From: Marc-André Lureau <marcandre.lur...@redhat.com>
Add qemu_memfd_alloc/free() helpers.
The function helps to allocate and seal shared memory.
Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
include/qemu/memfd.h | 4 +++
util/memfd.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 77 insertions(+), 2 deletions(-)
diff --git a/include/qemu/memfd.h b/include/qemu/memfd.h
index 8b1fe6a..950fb88 100644
--- a/include/qemu/memfd.h
+++ b/include/qemu/memfd.h
@@ -17,4 +17,8 @@
#define F_SEAL_WRITE 0x0008 /* prevent writes */
#endif
+void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
+ int *fd);
+void qemu_memfd_free(void *ptr, size_t size, int fd);
+
#endif /* QEMU_MEMFD_H */
diff --git a/util/memfd.c b/util/memfd.c
index a98d57e..dd47552 100644
--- a/util/memfd.c
+++ b/util/memfd.c
@@ -27,6 +27,14 @@
#include "config-host.h"
+#include <glib.h>
+#include <glib/gprintf.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+
#include "qemu/memfd.h"
#ifdef CONFIG_MEMFD
@@ -44,13 +52,76 @@
#define MFD_ALLOW_SEALING 0x0002U
#endif
-static inline int memfd_create(const char *name, unsigned int flags)
+static int memfd_create(const char *name, unsigned int flags)
{
return syscall(__NR_memfd_create, name, flags);
}
#else /* !LINUX */
-static inline int memfd_create(const char *name, unsigned int flags)
+static int memfd_create(const char *name, unsigned int flags)
{
return -1;
}
#endif
+
+/*
+ * 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)
+{
+ void *ptr;
+ int mfd = -1;
+
+ *fd = -1;
+
+ if (seals) {
+ mfd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC);
+ }
+
+ if (mfd == -1) {
+ /* some systems have memfd without sealing */
+ mfd = memfd_create(name, MFD_CLOEXEC);
+ seals = 0;
+ }
+
+ if (mfd != -1) {
+ if (ftruncate(mfd, size) == -1) {
+ perror("ftruncate");
+ close(mfd);
+ return NULL;
+ }
+
+ if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
+ perror("fcntl");
+ close(mfd);
+ return NULL;
+ }
+ } else {
+ perror("memfd");
+ return NULL;
+ }
+
+ ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
+ if (ptr == MAP_FAILED) {
+ perror("mmap");
+ close(mfd);
+ return NULL;
+ }
+
+ *fd = mfd;
+ return ptr;
+}
+
+void qemu_memfd_free(void *ptr, size_t size, int fd)
+{
+ if (ptr) {
+ munmap(ptr, size);
+ }
+
+ if (fd != -1) {
+ close(fd);
+ }
+}
--
2.4.3
