	$(if $(BR2_powerpc)$(BR2_powerpc64)$(BR2_powerpc64le),
 		$(call KCONFIG_ENABLE_OPT,CONFIG_PPC_DISABLE_WERROR))
-	$(if $(BR2_ARC_PAGE_SIZE_4K),
-		$(call KCONFIG_ENABLE_OPT,CONFIG_ARC_PAGE_SIZE_4K)
-		$(call KCONFIG_DISABLE_OPT,CONFIG_ARC_PAGE_SIZE_8K)
-		$(call KCONFIG_DISABLE_OPT,CONFIG_ARC_PAGE_SIZE_16K))
 	$(if $(BR2_ARC_PAGE_SIZE_8K),
 		$(call KCONFIG_DISABLE_OPT,CONFIG_ARC_PAGE_SIZE_4K)
 		$(call KCONFIG_ENABLE_OPT,CONFIG_ARC_PAGE_SIZE_8K)
-- 
2.36.1

_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

Re: [Buildroot] [arc-buildroot] [PATCH] arch: remove support for BR2_ARC_PAGE_SIZE_4K

[Alexey Brodkin via buildroot]

[-- Attachment #1.1: Type: text/plain, Size: 4975 bytes --]

Hi Thomas,

Please let me take a look at this one.

The point is we do use 4 KiB page for building for the ARCv3 processors,
see https://github.com/foss-for-synopsys-dwc-arc-processors/buildroot/blob/arc64/arch/Config.in.arc#L133.
And so far I haven't seen any problems with either uClibc or glibc.

And since I don't immediately see any changes in Binutils for ARCv3 which touch
"common-page-size", I'd like to figure out what goes wrong here.

I'll get back to you soon with some explanation of what we see here.

-Alexey
________________________________
From: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Sent: Monday, July 18, 2022 12:04 AM
To: buildroot@buildroot.org <buildroot@buildroot.org>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>; ARC Maintainers <arc-buildroot@synopsys.com>
Subject: [arc-buildroot] [PATCH] arch: remove support for BR2_ARC_PAGE_SIZE_4K

BR2_ARC_PAGE_SIZE_4K=y is broken with both glibc and uClibc. The link
of the C library fails with:

ld: common page size (0x2000) > maximum page size (0x1000)

This is due to BR2_ARC_PAGE_SIZE_4K=y settings
-Wl,-z,max-page-size=4096, but binutils apparently defaulting to
common-page-size=8192.

While this could potentially be fixed by passing
-Wl,-z,common-page-size=4096, these failures indicates that nobody has
tested 4KB page sizes on ARC in the context of Buildroot, so it is
more sensible to drop support for this feature. Should anybody need
this, and have the ability to ensure that it works, we would certainly
be able to re-introduce the feature.

Fixes:

  https://urldefense.com/v3/__http://autobuild.buildroot.net/results/c8b2f331c98453670cd982558144c4fd84674a3d/__;!!A4F2R9G_pg!d146KtaYDg9TTYEfT0WXaW0aZMlQQKFLOg2D6B-sBZTaF-Z9vn7WvMcW7awUpJi0eotuvN5Rby7WE8qT-3KSx15eJwata0p_gA$  (uclibc)
  https://urldefense.com/v3/__http://autobuild.buildroot.net/results/3a22f7aac38145b26c549254b819f87329e7a77e/__;!!A4F2R9G_pg!d146KtaYDg9TTYEfT0WXaW0aZMlQQKFLOg2D6B-sBZTaF-Z9vn7WvMcW7awUpJi0eotuvN5Rby7WE8qT-3KSx15eJwbxDr7yig$  (glibc)

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
---
 Config.in.legacy   | 7 +++++++
 arch/Config.in.arc | 5 -----
 arch/arch.mk.arc   | 4 +---
 linux/linux.mk     | 4 ----
 4 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/Config.in.legacy b/Config.in.legacy
index 956da10a9f..1590a9fa25 100644
--- a/Config.in.legacy
+++ b/Config.in.legacy
@@ -146,6 +146,13 @@ endif

 comment "Legacy options removed in 2022.08"

+config BR2_ARC_PAGE_SIZE_4K
+       bool "Support for 4KB pages on ARC removed"
+       select BR2_LEGACY
+       help
+         The support to use 4KB pages on the ARC architecture has
+         been removed, as it was broken with both glibc and uClibc.
+
 config BR2_PACKAGE_PHP_EXT_WDDX
         bool "php wddx removed"
         select BR2_LEGACY
diff --git a/arch/Config.in.arc b/arch/Config.in.arc
index 388d3496bc..58103ad171 100644
--- a/arch/Config.in.arc
+++ b/arch/Config.in.arc
@@ -103,10 +103,6 @@ choice
           size matching the hardware configuration. Otherwise
           user-space applications will fail at runtime.

