This will help prevent the CI loop from having build failures when
`checkpolicy` isn't available when doing "randconfig" jobs.

To prevent "randconfig" from selecting XSM_FLASK_POLICY when
`checkpolicy` isn't available, we will actually override the config
output with the use of KCONFIG_ALLCONFIG.

Doing this way still allow a user/developer to set XSM_FLASK_POLICY
even when "checkpolicy" isn't available. It also prevent the build
system from reset the config when "checkpolicy" isn't available
anymore. And XSM_FLASK_POLICY is still selected automatically when
`checkpolicy` is available.
But this also work well for "randconfig", as it will not select
XSM_FLASK_POLICY when "checkpolicy" is missing.

This patch allows to easily add more override which depends on the
environment.

Also, move the check out of Config.mk and into xen/ build system.
Nothing in tools/ is using that information as it's done by
./configure.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
v3:
- use KCONFIG_ALLCONFIG
- don't override XSM_FLASK_POLICY value unless we do randconfig.
- no more changes to the current behavior of kconfig, only to
  randconfig.

v2 was "[XEN PATCH v2] xen: allow XSM_FLASK_POLICY only if checkpolicy binary is available"
---
 Config.mk          |  6 ------
 xen/Makefile       | 18 ++++++++++++++++--
 xen/common/Kconfig |  2 +-
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/Config.mk b/Config.mk
index d0712724f8e4..144411133f38 100644
--- a/Config.mk
+++ b/Config.mk
@@ -137,12 +137,6 @@ export XEN_HAS_BUILD_ID=y
 build_id_linker := --build-id=sha1
 endif
 
-ifndef XEN_HAS_CHECKPOLICY
-    CHECKPOLICY ?= checkpolicy
-    XEN_HAS_CHECKPOLICY := $(shell $(CHECKPOLICY) -h 2>&1 | grep -q xen && echo y || echo n)
-    export XEN_HAS_CHECKPOLICY
-endif
-
 define buildmakevars2shellvars
     export PREFIX="$(prefix)";                                            \
     export XEN_SCRIPT_DIR="$(XEN_SCRIPT_DIR)";                            \
diff --git a/xen/Makefile b/xen/Makefile
index f47423dacd9a..89804aefe385 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -17,6 +17,8 @@ export XEN_BUILD_HOST	?= $(shell hostname)
 PYTHON_INTERPRETER	:= $(word 1,$(shell which python3 python python2 2>/dev/null) python)
 export PYTHON		?= $(PYTHON_INTERPRETER)
 
+export CHECKPOLICY	?= checkpolicy
+
 export BASEDIR := $(CURDIR)
 export XEN_ROOT := $(BASEDIR)/..
 
@@ -178,6 +180,8 @@ CFLAGS += $(CLANG_FLAGS)
 export CLANG_FLAGS
 endif
 
+export HAS_CHECKPOLICY := $(call success,$(CHECKPOLICY) -h 2>&1 | grep -q xen)
+
 export root-make-done := y
 endif # root-make-done
 
@@ -189,14 +193,24 @@ ifeq ($(config-build),y)
 # *config targets only - make sure prerequisites are updated, and descend
 # in tools/kconfig to make the *config target
 
+# Create a file for KCONFIG_ALLCONFIG which depends on the environment.
+# This will be use by kconfig targets allyesconfig/allmodconfig/allnoconfig/randconfig
+filechk_kconfig_allconfig = \
+    $(if $(findstring n,$(HAS_CHECKPOLICY)),echo 'CONFIG_XSM_FLASK_POLICY=n';) \
+    $(if $(KCONFIG_ALLCONFIG), cat $(KCONFIG_ALLCONFIG), :)
+
+
+.allconfig.tmp: FORCE
+	set -e; { $(call filechk_kconfig_allconfig); } > $@
+
 config: FORCE
 	$(MAKE) $(kconfig) $@
 
 # Config.mk tries to include .config file, don't try to remake it
 %/.config: ;
 
-%config: FORCE
-	$(MAKE) $(kconfig) $@
+%config: .allconfig.tmp FORCE
+	$(MAKE) $(kconfig) KCONFIG_ALLCONFIG=$< $@
 
 else # !config-build
 
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 0ddd18e11af3..73d8afb7bcbd 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -235,7 +235,7 @@ config XSM_FLASK_AVC_STATS
 
 config XSM_FLASK_POLICY
 	bool "Compile Xen with a built-in FLASK security policy"
-	default y if "$(XEN_HAS_CHECKPOLICY)" = "y"
+	default y if "$(HAS_CHECKPOLICY)"
 	depends on XSM_FLASK
 	---help---
 	  This includes a default XSM policy in the hypervisor so that the
-- 
Anthony PERARD

