[PATCH] powerpc/64: Make VDSO32 track COMPAT on 64-bit

When we added the VDSO32 kconfig symbol, which controls building of
the 32-bit VDSO, we made it depend on CPU_BIG_ENDIAN (for 64-bit).

That was because back then COMPAT was always enabled for 64-bit, so
depending on it would have left the 32-bit VDSO always enabled, which
we didn't want.

But since then we have made COMPAT selectable, and off by default for
ppc64le, so VDSO32 should really depend on that.

For most people this makes no difference, none of the defconfigs
change, it's only if someone is building ppc64le with COMPAT=y, they
will now also get VDSO32. If they've enabled COMPAT in order to run
32-bit binaries they presumably also want the 32-bit VDSO.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 arch/powerpc/platforms/Kconfig.cputype | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 87737ec86d39..a80ad0ef436e 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype

@@ -490,13 +490,12 @@ endmenu
 
 config VDSO32
 	def_bool y
-	depends on PPC32 || CPU_BIG_ENDIAN
+	depends on PPC32 || COMPAT
 	help
 	  This symbol controls whether we build the 32-bit VDSO. We obviously
 	  want to do that if we're building a 32-bit kernel. If we're building
-	  a 64-bit kernel then we only want a 32-bit VDSO if we're building for
-	  big endian. That is because the only little endian configuration we
-	  support is ppc64le which is 64-bit only.
+	  a 64-bit kernel then we only want a 32-bit VDSO if we're also enabling
+	  COMPAT.
 
 choice
 	prompt "Endianness selection"

-- 
2.25.1

Le 08/09/2020 à 14:58, Michael Ellerman a écrit :

When we added the VDSO32 kconfig symbol, which controls building of
the 32-bit VDSO, we made it depend on CPU_BIG_ENDIAN (for 64-bit).

That was because back then COMPAT was always enabled for 64-bit, so
depending on it would have left the 32-bit VDSO always enabled, which
we didn't want.

But since then we have made COMPAT selectable, and off by default for
ppc64le, so VDSO32 should really depend on that.

For most people this makes no difference, none of the defconfigs
change, it's only if someone is building ppc64le with COMPAT=y, they
will now also get VDSO32. If they've enabled COMPAT in order to run
32-bit binaries they presumably also want the 32-bit VDSO.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Reviewed-by: Christophe Leroy <redacted>

Michael, please note that christophe.leroy@c-s.fr is a deprecated 
address that will one day not work anymore. Please use the new one 
whenever possible.

Christophe

Christophe Leroy [off-list ref] writes:

Le 08/09/2020 à 14:58, Michael Ellerman a écrit :

quoted

When we added the VDSO32 kconfig symbol, which controls building of
the 32-bit VDSO, we made it depend on CPU_BIG_ENDIAN (for 64-bit).

That was because back then COMPAT was always enabled for 64-bit, so
depending on it would have left the 32-bit VDSO always enabled, which
we didn't want.

But since then we have made COMPAT selectable, and off by default for
ppc64le, so VDSO32 should really depend on that.

For most people this makes no difference, none of the defconfigs
change, it's only if someone is building ppc64le with COMPAT=y, they
will now also get VDSO32. If they've enabled COMPAT in order to run
32-bit binaries they presumably also want the 32-bit VDSO.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Reviewed-by: Christophe Leroy <redacted>

Michael, please note that christophe.leroy@c-s.fr is a deprecated 
address that will one day not work anymore. Please use the new one 
whenever possible.

OK, I had the old one in my ~/.mailrc, fixed now.

cheers

On Tue, 8 Sep 2020 22:58:50 +1000, Michael Ellerman wrote:

When we added the VDSO32 kconfig symbol, which controls building of
the 32-bit VDSO, we made it depend on CPU_BIG_ENDIAN (for 64-bit).

That was because back then COMPAT was always enabled for 64-bit, so
depending on it would have left the 32-bit VDSO always enabled, which
we didn't want.

[...]

Applied to powerpc/next.