-config BR2_ARC_PAGE_SIZE_4K
-       bool "4KB"
-       depends on !BR2_arc750d
-
 config BR2_ARC_PAGE_SIZE_8K
         bool "8KB"
         help
@@ -121,7 +117,6 @@ endchoice

 config BR2_ARC_PAGE_SIZE
         string
-       default "4K" if BR2_ARC_PAGE_SIZE_4K
         default "8K" if BR2_ARC_PAGE_SIZE_8K
         default "16K" if BR2_ARC_PAGE_SIZE_16K

diff --git a/arch/arch.mk.arc b/arch/arch.mk.arc
index 32b818b0e0..697c0ff524 100644
--- a/arch/arch.mk.arc
+++ b/arch/arch.mk.arc
@@ -6,9 +6,7 @@ ARCH_TOOLCHAIN_WRAPPER_OPTS = -matomic
 endif

 # Explicitly set LD's "max-page-size" instead of relying on some defaults
-ifeq ($(BR2_ARC_PAGE_SIZE_4K),y)
-ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=4096
-else ifeq ($(BR2_ARC_PAGE_SIZE_8K),y)
+ifeq ($(BR2_ARC_PAGE_SIZE_8K),y)
 ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=8192
 else ifeq ($(BR2_ARC_PAGE_SIZE_16K),y)
 ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=16384
diff --git a/linux/linux.mk b/linux/linux.mk
index 322ccabbd9..f012689a9e 100644
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -362,10 +362,6 @@ define LINUX_KCONFIG_FIXUP_CMDS
                 $(call KCONFIG_ENABLE_OPT,CONFIG_AEABI))
         $(if $(BR2_powerpc)$(BR2_powerpc64)$(BR2_powerpc64le),
                 $(call KCONFIG_ENABLE_OPT,CONFIG_PPC_DISABLE_WERROR))
-       $(if $(BR2_ARC_PAGE_SIZE_4K),
-               $(call KCONFIG_ENABLE_OPT,CONFIG_ARC_PAGE_SIZE_4K)
-               $(call KCONFIG_DISABLE_OPT,CONFIG_ARC_PAGE_SIZE_8K)
-               $(call KCONFIG_DISABLE_OPT,CONFIG_ARC_PAGE_SIZE_16K))
         $(if $(BR2_ARC_PAGE_SIZE_8K),
                 $(call KCONFIG_DISABLE_OPT,CONFIG_ARC_PAGE_SIZE_4K)
                 $(call KCONFIG_ENABLE_OPT,CONFIG_ARC_PAGE_SIZE_8K)
--
2.36.1


[-- Attachment #1.2: Type: text/html, Size: 9974 bytes --]

[-- Attachment #2: Type: text/plain, Size: 150 bytes --]

_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

Re: [Buildroot] [arc-buildroot] [PATCH] arch: remove support for BR2_ARC_PAGE_SIZE_4K

[Thomas Petazzoni via buildroot]

Hello Alexey,

On Sun, 17 Jul 2022 21:13:08 +0000
Alexey Brodkin <Alexey.Brodkin@synopsys.com> wrote:

> Please let me take a look at this one.
> 
> The point is we do use 4 KiB page for building for the ARCv3 processors,
> see https://github.com/foss-for-synopsys-dwc-arc-processors/buildroot/blob/arc64/arch/Config.in.arc#L133.
> And so far I haven't seen any problems with either uClibc or glibc.
> 
> And since I don't immediately see any changes in Binutils for ARCv3 which touch
> "common-page-size", I'd like to figure out what goes wrong here.
> 
> I'll get back to you soon with some explanation of what we see here.

Thanks for your feedback. Will definitely wait to hear from you before
merging this patch.