On 08.09.2021 13:17, Anthony PERARD wrote:
> --- a/Config.mk
> +++ b/Config.mk
> @@ -137,12 +137,6 @@ export XEN_HAS_BUILD_ID=y
>  build_id_linker := --build-id=sha1
>  endif
>  
> -ifndef XEN_HAS_CHECKPOLICY
> -    CHECKPOLICY ?= checkpolicy
> -    XEN_HAS_CHECKPOLICY := $(shell $(CHECKPOLICY) -h 2>&1 | grep -q xen && echo y || echo n)
> -    export XEN_HAS_CHECKPOLICY
> -endif

Is there a particular reason to go from XEN_HAS_CHECKPOLICY to ...

> --- a/xen/Makefile
> +++ b/xen/Makefile
> @@ -17,6 +17,8 @@ export XEN_BUILD_HOST	?= $(shell hostname)
>  PYTHON_INTERPRETER	:= $(word 1,$(shell which python3 python python2 2>/dev/null) python)
>  export PYTHON		?= $(PYTHON_INTERPRETER)
>  
> +export CHECKPOLICY	?= checkpolicy
> +
>  export BASEDIR := $(CURDIR)
>  export XEN_ROOT := $(BASEDIR)/..
>  
> @@ -178,6 +180,8 @@ CFLAGS += $(CLANG_FLAGS)
>  export CLANG_FLAGS
>  endif
>  
> +export HAS_CHECKPOLICY := $(call success,$(CHECKPOLICY) -h 2>&1 | grep -q xen)

... HAS_CHECKPOLICY? As soon as things get put in the environment,
I'm always suspecting possible name collisions ...

> @@ -189,14 +193,24 @@ ifeq ($(config-build),y)
>  # *config targets only - make sure prerequisites are updated, and descend
>  # in tools/kconfig to make the *config target
>  
> +# Create a file for KCONFIG_ALLCONFIG which depends on the environment.
> +# This will be use by kconfig targets allyesconfig/allmodconfig/allnoconfig/randconfig
> +filechk_kconfig_allconfig = \
> +    $(if $(findstring n,$(HAS_CHECKPOLICY)),echo 'CONFIG_XSM_FLASK_POLICY=n';) \
> +    $(if $(KCONFIG_ALLCONFIG), cat $(KCONFIG_ALLCONFIG), :)

Nit: It would be nice if you were consistent with the blanks after
commas in $(if ...). Personally I'm also considering $(if ...)s the
more difficult to follow the longer they are. Hence for the 2nd one
I wonder whether

    $(if $(KCONFIG_ALLCONFIG),cat,:) $(KCONFIG_ALLCONFIG)

wouldn't be easier to read.

> +
> +

Nit: Please avoid double blank lines.

> +.allconfig.tmp: FORCE
> +	set -e; { $(call filechk_kconfig_allconfig); } > $@

Is there a particular reason for the .tmp suffix?

Jan

On Thu, Sep 16, 2021 at 05:34:00PM +0200, Jan Beulich wrote:
> On 08.09.2021 13:17, Anthony PERARD wrote:
> > --- a/Config.mk
> > +++ b/Config.mk
> > @@ -137,12 +137,6 @@ export XEN_HAS_BUILD_ID=y
> >  build_id_linker := --build-id=sha1
> >  endif
> >  
> > -ifndef XEN_HAS_CHECKPOLICY
> > -    CHECKPOLICY ?= checkpolicy
> > -    XEN_HAS_CHECKPOLICY := $(shell $(CHECKPOLICY) -h 2>&1 | grep -q xen && echo y || echo n)
> > -    export XEN_HAS_CHECKPOLICY
> > -endif
> 
> Is there a particular reason to go from XEN_HAS_CHECKPOLICY to ...
> 
> > --- a/xen/Makefile
> > +++ b/xen/Makefile
> > @@ -17,6 +17,8 @@ export XEN_BUILD_HOST	?= $(shell hostname)
> >  PYTHON_INTERPRETER	:= $(word 1,$(shell which python3 python python2 2>/dev/null) python)
> >  export PYTHON		?= $(PYTHON_INTERPRETER)
> >  
> > +export CHECKPOLICY	?= checkpolicy
> > +
> >  export BASEDIR := $(CURDIR)
> >  export XEN_ROOT := $(BASEDIR)/..
> >  
> > @@ -178,6 +180,8 @@ CFLAGS += $(CLANG_FLAGS)
> >  export CLANG_FLAGS
> >  endif
> >  
> > +export HAS_CHECKPOLICY := $(call success,$(CHECKPOLICY) -h 2>&1 | grep -q xen)
> 
> ... HAS_CHECKPOLICY? As soon as things get put in the environment,

Not really anymore, it's just left over from having put this in Kconfig
in previous version of the patch.

