perf tools: Auto detecting kernel include options

To help user find correct kernel include options, this patch extracts
them from kbuild system by an embedded script kinc_fetch_script, which
creates a temporary directory, generates Makefile and an empty dummy.o
then use the Makefile to fetch $(NOSTDINC_FLAGS), $(LINUXINCLUDE) and
$(EXTRA_CFLAGS) options. The result is passed to compiler script using
'KERNEL_INC_OPTIONS' environment variable.

Because options from kbuild contains relative path like
'Iinclude/generated/uapi', the work directory must be changed. This is
done by previous patch.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1436445342-1402-16-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 55 insertions, 5 deletions

diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index 6bfcb2dd3161..5887bb8c1243 100644
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -246,15 +246,42 @@ static int detect_kbuild_dir(char **kbuild_dir)
         return -ENOENT;
 }
 
+static const char *kinc_fetch_script =
+"#!/usr/bin/env sh\n"
+"if ! test -d \"$KBUILD_DIR\"\n"
+"then\n"
+"       exit -1\n"
+"fi\n"
+"if ! test -f \"$KBUILD_DIR/include/generated/autoconf.h\"\n"
+"then\n"
+"       exit -1\n"
+"fi\n"
+"TMPDIR=`mktemp -d`\n"
+"if test -z \"$TMPDIR\"\n"
+"then\n"
+"    exit -1\n"
+"fi\n"
+"cat << EOF > $TMPDIR/Makefile\n"
+"obj-y := dummy.o\n"
+"\\$(obj)/%.o: \\$(src)/%.c\n"
+"\t@echo -n \"\\$(NOSTDINC_FLAGS) \\$(LINUXINCLUDE) \\$(EXTRA_CFLAGS)\"\n"
+"EOF\n"
+"touch $TMPDIR/dummy.c\n"
+"make -s -C $KBUILD_DIR M=$TMPDIR $KBUILD_OPTS dummy.o 2>/dev/null\n"
+"RET=$?\n"
+"rm -rf $TMPDIR\n"
+"exit $RET\n";
+
 static inline void
-get_kbuild_opts(char **kbuild_dir)
+get_kbuild_opts(char **kbuild_dir, char **kbuild_include_opts)
 {
         int err;
 
-        if (!kbuild_dir)
+        if (!kbuild_dir || !kbuild_include_opts)
                 return;
 
         *kbuild_dir = NULL;
+        *kbuild_include_opts = NULL;
 
         if (llvm_param.kbuild_dir && !llvm_param.kbuild_dir[0]) {
                 pr_debug("[llvm.kbuild-dir] is set to \"\" deliberately.\n");
@@ -271,6 +298,27 @@ get_kbuild_opts(char **kbuild_dir)
 "     \tdetection.\n\n");
                 return;
         }
+
+        pr_debug("Kernel build dir is set to %s\n", *kbuild_dir);
+        force_set_env("KBUILD_DIR", *kbuild_dir);
+        force_set_env("KBUILD_OPTS", llvm_param.kbuild_opts);
+        err = read_from_pipe(kinc_fetch_script,
+                             (void **)kbuild_include_opts,
+                             NULL);
+        if (err) {
+                pr_warning(
+"WARNING:\tunable to get kernel include directories from '%s'\n"
+"Hint:\tTry set clang include options using 'clang-bpf-cmd-template'\n"
+"     \toption in [llvm] section of ~/.perfconfig and set 'kbuild-dir'\n"
+"     \toption in [llvm] to \"\" to suppress this detection.\n\n",
+                        *kbuild_dir);
+
+                free(*kbuild_dir);
+                *kbuild_dir = NULL;
+                return;
+        }
+
+        pr_debug("include option is set to %s\n", *kbuild_include_opts);
 }
 
 int llvm__compile_bpf(const char *path, void **p_obj_buf,
@@ -280,7 +328,7 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
         char clang_path[PATH_MAX];
         const char *clang_opt = llvm_param.clang_opt;
         const char *template = llvm_param.clang_bpf_cmd_template;
-        char *kbuild_dir = NULL;
+        char *kbuild_dir = NULL, *kbuild_include_opts = NULL;
         void *obj_buf = NULL;
         size_t obj_buf_sz;
 
@@ -302,11 +350,11 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
          * This is an optional work. Even it fail we can continue our
          * work. Needn't to check error return.
          */
-        get_kbuild_opts(&kbuild_dir);
+        get_kbuild_opts(&kbuild_dir, &kbuild_include_opts);
 
         force_set_env("CLANG_EXEC", clang_path);
         force_set_env("CLANG_OPTIONS", clang_opt);
-        force_set_env("KERNEL_INC_OPTIONS", NULL);
+        force_set_env("KERNEL_INC_OPTIONS", kbuild_include_opts);
         force_set_env("WORKING_DIR", kbuild_dir ? : ".");
 
         /*
@@ -330,6 +378,7 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
         }
 
         free(kbuild_dir);
+        free(kbuild_include_opts);
         if (!p_obj_buf)
                 free(obj_buf);
         else
@@ -340,6 +389,7 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
         return 0;
 errout:
         free(kbuild_dir);
+        free(kbuild_include_opts);
         free(obj_buf);
         if (p_obj_buf)
                 *p_obj_buf = NULL;