Subject: [PATCH] advice user to run as root when paranoid_level==3

Corresponds with Debian patch 0003_Report_root_needed
https://sources.debian.org/patches/tiptop/2.3.1-4/0003-Report_root_needed.patch/

Signed-off-by: Pascal Jäger <pascal.jaeger@leimstift.de>
--- a/src/requisite.c
+++ b/src/requisite.c
@@ -17,13 +17,34 @@
 #include "pmc.h"
 #include "requisite.h"
 
+#define PARANOID1 "/proc/sys/kernel/perf_counter_paranoid"
+#define PARANOID2 "/proc/sys/kernel/perf_event_paranoid"
 
 void check()
 {
   int fd, cpu, grp, flags, pid;
+  FILE* paranoid;
+  int   paranoia_level = 999;
   struct utsname os;
   struct STRUCT_NAME events = {0, };
+  int    n;
 
+  paranoid = fopen(PARANOID1, "r");
+  if (!paranoid)
+    paranoid = fopen(PARANOID2, "r");
+
+  if (!paranoid) {
+    fprintf(stderr, "System does not support performance events.\n");
+    fprintf(stderr, "File '/proc/sys/kernel/perf_*_paranoid' is missing.\n");
+    exit(EXIT_FAILURE);
+  }
+  n = fscanf(paranoid, "%d", &paranoia_level);
+  if (n != 1) {
+    fprintf(stderr, "Could not read '/proc/sys/kernel/perf_*_paranoid'.\n");
+    fprintf(stderr, "Trying to proceed anyway...\n");
+  }
+
+  fclose(paranoid);
   events.disabled = 0;
   events.exclude_hv = 1;
   events.exclude_kernel = 1;
-- 
2.38.1