process: Add virProcessGetMaxMemLock()

This function can be used to retrieve the current locked memory
limit for a process, so that the setting can be later restored.

Add a configure check for getrlimit(), which we now use.

configure.ac

@@ -283,7 +283,7 @@ AC_CHECK_SIZEOF([long])
 dnl Availability of various common functions (non-fatal if missing),
 dnl and various less common threadsafe functions
 AC_CHECK_FUNCS_ONCE([cfmakeraw fallocate geteuid getgid getgrnam_r \
-  getmntent_r getpwuid_r getuid kill mmap newlocale posix_fallocate \
+  getmntent_r getpwuid_r getrlimit getuid kill mmap newlocale posix_fallocate \
   posix_memalign prlimit regexec sched_getaffinity setgroups setns \
   setrlimit symlink sysctlbyname getifaddrs sched_setscheduler])
 

src/libvirt_private.syms

@@ -2040,6 +2040,7 @@ virPortAllocatorSetUsed;
 virProcessAbort;
 virProcessExitWithStatus;
 virProcessGetAffinity;
+virProcessGetMaxMemLock;
 virProcessGetNamespaces;
 virProcessGetPids;
 virProcessGetStartTime;

src/util/virprocess.c

@@ -788,6 +788,51 @@ virProcessSetMaxMemLock(pid_t pid ATTRIBUTE_UNUSED, unsigned long long bytes)
 }
 #endif /* ! (HAVE_SETRLIMIT && defined(RLIMIT_MEMLOCK)) */
 
+#if HAVE_GETRLIMIT && defined(RLIMIT_MEMLOCK)
+int
+virProcessGetMaxMemLock(pid_t pid,
+                        unsigned long long *bytes)
+{
+    struct rlimit rlim;
+
+    if (!bytes)
+        return 0;
+
+    if (pid == 0) {
+        if (getrlimit(RLIMIT_MEMLOCK, &rlim) < 0) {
+            virReportSystemError(errno,
+                                 "%s",
+                                 _("cannot get locked memory limit"));
+            return -1;
+        }
+    } else {
+        if (virProcessPrLimit(pid, RLIMIT_MEMLOCK, NULL, &rlim) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot get locked memory limit "
+                                   "of process %lld"),
+                                 (long long int) pid);
+            return -1;
+        }
+    }
+
+    /* virProcessSetMaxMemLock() sets both rlim_cur and rlim_max to the
+     * same value, so we can retrieve just rlim_max here */
+    *bytes = rlim.rlim_max;
+
+    return 0;
+}
+#else /* ! (HAVE_GETRLIMIT && defined(RLIMIT_MEMLOCK)) */
+int
+virProcessGetMaxMemLock(pid_t pid ATTRIBUTE_UNUSED,
+                        unsigned long long *bytes)
+{
+    if (!bytes)
+        return 0;
+
+    virReportSystemError(ENOSYS, "%s", _("Not supported on this platform"));
+    return -1;
+}
+#endif /* ! (HAVE_GETRLIMIT && defined(RLIMIT_MEMLOCK)) */
 
 #if HAVE_SETRLIMIT && defined(RLIMIT_NPROC)
 int

src/util/virprocess.h

@@ -76,6 +76,8 @@ int virProcessSetMaxMemLock(pid_t pid, unsigned long long bytes);
 int virProcessSetMaxProcesses(pid_t pid, unsigned int procs);
 int virProcessSetMaxFiles(pid_t pid, unsigned int files);
 
+int virProcessGetMaxMemLock(pid_t pid, unsigned long long *bytes);
+
 /* Callback to run code within the mount namespace tied to the given
  * pid.  This function must use only async-signal-safe functions, as
  * it gets run after a fork of a multi-threaded process.  The return