selftests/nolibc: enable qemu-system tests with LLVM builds

[PATCH 2/3] selftests/nolibc: don't pass CC to toplevel Makefile

Posted by Thomas Weißschuh 2 months, 2 weeks ago

The toplevel Makefile is capable of calculating CC from CROSS_COMPILE
and/or ARCH.

Stop passing the unnecessary variable.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 tools/testing/selftests/nolibc/Makefile.nolibc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/nolibc/Makefile.nolibc b/tools/testing/selftests/nolibc/Makefile.nolibc
index 8e7a832ba3f6da3ca0d669b941acd1cf79813a8d..6e6dddaa2e3ed56886cd76c423297648d13027c7 100644
--- a/tools/testing/selftests/nolibc/Makefile.nolibc
+++ b/tools/testing/selftests/nolibc/Makefile.nolibc
@@ -263,7 +263,7 @@ REPORT  ?= awk '/\[OK\][\r]*$$/{p++} /\[FAIL\][\r]*$$/{if (!f) printf("\n"); f++
 		printf("\nSee all results in %s\n", ARGV[1]); }'
 
 # Execute the toplevel kernel Makefile
-KBUILD_MAKE = $(MAKE) -C $(srctree) ARCH=$(ARCH) CC=$(CC) CROSS_COMPILE=$(CROSS_COMPILE)
+KBUILD_MAKE = $(MAKE) -C $(srctree) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE)
 
 help:
 	@echo "Supported targets under selftests/nolibc:"

-- 
2.50.1

Re: [PATCH 2/3] selftests/nolibc: don't pass CC to toplevel Makefile

Posted by Willy Tarreau 2 months, 2 weeks ago

Hi Thomas,

On Sat, Jul 19, 2025 at 05:38:28PM +0200, Thomas Weißschuh wrote:
> The toplevel Makefile is capable of calculating CC from CROSS_COMPILE
> and/or ARCH.
> 
> Stop passing the unnecessary variable.
(...) 
>  # Execute the toplevel kernel Makefile
> -KBUILD_MAKE = $(MAKE) -C $(srctree) ARCH=$(ARCH) CC=$(CC) CROSS_COMPILE=$(CROSS_COMPILE)
> +KBUILD_MAKE = $(MAKE) -C $(srctree) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE)

Here the goal was not to help the toplevel Makefile figure CC, but rather
to permit the user to override it, and it's also listed in "make help",
and even used in cc-option.

I understnad that you're trying to avoid forcing CC to clang when
building, but in this case, what will CROSS_COMPILE contain ?  My
guess is that you intend to make CROSS_COMPILE point to the gcc-based
toolchain, and have CC point to clang for userland only. Is this the
case ? I think I'd be fine with this, but then we need to make it
explicit in the help message and fix the current one, possibly just
with this:

-	@echo "  nolibc-test       build the executable (uses \$$CC and \$$CROSS_COMPILE)"
+	@echo "  nolibc-test       build the executable (uses \$$CC)"
	@echo "  libc-test         build an executable using the compiler's default libc instead"
	@echo "  run-user          runs the executable under QEMU (uses \$$XARCH, \$$TEST)"
	@echo "  initramfs.cpio    prepare the initramfs archive with nolibc-test"
	@echo "  initramfs         prepare the initramfs tree with nolibc-test"
 	@echo "  defconfig         create a fresh new default config (uses \$$XARCH)"
-	@echo "  kernel            (re)build the kernel (uses \$$XARCH)"
+	@echo "  kernel            (re)build the kernel (uses \$$XARCH, \$$CROSS_COMPILE)"

