From 9fee532cb684ef053155b763db13401fd3da664c Mon Sep 17 00:00:00 2001
From: apocelipes <seve3r@outlook.com>
Date: Mon, 4 Dec 2023 17:36:45 +0900
Subject: [PATCH] fix(CPUUsage): fix reading procfs files and simplify data
 parsing

---
 src/detection/cpuusage/cpuusage_linux.c | 38 ++++++++++++++++---------
 1 file changed, 25 insertions(+), 13 deletions(-)

diff --git a/src/detection/cpuusage/cpuusage_linux.c b/src/detection/cpuusage/cpuusage_linux.c
index 784f680b5..cb6101a97 100644
--- a/src/detection/cpuusage/cpuusage_linux.c
+++ b/src/detection/cpuusage/cpuusage_linux.c
@@ -7,30 +7,42 @@
 
 const char* ffGetCpuUsageInfo(FFlist* cpuTimes)
 {
-    FF_AUTO_CLOSE_FILE FILE* procStat = fopen("/proc/stat", "r");
-    if(procStat == NULL)
+    char buf[PROC_FILE_BUFFSIZ];
+    ssize_t nRead = ffReadFileData("/proc/stat", sizeof(buf) - 1, buf);
+    if(nRead < 0)
     {
         #ifdef __ANDROID__
         return "Accessing \"/proc/stat\" is restricted on Android O+";
         #else
-        return "fopen(\"""/proc/stat\", \"r\") == NULL";
+        return "ffReadFileData(\"/proc/stat\", sizeof(buf) - 1, buf) failed";
         #endif
     }
+    buf[nRead] = '\0';
+
     // Skip first line
-    if (fscanf(procStat, "cpu%*[^\n]\n") < 0)
-        return "fscanf() first line failed";
+    char *start = NULL;
+    if((start = strchr(buf, '\n')) == NULL)
+        return "skip first line failed";
+    ++start;
 
     uint64_t user = 0, nice = 0, system = 0, idle = 0, iowait = 0, irq = 0, softirq = 0;
-    while (fscanf(procStat, "cpu%*d%" PRIu64 "%" PRIu64 "%" PRIu64 "%" PRIu64 "%" PRIu64 "%" PRIu64 "%" PRIu64 "%*[^\n]\n", &user, &nice, &system, &idle, &iowait, &irq, &softirq) == 7)
+    char *token = NULL;
+    while ((token = strchr(start, '\n')))
     {
-        uint64_t inUse = user + nice + system;
-        uint64_t total = inUse + idle + iowait + irq + softirq;
+        if(sscanf(start, "cpu%*d%" PRIu64 "%" PRIu64 "%" PRIu64 "%" PRIu64 "%" PRIu64 "%" PRIu64 "%" PRIu64 "%*[^\n]\n", &user, &nice, &system, &idle, &iowait, &irq, &softirq) == 7)
+        {
+            uint64_t inUse = user + nice + system;
+            uint64_t total = inUse + idle + iowait + irq + softirq;
 
-        FFCpuUsageInfo* info = (FFCpuUsageInfo*) ffListAdd(cpuTimes);
-        *info = (FFCpuUsageInfo) {
-            .inUseAll = (uint64_t)inUse,
-            .totalAll = (uint64_t)total,
-        };
+            FFCpuUsageInfo* info = (FFCpuUsageInfo*) ffListAdd(cpuTimes);
+            *info = (FFCpuUsageInfo) {
+                .inUseAll = (uint64_t)inUse,
+                .totalAll = (uint64_t)total,
+            };
+        }
+        else
+            break; // because we read the whole /proc/stat, we can safely quit when the line does not start with "cpuN" 
+        start = token + 1;
     }
 
     return NULL;