perf llvm: Fix script used to obtain kernel make directives to work with new kbuild

Before this patch:

  # ./perf test 39 41
  39: LLVM search and compile                               :
  39.1: Basic BPF llvm compile                              : Ok
  39.2: kbuild searching                                    : FAILED!
  39.3: Compile source for BPF prologue generation          : Skip
  39.4: Compile source for BPF relocation                   : Skip
  41: BPF filter                                            :
  41.1: Basic BPF filtering                                 : Ok
  41.2: BPF pinning                                         : Ok
  41.3: BPF prologue generation                             : FAILED!
  41.4: BPF relocation checker                              : Skip
  #

Using 'perf test -v' for these tests shows that it is not finding
uapi/linux/fs.h, which ends up being because we don't setup the right header
path. Fix it.

After this patch:

  # perf test 39 41
  39: LLVM search and compile                               :
  39.1: Basic BPF llvm compile                              : Ok
  39.2: kbuild searching                                    : Ok
  39.3: Compile source for BPF prologue generation          : Ok
  39.4: Compile source for BPF relocation                   : Ok
  41: BPF filter                                            :
  41.1: Basic BPF filtering                                 : Ok
  41.2: BPF pinning                                         : Ok
  41.3: BPF prologue generation                             : Ok
  41.4: BPF relocation checker                              : Ok
  #

Longer description:

In llvm-utils.c we use some techniques to obtain the kbuild make
directives and that recently stopped working as now 'ar' gets called and
expects to find the dummy.o used to echo these variables:

  $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS)

Add the $(CC) line to satisfy that, making sure this works with all
kernels, i.e. preserving the temp directory and files in it used for
this technique we can see that it works everywhere:

  # make -s -C /lib/modules/5.4.18-100.fc30.x86_64/build M=/tmp/tmp.qgaFHgxjZ4/ clean
  # ls -la /tmp/tmp.qgaFHgxjZ4/
  total 4
  drwx------.  2 root root   80 Feb 14 09:42 .
  drwxrwxrwt. 47 root root 1200 Feb 14 09:42 ..
  -rw-r--r--.  1 root root    0 Feb 13 17:14 dummy.c
  -rw-r--r--.  1 root root  121 Feb 13 17:14 Makefile
  #
  # cat /tmp/tmp.qgaFHgxjZ4/Makefile
  obj-y := dummy.o
  $(obj)/%.o: $(src)/%.c
          @echo -n "$(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS)"
          $(CC) -c -o $@ $<
  #

Then build with an old kernel Makefile:

  # make -s -C /lib/modules/5.4.18-100.fc30.x86_64/build M=/tmp/tmp.qgaFHgxjZ4/ dummy.o
  -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/9/include -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/kconfig.h
  #
  # ls -la /tmp/tmp.qgaFHgxjZ4/
  total 8
  drwx------.  2 root root  100 Feb 14 09:43 .
  drwxrwxrwt. 47 root root 1200 Feb 14 09:43 ..
  -rw-r--r--.  1 root root    0 Feb 13 17:14 dummy.c
  -rw-r--r--.  1 root root  936 Feb 14 09:43 dummy.o
  -rw-r--r--.  1 root root  121 Feb 13 17:14 Makefile
  #

And a new one:

  # make -s -C /lib/modules/5.4.18-100.fc30.x86_64/build M=/tmp/tmp.qgaFHgxjZ4/ clean
  # ls -la /tmp/tmp.qgaFHgxjZ4/
  total 4
  drwx------.  2 root root   80 Feb 14 09:43 .
  drwxrwxrwt. 47 root root 1200 Feb 14 09:43 ..
  -rw-r--r--.  1 root root    0 Feb 13 17:14 dummy.c
  -rw-r--r--.  1 root root  121 Feb 13 17:14 Makefile
  # make -s -C /lib/modules/5.6.0-rc1+/build M=/tmp/tmp.qgaFHgxjZ4/ dummy.o
   -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/9/include -I/home/acme/git/linux/arch/x86/include -I./arch/x86/include/generated -I/home/acme/git/linux/include -I./include -I/home/acme/git/linux/arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I/home/acme/git/linux/include/uapi -I./include/generated/uapi -include /home/acme/git/linux/include/linux/kconfig.h
  #
  # ls -la /tmp/tmp.qgaFHgxjZ4/
  total 16
  drwx------.  2 root root  160 Feb 14 09:44 .
  drwxrwxrwt. 47 root root 1200 Feb 14 09:44 ..
  -rw-r--r--.  1 root root  158 Feb 14 09:44 built-in.a
  -rw-r--r--.  1 root root  149 Feb 14 09:44 .built-in.a.cmd
  -rw-r--r--.  1 root root    0 Feb 13 17:14 dummy.c
  -rw-r--r--.  1 root root  936 Feb 14 09:44 dummy.o
  -rw-r--r--.  1 root root  121 Feb 13 17:14 Makefile
  -rw-r--r--.  1 root root    0 Feb 14 09:44 modules.order
  #

Reported-by: Thomas Richter <[email protected]>
Tested-by: Thomas Richter <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: He Kuang <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Sumanth Korikkar <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Wang Nan <[email protected]>
Cc: Zefan Li <[email protected]>
Link: https://www.spinics.net/lists/linux-perf-users/msg10600.html
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: acmel

tools/perf/util/llvm-utils.c

@@ -288,6 +288,7 @@ static const char *kinc_fetch_script =
 "obj-y := dummy.o\n"
 "\\$(obj)/%.o: \\$(src)/%.c\n"
 "\t@echo -n \"\\$(NOSTDINC_FLAGS) \\$(LINUXINCLUDE) \\$(EXTRA_CFLAGS)\"\n"
+"\t\\$(CC) -c -o \\$@ \\$<\n"
 "EOF\n"
 "touch $TMPDIR/dummy.c\n"
 "make -s -C $KBUILD_DIR M=$TMPDIR $KBUILD_OPTS dummy.o 2>/dev/null\n"