Add qemu_memfd_alloc/free() helpers.
The function helps to allocate and seal a memfd, and implements an
open/unlink/mmap fallback for system that do not support memfd.
Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
include/qemu/osdep.h | 5 +++++
util/oslib-posix.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 67 insertions(+)
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index adc138b..c49145f 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -167,6 +167,11 @@ void *qemu_anon_ram_alloc(size_t size, uint64_t *align);
void qemu_vfree(void *ptr);
void qemu_anon_ram_free(void *ptr, size_t size);
+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);
+
+
#define QEMU_MADV_INVALID -1
#if defined(CONFIG_MADVISE)
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 3ae4987..6e5a143 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -482,3 +482,65 @@ int qemu_read_password(char *buf, int buf_size)
printf("\n");
return ret;
}
+
+void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
+ int *fd)
+{
+ void *ptr;
+ int mfd;
+
+ mfd = memfd_create(name, MFD_ALLOW_SEALING|MFD_CLOEXEC);
+ if (mfd != -1) {
+ if (ftruncate(mfd, size) == -1) {
+ perror("ftruncate");
+ close(mfd);
+ return NULL;
+ }
+
+ if (fcntl(mfd, F_ADD_SEALS, seals) == -1) {
+ perror("fcntl");
+ close(mfd);
+ return NULL;
+ }
+ } else {
+ const char *tmpdir = getenv("TMPDIR");
+ gchar *fname;
+
+ tmpdir = tmpdir ? tmpdir : "/tmp";
+
+ fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir);
+ mfd = mkstemp(fname);
+ unlink(fname);
+ g_free(fname);
+
+ if (mfd == -1) {
+ perror("mkstemp");
+ return NULL;
+ }
+
+ if (ftruncate(mfd, size) == -1) {
+ perror("ftruncate");
+ close(mfd);
+ 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);
+ }
+
+ close(fd);
+}
--
2.4.3
