[PATCH v1] perf: extend message to mention CAP_SYS_PTRACE and perf security doc link

[Alexey Budankov]

Adjust limited access message to mention CAP_SYS_PTRACE capability
for processes of unprivileged users. Add link to perf security
document in the end of the section about capabilities.
The change has been inspired by this discussion:
https://lore.kernel.org/lkml/20200722113007.GI77866@xxxxxxxxxx/

Signed-off-by: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
---
 tools/perf/util/evsel.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 9aa51a65593d..e241ee773ccb 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2500,8 +2500,10 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
 
 		return scnprintf(msg + printed, size - printed,
 		 "Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open\n"
-		 "access to performance monitoring and observability operations for users\n"
-		 "without CAP_PERFMON or CAP_SYS_ADMIN Linux capability.\n"
+		 "access to performance monitoring and observability operations for processes\n"
+		 "without CAP_PERFMON, CAP_SYS_PTRACE or CAP_SYS_ADMIN Linux capability.\n"
+		 "More information can be found at 'Perf events and tool security' document:\n"
+		 "https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html\n";
 		 "perf_event_paranoid setting is %d:\n"
 		 "  -1: Allow use of (almost) all events by all users\n"
 		 "      Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK\n"
-- 
2.24.1