Fix kselftest builds when specifying an output dir

From: "Tyler Hicks" <[email protected]>

When attempting to build kselftests with a separate output directory, a number of the tests fail to build.

For example,

 $ rm -rf build && \
   make INSTALL_HDR_PATH=build/usr headers_install > /dev/null && \
   make O=build FORCE_TARGETS=1 TARGETS=breakpoints -C tools/testing/selftests > /dev/null
 /usr/bin/ld: cannot open output file
 build/kselftest/breakpoints/step_after_suspend_test: No such file or directory
 collect2: error: ld returned 1 exit status
 make[1]: *** [../lib.mk:146: build/kselftest/breakpoints/step_after_suspend_test] Error 1
 make: *** [Makefile:163: all] Error 2

This has already been addressed upstream with v5.18 commit 5ad51ab618de ("selftests: set the BUILD variable to absolute path"). It is a clean cherry pick to the linux-5.15.y and linux-5.10.y branches.

Tyler

Muhammad Usama Anjum (1):
selftests: set the BUILD variable to absolute path

 tools/testing/selftests/Makefile | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

2.34.1

From: Muhammad Usama Anjum <[email protected]>

commit 5ad51ab618de5d05f4e692ebabeb6fe6289aaa57 upstream.

The build of kselftests fails if relative path is specified through KBUILD_OUTPUT or O=<path> method. BUILD variable is used to determine the path of the output objects. When make is run from other directories with relative paths, the exact path of the build objects is ambiguous and build fails.

make[1]: Entering directory '/home/usama/repos/kernel/linux_mainline2/tools/testing/selftests/alsa'
gcc mixer-test.c -L/usr/lib/x86_64-linux-gnu -lasound -o build/kselftest/alsa/mixer-test
/usr/bin/ld: cannot open output file build/kselftest/alsa/mixer-test

Set the BUILD variable to the absolute path of the output directory. Make the logic readable and easy to follow. Use spaces instead of tabs for indentation as if with tab indentation is considered recipe in make.

---
 tools/testing/selftests/Makefile | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

index 14206d1d1efe..56a4873a343c 100644
@@ -114,19 +114,27 @@ ifdef building_out_of_srctree
 override LDFLAGS =
 endif
 
-ifneq ($(O),)
-	BUILD := $(O)/kselftest
+top_srcdir ?= ../../..
+
+ifeq ("$(origin O)", "command line")
+  KBUILD_OUTPUT := $(O)
+endif
+
+ifneq ($(KBUILD_OUTPUT),)
+  # Make's built-in functions such as $(abspath ...), $(realpath ...) cannot
+  # expand a shell special character '~'. We use a somewhat tedious way here.
+  abs_objtree := $(shell cd $(top_srcdir) && mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) && pwd)
+  $(if $(abs_objtree),, \
+    $(error failed to create output directory "$(KBUILD_OUTPUT)"))
+  # $(realpath ...) resolves symlinks
+  abs_objtree := $(realpath $(abs_objtree))
+  BUILD := $(abs_objtree)/kselftest
 else
-	ifneq ($(KBUILD_OUTPUT),)
-		BUILD := $(KBUILD_OUTPUT)/kselftest
-	else
-		BUILD := $(shell pwd)
-		DEFAULT_INSTALL_HDR_PATH := 1
-	endif
+  BUILD := $(CURDIR)
+  DEFAULT_INSTALL_HDR_PATH := 1
 endif
 
 # Prepare for headers install
-top_srcdir ?= ../../..
 include $(top_srcdir)/scripts/subarch.include
 ARCH           ?= $(SUBARCH)
 export KSFT_KHDR_INSTALL_DONE := 1

2.34.1

Now queued up, thanks.

greg k-h