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

Re: [Buildroot] [arc-buildroot] [PATCH] arch: remove support for BR2_ARC_PAGE_SIZE_4K

[Alexey Brodkin via buildroot]

Hi Thomas, Claudiu,
 
> On Sun, 17 Jul 2022 21:13:08 +0000
> Alexey Brodkin <Alexey.Brodkin@synopsys.com> wrote:
> 
> > Please let me take a look at this one.
> > 
> > The point is we do use 4 KiB page for building for the ARCv3 processors,
> > see https://urldefense.com/v3/__https://github.com/foss-for-synopsys-dwc-arc-processors/buildroot/blob/arc64/arch/Config.in.arc*L133__;Iw!!A4F2R9G_pg!cxR1QodBjZ2_XZsfTSe3ThcFYm_X7BN7ERYq6smx9IqcZZUrUzXD2gEF1R_oFrKNb0SrguAeGg-kt6hFvkHhbcQpTs3QXHvksOs$ .
> > And so far I haven't seen any problems with either uClibc or glibc.
> > 
> > And since I don't immediately see any changes in Binutils for ARCv3 which touch
> > "common-page-size", I'd like to figure out what goes wrong here.
> > 
> > I'll get back to you soon with some explanation of what we see here.
> 
> Thanks for your feedback. Will definitely wait to hear from you before
> merging this patch.

So that seems to be a good catch indeed.

1. In older GNU LD such a check doesn't exist and so LD never craps out.
   And here I mean the latest ARC Binutils ("arc-2020.09-release"), which are based
   on upstream v2.35. Thus if building with 4KiB pages but ARC Binutils,
   the problem is not seen. I'm sure even built that way binaries work perfectly
   fine as I do remember trying it not that long ago myself.
   
   BTW that pre-defined "common-page-size" comes from GCC actually, see
   https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/arc/linux.h;h=0f1ff055be757ad1483910fc4918e7fef7fe4d5e;hb=1ea978e3066ac565a1ec28a96a4d61eaf38e2726#l48
   
2. And in case of building for ARCv3 processors we don't mess with "page-size"
   stuff in the "LINK_SPEC", see https://github.com/foss-for-synopsys-dwc-arc-processors/gcc/blob/arc64/gcc/config/arc64/linux32.h#L26

That said I'd like to get our GCC & Binutils maintainer input on what needs
to be done with these "page-size" options in the "LINK_SPEC".

Maybe with use of up-to-date Binutils those default values are no longer needed?
Or we may keep default "max" value and then not explicitly set outside "common"
value will be adjusted as needed automatically.

See https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=ld/ldelf.c;h=bfa0d54753ad8a7de02b4bae999119588ef982c6;hb=refs/heads/master#l90

-Alexey
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

Re: [Buildroot] [arc-buildroot] [PATCH] arch: remove support for BR2_ARC_PAGE_SIZE_4K

[Thomas Petazzoni via buildroot]

Hello Alexey,

On Tue, 19 Jul 2022 18:20:25 +0000
Alexey Brodkin via buildroot <buildroot@buildroot.org> wrote:

> So that seems to be a good catch indeed.
> 
> 1. In older GNU LD such a check doesn't exist and so LD never craps out.
>    And here I mean the latest ARC Binutils ("arc-2020.09-release"), which are based
>    on upstream v2.35. Thus if building with 4KiB pages but ARC Binutils,
>    the problem is not seen. I'm sure even built that way binaries work perfectly
>    fine as I do remember trying it not that long ago myself.
>    
>    BTW that pre-defined "common-page-size" comes from GCC actually, see
>    https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/arc/linux.h;h=0f1ff055be757ad1483910fc4918e7fef7fe4d5e;hb=1ea978e3066ac565a1ec28a96a4d61eaf38e2726#l48

OK.

> 2. And in case of building for ARCv3 processors we don't mess with "page-size"
>    stuff in the "LINK_SPEC", see https://github.com/foss-for-synopsys-dwc-arc-processors/gcc/blob/arc64/gcc/config/arc64/linux32.h#L26

OK, but I don't really see the relationship.

> That said I'd like to get our GCC & Binutils maintainer input on what needs
> to be done with these "page-size" options in the "LINK_SPEC".
> 
> Maybe with use of up-to-date Binutils those default values are no longer needed?

