util: Introduce qemu_get_pid_name

This is a small helper that tries to fetch binary name for given
PID.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Message-Id: <4d75d475c1884f8e94ee8b1e57273ddf3ed68bf7.1474987617.git.mprivozn@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qemu/osdep.h

@@ -387,6 +387,16 @@ void os_mem_prealloc(int fd, char *area, size_t sz, Error **errp);
 
 int qemu_read_password(char *buf, int buf_size);
 
+/**
+ * qemu_get_pid_name:
+ * @pid: pid of a process
+ *
+ * For given @pid fetch its name. Caller is responsible for
+ * freeing the string when no longer needed.
+ * Returns allocated string on success, NULL on failure.
+ */
+char *qemu_get_pid_name(pid_t pid);
+
 /**
  * qemu_fork:
  *

util/oslib-posix.c

@@ -46,6 +46,7 @@
 
 #ifdef __FreeBSD__
 #include <sys/sysctl.h>
+#include <libutil.h>
 #endif
 
 #include "qemu/mmap-alloc.h"
@@ -430,6 +431,32 @@ int qemu_read_password(char *buf, int buf_size)
 }
 
 
+char *qemu_get_pid_name(pid_t pid)
+{
+    char *name = NULL;
+
+#if defined(__FreeBSD__)
+    /* BSDs don't have /proc, but they provide a nice substitute */
+    struct kinfo_proc *proc = kinfo_getproc(pid);
+
+    if (proc) {
+        name = g_strdup(proc->ki_comm);
+        free(proc);
+    }
+#else
+    /* Assume a system with reasonable procfs */
+    char *pid_path;
+    size_t len;
+
+    pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
+    g_file_get_contents(pid_path, &name, &len, NULL);
+    g_free(pid_path);
+#endif
+
+    return name;
+}
+
+
 pid_t qemu_fork(Error **errp)
 {
     sigset_t oldmask, newmask;

util/oslib-win32.c

@@ -575,6 +575,13 @@ int qemu_read_password(char *buf, int buf_size)
 }
 
 
+char *qemu_get_pid_name(pid_t pid)
+{
+    /* XXX Implement me */
+    abort();
+}
+
+
 pid_t qemu_fork(Error **errp)
 {
     errno = ENOSYS;