[PATCH] kbuild: Allow gcov to be enabled on the command line

[PATCH] kbuild: Allow gcov to be enabled on the command line

[Kent Overstreet]

This allows gcov to be enabled for a particular kernel source
subdirectory on the command line, without editing makefiles, like so:

  make GCOV_PROFILE_fs_bcachefs=y

Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: linux-kbuild@vger.kernel.org
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 scripts/Kbuild.include | 10 ++++++++++
 scripts/Makefile.lib   |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 7778cc97a4e0..5341736f2e30 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -277,3 +277,13 @@ ifneq ($(and $(filter notintermediate, $(.FEATURES)),$(filter-out 4.4,$(MAKE_VER
 else
 .SECONDARY:
 endif
+
+ # expand_parents(a/b/c) = a/b/c a/b a
+expand_parents2 = $(if $(subst .,,$(1)),$(call expand_parents,$(1)),)
+expand_parents  = $(1) $(call expand_parents2,$(patsubst %/,%,$(dir $(1))))
+
+# flatten_dirs(a/b/c) = a_b_c a_b a
+flatten_dirs = $(subst /,_,$(call expand_parents,$(1)))
+
+# eval_vars(X_,a/b/c) = $(X_a_b_c) $(X_a_b) $(X_a)
+eval_vars = $(foreach var,$(call flatten_dirs,$(2)),$($(1)$(var)))
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 1a965fe68e01..0b4581a8bc33 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -148,7 +148,7 @@ _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(target-stem).lds)
 #
 ifeq ($(CONFIG_GCOV_KERNEL),y)
 _c_flags += $(if $(patsubst n%,, \
-		$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
+		$(GCOV_PROFILE_$(basetarget).o)$(call eval_vars,GCOV_PROFILE_,$(src))$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
 		$(CFLAGS_GCOV))
 endif
 
-- 
2.42.0

Re: [PATCH] kbuild: Allow gcov to be enabled on the command line

[Masahiro Yamada]

On Thu, Nov 23, 2023 at 8:55 AM Kent Overstreet
<kent.overstreet@linux.dev> wrote:
>
> This allows gcov to be enabled for a particular kernel source
> subdirectory on the command line, without editing makefiles, like so:
>
>   make GCOV_PROFILE_fs_bcachefs=y
>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Nicolas Schier <nicolas@fjasle.eu>
> Cc: linux-kbuild@vger.kernel.org
> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
> ---
>  scripts/Kbuild.include | 10 ++++++++++
>  scripts/Makefile.lib   |  2 +-
>  2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> index 7778cc97a4e0..5341736f2e30 100644
> --- a/scripts/Kbuild.include
> +++ b/scripts/Kbuild.include
> @@ -277,3 +277,13 @@ ifneq ($(and $(filter notintermediate, $(.FEATURES)),$(filter-out 4.4,$(MAKE_VER
>  else
>  .SECONDARY:
>  endif
> +
> + # expand_parents(a/b/c) = a/b/c a/b a
> +expand_parents2 = $(if $(subst .,,$(1)),$(call expand_parents,$(1)),)
> +expand_parents  = $(1) $(call expand_parents2,$(patsubst %/,%,$(dir $(1))))
> +
> +# flatten_dirs(a/b/c) = a_b_c a_b a
> +flatten_dirs = $(subst /,_,$(call expand_parents,$(1)))
> +
> +# eval_vars(X_,a/b/c) = $(X_a_b_c) $(X_a_b) $(X_a)
> +eval_vars = $(foreach var,$(call flatten_dirs,$(2)),$($(1)$(var)))



I do not like tricky code like this.

Also, with "fs_bcachefs", it is unclear which directory
is enabled.




How about this?



[1] Specify the list of directories by GCOV_PROFILE_DIRS


diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 1a965fe68e01..286a569556b3 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -147,8 +147,12 @@ _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y)
$(CPPFLAGS_$(target-stem).lds)
 # (in this order)
 #
 ifeq ($(CONFIG_GCOV_KERNEL),y)
+ifneq ($(filter $(obj),$(GCOV_PROFILE_DIRS)),)
+export GCOV_PROFILE_SUBDIR := y
+endif
+
 _c_flags += $(if $(patsubst n%,, \
-
$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)),
\
+
$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(GCOV_PROFILE_SUBDIR)$(CONFIG_GCOV_PROFILE_ALL)),
\
                $(CFLAGS_GCOV))
 endif



Usage:

  $ make GCOV_PROFILE_DIRS=fs/bcachefs

   ->  enable GCOV in fs/bachefs and its subdirectories.

or

  $ make GCOV_PROFILE_DIRS="drivers/gpio drivers/pinctrl"

   -> enable GCOV in drivers/gpio, drivers/pinctrl, and their subdirectories.




