[RFC PATCH v7 27/37] perf tools: Auto detecting kernel include options

Wang Nan
2015-06-12T05:40:54Z

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>
---
tools/perf/util/llvm-utils.c | 59 ++++++++++++++++++++++++++++++++++++++++----
1 file changed, 54 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index 7b2217a..3c43fcf 100644
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -215,15 +215,42 @@ static const char *kbuild_detector =
"fi\n"
"exit -1\n";

+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");
@@ -244,6 +271,26 @@ 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);
+ 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,
@@ -253,7 +300,7 @@ 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;

@@ -275,11 +322,11 @@ 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 ? : ".");

/*
@@ -302,6 +349,7 @@ 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
@@ -312,6 +360,7 @@ 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;
--
1.8.3.4