[XEN PATCH v2] build: Fix x86 out-of-tree build without EFI

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

We can't have a source file with the same name that exist in both the
common code and in the arch specific code for efi/. This can lead to
comfusion in make and it can pick up the wrong source file. This issue
lead to a failure to build a pv-shim for x86 out-of-tree, as this is
one example of an x86 build using the efi/stub.c.

The issue is that in out-of-tree, make might find x86/efi/stub.c via
VPATH, but as the target needs to be rebuilt due to FORCE, make
actually avoid changing the source tree and rebuilt the target with
VPATH ignored, so $@ lead to the build tree where "stub.c" dosen't
exist yet so a link is made to "common/stub.c".

Rework the new common/stub.c file to have a different name than the
already existing one, by renaming the existing one. We will take
example of efi/boot.c and have the common stub.c include a per-arch
stub.h. This at least avoid the need to expose to Arm both alias
efi_compat_get_info and efi_compat_runtime_call.

Avoid using $(EFIOBJ-y) as an alias for $(clean-files), add
"stub.c" directly to $(clean-files).

Also update .gitignore as this was also missing from the original
patch.

Fixes: 7f96859b0d00 ("xen: reuse x86 EFI stub functions for Arm")
Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---

Notes:
    v2:
    - instead of renaming common/efi/stub.c to common_stub.c; we rename
      arch/*/efi/stub.c to stub.h and include it from common/stub.c
    - update .gitignore
    
    CC: Jan Beulich <jbeulich@xxxxxxxx>
    CC: Wei Chen <wei.chen@xxxxxxx>

 xen/arch/arm/efi/Makefile           | 4 ----
 xen/common/efi/efi-common.mk        | 4 ++--
 xen/arch/arm/efi/stub.h             | 4 ++++
 xen/arch/x86/efi/{stub.c => stub.h} | 5 ++++-
 xen/common/efi/stub.c               | 5 +++++
 .gitignore                          | 1 +
 6 files changed, 16 insertions(+), 7 deletions(-)
 create mode 100644 xen/arch/arm/efi/stub.h
 rename xen/arch/x86/efi/{stub.c => stub.h} (93%)

diff --git a/xen/arch/arm/efi/Makefile b/xen/arch/arm/efi/Makefile
index bd954a3b2d..ff1bcd6c50 100644
--- a/xen/arch/arm/efi/Makefile
+++ b/xen/arch/arm/efi/Makefile
@@ -4,10 +4,6 @@ ifeq ($(CONFIG_ARM_EFI),y)
 obj-y += $(EFIOBJ-y)
 obj-$(CONFIG_ACPI) +=  efi-dom0.init.o
 else
-# Add stub.o to EFIOBJ-y to re-use the clean-files in
-# efi-common.mk. Otherwise the link of stub.c in arm/efi
-# will not be cleaned in "make clean".
-EFIOBJ-y += stub.o
 obj-y += stub.o
 
 $(obj)/stub.o: CFLAGS-y += -fno-short-wchar
diff --git a/xen/common/efi/efi-common.mk b/xen/common/efi/efi-common.mk
index ec2c34f198..950f564575 100644
--- a/xen/common/efi/efi-common.mk
+++ b/xen/common/efi/efi-common.mk
@@ -9,9 +9,9 @@ CFLAGS-y += -iquote $(srcdir)
 # e.g.: It transforms "dir/foo/bar" into successively
 #       "dir foo bar", ".. .. ..", "../../.."
 $(obj)/%.c: $(srctree)/common/efi/%.c FORCE
-       $(Q)test -f $@ || \
-           ln -nfs $(subst $(space),/,$(patsubst %,..,$(subst /, 
,$(obj))))/source/common/efi/$(<F) $@
+       $(Q)ln -nfs $(subst $(space),/,$(patsubst %,..,$(subst /, 
,$(obj))))/source/common/efi/$(<F) $@
 
 clean-files += $(patsubst %.o, %.c, $(EFIOBJ-y:.init.o=.o) $(EFIOBJ-))
+clean-files += stub.c
 
 .PRECIOUS: $(obj)/%.c
diff --git a/xen/arch/arm/efi/stub.h b/xen/arch/arm/efi/stub.h
new file mode 100644
index 0000000000..b0a9b03e59
--- /dev/null
+++ b/xen/arch/arm/efi/stub.h
@@ -0,0 +1,4 @@
+/*
+ * Architecture specific implementation for EFI stub code.  This file
+ * is intended to be included by common/efi/stub.c _only_.
+ */
diff --git a/xen/arch/x86/efi/stub.c b/xen/arch/x86/efi/stub.h
similarity index 93%
rename from xen/arch/x86/efi/stub.c
rename to xen/arch/x86/efi/stub.h
index f2365bc041..9d2845b833 100644
--- a/xen/arch/x86/efi/stub.c
+++ b/xen/arch/x86/efi/stub.h
@@ -1,3 +1,7 @@
+/*
+ * Architecture specific implementation for EFI stub code.  This file
+ * is intended to be included by common/efi/stub.c _only_.
+ */
 #include <xen/efi.h>
 #include <xen/init.h>
 #include <asm/asm_defns.h>
@@ -8,7 +12,6 @@
 #include <efi/eficon.h>
 #include <efi/efidevp.h>
 #include <efi/efiapi.h>
-#include "../../../common/efi/stub.c"
 
 /*
  * Here we are in EFI stub. EFI calls are not supported due to lack
diff --git a/xen/common/efi/stub.c b/xen/common/efi/stub.c
index 15694632c2..854efd9c99 100644
--- a/xen/common/efi/stub.c
+++ b/xen/common/efi/stub.c
@@ -30,3 +30,8 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
 {
     return -ENOSYS;
 }
+
+/*
+ * Include architecture specific implementation here.
+ */
+#include "stub.h"
diff --git a/.gitignore b/.gitignore
index ed7bd8bdc7..3a91e79672 100644
--- a/.gitignore
+++ b/.gitignore
@@ -311,6 +311,7 @@ xen/arch/*/efi/ebmalloc.c
 xen/arch/*/efi/efi.h
 xen/arch/*/efi/pe.c
 xen/arch/*/efi/runtime.c
+xen/arch/*/efi/stub.c
 xen/arch/*/include/asm/asm-offsets.h
 xen/common/config_data.S
 xen/common/config.gz
-- 
Anthony PERARD