kbuild: introduce ld-option

ld-option is used to check if $(LD) supports a specific option.

Based on patch from Andi Kleen.

Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
First use is to check if option -X is supported (upcoming patch).
Theis is ne

2 files changed, 21 insertions, 1 deletions

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 7847fce13bd6..71c602d61680 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -18,6 +18,7 @@ This document describes the Linux kernel Makefiles.
            --- 3.9 Dependency tracking
            --- 3.10 Special Rules
            --- 3.11 $(CC) support functions
+           --- 3.12 $(LD) support functions
 
         === 4 Host Program support
            --- 4.1 Simple Host Program
@@ -570,6 +571,19 @@ more details, with real examples.
                         endif
                 endif
 
+--- 3.12 $(LD) support functions
+
+    ld-option
+        ld-option is used to check if $(LD) supports the supplied option.
+        ld-option takes two options as arguments.
+        The second argument is an optional option that can be used if the
+        first option is not supported by $(LD).
+
+        Example:
+                #Makefile
+                LDFLAGS_vmlinux += $(call really-ld-option, -X)
+
+
 === 4 Host Program support
 
 Kbuild supports building executables on the host for use during the
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 94a4f682f385..b3452601b0b1 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -83,11 +83,12 @@ TMPOUT := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)
 # is automatically cleaned up.
 try-run = $(shell set -e;               \
         TMP="$(TMPOUT).$$$$.tmp";       \
+        TMPO="$(TMPOUT).$$$$.o";        \
         if ($(1)) >/dev/null 2>&1;      \
         then echo "$(2)";               \
         else echo "$(3)";               \
         fi;                             \
-        rm -f "$$TMP")
+        rm -f "$$TMP" "$$TMPO")
 
 # as-option
 # Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
@@ -135,6 +136,11 @@ cc-ifversion = $(shell [ $(call cc-version, $(CC)) $(1) $(2) ] && echo $(3))
 cc-ldoption = $(call try-run,\
         $(CC) $(1) -nostdlib -xc /dev/null -o "$$TMP",$(1),$(2))
 
+# ld-option
+# Usage: LDFLAGS += $(call ld-option, -X)
+ld-option = $(call try-run,\
+        $(CC) /dev/null -c -o "$$TMPO" ; $(LD) $(1) "$$TMPO" -o "$$TMP",$(1),$(2))
+
 ######
 
 ###