From 4222b140ec594e99e77cda8539b16f21820ae155 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alessandro=C2=A0Decina?= <alessandro.d@gmail.com>
Date: Wed, 28 Apr 2021 09:45:25 +0000
Subject: [PATCH] aya: perf_map: fix bug when max_entries=0

When a perf map has max_entries=0, max_entries is dynamically set at
load time to the number of possible cpus as reported by
/sys/devices/system/cpu/possible.

This change fixes a bug where instead of setting max_entries to the
number of possible cpus, we were setting it to the cpu index of the last
possible cpu.
---
 aya/src/bpf.rs | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/aya/src/bpf.rs b/aya/src/bpf.rs
index b3e94f59..bed764cd 100644
--- a/aya/src/bpf.rs
+++ b/aya/src/bpf.rs
@@ -117,13 +117,12 @@ impl Bpf {
         for (_, mut obj) in obj.maps.drain() {
             if obj.def.map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY as u32 && obj.def.max_entries == 0
             {
-                obj.def.max_entries = *possible_cpus()
+                obj.def.max_entries = possible_cpus()
                     .map_err(|error| BpfError::FileError {
                         path: PathBuf::from(POSSIBLE_CPUS),
                         error,
                     })?
-                    .last()
-                    .unwrap_or(&0);
+                    .len() as u32;
             }
             let mut map = Map { obj, fd: None };
             let fd = map.create()?;