1 files changed, 206 insertions, 0 deletions
diff --git a/util/memfd.c b/util/memfd.c
new file mode 100644
index 000000000..4a3c07e0b
--- /dev/null
+++ b/util/memfd.c
@@ -0,0 +1,206 @@
+/*
+ * memfd.c
+ *
+ * Copyright (c) 2015 Red Hat, Inc.
+ *
+ * QEMU library functions on POSIX which are shared between QEMU and
+ * the QEMU tools.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+
+#include "qapi/error.h"
+#include "qemu/memfd.h"
+#include "qemu/host-utils.h"
+
+#if defined CONFIG_LINUX && !defined CONFIG_MEMFD
+#include <sys/syscall.h>
+#include <asm/unistd.h>
+
+int memfd_create(const char *name, unsigned int flags)
+{
+#ifdef __NR_memfd_create
+    return syscall(__NR_memfd_create, name, flags);
+#else
+    errno = ENOSYS;
+    return -1;
+#endif
+}
+#endif
+
+int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
+                      uint64_t hugetlbsize, unsigned int seals, Error **errp)
+{
+    int htsize = hugetlbsize ? ctz64(hugetlbsize) : 0;
+
+    if (htsize && 1ULL << htsize != hugetlbsize) {
+        error_setg(errp, "Hugepage size must be a power of 2");
+        return -1;
+    }
+
+    htsize = htsize << MFD_HUGE_SHIFT;
+
+#ifdef CONFIG_LINUX
+    int mfd = -1;
+    unsigned int flags = MFD_CLOEXEC;
+
+    if (seals) {
+        flags |= MFD_ALLOW_SEALING;
+    }
+    if (hugetlb) {
+        flags |= MFD_HUGETLB;
+        flags |= htsize;
+    }
+    mfd = memfd_create(name, flags);
+    if (mfd < 0) {
+        error_setg_errno(errp, errno,
+                         "failed to create memfd with flags 0x%x", flags);
+        goto err;
+    }
+
+    if (ftruncate(mfd, size) == -1) {
+        error_setg_errno(errp, errno, "failed to resize memfd to %zu", size);
+        goto err;
+    }
+
+    if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
+        error_setg_errno(errp, errno, "failed to add seals 0x%x", seals);
+        goto err;
+    }
+
+    return mfd;
+
+err:
+    if (mfd >= 0) {
+        close(mfd);
+    }
+#else
+    error_setg_errno(errp, ENOSYS, "failed to create memfd");
+#endif
+    return -1;
+}
+
+/*
+ * This is a best-effort helper for shared memory allocation, with
+ * optional sealing. The helper will do his best to allocate using
+ * memfd with sealing, but may fallback on other methods without
+ * sealing.
+ */
+void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
+                       int *fd, Error **errp)
+{
+    void *ptr;
+    int mfd = qemu_memfd_create(name, size, false, 0, seals, NULL);
+
+    /* some systems have memfd without sealing */
+    if (mfd == -1) {
+        mfd = qemu_memfd_create(name, size, false, 0, 0, NULL);
+    }
+
+    if (mfd == -1) {
+        const char *tmpdir = g_get_tmp_dir();
+        gchar *fname;
+
+        fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir);
+        mfd = mkstemp(fname);
+        unlink(fname);
+        g_free(fname);
+
+        if (mfd == -1 ||
+            ftruncate(mfd, size) == -1) {
+            goto err;
+        }
+    }
+
+    ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
+    if (ptr == MAP_FAILED) {
+        goto err;
+    }
+
+    *fd = mfd;
+    return ptr;
+
+err:
+    error_setg_errno(errp, errno, "failed to allocate shared memory");
+    if (mfd >= 0) {
+        close(mfd);
+    }
+    return NULL;
+}
+
+void qemu_memfd_free(void *ptr, size_t size, int fd)
+{
+    if (ptr) {
+        munmap(ptr, size);
+    }
+
+    if (fd != -1) {
+        close(fd);
+    }
+}
+
+enum {
+    MEMFD_KO,
+    MEMFD_OK,
+    MEMFD_TODO
+};
+
+/**
+ * qemu_memfd_alloc_check():
+ *
+ * Check if qemu_memfd_alloc() can allocate, including using a
+ * fallback implementation when host doesn't support memfd.
+ */
+bool qemu_memfd_alloc_check(void)
+{
+    static int memfd_check = MEMFD_TODO;
+
+    if (memfd_check == MEMFD_TODO) {
+        int fd;
+        void *ptr;
+
+        fd = -1;
+        ptr = qemu_memfd_alloc("test", 4096, 0, &fd, NULL);
+        memfd_check = ptr ? MEMFD_OK : MEMFD_KO;
+        qemu_memfd_free(ptr, 4096, fd);
+    }
+
+    return memfd_check == MEMFD_OK;
+}
+
+/**
+ * qemu_memfd_check():
+ *
+ * Check if host supports memfd.
+ */
+bool qemu_memfd_check(unsigned int flags)
+{
+#ifdef CONFIG_LINUX
+    int mfd = memfd_create("test", flags | MFD_CLOEXEC);
+
+    if (mfd >= 0) {
+        close(mfd);
+        return true;
+    }
+#endif
+
+    return false;
+}