[2] Do equivalent, but from a CONFIG option


config GCOV_PROFILE_DIRS
      string "Directories to enable GCOV"


Then, you can set CONFIG_GCOV_PROFILE_DIRS="fs/bcachefs"


This might be a more natural approach because we already have
CONFIG_GCOV_PROFILE_ALL, although it might eventually go away
because CONFIG_GCOV_PROFILE_ALL=y is almost equivalent to
CONFIG_GCOV_PROFILE_DIRS="."




diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 1a965fe68e01..286a569556b3 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -147,8 +147,12 @@ _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y)
$(CPPFLAGS_$(target-stem).lds)
 # (in this order)
 #
 ifeq ($(CONFIG_GCOV_KERNEL),y)
+ifneq ($(filter $(obj),$(CONFIG_GCOV_PROFILE_DIRS)),)
+export GCOV_PROFILE_SUBDIR := y
+endif
+
 _c_flags += $(if $(patsubst n%,, \
-
$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)),
\
+
$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(GCOV_PROFILE_SUBDIR)$(CONFIG_GCOV_PROFILE_ALL)),
\
                $(CFLAGS_GCOV))
 endif







> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 1a965fe68e01..0b4581a8bc33 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -148,7 +148,7 @@ _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(target-stem).lds)
>  #
>  ifeq ($(CONFIG_GCOV_KERNEL),y)
>  _c_flags += $(if $(patsubst n%,, \
> -               $(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
> +               $(GCOV_PROFILE_$(basetarget).o)$(call eval_vars,GCOV_PROFILE_,$(src))$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
>                 $(CFLAGS_GCOV))
>  endif
>
> --
> 2.42.0
>


--
Best Regards
Masahiro Yamada

Re: [PATCH] kbuild: Allow gcov to be enabled on the command line

[Kent Overstreet]

On Fri, Nov 24, 2023 at 11:02:00AM +0900, Masahiro Yamada wrote:
> On Thu, Nov 23, 2023 at 8:55 AM Kent Overstreet
> <kent.overstreet@linux.dev> wrote:
> >
> > This allows gcov to be enabled for a particular kernel source
> > subdirectory on the command line, without editing makefiles, like so:
> >
> >   make GCOV_PROFILE_fs_bcachefs=y
> >
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: Nathan Chancellor <nathan@kernel.org>
> > Cc: Nick Desaulniers <ndesaulniers@google.com>
> > Cc: Nicolas Schier <nicolas@fjasle.eu>
> > Cc: linux-kbuild@vger.kernel.org
> > Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
> > ---
> >  scripts/Kbuild.include | 10 ++++++++++
> >  scripts/Makefile.lib   |  2 +-
> >  2 files changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> > index 7778cc97a4e0..5341736f2e30 100644
> > --- a/scripts/Kbuild.include
> > +++ b/scripts/Kbuild.include
> > @@ -277,3 +277,13 @@ ifneq ($(and $(filter notintermediate, $(.FEATURES)),$(filter-out 4.4,$(MAKE_VER
> >  else
> >  .SECONDARY:
> >  endif
> > +
> > + # expand_parents(a/b/c) = a/b/c a/b a
> > +expand_parents2 = $(if $(subst .,,$(1)),$(call expand_parents,$(1)),)
> > +expand_parents  = $(1) $(call expand_parents2,$(patsubst %/,%,$(dir $(1))))
> > +
> > +# flatten_dirs(a/b/c) = a_b_c a_b a
> > +flatten_dirs = $(subst /,_,$(call expand_parents,$(1)))
> > +
> > +# eval_vars(X_,a/b/c) = $(X_a_b_c) $(X_a_b) $(X_a)
> > +eval_vars = $(foreach var,$(call flatten_dirs,$(2)),$($(1)$(var)))
> 
> 
> 
> I do not like tricky code like this.
> 
> Also, with "fs_bcachefs", it is unclear which directory
> is enabled.

It's consistent with how we can specify options in makefiles for a
particular file.

I suppose CONFIG_GCOV_PROFILE_DIRS would be fine, but your patch isn't
complete so I can't test it.


