[PATCH v7 0/2] introduce stub directory to storing empty/stub headers

[PATCH v7 0/2] introduce stub directory to storing empty/stub headers

[Oleksii Kurochko]

A lot of empty/stub headers should be introduced during the early steps of adding
support of new architecture.

An example can be found here:
1. https://lore.kernel.org/xen-devel/cover.1692181079.git.oleksii.kurochko@gmail.com/
2. https://lore.kernel.org/xen-devel/a92f99e8f697da99d77bfde562a549dbef3760ce.1692816595.git.sanastasio@raptorengineering.com/

As part of the patch series, asm/vm_event.h was moved to the stubs directory because
It is the same for ARM, PPC, and RISC-V.
---
Changes in V7:
- update warning message in Makefile.asm-generic
- add Reviewed-by: Anthony PERARD <anthony.perard@citrix.com> for patch 1
- add Acked-by: Jan Beulich <jbeulich@suse.com> for patch 1
- update header guards in asm-generic/vm_event.h.
- add Acked-by: Tamas K Lengyel <tamas@tklengyel.com> for patch 2
---
Changes in V6:
 - introduce $(asm-generic) macro in Kbuild.include.
 - move "asm-generic" after the rule "__distclean".
 - update the commit message.
---
Changes in V5:
- Update SPDX license.
- Remove code related to UML in Makefile.asm-generic.
- Include $(src)/Makefile instead of $(kbuild-file).
- Update comment message in Makefile.asm-generic.
- Update .gitignore.
- Update path to generated headers in CFLAGS.
- Use the latest version of Linux's Makefile.asm-generic.
- Introduce asm-generic's vm_event.h.
- Switch ARM to use asm-generic/vm_event.h.
---
Changes in V4:
 - add asm-generic support
 - update path of vm_event.h from include/asm-generic/asm to include/asm-generic
---
Changes in V3:
 - add Acked-by: Stefano Stabellini <sstabellini@kernel.org> for "xen: move arm/include/asm/vm_event.h to asm-generic"
 - update SPDX tag.
 - move asm/vm_event.h to asm-generic.
 - rename stubs dir to asm-generic.

---
Changes in V2:
 - change public/domctl.h to public/vm_event.h.
 - update commit message of [PATCH v2 2/2] xen: move arm/include/asm/vm_event.h to stubs

Oleksii Kurochko (2):
  xen: asm-generic support
  xen: move arm/include/asm/vm_event.h to asm-generic

 .gitignore                          |  1 +
 xen/Makefile                        |  9 +++-
 xen/arch/arm/include/asm/Makefile   |  2 +
 xen/arch/arm/include/asm/vm_event.h | 66 -----------------------------
 xen/include/asm-generic/vm_event.h  | 55 ++++++++++++++++++++++++
 xen/scripts/Kbuild.include          |  6 +++
 xen/scripts/Makefile.asm-generic    | 53 +++++++++++++++++++++++
 7 files changed, 125 insertions(+), 67 deletions(-)
 create mode 100644 xen/arch/arm/include/asm/Makefile
 delete mode 100644 xen/arch/arm/include/asm/vm_event.h
 create mode 100644 xen/include/asm-generic/vm_event.h
 create mode 100644 xen/scripts/Makefile.asm-generic

-- 
2.41.0

[PATCH v7 1/2] xen: asm-generic support

[Oleksii Kurochko]

Some headers are shared between individual architectures or are empty.
To avoid duplication of these headers, asm-generic is introduced.

With the following patch, an architecture uses generic headers
mentioned in the file arch/$(ARCH)/include/asm/Makefile

To use a generic header is needed to add to
arch/$(ARCH)/include/asm/Makefile :
	generic-y += <name-of-header-file.h>

For each mentioned header in arch/$(ARCH)/include/asm/Makefile,
the necessary wrapper in arch/$(ARCH)/include/generated/asm will be
generated.

As the base Makefile.asm-generic from Linux kernel was taken.
( 06c2afb862f9da8 "Linux 6.5-rc1" ).

