lkl: add lld support for x86_64

lld, the LLVM linker, can link recent mainline Linux kernel. This commit adds lld support to lkl for x86_64 Linux host with clang. To build with lld, invoke make like below: make -C tools/lkl CC=clang LD=ld.lld Signed-off-by: Akira Moroo <[email protected]>
lkl · Oct 21, 2019 · 66208e2 · 66208e2
1 parent 8a1fc6c
commit 66208e2
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Showing 2 changed files with 21 additions and 2 deletions.
diff --git a/arch/lkl/auto.conf b/arch/lkl/auto.conf
@@ -1,2 +1,9 @@
-export OUTPUT_FORMAT=$(shell $(LD) -r -print-output-format)
+ifneq ($(shell $(LD) --version 2>&1 | head -n 1 | grep LLD),)
+  CC_TARGET=$(shell $(CC) --version 2>&1 | grep Target | cut -d " " -f2)
+  ifeq ($(CC_TARGET),x86_64-unknown-linux-gnu)
+    export OUTPUT_FORMAT=elf64-x86-64
+  endif
+else
+  export OUTPUT_FORMAT=$(shell $(LD) -r -print-output-format)
+endif
 export EXEC_FORMAT=$(shell echo $(OUTPUT_FORMAT) | cut -d - -f1)
diff --git a/tools/lkl/Makefile.autoconf b/tools/lkl/Makefile.autoconf
@@ -8,6 +8,17 @@ define set_autoconf_var
   export LKL_HOST_CONFIG_$(1)=$(2)
 endef
 
+define output_format
+  $(if $(shell $(LD) --version 2>&1 | head -n 1 \
+	  | grep LLD),$(eval lld=yes),$(eval lld=no))
+  $(if $(filter yes,$(lld)),$(eval target=$(shell $(CC) --version 2>&1 \
+	  | grep Target | cut -d " " -f2)))
+  $(if $(filter x86_64-unknown-linux-gnu,$(target)),$(call \
+	  set_autoconf_var,OUTPUT_FORMAT,"elf64-x86-64"))
+  $(if $(filter no,$(lld)),$(call set_autoconf_var,OUTPUT_FORMAT,"$(shell \
+	  $(LD) -r -print-output-format)"))
+endef
+
 define find_include
   $(eval include_paths=$(shell $(CC) -E -Wp,-v -xc /dev/null 2>&1 | grep '^ '))
   $(foreach f, $(include_paths), $(wildcard $(f)/$(1)))
@@ -98,7 +109,8 @@ define do_autoconf
   export AR := $(CROSS_COMPILE)ar
   $(eval LD := $(CROSS_COMPILE)ld)
   $(eval CC := $(CROSS_COMPILE)gcc)
-  $(eval LD_FMT := $(shell $(LD) -r -print-output-format))
+  $(call output_format)
+  $(eval LD_FMT := $(shell echo $(LKL_HOST_CONFIG_OUTPUT_FORMAT)))
   $(eval EXEC_FMT := $(shell echo $(LD_FMT) | cut -d "-" -f1))
   $(if $(filter $(EXEC_FMT),$(POSIX_HOSTS)),$(call posix_host,$(LD_FMT)))
   $(if $(filter $(EXEC_FMT),$(NT_HOSTS)),$(call nt_host,$(LD_FMT)))