> 
> 
> 
> 
> How about this?
> 
> 
> 
> [1] Specify the list of directories by GCOV_PROFILE_DIRS
> 
> 
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 1a965fe68e01..286a569556b3 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -147,8 +147,12 @@ _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y)
> $(CPPFLAGS_$(target-stem).lds)
>  # (in this order)
>  #
>  ifeq ($(CONFIG_GCOV_KERNEL),y)
> +ifneq ($(filter $(obj),$(GCOV_PROFILE_DIRS)),)
> +export GCOV_PROFILE_SUBDIR := y
> +endif
> +
>  _c_flags += $(if $(patsubst n%,, \
> -
> $(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)),
> \
> +
> $(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(GCOV_PROFILE_SUBDIR)$(CONFIG_GCOV_PROFILE_ALL)),
> \
>                 $(CFLAGS_GCOV))
>  endif
> 
> 
> 
> Usage:
> 
>   $ make GCOV_PROFILE_DIRS=fs/bcachefs
> 
>    ->  enable GCOV in fs/bachefs and its subdirectories.
> 
> or
> 
>   $ make GCOV_PROFILE_DIRS="drivers/gpio drivers/pinctrl"
> 
>    -> enable GCOV in drivers/gpio, drivers/pinctrl, and their subdirectories.
> 
> 
> 
> 
> [2] Do equivalent, but from a CONFIG option
> 
> 
> config GCOV_PROFILE_DIRS
>       string "Directories to enable GCOV"
> 
> 
> Then, you can set CONFIG_GCOV_PROFILE_DIRS="fs/bcachefs"
> 
> 
> This might be a more natural approach because we already have
> CONFIG_GCOV_PROFILE_ALL, although it might eventually go away
> because CONFIG_GCOV_PROFILE_ALL=y is almost equivalent to
> CONFIG_GCOV_PROFILE_DIRS="."
> 
> 
> 
> 
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 1a965fe68e01..286a569556b3 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -147,8 +147,12 @@ _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y)
> $(CPPFLAGS_$(target-stem).lds)
>  # (in this order)
>  #
>  ifeq ($(CONFIG_GCOV_KERNEL),y)
> +ifneq ($(filter $(obj),$(CONFIG_GCOV_PROFILE_DIRS)),)
> +export GCOV_PROFILE_SUBDIR := y
> +endif
> +
>  _c_flags += $(if $(patsubst n%,, \
> -
> $(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)),
> \
> +
> $(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(GCOV_PROFILE_SUBDIR)$(CONFIG_GCOV_PROFILE_ALL)),
> \
>                 $(CFLAGS_GCOV))
>  endif
> 
> 
> 
> 
> 
> 
> 
> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > index 1a965fe68e01..0b4581a8bc33 100644
> > --- a/scripts/Makefile.lib
> > +++ b/scripts/Makefile.lib
> > @@ -148,7 +148,7 @@ _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(target-stem).lds)
> >  #
> >  ifeq ($(CONFIG_GCOV_KERNEL),y)
> >  _c_flags += $(if $(patsubst n%,, \
> > -               $(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
> > +               $(GCOV_PROFILE_$(basetarget).o)$(call eval_vars,GCOV_PROFILE_,$(src))$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
> >                 $(CFLAGS_GCOV))
> >  endif
> >
> > --
> > 2.42.0
> >
> 
> 
> --
> Best Regards
> Masahiro Yamada

Re: [PATCH] kbuild: Allow gcov to be enabled on the command line

[Masahiro Yamada]

[-- Attachment #1: Type: text/plain, Size: 2765 bytes --]