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
Changes in V7:
 - update warning message in Makefile.asm-generic
 - add Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
 - add Acked-by: Jan Beulich <jbeulich@suse.com>
---
Changes in V6:
 - introduce $(asm-generic) macro in Kbuild.include.
 - move "asm-generic" after the rule "__distclean".
---
Changes in V5:
 - Update the commit message
 - Update SPDX license in Makefile.
 - Remove code related to UML
 - Include $(src)/Makefile instead of $(kbuild-file) 
 - Update comment message in Makefile.asm-generic
 - Update .gitignore
 - Update path to generated headers in CFLAGS.
 - Use the latest version of Linux's Makefile.asm-generic
---
Changes in V4:
 - introduce asm-generic support
 - update commit message
---
Changes in V3:
 - Rename stubs dir to asm-generic
---
Changes in V2:
 - Nothing changed.
---
 .gitignore                       |  1 +
 xen/Makefile                     |  9 +++++-
 xen/scripts/Kbuild.include       |  6 ++++
 xen/scripts/Makefile.asm-generic | 53 ++++++++++++++++++++++++++++++++
 4 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 xen/scripts/Makefile.asm-generic

diff --git a/.gitignore b/.gitignore
index 50273adb8d..287166f8fc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -267,6 +267,7 @@ xen/arch/*/efi/efi.h
 xen/arch/*/efi/pe.c
 xen/arch/*/efi/runtime.c
 xen/arch/*/include/asm/asm-offsets.h
+xen/arch/*/include/generated
 xen/build-dir-cppcheck/
 xen/common/config_data.S
 xen/common/config.gz
diff --git a/xen/Makefile b/xen/Makefile
index f57e5a596c..2dc5e3526d 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -438,6 +438,7 @@ ifdef building_out_of_srctree
 endif
 CFLAGS += -I$(srctree)/include
 CFLAGS += -I$(srctree)/arch/$(SRCARCH)/include
+CFLAGS += -I$(objtree)/arch/$(SRCARCH)/include/generated
 
 # Note that link order matters!
 ALL_OBJS-y                := common/built_in.o
@@ -580,16 +581,22 @@ _clean:
 	rm -f $(TARGET).efi $(TARGET).efi.map $(TARGET).efi.elf $(TARGET).efi.stripped
 	rm -f asm-offsets.s arch/*/include/asm/asm-offsets.h
 	rm -f .banner .allconfig.tmp include/xen/compile.h
+	rm -rf $(objtree)/arch/*/include/generated
 
 .PHONY: _distclean
 _distclean: clean
 	rm -f tags TAGS cscope.files cscope.in.out cscope.out cscope.po.out GTAGS GPATH GRTAGS GSYMS .config source
 
+# Support for using generic headers in asm-generic
+PHONY += asm-generic
+asm-generic:
+	$(Q)$(MAKE) $(asm-generic)=arch/$(SRCARCH)/include/generated/asm
+
 $(TARGET).gz: $(TARGET)
 	gzip -n -f -9 < $< > $@.new
 	mv $@.new $@
 
-$(TARGET): outputmakefile FORCE
+$(TARGET): outputmakefile asm-generic FORCE
 	$(Q)$(MAKE) $(build)=tools
 	$(Q)$(MAKE) $(build)=. include/xen/compile.h
 	$(Q)$(MAKE) $(build)=include all
diff --git a/xen/scripts/Kbuild.include b/xen/scripts/Kbuild.include
index 785a32c32e..c2bd8498e1 100644
--- a/xen/scripts/Kbuild.include
+++ b/xen/scripts/Kbuild.include
@@ -91,6 +91,12 @@ cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3) || e
 
 clang-ifversion = $(shell [ $(CONFIG_CLANG_VERSION)0 $(1) $(2)000 ] && echo $(3) || echo $(4))
 