> I'm always suspecting possible name collisions ...

Yes, it's probably better to keep the XEN_ prefix.

> > @@ -189,14 +193,24 @@ ifeq ($(config-build),y)
> >  # *config targets only - make sure prerequisites are updated, and descend
> >  # in tools/kconfig to make the *config target
> >  
> > +# Create a file for KCONFIG_ALLCONFIG which depends on the environment.
> > +# This will be use by kconfig targets allyesconfig/allmodconfig/allnoconfig/randconfig
> > +filechk_kconfig_allconfig = \
> > +    $(if $(findstring n,$(HAS_CHECKPOLICY)),echo 'CONFIG_XSM_FLASK_POLICY=n';) \
> > +    $(if $(KCONFIG_ALLCONFIG), cat $(KCONFIG_ALLCONFIG), :)
> 
> Nit: It would be nice if you were consistent with the blanks after
> commas in $(if ...). Personally I'm also considering $(if ...)s the
> more difficult to follow the longer they are. Hence for the 2nd one
> I wonder whether
> 
>     $(if $(KCONFIG_ALLCONFIG),cat,:) $(KCONFIG_ALLCONFIG)
> 
> wouldn't be easier to read.

How about:

    $(if $(KCONFIG_ALLCONFIG), cat $(KCONFIG_ALLCONFIG);) \
    :

.. instead, as that would be more consistent with the previous line,
that is there would be only one branch to the $(if ) and no else, and
thus probably easier to read.

> > +.allconfig.tmp: FORCE
> > +	set -e; { $(call filechk_kconfig_allconfig); } > $@
> 
> Is there a particular reason for the .tmp suffix?

Yes, .*.tmp are already ignored via .gitignore.

Thanks,

-- 
Anthony PERARD

On 27.09.2021 11:46, Anthony PERARD wrote:
> On Thu, Sep 16, 2021 at 05:34:00PM +0200, Jan Beulich wrote:
>> On 08.09.2021 13:17, Anthony PERARD wrote:
>>> @@ -189,14 +193,24 @@ ifeq ($(config-build),y)
>>>  # *config targets only - make sure prerequisites are updated, and descend
>>>  # in tools/kconfig to make the *config target
>>>  
>>> +# Create a file for KCONFIG_ALLCONFIG which depends on the environment.
>>> +# This will be use by kconfig targets allyesconfig/allmodconfig/allnoconfig/randconfig
>>> +filechk_kconfig_allconfig = \
>>> +    $(if $(findstring n,$(HAS_CHECKPOLICY)),echo 'CONFIG_XSM_FLASK_POLICY=n';) \
>>> +    $(if $(KCONFIG_ALLCONFIG), cat $(KCONFIG_ALLCONFIG), :)
>>
>> Nit: It would be nice if you were consistent with the blanks after
>> commas in $(if ...). Personally I'm also considering $(if ...)s the
>> more difficult to follow the longer they are. Hence for the 2nd one
>> I wonder whether
>>
>>     $(if $(KCONFIG_ALLCONFIG),cat,:) $(KCONFIG_ALLCONFIG)
>>
>> wouldn't be easier to read.
> 
> How about:
> 
>     $(if $(KCONFIG_ALLCONFIG), cat $(KCONFIG_ALLCONFIG);) \
>     :
> 
> .. instead, as that would be more consistent with the previous line,
> that is there would be only one branch to the $(if ) and no else, and
> thus probably easier to read.

Oh, sure, even better if that works.

>>> +.allconfig.tmp: FORCE
>>> +	set -e; { $(call filechk_kconfig_allconfig); } > $@
>>
>> Is there a particular reason for the .tmp suffix?
> 
> Yes, .*.tmp are already ignored via .gitignore.

I see. Could you add two words to the description saying so? Or
maybe even just a post-commit-message remark would do.

Jan