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authorDon Dugger <n0ano@n0ano.com>2016-06-03 03:33:22 +0000
committerGerrit Code Review <gerrit@172.30.200.206>2016-06-03 03:33:23 +0000
commitda27230f80795d0028333713f036d44c53cb0e68 (patch)
treeb3d379eaf000adf72b36cb01cdf4d79c3e3f064c /qemu/util/mmap-alloc.c
parent0e68cb048bb8aadb14675f5d4286d8ab2fc35449 (diff)
parent437fd90c0250dee670290f9b714253671a990160 (diff)
Merge "These changes are the raw update to qemu-2.6."
Diffstat (limited to 'qemu/util/mmap-alloc.c')
-rw-r--r--qemu/util/mmap-alloc.c110
1 files changed, 110 insertions, 0 deletions
diff --git a/qemu/util/mmap-alloc.c b/qemu/util/mmap-alloc.c
new file mode 100644
index 000000000..0b4cc7f7f
--- /dev/null
+++ b/qemu/util/mmap-alloc.c
@@ -0,0 +1,110 @@
+/*
+ * Support for RAM backed by mmaped host memory.
+ *
+ * Copyright (c) 2015 Red Hat, Inc.
+ *
+ * Authors:
+ * Michael S. Tsirkin <mst@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * later. See the COPYING file in the top-level directory.
+ */
+#include "qemu/osdep.h"
+#include <qemu/mmap-alloc.h>
+#include <sys/mman.h>
+
+#define HUGETLBFS_MAGIC 0x958458f6
+
+#ifdef CONFIG_LINUX
+#include <sys/vfs.h>
+#endif
+
+size_t qemu_fd_getpagesize(int fd)
+{
+#ifdef CONFIG_LINUX
+ struct statfs fs;
+ int ret;
+
+ if (fd != -1) {
+ do {
+ ret = fstatfs(fd, &fs);
+ } while (ret != 0 && errno == EINTR);
+
+ if (ret == 0 && fs.f_type == HUGETLBFS_MAGIC) {
+ return fs.f_bsize;
+ }
+ }
+#endif
+
+ return getpagesize();
+}
+
+void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
+{
+ /*
+ * Note: this always allocates at least one extra page of virtual address
+ * space, even if size is already aligned.
+ */
+ size_t total = size + align;
+#if defined(__powerpc64__) && defined(__linux__)
+ /* On ppc64 mappings in the same segment (aka slice) must share the same
+ * page size. Since we will be re-allocating part of this segment
+ * from the supplied fd, we should make sure to use the same page size, to
+ * this end we mmap the supplied fd. In this case, set MAP_NORESERVE to
+ * avoid allocating backing store memory.
+ * We do this unless we are using the system page size, in which case
+ * anonymous memory is OK.
+ */
+ int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 : fd;
+ int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE;
+ void *ptr = mmap(0, total, PROT_NONE, flags | MAP_PRIVATE, anonfd, 0);
+#else
+ void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+#endif
+ size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
+ void *ptr1;
+
+ if (ptr == MAP_FAILED) {
+ return MAP_FAILED;
+ }
+
+ /* Make sure align is a power of 2 */
+ assert(!(align & (align - 1)));
+ /* Always align to host page size */
+ assert(align >= getpagesize());
+
+ ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE,
+ MAP_FIXED |
+ (fd == -1 ? MAP_ANONYMOUS : 0) |
+ (shared ? MAP_SHARED : MAP_PRIVATE),
+ fd, 0);
+ if (ptr1 == MAP_FAILED) {
+ munmap(ptr, total);
+ return MAP_FAILED;
+ }
+
+ ptr += offset;
+ total -= offset;
+
+ if (offset > 0) {
+ munmap(ptr - offset, offset);
+ }
+
+ /*
+ * Leave a single PROT_NONE page allocated after the RAM block, to serve as
+ * a guard page guarding against potential buffer overflows.
+ */
+ if (total > size + getpagesize()) {
+ munmap(ptr + size + getpagesize(), total - size - getpagesize());
+ }
+
+ return ptr;
+}
+
+void qemu_ram_munmap(void *ptr, size_t size)
+{
+ if (ptr) {
+ /* Unmap both the RAM block and the guard page */
+ munmap(ptr, size + getpagesize());
+ }
+}