[xen master] build: fix enforce unique symbols for recent clang version

[patchbot@xxxxxxx]

commit 035ab75d8e37b63729886d7cb760b085ffde9977
Author:     Anthony PERARD <anthony.perard@xxxxxxxxxx>
AuthorDate: Fri Feb 18 08:59:03 2022 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Feb 18 08:59:03 2022 +0100

    build: fix enforce unique symbols for recent clang version
    
    clang 6.0 and newer behave like gcc in regards for the FILE symbol, so
    only the filename rather than the full path to the source file.
    
    clang 3.8.1-24 (in our debian:stretch container) and 3.5.0-10
    (in our debian:jessie container) do store the full path to the source
    file in the FILE symbol.
    
    Also we have commit 81ecb38b83 ("build: provide option to disambiguate
    symbol names") which were using clang 5, and LLVM's commit f5040b9685a7
    [1] ("Make .file directive to have basename only") which is part of
    "llvmorg-6.0.0" tag but not "release/5.x" branch. Both suggest that
    clang change of behavior happened with clang 6.0.
    
    This means that we also need to check clang version to figure out
    which command we need to use to redefine symbol.
    
    Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    
    [1] 
https://github.com/llvm/llvm-project/commit/f5040b9685a760e584c576e9185295e54635d51e
---
 xen/Rules.mk               | 2 +-
 xen/scripts/Kbuild.include | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/xen/Rules.mk b/xen/Rules.mk
index 60d1d6c4f5..1e7f47a3d8 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -166,7 +166,7 @@ SRCPATH := $(patsubst $(BASEDIR)/%,%,$(CURDIR))
 quiet_cmd_cc_o_c = CC      $@
 ifeq ($(CONFIG_ENFORCE_UNIQUE_SYMBOLS),y)
     cmd_cc_o_c = $(CC) $(c_flags) -c $< -o $(dot-target).tmp -MQ $@
-    ifeq ($(CONFIG_CC_IS_CLANG),y)
+    ifeq ($(CONFIG_CC_IS_CLANG)$(call clang-ifversion,-lt,600,y),yy)
         cmd_objcopy_fix_sym = $(OBJCOPY) --redefine-sym $<=$(SRCPATH)/$< 
$(dot-target).tmp $@
     else
         cmd_objcopy_fix_sym = $(OBJCOPY) --redefine-sym $(<F)=$(SRCPATH)/$< 
$(dot-target).tmp $@
diff --git a/xen/scripts/Kbuild.include b/xen/scripts/Kbuild.include
index f75d724ed7..2d482d1cb9 100644
--- a/xen/scripts/Kbuild.include
+++ b/xen/scripts/Kbuild.include
@@ -59,6 +59,8 @@ ld-option = $(call success,$(LD) -v $(1))
 # Usage:  EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)
 cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3) || 
echo $(4))
 
+clang-ifversion = $(shell [ $(CONFIG_CLANG_VERSION)0 $(1) $(2)000 ] && echo 
$(3) || echo $(4))
+
 # Shorthand for $(MAKE) clean
 # Usage:
 # $(MAKE) $(clean) dir
--
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