Thanks,
Willy

Re: [PATCH 2/3] selftests/nolibc: don't pass CC to toplevel Makefile

Posted by Thomas Weißschuh 1 month, 2 weeks ago

Hi Willy,

On 2025-07-21 04:56:27+0200, Willy Tarreau wrote:
> On Sat, Jul 19, 2025 at 05:38:28PM +0200, Thomas Weißschuh wrote:
> > The toplevel Makefile is capable of calculating CC from CROSS_COMPILE
> > and/or ARCH.
> > 
> > Stop passing the unnecessary variable.
> (...) 
> >  # Execute the toplevel kernel Makefile
> > -KBUILD_MAKE = $(MAKE) -C $(srctree) ARCH=$(ARCH) CC=$(CC) CROSS_COMPILE=$(CROSS_COMPILE)
> > +KBUILD_MAKE = $(MAKE) -C $(srctree) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE)
> 
> Here the goal was not to help the toplevel Makefile figure CC, but rather
> to permit the user to override it, and it's also listed in "make help",
> and even used in cc-option.
> 
> I understnad that you're trying to avoid forcing CC to clang when
> building, but in this case, what will CROSS_COMPILE contain ?  My
> guess is that you intend to make CROSS_COMPILE point to the gcc-based
> toolchain, and have CC point to clang for userland only. Is this the
> case ?

Correct.

> I think I'd be fine with this, but then we need to make it
> explicit in the help message and fix the current one, possibly just
> with this:
> 
> -	@echo "  nolibc-test       build the executable (uses \$$CC and \$$CROSS_COMPILE)"
> +	@echo "  nolibc-test       build the executable (uses \$$CC)"

I don't think this is correct. $CC itself depends on $CROSS_COMPILE
through tools/scripts/Makefile.include.

> 	@echo "  libc-test         build an executable using the compiler's default libc instead"
> 	@echo "  run-user          runs the executable under QEMU (uses \$$XARCH, \$$TEST)"
> 	@echo "  initramfs.cpio    prepare the initramfs archive with nolibc-test"
> 	@echo "  initramfs         prepare the initramfs tree with nolibc-test"
>  	@echo "  defconfig         create a fresh new default config (uses \$$XARCH)"
> -	@echo "  kernel            (re)build the kernel (uses \$$XARCH)"
> +	@echo "  kernel            (re)build the kernel (uses \$$XARCH, \$$CROSS_COMPILE)"

I'll fold this into the last commit of the series.


Thomas

Re: [PATCH 2/3] selftests/nolibc: don't pass CC to toplevel Makefile

Posted by Willy Tarreau 1 month, 2 weeks ago

Hi Thomas!

On Sun, Aug 17, 2025 at 10:30:52AM +0200, Thomas Weißschuh wrote:
> Hi Willy,
> 
> On 2025-07-21 04:56:27+0200, Willy Tarreau wrote:
> > On Sat, Jul 19, 2025 at 05:38:28PM +0200, Thomas Weißschuh wrote:
> > > The toplevel Makefile is capable of calculating CC from CROSS_COMPILE
> > > and/or ARCH.
> > > 
> > > Stop passing the unnecessary variable.
> > (...) 
> > >  # Execute the toplevel kernel Makefile
> > > -KBUILD_MAKE = $(MAKE) -C $(srctree) ARCH=$(ARCH) CC=$(CC) CROSS_COMPILE=$(CROSS_COMPILE)
> > > +KBUILD_MAKE = $(MAKE) -C $(srctree) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE)
> > 
> > Here the goal was not to help the toplevel Makefile figure CC, but rather
> > to permit the user to override it, and it's also listed in "make help",
> > and even used in cc-option.
> > 
> > I understnad that you're trying to avoid forcing CC to clang when
> > building, but in this case, what will CROSS_COMPILE contain ?  My
> > guess is that you intend to make CROSS_COMPILE point to the gcc-based
> > toolchain, and have CC point to clang for userland only. Is this the
> > case ?
> 
> Correct.
> 
> > I think I'd be fine with this, but then we need to make it
> > explicit in the help message and fix the current one, possibly just
> > with this:
> > 
> > -	@echo "  nolibc-test       build the executable (uses \$$CC and \$$CROSS_COMPILE)"
> > +	@echo "  nolibc-test       build the executable (uses \$$CC)"
> 
> I don't think this is correct. $CC itself depends on $CROSS_COMPILE
> through tools/scripts/Makefile.include.

