Following commits will use builtin clang to compile BPF script.
llvm__get_kbuild_opts() is extracted to help it detect kbuild dir
and include options.

Signed-off-by: Wang Nan <wangn...@huawei.com>
Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: Alexei Starovoitov <a...@fb.com>
Cc: He Kuang <heku...@huawei.com>
Cc: Jiri Olsa <jo...@kernel.org>
---
 tools/perf/util/llvm-utils.c | 44 ++++++++++++++++++++++++++++++++++++++------
 tools/perf/util/llvm-utils.h |  3 +++
 2 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index bf7216b..d780a82 100644
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -7,6 +7,7 @@
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <linux/err.h>
 #include "debug.h"
 #include "llvm-utils.h"
 #include "config.h"
@@ -282,9 +283,10 @@ static const char *kinc_fetch_script =
 "rm -rf $TMPDIR\n"
 "exit $RET\n";
 
-static inline void
-get_kbuild_opts(char **kbuild_dir, char **kbuild_include_opts)
+void llvm__get_kbuild_opts(char **kbuild_dir, char **kbuild_include_opts)
 {
+       static char *saved_kbuild_dir;
+       static char *saved_kbuild_include_opts;
        int err;
 
        if (!kbuild_dir || !kbuild_include_opts)
@@ -293,10 +295,28 @@ get_kbuild_opts(char **kbuild_dir, char 
**kbuild_include_opts)
        *kbuild_dir = NULL;
        *kbuild_include_opts = NULL;
 
+       if (saved_kbuild_dir && saved_kbuild_include_opts &&
+           !IS_ERR(saved_kbuild_dir) && !IS_ERR(saved_kbuild_include_opts)) {
+               *kbuild_dir = strdup(saved_kbuild_dir);
+               *kbuild_include_opts = strdup(saved_kbuild_include_opts);
+
+               if (*kbuild_dir && *kbuild_include_opts)
+                       return;
+
+               zfree(kbuild_dir);
+               zfree(kbuild_include_opts);
+               /*
+                * Don't fall through: it may breaks saved_kbuild_dir and
+                * saved_kbuild_include_opts if detect them again when
+                * memory is low.
+                */
+               return;
+       }
+
        if (llvm_param.kbuild_dir && !llvm_param.kbuild_dir[0]) {
                pr_debug("[llvm.kbuild-dir] is set to \"\" deliberately.\n");
                pr_debug("Skip kbuild options detection.\n");
-               return;
+               goto errout;
        }
 
        err = detect_kbuild_dir(kbuild_dir);
@@ -306,7 +326,7 @@ get_kbuild_opts(char **kbuild_dir, char 
**kbuild_include_opts)
 "Hint:\tSet correct kbuild directory using 'kbuild-dir' option in [llvm]\n"
 "     \tsection of ~/.perfconfig or set it to \"\" to suppress kbuild\n"
 "     \tdetection.\n\n");
-               return;
+               goto errout;
        }
 
        pr_debug("Kernel build dir is set to %s\n", *kbuild_dir);
@@ -325,10 +345,22 @@ get_kbuild_opts(char **kbuild_dir, char 
**kbuild_include_opts)
 
                free(*kbuild_dir);
                *kbuild_dir = NULL;
-               return;
+               goto errout;
        }
 
        pr_debug("include option is set to %s\n", *kbuild_include_opts);
+
+       saved_kbuild_dir = strdup(*kbuild_dir);
+       saved_kbuild_include_opts = strdup(*kbuild_include_opts);
+
+       if (!saved_kbuild_dir || !saved_kbuild_include_opts) {
+               zfree(&saved_kbuild_dir);
+               zfree(&saved_kbuild_include_opts);
+       }
+       return;
+errout:
+       saved_kbuild_dir = ERR_PTR(-EINVAL);
+       saved_kbuild_include_opts = ERR_PTR(-EINVAL);
 }
 
 static void
@@ -406,7 +438,7 @@ 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, &kbuild_include_opts);
+       llvm__get_kbuild_opts(&kbuild_dir, &kbuild_include_opts);
 
        nr_cpus_avail = sysconf(_SC_NPROCESSORS_CONF);
        if (nr_cpus_avail <= 0) {
diff --git a/tools/perf/util/llvm-utils.h b/tools/perf/util/llvm-utils.h
index 9f501ce..d3f410d 100644
--- a/tools/perf/util/llvm-utils.h
+++ b/tools/perf/util/llvm-utils.h
@@ -50,4 +50,7 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf, 
size_t *p_obj_buf_sz);
 
 /* This function is for test__llvm() use only */
 int llvm__search_clang(void);
+
+/* This function is reused by builtin clang support */
+void llvm__get_kbuild_opts(char **kbuild_dir, char **kbuild_include_opts);
 #endif
-- 
1.8.3.4

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