selftests/nolibc: add support for LLVM= parameter

Makefile.include can modify CC and CFLAGS for usage with clang.
Make use of it.

Makefile.include is currently used to handle the O= variable.
This

selftests/nolibc: add support for LLVM= parameter

Makefile.include can modify CC and CFLAGS for usage with clang.
Make use of it.

Makefile.include is currently used to handle the O= variable.
This is incompatible with the LLVM= handling as for O= it has to be
included as early as possible, while for LLVM= it needs to be included
after CFLAGS are set up.

To avoid this incompatibility, switch the O= handling to custom logic.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20240807-nolibc-llvm-v2-10-c20f2f5fc7c2@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

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selftests/nolibc: determine $(srctree) first

The nolibc-test Makefile includes various other Makefiles from the tree.
At first these are included with relative paths like
"../../../build/Build.inclu

selftests/nolibc: determine $(srctree) first

The nolibc-test Makefile includes various other Makefiles from the tree.
At first these are included with relative paths like
"../../../build/Build.include" but as soon as $(srctree) is set up,
the inclusions use that instead to build full paths.

To keep the style of inclusions consistent, perform the setup
$(srctree) as early as possible and use it for all inclusions.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20240807-nolibc-llvm-v2-9-c20f2f5fc7c2@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

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selftests/nolibc: avoid passing NULL to printf("%s")

Clang on higher optimization levels detects that NULL is passed to
printf("%s") and warns about it.
While printf() from nolibc gracefully handles

selftests/nolibc: avoid passing NULL to printf("%s")

Clang on higher optimization levels detects that NULL is passed to
printf("%s") and warns about it.
While printf() from nolibc gracefully handles that NULL,
it is undefined behavior as per POSIX, so the warning is reasonable.
Avoid the warning by transforming NULL into a non-NULL placeholder.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20240807-nolibc-llvm-v2-8-c20f2f5fc7c2@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

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selftests/nolibc: report failure if no testcase passed

When nolibc-test is so broken, it doesn't even start,
don't report success.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Will

selftests/nolibc: report failure if no testcase passed

When nolibc-test is so broken, it doesn't even start,
don't report success.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20240807-nolibc-llvm-v2-7-c20f2f5fc7c2@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

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tools/nolibc: pass argc, argv and envp to constructors

Since 2005 glibc has passed argc, argv, and envp to all constructors.
As it is cheap and easy to do so, mirror that behaviour in nolibc.
This m

tools/nolibc: pass argc, argv and envp to constructors

Since 2005 glibc has passed argc, argv, and envp to all constructors.
As it is cheap and easy to do so, mirror that behaviour in nolibc.
This makes it easier to migrate applications to nolibc.

Link: https://lore.kernel.org/r/20240728-nolibc-constructor-args-v1-1-36d0bf5cd4c0@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

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