[1/1] powerpc/64: Make VDSO32 track COMPAT on 64-bit
      https://git.kernel.org/powerpc/c/231b232df8f67e7d37af01259c21f2a131c3911e

cheers

* Michael Ellerman [off-list ref] [2020-09-17 21:28:46]:

On Tue, 8 Sep 2020 22:58:50 +1000, Michael Ellerman wrote:

quoted

When we added the VDSO32 kconfig symbol, which controls building of
the 32-bit VDSO, we made it depend on CPU_BIG_ENDIAN (for 64-bit).

That was because back then COMPAT was always enabled for 64-bit, so
depending on it would have left the 32-bit VDSO always enabled, which
we didn't want.

[...]

Applied to powerpc/next.

[1/1] powerpc/64: Make VDSO32 track COMPAT on 64-bit
      https://git.kernel.org/powerpc/c/231b232df8f67e7d37af01259c21f2a131c3911e

cheers

With this commit which is part of powerpc/next and with
/opt/at12.0/bin/gcc --version
gcc (GCC) 8.4.1 20191125 (Advance-Toolchain 12.0-3) [e25f27eea473]
throws up a compile error on a witherspoon/PowerNV with CONFIG_COMPAT.
CONFIG_COMPAT got carried from the distro config. (And looks like most
distros seem to be having this config)

cc1: error: _-m32_ not supported in this configuration
make[4]: *** [arch/powerpc/kernel/vdso32/sigtramp.o] Error 1
make[4]: *** Waiting for unfinished jobs....
cc1: error: _-m32_ not supported in this configuration
make[4]: *** [arch/powerpc/kernel/vdso32/gettimeofday.o] Error 1
make[3]: *** [arch/powerpc/kernel/vdso32] Error 2
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [arch/powerpc/kernel] Error 2
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [arch/powerpc] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [__sub-make] Error 2

I don't seem to be facing with other compilers like "gcc (Ubuntu
7.4.0-1ubuntu1~18.04.1) 7.4.0" and I was able to disable CONFIG_COMPAT and
proceed with the build.

-- 
Thanks and Regards
Srikar Dronamraju

Srikar Dronamraju [off-list ref] writes:

* Michael Ellerman [off-list ref] [2020-09-17 21:28:46]:

quoted

On Tue, 8 Sep 2020 22:58:50 +1000, Michael Ellerman wrote:

quoted

When we added the VDSO32 kconfig symbol, which controls building of
the 32-bit VDSO, we made it depend on CPU_BIG_ENDIAN (for 64-bit).

That was because back then COMPAT was always enabled for 64-bit, so
depending on it would have left the 32-bit VDSO always enabled, which
we didn't want.

[...]

Applied to powerpc/next.

[1/1] powerpc/64: Make VDSO32 track COMPAT on 64-bit
      https://git.kernel.org/powerpc/c/231b232df8f67e7d37af01259c21f2a131c3911e

cheers

With this commit which is part of powerpc/next and with
/opt/at12.0/bin/gcc --version
gcc (GCC) 8.4.1 20191125 (Advance-Toolchain 12.0-3) [e25f27eea473]
throws up a compile error on a witherspoon/PowerNV with CONFIG_COMPAT.
CONFIG_COMPAT got carried from the distro config. (And looks like most
distros seem to be having this config)

This distro config will have it because previously it couldn't be
disabled. But now that it's selectable all LE distros should disable it.

cc1: error: _-m32_ not supported in this configuration
make[4]: *** [arch/powerpc/kernel/vdso32/sigtramp.o] Error 1
make[4]: *** Waiting for unfinished jobs....
cc1: error: _-m32_ not supported in this configuration
make[4]: *** [arch/powerpc/kernel/vdso32/gettimeofday.o] Error 1
make[3]: *** [arch/powerpc/kernel/vdso32] Error 2
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [arch/powerpc/kernel] Error 2
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [arch/powerpc] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [__sub-make] Error 2

I don't seem to be facing with other compilers like "gcc (Ubuntu
7.4.0-1ubuntu1~18.04.1) 7.4.0" and I was able to disable CONFIG_COMPAT and
proceed with the build.

It seems your compiler doesn't support building 32-bit binaries. I'm
pretty sure the kernel.org ones do, or you can just turn off COMPAT.

cheers