From: Marc-André Lureau <marcandre.lur...@redhat.com>
Add a function to only create a memfd, without mmap. The function is
used in the following memory backend.
Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>
Message-Id: <20171023141815.17709-2-marcandre.lur...@redhat.com>
Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
---
include/qemu/memfd.h | 1 +
util/memfd.c | 61 +++++++++++++++++++++++++++++++---------------------
2 files changed, 37 insertions(+), 25 deletions(-)
diff --git a/include/qemu/memfd.h b/include/qemu/memfd.h
index 745a8c501e..41c24d807c 100644
--- a/include/qemu/memfd.h
+++ b/include/qemu/memfd.h
@@ -16,6 +16,7 @@
#define F_SEAL_WRITE 0x0008 /* prevent writes */
#endif
+int qemu_memfd_create(const char *name, size_t size, unsigned int seals);
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);
diff --git a/util/memfd.c b/util/memfd.c
index 412e94a405..3a82505f8d 100644
--- a/util/memfd.c
+++ b/util/memfd.c
@@ -53,6 +53,38 @@ static int memfd_create(const char *name, unsigned int flags)
#define MFD_ALLOW_SEALING 0x0002U
#endif
+int qemu_memfd_create(const char *name, size_t size, unsigned int seals)
+{
+ int mfd = -1;
+
+#ifdef CONFIG_LINUX
+ unsigned int flags = MFD_CLOEXEC;
+
+ if (seals) {
+ flags |= MFD_ALLOW_SEALING;
+ }
+
+ mfd = memfd_create(name, flags);
+ if (mfd < 0) {
+ return -1;
+ }
+
+ if (ftruncate(mfd, size) == -1) {
+ perror("ftruncate");
+ close(mfd);
+ return -1;
+ }
+
+ if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
+ perror("fcntl");
+ close(mfd);
+ return -1;
+ }
+#endif
+
+ return mfd;
+}
+
/*
* This is a best-effort helper for shared memory allocation, with
* optional sealing. The helper will do his best to allocate using
@@ -63,35 +95,14 @@ void *qemu_memfd_alloc(const char *name, size_t size,
unsigned int seals,
int *fd)
{
void *ptr;
- int mfd = -1;
-
- *fd = -1;
-
-#ifdef CONFIG_LINUX
- if (seals) {
- mfd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC);
- }
+ int mfd = qemu_memfd_create(name, size, seals);
+ /* some systems have memfd without sealing */
if (mfd == -1) {
- /* some systems have memfd without sealing */
- mfd = memfd_create(name, MFD_CLOEXEC);
- seals = 0;
+ mfd = qemu_memfd_create(name, size, 0);
}
-#endif
-
- 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 {
+ if (mfd == -1) {
const char *tmpdir = g_get_tmp_dir();
gchar *fname;
--
2.14.3
