KUnit's 'hooks.o' file need to be built-in whenever KUnit is enabled (even if CONFIG_KUNIT=m). We'd previously attemtped to do this by adding 'kunit/hooks.o' to obj-y in lib/Makefile, but this caused hooks.c to be rebuilt even when it was unchanged.
Instead, always recurse into lib/kunit using obj-y when KUnit is enabled, and add the hooks there.
Fixes: 7170b7ed6acb ("kunit: Add "hooks" to call into KUnit when it's built as a module"). Reported-by: Linus Torvalds torvalds@linux-foundation.org Link: https://lore.kernel.org/linux-kselftest/CAHk-=wiEf7irTKwPJ0jTMOF3CS-13UXmF6F... Signed-off-by: David Gow davidgow@google.com ---
I like this way of handling the makefiles much better. I had tried it when originally writing the hooks patch and not managed to get it working. Not sure what's changed now, but it works in all of the usual cases (CONFIG_KUNIT={n,y,m}, kunit.py run, etc).
Linus, Shuah: Let me know if you want this to go via the KUnit branch, or if you just want to apply it directly and get rid of the annoyances ASAP.
--- lib/Makefile | 12 ++++-------- lib/kunit/Makefile | 2 +- 2 files changed, 5 insertions(+), 9 deletions(-)
diff --git a/lib/Makefile b/lib/Makefile index 469be6240523..baf2821f7a00 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -127,14 +127,10 @@ CFLAGS_test_fpu.o += $(FPU_CFLAGS)
obj-$(CONFIG_TEST_LIVEPATCH) += livepatch/
-obj-$(CONFIG_KUNIT) += kunit/ -# Include the KUnit hooks unconditionally. They'll compile to nothing if -# CONFIG_KUNIT=n, otherwise will be a small table of static data (static key, -# function pointers) which need to be built-in even when KUnit is a module. -ifeq ($(CONFIG_KUNIT), m) -obj-y += kunit/hooks.o -else -obj-$(CONFIG_KUNIT) += kunit/hooks.o +# Some KUnit files (hooks.o) need to be built-in even when KUnit is a module, +# so we can't just use obj-$(CONFIG_KUNIT). +ifdef CONFIG_KUNIT +obj-y += kunit/ endif
ifeq ($(CONFIG_DEBUG_KOBJECT),y) diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile index da665cd4ea12..cb417f504996 100644 --- a/lib/kunit/Makefile +++ b/lib/kunit/Makefile @@ -13,7 +13,7 @@ kunit-objs += debugfs.o endif
# KUnit 'hooks' are built-in even when KUnit is built as a module. -lib-y += hooks.o +obj-y += hooks.o
obj-$(CONFIG_KUNIT_TEST) += kunit-test.o
On Fri, Feb 24, 2023 at 8:45 PM 'David Gow' via KUnit Development kunit-dev@googlegroups.com wrote:
KUnit's 'hooks.o' file need to be built-in whenever KUnit is enabled (even if CONFIG_KUNIT=m). We'd previously attemtped to do this by adding 'kunit/hooks.o' to obj-y in lib/Makefile, but this caused hooks.c to be rebuilt even when it was unchanged.
Instead, always recurse into lib/kunit using obj-y when KUnit is enabled, and add the hooks there.
Fixes: 7170b7ed6acb ("kunit: Add "hooks" to call into KUnit when it's built as a module"). Reported-by: Linus Torvalds torvalds@linux-foundation.org Link: https://lore.kernel.org/linux-kselftest/CAHk-=wiEf7irTKwPJ0jTMOF3CS-13UXmF6F... Signed-off-by: David Gow davidgow@google.com
Reviewed-by: Brendan Higgins brendanhiggins@google.com
On Fri, Feb 24, 2023 at 5:45 PM David Gow davidgow@google.com wrote:
+# Some KUnit files (hooks.o) need to be built-in even when KUnit is a module, +# so we can't just use obj-$(CONFIG_KUNIT). +ifdef CONFIG_KUNIT +obj-y += kunit/ endif
We actually have a pattern for this, although I guess it's rare enough that "pattern" isn't necessarily the right word.
But you can find things like the Hyper-V drivers having similar issues, and so the driver Makefile has
obj-$(subst m,y,$(CONFIG_HYPERV)) += hv/
See a few other cases with
git grep "subst m,y,"
but I guess the "ifdef CONFIG_KUNIT" thing works too. I can only find one case of that (in arch/mips/Kbuild).
Another way of dealing with this - that is more common for individual object files rather than directories - is to just do
kunit-dir-$(CONFIG_KUNIT) := kunit/ obj-y += $(kunit-dir-y) $(kunit-dir-m)
which admittedly is also not a hugely common pattern, but does exist in various places (see for example the 'sfp-bus.o' file and CONFIG_SFP in drivers/net/phy/Makefile.
That last pattern is probably most common in scripts/Makefile.lib, where we have things like
hostprogs += $(hostprogs-always-y) $(hostprogs-always-m)
which is similar but not the exact same thing.
Anyway, I guess I'll just apply that patch as-is, I just wanted to point out that the particular pattern it uses may be simple, but we've generally tried to just do our Makefile evaluations with "arithmetic" rather than conditionals.
Linus
On Tue, 28 Feb 2023 at 06:43, Linus Torvalds torvalds@linux-foundation.org wrote:
On Fri, Feb 24, 2023 at 5:45 PM David Gow davidgow@google.com wrote:
+# Some KUnit files (hooks.o) need to be built-in even when KUnit is a module, +# so we can't just use obj-$(CONFIG_KUNIT). +ifdef CONFIG_KUNIT +obj-y += kunit/ endif
We actually have a pattern for this, although I guess it's rare enough that "pattern" isn't necessarily the right word.
But you can find things like the Hyper-V drivers having similar issues, and so the driver Makefile has
obj-$(subst m,y,$(CONFIG_HYPERV)) += hv/See a few other cases with
git grep "subst m,y,"but I guess the "ifdef CONFIG_KUNIT" thing works too. I can only find one case of that (in arch/mips/Kbuild).
Another way of dealing with this - that is more common for individual object files rather than directories - is to just do
kunit-dir-$(CONFIG_KUNIT) := kunit/ obj-y += $(kunit-dir-y) $(kunit-dir-m)which admittedly is also not a hugely common pattern, but does exist in various places (see for example the 'sfp-bus.o' file and CONFIG_SFP in drivers/net/phy/Makefile.
That last pattern is probably most common in scripts/Makefile.lib, where we have things like
hostprogs += $(hostprogs-always-y) $(hostprogs-always-m)which is similar but not the exact same thing.
Anyway, I guess I'll just apply that patch as-is, I just wanted to point out that the particular pattern it uses may be simple, but we've generally tried to just do our Makefile evaluations with "arithmetic" rather than conditionals.
Linus
Thanks, Linus.
(And also thanks to Mikhail Gavrilov and Thorsten Leemhuis for testing this change as well.)
It's certainly been an educational experience!
Of those other options, personally I find the "subst m,y" one most obvious, but I'll probably leave it as the conditional for now, unless you think trying to make it more consistent is worth the extra churn.
Regardless, I'll look into adding a note about this to Documentation/kbuild/makefiles.rst.
Cheers, -- David
linux-kselftest-mirror@lists.linaro.org
-
Brendan Higgins -
David Gow -
Linus Torvalds