[v1.00][X86] Retrieve topology from udev when APIC fails (like #119)

src/common/udev.c

@@ -2,6 +2,48 @@
 #include "global.h"
 #include "cpu.h"
 
+// https://www.kernel.org/doc/html/latest/core-api/cpu_hotplug.html
+int get_ncores_from_cpuinfo() {
+  // Examples:
+  // 0-271
+  // 0-7
+  // 0
+
+  int filelen;
+  char* buf;
+  if((buf = read_file(_PATH_CPUS_PRESENT, &filelen)) == NULL) {
+    printWarn("read_file: %s: %s\n", _PATH_CPUS_PRESENT, strerror(errno));
+    return -1;
+  }
+
+  int ncores;
+  char* tmp1;
+  if((tmp1 = strstr(buf, "-")) == NULL) {
+    // file contains no - character, we assume that it contains 0,
+    // which means that the CPU contains only one core
+    return 1;
+  }
+  else {
+    tmp1++;
+  }
+  char* tmp2 = strstr(buf, "\n");
+  char ncores_str[filelen];
+  memset(ncores_str, 0, sizeof(char) * filelen);
+  memcpy(ncores_str, tmp1, tmp2-tmp1);
+
+  char* end;
+  errno = 0;
+  ncores = strtol(ncores_str, &end, 10) + 1;
+  if(errno != 0) {
+    printWarn("strtol: %s:\n", strerror(errno));
+    return -1;
+  }
+
+  free(buf);
+
+  return ncores;
+}
+
 char* read_file(char* path, int* len) {
   int fd = open(path, O_RDONLY);
 

src/common/udev.h

@@ -23,6 +23,7 @@
 #define _PATH_CACHE_L3          "/cache/index3"
 #define _PATH_CACHE_SIZE        "/size"
 #define _PATH_CACHE_SHARED_MAP  "/shared_cpu_map"
+#define _PATH_CPUS_PRESENT           _PATH_SYS_SYSTEM _PATH_SYS_CPU "/present"
 
 #define _PATH_FREQUENCY_MAX_LEN 100
 #define _PATH_CACHE_MAX_LEN     200
@@ -36,5 +37,6 @@ long get_l1d_cache_size(uint32_t core);
 long get_l2_cache_size(uint32_t core);
 long get_l3_cache_size(uint32_t core);
 int get_num_caches_by_level(struct cpuInfo* cpu, uint32_t level);
+int get_ncores_from_cpuinfo();
 
 #endif