linux-kernel - [PATCH] perf bpf augmented_raw_syscalls: Add an assert to make sure sizeof(augmented

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Date:   Mon, 21 Aug 2023 10:48:46 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] perf bpf augmented_raw_syscalls: Add an assert to make sure
 sizeof(augmented_arg->value) is a power of two.

Similar to what was done in the previous cset for sizeof(saddr), we need
to make sure sizeof(augmented_arg->value) is a power of two to do bounds
checking using &=:

  augmented_len &= sizeof(augmented_arg->value) - 1;

Suggested-by: Ian Rogers <irogers@...gle.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Link: https://lore.kernel.org/lkml/
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
index 43549b63b433d81e..90ce22f9c1a94004 100644
--- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
+++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
@@ -160,6 +160,7 @@ unsigned int augmented_arg__read_str(struct augmented_arg *augmented_arg, const
 	 */
 	if (string_len > 0) {
 		augmented_len -= sizeof(augmented_arg->value) - string_len;
+		_Static_assert(is_power_of_2(sizeof(augmented_arg->value)), "sizeof(augmented_arg->value) needs to be a power of two");
 		augmented_len &= sizeof(augmented_arg->value) - 1;
 		augmented_arg->size = string_len;
 	} else {
-- 
2.37.1