linux-kernel - [PATCHv2] perf tools: Convert legacy map definition to BTF-defined

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Date:   Mon,  4 Jul 2022 17:27:21 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        linux-perf-users@...r.kernel.org, bpf@...r.kernel.org,
        Andrii Nakryiko <andrii@...nel.org>
Subject: [PATCHv2] perf tools: Convert legacy map definition to BTF-defined

The libbpf is switching off support for legacy map definitions [1],
which will break the perf llvm tests.

Moving the base source map definition to BTF-defined, so we need
to use -g compile option for to add debug/BTF info.

[1] https://lore.kernel.org/bpf/20220627211527.2245459-1-andrii@kernel.org/
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/tests/bpf-script-example.c | 35 ++++++++++++++++++---------
 tools/perf/util/llvm-utils.c          |  2 +-
 2 files changed, 24 insertions(+), 13 deletions(-)

v2 changes:
  - added comments to macros [Ian]
  - removed struct bpf_map_def, it's no longer needed

diff --git a/tools/perf/tests/bpf-script-example.c b/tools/perf/tests/bpf-script-example.c
index ab4b98b3165d..7981c69ed1b4 100644
--- a/tools/perf/tests/bpf-script-example.c
+++ b/tools/perf/tests/bpf-script-example.c
@@ -17,20 +17,31 @@ static void *(*bpf_map_lookup_elem)(void *map, void *key) =
 static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
 	(void *) BPF_FUNC_map_update_elem;
 
-struct bpf_map_def {
-	unsigned int type;
-	unsigned int key_size;
-	unsigned int value_size;
-	unsigned int max_entries;
-};
+/*
+ * Following macros are taken from tools/lib/bpf/bpf_helpers.h,
+ * and are used to create BTF defined maps. It is easier to take
+ * 2 simple macros, than being able to include above header in
+ * runtime.
+ *
+ * __uint - defines integer attribute of BTF map definition,
+ * Such attributes are represented using a pointer to an array,
+ * in which dimensionality of array encodes specified integer
+ * value.
+ *
+ * __type - defines pointer variable with typeof(val) type for
+ * attributes like key or value, which will be defined by the
+ * size of the type.
+ */
+#define __uint(name, val) int (*name)[val]
+#define __type(name, val) typeof(val) *name
 
 #define SEC(NAME) __attribute__((section(NAME), used))
-struct bpf_map_def SEC("maps") flip_table = {
-	.type = BPF_MAP_TYPE_ARRAY,
-	.key_size = sizeof(int),
-	.value_size = sizeof(int),
-	.max_entries = 1,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 1);
+	__type(key, int);
+	__type(value, int);
+} flip_table SEC(".maps");
 
 SEC("func=do_epoll_wait")
 int bpf_func__SyS_epoll_pwait(void *ctx)
diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index 96c8ef60f4f8..2dc797007419 100644
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -25,7 +25,7 @@
 		"$CLANG_OPTIONS $PERF_BPF_INC_OPTIONS $KERNEL_INC_OPTIONS " \
 		"-Wno-unused-value -Wno-pointer-sign "		\
 		"-working-directory $WORKING_DIR "		\
-		"-c \"$CLANG_SOURCE\" -target bpf $CLANG_EMIT_LLVM -O2 -o - $LLVM_OPTIONS_PIPE"
+		"-c \"$CLANG_SOURCE\" -target bpf $CLANG_EMIT_LLVM -g -O2 -o - $LLVM_OPTIONS_PIPE"
 
 struct llvm_param llvm_param = {
 	.clang_path = "clang",
-- 
2.35.3