On Sun, Nov 26, 2023 at 4:56 AM Kent Overstreet
<kent.overstreet@linux.dev> wrote:
>
> On Fri, Nov 24, 2023 at 11:02:00AM +0900, Masahiro Yamada wrote:
> > On Thu, Nov 23, 2023 at 8:55 AM Kent Overstreet
> > <kent.overstreet@linux.dev> wrote:
> > >
> > > This allows gcov to be enabled for a particular kernel source
> > > subdirectory on the command line, without editing makefiles, like so:
> > >
> > >   make GCOV_PROFILE_fs_bcachefs=y
> > >
> > > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > > Cc: Nathan Chancellor <nathan@kernel.org>
> > > Cc: Nick Desaulniers <ndesaulniers@google.com>
> > > Cc: Nicolas Schier <nicolas@fjasle.eu>
> > > Cc: linux-kbuild@vger.kernel.org
> > > Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
> > > ---
> > >  scripts/Kbuild.include | 10 ++++++++++
> > >  scripts/Makefile.lib   |  2 +-
> > >  2 files changed, 11 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> > > index 7778cc97a4e0..5341736f2e30 100644
> > > --- a/scripts/Kbuild.include
> > > +++ b/scripts/Kbuild.include
> > > @@ -277,3 +277,13 @@ ifneq ($(and $(filter notintermediate, $(.FEATURES)),$(filter-out 4.4,$(MAKE_VER
> > >  else
> > >  .SECONDARY:
> > >  endif
> > > +
> > > + # expand_parents(a/b/c) = a/b/c a/b a
> > > +expand_parents2 = $(if $(subst .,,$(1)),$(call expand_parents,$(1)),)
> > > +expand_parents  = $(1) $(call expand_parents2,$(patsubst %/,%,$(dir $(1))))
> > > +
> > > +# flatten_dirs(a/b/c) = a_b_c a_b a
> > > +flatten_dirs = $(subst /,_,$(call expand_parents,$(1)))
> > > +
> > > +# eval_vars(X_,a/b/c) = $(X_a_b_c) $(X_a_b) $(X_a)
> > > +eval_vars = $(foreach var,$(call flatten_dirs,$(2)),$($(1)$(var)))
> >
> >
> >
> > I do not like tricky code like this.
> >
> > Also, with "fs_bcachefs", it is unclear which directory
> > is enabled.
>
> It's consistent with how we can specify options in makefiles for a
> particular file.


It is consistent in a bad way.

You used "GCOV_PROFILE_" prefix
for the full directory path, while it is already
used as a file name which is relative to the
current directory.



>
> I suppose CONFIG_GCOV_PROFILE_DIRS would be fine, but your patch isn't
> complete so I can't test it.


I do not understand what you mean by "isn't complete".

It is just a matter of adding the config entry somewhere.

I added a patch just in case, though.


Note, both approach pros and cons.


The command line approach works for external modules.


With the CONFIG option approach, you can easily see
which directories are profiled by checking the .config,
but it is not easy to enable gcov for external modules.







-- 
Best Regards
Masahiro Yamada

[-- Attachment #2: per-dir-gcov.diff --]
[-- Type: text/x-patch, Size: 1068 bytes --]

diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig
index 04f4ebdc3cf5..c95d93189ecc 100644
--- a/kernel/gcov/Kconfig
+++ b/kernel/gcov/Kconfig
@@ -37,6 +37,10 @@ config GCOV_KERNEL
 config ARCH_HAS_GCOV_PROFILE_ALL
 	def_bool n
 
+config GCOV_PROFILE_DIRS
+	string "Directories to enable gcov profiling"
+	depends on GCOV_KERNEL
+
 config GCOV_PROFILE_ALL
 	bool "Profile entire Kernel"
 	depends on !COMPILE_TEST
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 1a965fe68e01..5d80f784b922 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -147,8 +147,12 @@ _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(target-stem).lds)
 # (in this order)
 #
 ifeq ($(CONFIG_GCOV_KERNEL),y)
+ifneq ($(filter $(obj),$(CONFIG_GCOV_PROFILE_DIRS)),)
+export GCOV_PROFILE_SUBDIR := y
+endif
+
 _c_flags += $(if $(patsubst n%,, \
-		$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
+		$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(GCOV_PROFILE_SUBDIR)$(CONFIG_GCOV_PROFILE_ALL)), \
 		$(CFLAGS_GCOV))
 endif
 

Re: [PATCH] kbuild: Allow gcov to be enabled on the command line

[Kent Overstreet]

On Tue, Nov 28, 2023 at 08:44:11PM +0900, Masahiro Yamada wrote:
> On Sun, Nov 26, 2023 at 4:56 AM Kent Overstreet
> > It's consistent with how we can specify options in makefiles for a
> > particular file.
> 
> 
> It is consistent in a bad way.

That's a new meaning for consistent that I'm unfamiliar with.

> You used "GCOV_PROFILE_" prefix
> for the full directory path, while it is already
> used as a file name which is relative to the
> current directory.

And the current directory when you're building the entire kernel is the
top level directory.

> > I suppose CONFIG_GCOV_PROFILE_DIRS would be fine, but your patch isn't
> > complete so I can't test it.
> 
> 
> I do not understand what you mean by "isn't complete".
> 
> It is just a matter of adding the config entry somewhere.

Yes, not complete, meaning you haven't even tested it.