Why no longer needed? Of course is you change the page size, you need
to pass some options to the linker so that it can place sections and
define load addresses (and other related stuff) accordingly.

> Or we may keep default "max" value and then not explicitly set outside "common"
> value will be adjusted as needed automatically.

I don't understand what you mean here. Today, we are setting
max-page-size, and that doesn't work because the common-page-size value
is higher. As I mentioned in my initial patch, passing
-Wl,-z,max-page-size=4096 (already done) and
-Wl,-z,common-page-size=4096 would most likely fix the error, but I
wasn't sure it was the correct thing to do.

Do you have more feedback from your GCC and binutils maintainer perhaps?

Thanks a lot!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

Re: [Buildroot] [arc-buildroot] [PATCH] arch: remove support for BR2_ARC_PAGE_SIZE_4K

[Thomas Petazzoni via buildroot]

Hello,

Re-adding Buildroot mailing list in Cc.

On Thu, 28 Jul 2022 20:25:47 +0000
Alexey Brodkin <Alexey.Brodkin@synopsys.com> wrote:

> > I don't understand what you mean here. Today, we are setting
> > max-page-size, and that doesn't work because the common-page-size value
> > is higher. As I mentioned in my initial patch, passing
> > -Wl,-z,max-page-size=4096 (already done) and
> > -Wl,-z,common-page-size=4096 would most likely fix the error, but I
> > wasn't sure it was the correct thing to do.  
> 
> So, right, suggested change of explicit setup of "common-page-size=max-page-size"
> is a good fix as it is compatible with older Binutils (before the change
> referred above, i.e. before 2.38).

Could you provide the patch?

Keep in mind that this block of code:

# Explicitly set LD's "max-page-size" instead of relying on some defaults
ifeq ($(BR2_ARC_PAGE_SIZE_4K)$(BR2_ARM64_PAGE_SIZE_4K),y)
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=4096
else ifeq ($(BR2_ARC_PAGE_SIZE_8K),y)
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=8192
else ifeq ($(BR2_ARC_PAGE_SIZE_16K),y)
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=16384
else ifeq ($(BR2_ARM64_PAGE_SIZE_64K),y)
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=65536
endif

in arch/arch.mk, has been recently modified to be used for configurable
page sizes on ARM64. So, if we decide to add
-Wl,-z,common-page-size=XYZ, it also needs to work for ARM64 (I think
it should, but I just want to warn that this code is no longer
ARC-specific).

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

Re: [Buildroot] [arc-buildroot] [PATCH] arch: remove support for BR2_ARC_PAGE_SIZE_4K

[Thomas Petazzoni via buildroot]

Hello Alexey,

On Wed, 3 Aug 2022 19:22:29 +0200
Thomas Petazzoni <thomas.petazzoni@bootlin.com> wrote:

> > So, right, suggested change of explicit setup of "common-page-size=max-page-size"
> > is a good fix as it is compatible with older Binutils (before the change
> > referred above, i.e. before 2.38).  
> 
> Could you provide the patch?
> 
> Keep in mind that this block of code:
> 
> # Explicitly set LD's "max-page-size" instead of relying on some defaults
> ifeq ($(BR2_ARC_PAGE_SIZE_4K)$(BR2_ARM64_PAGE_SIZE_4K),y)
> ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=4096
> else ifeq ($(BR2_ARC_PAGE_SIZE_8K),y)
> ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=8192
> else ifeq ($(BR2_ARC_PAGE_SIZE_16K),y)
> ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=16384
> else ifeq ($(BR2_ARM64_PAGE_SIZE_64K),y)
> ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=65536
> endif
> 
> in arch/arch.mk, has been recently modified to be used for configurable
> page sizes on ARM64. So, if we decide to add
> -Wl,-z,common-page-size=XYZ, it also needs to work for ARM64 (I think
> it should, but I just want to warn that this code is no longer
> ARC-specific).

Do you think you will be able to provide a patch to fix support for 4K
page size support on ARC in Buildroot?

It is not really a major feature of Buildroot, and it's causing some
build failures in our autobuilders, so if no fix is provided, we'll
probably end up dropping support, as proposed by my patch posted on
July 17.

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot