Add "per-process" file caching feature

Allows chosing page caching based on process name.

src/procfs_get_name.cpp

@@ -0,0 +1,54 @@
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include "procfs_get_name.hpp"
+
+#include "errno.hpp"
+#include "fs_close.hpp"
+#include "fs_open.hpp"
+#include "fs_openat.hpp"
+#include "fs_read.hpp"
+
+#include <pthread.h>
+
+static int g_PROCFS_DIR_FD = -1;
+const char PROCFS_PATH[] = "/proc";
+
+int
+procfs::init()
+{
+  if(g_PROCFS_DIR_FD != -1)
+    return 0;
+
+  g_PROCFS_DIR_FD = fs::open(PROCFS_PATH,O_PATH|O_DIRECTORY);
+  if(g_PROCFS_DIR_FD == -1)
+    return -errno;
+
+  return 0;
+}
+
+std::string
+procfs::get_name(const int tid_)
+{
+  int fd;
+  int rv;
+  char commpath[256];
+
+  snprintf(commpath,sizeof(commpath),"%d/comm",tid_);
+
+  fd = fs::openat(g_PROCFS_DIR_FD,commpath,O_RDONLY);
+  if(fd < 0)
+    return {};
+
+  rv = fs::read(fd,commpath,sizeof(commpath));
+  if(rv == -1)
+    return {};
+
+  // Overwrite the newline with NUL
+  commpath[rv-1] = '\0';
+
+  fs::close(fd);
+
+  return commpath;
+}