+###
+# Shorthand for $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.asm-generic obj
+# Usage:
+# $(Q)$(MAKE) $(asm-generic)=dir
+asm-generic := -f $(srctree)/scripts/Makefile.asm-generic obj
+
 ###
 # Shorthand for $(Q)$(MAKE) -f scripts/Makefile.build obj=
 # Usage:
diff --git a/xen/scripts/Makefile.asm-generic b/xen/scripts/Makefile.asm-generic
new file mode 100644
index 0000000000..b0d356bfa3
--- /dev/null
+++ b/xen/scripts/Makefile.asm-generic
@@ -0,0 +1,53 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# include/asm-generic contains a lot of files that are used
+# verbatim by several architectures.
+#
+# This Makefile reads the file arch/$(SRCARCH)/include/asm/Makefile
+# and for each file listed in this file with generic-y creates
+# a small wrapper file in arch/$(SRCARCH)/include/generated/asm.
+
+PHONY := all
+all:
+
+src := $(subst /generated,,$(obj))
+
+include $(srctree)/scripts/Kbuild.include
+-include $(src)/Makefile
+
+redundant := $(filter $(mandatory-y) $(generated-y), $(generic-y))
+redundant += $(foreach f, $(generic-y), $(if $(wildcard $(srctree)/$(src)/$(f)),$(f)))
+redundant := $(sort $(redundant))
+$(if $(redundant),\
+	$(warning redundant generic-y found in $(src)/Makefile: $(redundant)))
+
+# If arch does not implement mandatory headers, fallback to asm-generic ones.
+mandatory-y := $(filter-out $(generated-y), $(mandatory-y))
+generic-y   += $(foreach f, $(mandatory-y), $(if $(wildcard $(srctree)/$(src)/$(f)),,$(f)))
+
+generic-y   := $(addprefix $(obj)/, $(generic-y))
+generated-y := $(addprefix $(obj)/, $(generated-y))
+
+# Remove stale wrappers when the corresponding files are removed from generic-y
+old-headers := $(wildcard $(obj)/*.h)
+unwanted    := $(filter-out $(generic-y) $(generated-y),$(old-headers))
+
+quiet_cmd_wrap = WRAP    $@
+      cmd_wrap = echo "\#include <asm-generic/$*.h>" > $@
+
+quiet_cmd_remove = REMOVE  $(unwanted)
+      cmd_remove = rm -f $(unwanted)
+
+all: $(generic-y)
+	$(if $(unwanted),$(call cmd,remove))
+	@:
+
+$(obj)/%.h:
+	$(call cmd,wrap)
+
+# Create output directory. Skip it if at least one old header exists
+# since we know the output directory already exists.
+ifeq ($(old-headers),)
+$(shell mkdir -p $(obj))
+endif
+
+.PHONY: $(PHONY)
-- 
2.41.0

[PATCH v7 2/2] xen: move arm/include/asm/vm_event.h to asm-generic

[Oleksii Kurochko]

asm/vm_event.h is common for ARM and RISC-V so it will be moved to
asm-generic dir.

Original asm/vm_event.h from ARM was updated:
 * use SPDX-License-Identifier.
 * update comment messages of stubs.
 * update #ifdef
 * instead of "include <public/domctl.h>" -> "public/vm_event.h"

As vm_event.h was moved to asm-generic then it is needed to create
Makefile in arm/include/asm/ and add generated-y += vm_event.h to
it.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
---
Changes in V7:
 - update guards in asm-generic/vm_event.h.
 - add Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
---
Changes in V6:
 - update the commit message.
---
Changes in V5:
 - Update the commit message
 - Remove Acked-by:...
 - Switch ARM to use asm-generic/vm_event.h
---
Changes in V4:
 - update path of vm_event.h from include/asm-generic/asm to include/asm-generic
---
Changes in V3:
 - add Acked-by: Stefano Stabellini <sstabellini@kernel.org> for "xen: move arm/include/asm/vm_event.h to asm-generic"
 - update SPDX tag.
 - move asm/vm_event.h to asm-generic.
---
Changes in V2:
 - change public/domctl.h to public/vm_event.h.
 - update commit message of [PATCH v2 2/2] xen: move arm/include/asm/vm_event.h to stubs
---
 xen/arch/arm/include/asm/Makefile   |  2 +
 xen/arch/arm/include/asm/vm_event.h | 66 -----------------------------
 xen/include/asm-generic/vm_event.h  | 55 ++++++++++++++++++++++++
 3 files changed, 57 insertions(+), 66 deletions(-)
 create mode 100644 xen/arch/arm/include/asm/Makefile
 delete mode 100644 xen/arch/arm/include/asm/vm_event.h
 create mode 100644 xen/include/asm-generic/vm_event.h