I don't understand what you mean by "depends on" here. CC defaults
to ${CROSS_COMPILE}gcc and may override it if set. So if one sets
CC, CROSS_COMPILE will not be used for it. Or maybe we could change
it to this to indicate a precedence if that's the idea you want to
convey ?

 -	@echo "  nolibc-test       build the executable (uses \$$CC and \$$CROSS_COMPILE)"
 +	@echo "  nolibc-test       build the executable (uses \$$CC or \$$CROSS_COMPILE)"

Willy

Re: [PATCH 2/3] selftests/nolibc: don't pass CC to toplevel Makefile

Posted by Thomas Weißschuh 1 month, 2 weeks ago

On 2025-08-17 11:39:05+0200, Willy Tarreau wrote:
> On Sun, Aug 17, 2025 at 10:30:52AM +0200, Thomas Weißschuh wrote:
> > On 2025-07-21 04:56:27+0200, Willy Tarreau wrote:
> > > On Sat, Jul 19, 2025 at 05:38:28PM +0200, Thomas Weißschuh wrote:

(...)

> > > I think I'd be fine with this, but then we need to make it
> > > explicit in the help message and fix the current one, possibly just
> > > with this:
> > > 
> > > -	@echo "  nolibc-test       build the executable (uses \$$CC and \$$CROSS_COMPILE)"
> > > +	@echo "  nolibc-test       build the executable (uses \$$CC)"
> > 
> > I don't think this is correct. $CC itself depends on $CROSS_COMPILE
> > through tools/scripts/Makefile.include.
> 
> I don't understand what you mean by "depends on" here. CC defaults
> to ${CROSS_COMPILE}gcc and may override it if set. So if one sets
> CC, CROSS_COMPILE will not be used for it. Or maybe we could change
> it to this to indicate a precedence if that's the idea you want to
> convey ?
> 
>  -	@echo "  nolibc-test       build the executable (uses \$$CC and \$$CROSS_COMPILE)"
>  +	@echo "  nolibc-test       build the executable (uses \$$CC or \$$CROSS_COMPILE)"

Yes, that is the idea. 
I pushed a commit to this effect to nolibc/for-next.


Thomas

Re: [PATCH 2/3] selftests/nolibc: don't pass CC to toplevel Makefile

Posted by Willy Tarreau 1 month, 2 weeks ago

On Mon, Aug 18, 2025 at 04:07:21PM +0200, Thomas Weißschuh wrote:
> On 2025-08-17 11:39:05+0200, Willy Tarreau wrote:
> > On Sun, Aug 17, 2025 at 10:30:52AM +0200, Thomas Weißschuh wrote:
> > > On 2025-07-21 04:56:27+0200, Willy Tarreau wrote:
> > > > On Sat, Jul 19, 2025 at 05:38:28PM +0200, Thomas Weißschuh wrote:
> 
> (...)
> 
> > > > I think I'd be fine with this, but then we need to make it
> > > > explicit in the help message and fix the current one, possibly just
> > > > with this:
> > > > 
> > > > -	@echo "  nolibc-test       build the executable (uses \$$CC and \$$CROSS_COMPILE)"
> > > > +	@echo "  nolibc-test       build the executable (uses \$$CC)"
> > > 
> > > I don't think this is correct. $CC itself depends on $CROSS_COMPILE
> > > through tools/scripts/Makefile.include.
> > 
> > I don't understand what you mean by "depends on" here. CC defaults
> > to ${CROSS_COMPILE}gcc and may override it if set. So if one sets
> > CC, CROSS_COMPILE will not be used for it. Or maybe we could change
> > it to this to indicate a precedence if that's the idea you want to
> > convey ?
> > 
> >  -	@echo "  nolibc-test       build the executable (uses \$$CC and \$$CROSS_COMPILE)"
> >  +	@echo "  nolibc-test       build the executable (uses \$$CC or \$$CROSS_COMPILE)"
> 
> Yes, that is the idea. 
> I pushed a commit to this effect to nolibc/for-next.

OK perfect, thank you!
Willy