From 9a241805673ec0a826b7ddf84b00f4e03adb0a5e Mon Sep 17 00:00:00 2001 From: Ian Rogers Date: Tue, 26 Jul 2022 15:09:21 -0700 Subject: [PATCH] perf bpf: Remove undefined behavior from bpf_perf_object__next() bpf_perf_object__next() folded the last element in the list test with the empty list test. However, this meant that offsets were computed against null and that a struct list_head was compared against a 'struct bpf_perf_object'. Working around this with clang's undefined behavior sanitizer required -fno-sanitize=null and -fno-sanitize=object-size. Remove the undefined behavior by using the regular Linux list APIs and handling the starting case separately from the end testing case. Looking at uses like bpf_perf_object__for_each(), as the constant NULL or non-NULL argument can be constant propagated, the code is no less efficient. Signed-off-by: Ian Rogers Cc: Alexander Shishkin Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Christy Lee Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mark Rutland Cc: Miaoqian Lin Cc: Namhyung Kim Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Tom Rix Cc: bpf@vger.kernel.org Cc: llvm@lists.linux.dev Link: https://lore.kernel.org/r/20220726220921.2567761-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/bpf-loader.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c index f8ad581..cdd6463 100644 --- a/tools/perf/util/bpf-loader.c +++ b/tools/perf/util/bpf-loader.c @@ -63,20 +63,16 @@ static struct hashmap *bpf_map_hash; static struct bpf_perf_object * bpf_perf_object__next(struct bpf_perf_object *prev) { - struct bpf_perf_object *next; - - if (!prev) - next = list_first_entry(&bpf_objects_list, - struct bpf_perf_object, - list); - else - next = list_next_entry(prev, list); + if (!prev) { + if (list_empty(&bpf_objects_list)) + return NULL; - /* Empty list is noticed here so don't need checking on entry. */ - if (&next->list == &bpf_objects_list) + return list_first_entry(&bpf_objects_list, struct bpf_perf_object, list); + } + if (list_is_last(&prev->list, &bpf_objects_list)) return NULL; - return next; + return list_next_entry(prev, list); } #define bpf_perf_object__for_each(perf_obj, tmp) \ -- 2.7.4