diff --git a/xen/arch/arm/include/asm/Makefile b/xen/arch/arm/include/asm/Makefile
new file mode 100644
index 0000000000..821addb0bf
--- /dev/null
+++ b/xen/arch/arm/include/asm/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+generic-y += vm_event.h
diff --git a/xen/arch/arm/include/asm/vm_event.h b/xen/arch/arm/include/asm/vm_event.h
deleted file mode 100644
index 4d861373b3..0000000000
--- a/xen/arch/arm/include/asm/vm_event.h
+++ /dev/null
@@ -1,66 +0,0 @@
-/*
- * vm_event.h: architecture specific vm_event handling routines
- *
- * Copyright (c) 2015 Tamas K Lengyel (tamas@tklengyel.com)
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms and conditions of the GNU General Public License,
- * version 2, as published by the Free Software Foundation.
- *
- * This program is distributed in the hope it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along with
- * this program; If not, see <http://www.gnu.org/licenses/>.
- */
-
-#ifndef __ASM_ARM_VM_EVENT_H__
-#define __ASM_ARM_VM_EVENT_H__
-
-#include <xen/sched.h>
-#include <public/domctl.h>
-
-static inline int vm_event_init_domain(struct domain *d)
-{
-    /* Nothing to do. */
-    return 0;
-}
-
-static inline void vm_event_cleanup_domain(struct domain *d)
-{
-    memset(&d->monitor, 0, sizeof(d->monitor));
-}
-
-static inline void vm_event_toggle_singlestep(struct domain *d, struct vcpu *v,
-                                              vm_event_response_t *rsp)
-{
-    /* Not supported on ARM. */
-}
-
-static inline
-void vm_event_register_write_resume(struct vcpu *v, vm_event_response_t *rsp)
-{
-    /* Not supported on ARM. */
-}
-
-static inline
-void vm_event_emulate_check(struct vcpu *v, vm_event_response_t *rsp)
-{
-    /* Not supported on ARM. */
-}
-
-static inline
-void vm_event_sync_event(struct vcpu *v, bool value)
-{
-    /* Not supported on ARM. */
-}
-
-static inline
-void vm_event_reset_vmtrace(struct vcpu *v)
-{
-    /* Not supported on ARM. */
-}
-
-#endif /* __ASM_ARM_VM_EVENT_H__ */
diff --git a/xen/include/asm-generic/vm_event.h b/xen/include/asm-generic/vm_event.h
new file mode 100644
index 0000000000..620c7b971c
--- /dev/null
+++ b/xen/include/asm-generic/vm_event.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier:  GPL-2.0-only */
+/*
+ * vm_event.h: stubs for architecture specific vm_event handling routines
+ *
+ * Copyright (c) 2015 Tamas K Lengyel (tamas@tklengyel.com)
+ */
+
+#ifndef __ASM_GENERIC_VM_EVENT_H__
+#define __ASM_GENERIC_VM_EVENT_H__
+
+#include <xen/sched.h>
+#include <public/vm_event.h>
+
+static inline int vm_event_init_domain(struct domain *d)
+{
+    /* Nothing to do. */
+    return 0;
+}
+
+static inline void vm_event_cleanup_domain(struct domain *d)
+{
+    memset(&d->monitor, 0, sizeof(d->monitor));
+}
+
+static inline void vm_event_toggle_singlestep(struct domain *d, struct vcpu *v,
+                                              vm_event_response_t *rsp)
+{
+    /* Nothing to do. */
+}
+
+static inline
+void vm_event_register_write_resume(struct vcpu *v, vm_event_response_t *rsp)
+{
+    /* Nothing to do. */
+}
+
+static inline
+void vm_event_emulate_check(struct vcpu *v, vm_event_response_t *rsp)
+{
+    /* Nothing to do. */
+}
+
+static inline
+void vm_event_sync_event(struct vcpu *v, bool value)
+{
+    /* Nothing to do. */
+}
+
+static inline
+void vm_event_reset_vmtrace(struct vcpu *v)
+{
+    /* Nothing to do. */
+}
+
+#endif /* __ASM_GENERIC_VM_EVENT_H__ */
-- 
2.41.0