From 262b54b6c9396823ab06df46a1be475c44b28b5f Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Mon, 21 Aug 2023 10:40:09 -0300 Subject: [PATCH] perf bpf augmented_raw_syscalls: Add an assert to make sure sizeof(saddr) is a power of two. We're using the BPF verifier suggestion: 22: (85) call bpf_probe_read#4 R2 min value is negative, either use unsigned or 'var &= const' That works only when const is a (power of two - 1) so add an assert to make sure that that is the case. Suggested-by: Ian Rogers Cc: Adrian Hunter Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lore.kernel.org/lkml/ZONrFmJBNlQpSpZj@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c | 11 +++++++++++ 1 file changed, 11 insertions(+) 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 9c1d0b2..43549b6 100644 --- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c +++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c @@ -10,6 +10,16 @@ #include #include +/** + * is_power_of_2() - check if a value is a power of two + * @n: the value to check + * + * Determine whether some value is a power of two, where zero is *not* + * considered a power of two. Return: true if @n is a power of 2, otherwise + * false. + */ +#define is_power_of_2(n) (n != 0 && ((n & (n - 1)) == 0)) + #define MAX_CPUS 4096 // FIXME: These should come from system headers @@ -187,6 +197,7 @@ int sys_enter_connect(struct syscall_enter_args *args) if (augmented_args == NULL) return 1; /* Failure: don't filter */ + _Static_assert(is_power_of_2(sizeof(augmented_args->saddr)), "sizeof(augmented_args->saddr) needs to be a power of two"); socklen &= sizeof(augmented_args->saddr) - 1; bpf_probe_read(&augmented_args->saddr, socklen, sockaddr_arg); -- 2.7.4